( PDF ) Análise comparada de caracteres reprodutivos e diversidade do gênero Brachyhypopomus Mago-Leccia, 1994 no Rio Grande do Sul

Download PDF

ads:

JÚLIA GIORA

ANÁLISE COMPARADA DE CARACTERES REPRODUTIVOS E

DIVERSIDADE DO GÊNERO Brachyhypopomus Mago-Leccia, 1994 NO RIO

GRANDE DO SUL.

Tese apresentada ao Programa de Pós-Graduação

em Biologia Animal, Instituto de Biociências,

Universidade Federal do Rio Grande do Sul, como

requisito parcial à obtenção do título de Doutora em

Biologia Animal.

Área de Concentração: Biologia Comparada

Orientadora: Profa. Dra. Clarice Bernhardt Fialho

Co-orientador: Prof. Dr. Luiz Roberto Malabarba

Co-orientador PDEE: Prof. Dr. John Robert Burns

UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL

PORTO ALEGRE

2008

ads:

Livros Grátis

http://www.livrosgratis.com.br

Milhares de livros grátis para download.

ANÁLISE COMPARADA DE CARACTERES REPRODUTIVOS E

DIVERSIDADE DO GÊNERO Brachyhypopomus Mago-Leccia, 1994 NO RIO

GRANDE DO SUL.

JÚLIA GIORA

___________________________________

Prof. Dr. José Alves Gomes

___________________________________

Prof. Dr. Roberto Esser dos Reis

___________________________________

Prof. Dr. Nelson Fontoura

___________________________________

Prof. Dra. Clarice Bernhardt Fialho

ads:

“As coisas estão no mundo, só que eu preciso aprender”

Paulinho da Viola.

iii

Agradecimentos

A CAPES, pela bolsa propiciada e ao CNPq pelos auxílios concedidos

(processo 476821/2003-7; 478002/2006-8).

À Profª. Dra. Clarice Bernhardt Fialho, pela orientação, confiança e

vários pelos anos de bom convívio.

Ao Prof. Dr. Luiz Roberto Malabarba, pela orientação, incentivo, pelos

grandes ensinamentos em sistemática e por sua amizade.

Ao Prof. Dr. John Robert Burns por ter aceitado orientar meu estagio de

doutorado na George Washington University e por seus ensinamentos em

histologia e microscopia eletrônica.

Aos Drs. Richard Vari e Stanley Weitzman pela gentil recepção e

suporte ao meu trabalho no National Museum of Natural History.

Aos Drs. John Lundberg e John Sullivan da Academy of Natural

Sciences of Philadelphia e ao Dr. Marcelo Loureiro do Museo Nacional de

Ciencias Naturales de Montevideo por me receberem e auxiliarem minha

pesquisa na coleção científica de suas instituições.

Ao Suresh Benjamim, pelo auxilio na operação do microscópio

eletrônico de varredura da GWU.

A todos aqueles que me auxiliaram nos dois anos de trabalho de

campo: Daniel de Borba Rocha, Adriana Saccol Pereira, Andréa Brandreli

Schaan, Ana Paula S. Dufech, Ariane Ribeiro, Carlos Eduardo Machado, Diego

Cognato, Giovanni Neves, Juan A. Anza, Juliano Ferrer, Paulo Roberto

Werlang, Renata Bocorny de Azevedo, Renata Bornholdt, Rodrigo Hirano,

Rodrigo Quevedo, Tiago Giora e Ítalo Giora.

A todos os colegas que trabalham ou trabalharam no Laboratório de

Ictiologia durante estes quatro anos, pelas pequenas e grandes ajudas no dia-

a-dia e pela sempre agradável companhia.

Ao Juliano Ferrer pelo auxilio com os dados e lotes da coleção científica

do Laboratório de Ictiologia UFRGS.

A Andréa Brandreli Schaan e Hellen Tarrasconi de Moraes por seus

trabalhos com Brachyhypopomus e por aceitarem minha parceria nos mesmos.

A Fabi Ferraz pela amizade e por toda sua incansável ajuda no

progresso do meu inglês.

A toda minha família e em especial a meu pai, Ítalo, minha mãe,

Jamaira, pelo apoio incondicional, carinho, compreensão, e ajuda nos

momentos de maior correria e nervosismo.

Ao meu amor, Daniel, por sua participação ativa em todas as etapas

deste trabalho. Por ser meu maior e mais freqüente ajudante de campo, por ter

viajado comigo para Washington DC, por discutir minhas idéias e ouvir minhas

dúvidas... Por ser meu maravilhoso companheiro.

Sumário

Agradecimentos iv

Resumo 1

Abstract 3

Introdução Geral 5

Capítulo I: 22

Brachyhypopomus draco, a new sexually dimorphic species of Neotropical

electric fish from southern South America (Gymnotiformes: Hypopomidae)

Capítulo II: 55

A new species of the Neotropical electric fish genera Brachyhypopomus from

southern South America (Gymnotiformes: Hypopomidae).

Capítulo III: 78

Reproduction of two species of the Neotropical electric fish Brachyhypopomus

(Teleostei: Hypopomidae) from southern Brazil.

Capítulo IV: 114

Oogenesis and spermatogenesis in two species of Brachyhypopomus

(Gymnotiformes: Hypopomidae) from Southern Brazil.

Capítulo V: 149

Sperm ultrastructure in three different families of weakly electric fishes

(Teleostei: Gymnotiformes).

Capítulo VI: 170

Reproductive characters and spermatozoa structure in Gymnotiformes species

(Teleostei: Ostariophysi) with phylogenetic considerations.

Síntese dos Resultados 196

vii

Resumo

A Ordem Gymnotiformes compreende os peixes popularmente

conhecidos como “peixes elétricos”, os quais têm sua distribuição geográfica

restrita a região Neotropical. Os Gymnotiformes podem ser encontrados na

grande maioria dos ambientes aquáticos existentes em sua área de ocorrência,

sendo especialmente diversos e abundantes em áreas alagadas com grandes

quantidades de macrófitas aquáticas e no fundo dos canais de grandes rios. A

família Hypopomidae está distribuída do rio la Plata, na Argentina (35°S) ao rio

Tuira, no Panamá (8°N). A ecologia e história de vida da maioria das espécies

de Hypopomidae permanecem praticamente desconhecidas, sendo talvez o

gênero Brachyhypopomus o grupo mais estudado dentro da família. No Rio

Grande do Sul, não existem estudos a respeito da diversidade de espécies

pertencentes ao gênero Brachyhypopomus exceto por menções ocasionais em

revisões e listas de espécies. Este trabalho visa contribuir para o conhecimento

da diversidade do gênero Brachyhypopomus na região sul do Brasil, bem como

para uma melhor compreensão da biologia reprodutiva e ecologia das espécies

do gênero. O estudo visa ainda apresentar informações a respeito da morfologia

das gônadas e da célula espermática das espécies de Brachyhypopomus

ocorrentes no Estado. Os dois primeiros capítulos apresentam descrições de

duas novas espécies pertencentes ao gênero Brachyhypopomus com ocorrência

registrada para as bacias da laguna dos Patos, rio Tramandaí e rio Uruguai, no

Rio Grande do Sul, além de localidades nos países do Paraguai e Uruguai. O

terceiro capítulo aborda características da biologia reprodutiva das espécies B.

bombilla e Brachyhypopomus “G” n. sp. do Rio Grande do Sul tais como período

reprodutivo e suas relações com fatores ambientais, fecundidade, tipo de

desova, tamanho de primeira maturação gonadal, proporção sexual e

dimorfismo sexual. O capítulo IV apresenta uma descrição histológica das

gônadas de machos e fêmeas das espécies B. bombilla e Brachyhypopomus “G”

n. sp. ao longo do ciclo reprodutivo das mesmas. O quinto capítulo contém a

descrição da ultraestrutura dos espermatozóides das três espécies de

Brachyhypopomus registradas para o sul do Brasil e das espécies Eigenmannia

trilineata e Gymnotus aff. carapo, visando a observação das variações entre

espécies de um mesmo gênero e a comparação dos caracteres descritos entre

diferentes famílias de Gymnotiformes. Por fim, o capítulo VI reúne os resultados

obtidos nos demais capítulos da tese juntamente com dados disponíveis na

literatura com respeito à história de vida e morfologia do espermatozóide das

espécies já estudadas da ordem Gymnotiformes, visando à construção de

hipóteses sobre a existência de padrões reprodutivos e suas possíveis

explicações filogenéticas.

Abstract

The order Gymnotiformes comprise the fishes popularly known as “electric

fishes”, which have geographic distribution restricted to the Neotropical region.

Gymnotiformes can be found in most aquatic habitats of their area of occurrence

and are especially diverse and abundant in floodplains with great amounts of

aquatic macrophytes and in deep river channels. The family Hypopomidae is

distributed from rio la Plata, in Argentina (35°S) to rio Tuira, in Panamá (8°N).

Ecology and life-history of the majority of Hypopomidae species remain mostly

unknown. Brachyhypopomus is the most extensively studied genera of this

family. In Rio Grande do Sul state, there have been no previous studies on

Brachyhypopomus species diversity except for the occasional mention of the

genus in checklists and reviews. This study aims to contribute for the increase on

knowledge of Brachyhypopomus genus diversity in southern Brazil, as well as,

for a better understanding of the reproductive biology and ecology of its species.

The study also intends to present information concerning morphology of gonads

and sperm cells of the species occurring in the state area. The first two chapters

have descriptions of two new species included in the Brachyhypopomus genus

distributed in the laguna dos Patos, rio Tramandaí and rio Uruguay river basins

and also in localities from Uruguay and Paraguay. The third chapter regards

features of reproductive biology of the species B. bombilla and

Brachyhypopomus “G” n. sp. from Rio Grande do Sul, such as the reproductive

period and its relations with environmental factors, fecundity, spawning type, first

gonadal maturation size, sex proportion and sexual dimorphism. Chapter IV

presents a histological description of male and female gonads of the species B.

bombilla and Brachyhypopomus “G” n. sp. throughout their reproductive cycles.

The fifth chapter contains a description of the sperm ultrastructure of the three

Brachyhypopomus species recorded for the southern Brazil and of the species

Eigenmannia trilineata and Gymnotus aff. carapo. This chapter aim is to observe

the variations among species from the same genus and to compare the

described characters among different Gymnotiformes species. At last, chapter VI

brings together the results obtained in the remaining chapters, as well as, data

available in literature concerning life-history and spermatozoa morphology of the

Gymnotiformes species currently studied, hypothesizing the existence of

reproductive patterns and its possible phylogenetic explanations.

Introdução Geral

A Ordem Gymnotiformes compreende os peixes popularmente

conhecidos como “peixes elétricos” assim chamados por serem capazes de

gerar uma corrente elétrica, através de tecidos especializados, os quais formam

o órgão elétrico. A partir das descargas do órgão elétrico (EODs) e de um

sistema complementar de órgãos eletroreceptores distribuídos por quase toda

superfície do corpo, o peixe pode perceber o ambiente utilizando estas

informações para navegar, forragear e se orientar em águas de pouca

visibilidade. As EODs também são determinantes na escolha do habitat por

parte dos peixes (Crampton, 1998), em comportamentos predatórios (Westby,

1988), e interações intraespecíficas em geral (Kramer, 1983), especialmente no

comportamento reprodutivo (Kramer, 1985), sendo atualmente usadas como

base para análise das relações filogenéticas dentro do grupo (Alves-Gomes et

al. 1995; Alves-Gomes, 2001), identificação de espécies morfologicamente

crípticas e para muitas descrições de novas espécies. Sendo as EODs usadas

em ambos navegação e reconhecimento de parceiros reprodutivos (isto é,

isolamento reprodutivo pre-zigótico), elas possuem um papel central na

diversificação evolutiva e especialização ecológica das espécies (Albert &

Crampton, 2005).

Os gimnotiformes têm sua distribuição geográfica restrita a região

Neotropical, ocorrendo do sul do México ao norte da Argentina (Mago-Leccia,

1994), sendo possível encontrá-los em córregos, pequenos canais e lagoas

isoladas, onde podem suportar condições muito baixas de oxigênio durante os

períodos de seca. Também são encontrados em lagunas, áreas inundadas nos

períodos chuvosos e, principalmente, no fundo dos canais principais dos

grandes rios, onde encontram alimento abundante durante todo o ano. A ordem

é constituida por 117 espécies, 30 gêneros e 5 famílias (Reis et al., 2003) e,

segundo Albert & Crampton (2005), a mesma é consideravelmente mais diversa

do que o anteriormente reconhecido, sendo que cerca de apenas 78% das

espécies foram formalmente descritas e talvez metade delas permaneça ainda

não descoberta na natureza. Os peixes elétricos atingem seu mais alto grau de

diversidade nas bacias Amazônica e do Orinoco, formando um componente

abundante e rico de espécies com amplo alcance de habitats (Crampton, 1996).

Na ultima década, têm sido realizados enormes avanços no

conhecimento da diversidade e filogenia dos peixes gimnotiformes, novos

campos sendo abertos para a pesquisa em ecologia e etologia dos sinais

elétricos, bem como em evolução das diversas assembléias de espécies

tropicais (Albert & Crampton, 2005).

Hypopomidae

A família Hypopomidae, a qual pertence o gênero em questão, foi

proposta por Mago-Leccia (1978) e posteriormente revisada por Mago-Leccia

(1994), Sullivan (1997), Albert & Campos-da-Paz (1998) e Albert (2001), o qual

propôs como novo táxon, a tribo Brachyhypopominae. Albert & Crampton (2003)

em recente lista de espécies da família, consideraram válidos um total de 6

gêneros e 25 espécies de hipopomideos, além de citarem a existência de 10

manuscritos em preparação sugerindo nomes de novas espécies.

Esta família está distribuída do rio la Plata, na Argentina (35°S) ao rio

Tuira, no Panamá (8°N), estando presente em todos os países da América do

Sul exceto o Chile (Albert, 2001). A ecologia e história de vida da maioria das

espécies de Hypopomidae são praticamente desconhecidas, sendo talvez o

gênero Brachyhypopomus o grupo mais estudado dentro da família (Albert &

Crampton, 2003).

O gênero Brachyhypopomus foi descrito por Mago-Leccia (1994), tendo

como espécie tipo Rhamphichthys brevirostris Steindachner, 1868 e

compreendendo as seis espécies previamente incluídas no gênero Hypopomus.

Atualmente o gênero é constituído por oito espécies sendo elas B. brevirostris

(Steindachner, 1868), B. occidentalis (Regan, 1914), B. beebei (Schultz, 1944),

B. diazi (Fernández-Yépez, 1972), B. pinnicaudatus (Hopkins, 1991), B.

janeiroensis (Costa & Campos-da-Paz, 1992), B. jureiae Triques & Khamis,

2003, and B. bombilla Loureiro & Silva, 2006. As espécies do gênero

Brachyhypopomus ocorrem em todas as maiores bacias hidrográficas

Neotropicais e habitam uma grande variedade de ambientes aquáticos (Albert &

Crampton, 2005). O gênero prefere águas relativamente rasas, onde exista

vegetação mais ou menos densa que possa servir de abrigo ou locais com

folhiço no fundo, sendo típico de águas calmas (Alves-Gomes, 1997). As

espécies de Brachyhypopomus são altamente diversas e abundantes nas

planícies de inundação amazônicas, onde constituem uma fração significativa da

biomassa, apresentando-se ecologicamente importantes (Crampton, 1996).

No Rio Grande do Sul, não existem estudos a respeito da diversidade de

espécies pertencentes ao gênero Brachyhypopomus exceto por menções

ocasionais em revisões e listas de espécies. A citação mais antiga para o Estado

foi feita por Ellis (1913) baseada em espécimes identificados como Hypopomus

brevirostris (=Brachyhypopomus brevirostris) coletados por Herman von Ihering

na bacia da laguna dos Patos (Malabarba, 1989). Brachyhypopomus

pinnicaudatus, B. beebei e uma espécie não descrita do gênero foram citadas

por Sullivan (1997) como amplamente distribuídas nas bacias hidrográficas da

América do Sul cis-Andina, incluindo análise de material proveniente do Rio

Grande do Sul. Brachyhypopomus brevirostris e B. pinnicaudatus foram citadas

como ocorrendo na drenagem do rio de la Plata (Campos-da-Paz, 1997; Albert &

Crampton, 2003) e B. beebei como ocorrendo na drenagem da laguna dos Patos

(Campos-da-Paz, 1997). Após coletas exploratórias realizadas pela equipe do

Laboratório de Ictiologia da UFRGS, esta identificou para o estado do Rio

Grande do Sul a presença de três espécies do gênero Brachyhypopomus:

Brachyhypopomus bombilla, uma segunda espécies não identificada, e uma

terceira espécie que tem sido largamente identificada na literatura como B.

pinnicaudatus, as duas últimas sendo distribuídas no sul do Brasil e Uruguai nas

bacias do rio Uruguai, laguna dos Patos e rio Tramandaí.

Reprodução

A história de vida de um organismo foi conceituada por Begon et al.

(1987) como sendo o padrão de seu crescimento, diferenciação e,

especialmente, reprodução, ao longo de sua vida. De acordo com Nikolskii

(1969), os problemas básicos para o estudo de peixes se apóiam entre outros

fatores na dinâmica de populações, esta se relacionando com a solução de

problemas ligados aos fatores que governam o desenvolvimento individual de

peixes como o crescimento, a reprodução e a mortalidade. A reprodução é o

processo que assegura a preservação e abundância de uma espécie. O

conhecimento de sua biologia reprodutiva é de fundamental importância para a

manutenção e proteção de seus estoques naturais, cultivo para fins econômicos

e repovoamento de áreas (Agostinho & Júlio Jr, 1999).

Segundo Vazzoler (1996), praticamente todas as estratégias reprodutivas

conhecidas podem ser encontradas em espécies de peixes. Diante disto, é

possível afirmar que a definição das estratégias reprodutivas e padrões

ecológicos apresentados pelos grupos de espécies fornece importantes

informações não somente sobre a adaptação dos mesmos ao ambiente em

curso, mas também sobre sua evolução.

Morfologia gonadal em nível anatômico e histológico tem sido estudada

principalmente em espécies de peixes de interesse econômico com o intuito de

identificar ciclos reprodutivos anuais, duração da estação reprodutiva, início da

maturidade reprodutiva, ritmos de desova, fecundidade e vários outros aspectos

da biologia reprodutiva que podem ser aplicados a questões ligadas a pesca

(Parenti & Grier, 2004). Ainda que existam alguns resultados disponíveis a

respeito do desenvolvimento gonadal de gimnotiformes (Barbieri & Barbieri,

1984a, 1984b, 1985; Cognato & Fialho, 2006; Quintana et al., 2004; Giora and

Fialho, in press), o número de espécies estudadas e o nível de conhecimento

atingido continua extremamente limitado.

Estudos a respeito da estrutura de espermatozóides de peixes teleósteos

têm fornecido valiosas informações sobre modificações celulares associadas

aos hábitos reprodutivos, sendo realizados principalmente para espécies com

inseminação (Jamieson, 1991; Mattei, 1991; Burns et al., 1998). Além disto,

pesquisas em ultraestrutura do esperma têm revelado caracteres morfológicos

utilizáveis na formação de hipóteses filogenéticas (Jamieson, 1991; Mattei,

1991). Ultraestrutura do espermatozóide de espécies da ordem Gymnotiformes

foram realizados para Apteronotus albifrons (= Sternarchus albifrons) por

Jamieson (1991), para Gymnotus cf. anguilaris e Brachyhypopomus cf.

pinnicaudatus por França et al. (2007), e para Rhamphichthys cf. hahni,

Eigenmannia cf. virescens e Apteronotus cf. albifrons por França (2006).

Entretanto, muitas questões ainda permanecem e mais estudos são necessários

para um melhor entendimento da evolução do espermatozóide em

gimnotiformes (França, 2006).

Aspectos da biologia reprodutiva, ecologia e dinâmica populacional de

espécies de gimnotiformes ainda têm sido relativamente pouco estudados

(Hopkins, 1974a, 1974 b; Kirschbaum, 1975, 1979, 1984, 2000; Schwassmann,

1976; Barbieri & Barbieri, 1982, 1983a, 1983b, 1984a, 1984b, 1985; Provenzano,

1984; Hagedorn, 1988; Kirschbaum & Schugardt, 2002; Cognato & Fialho, 2006;

Giora & Fialho in press), a falta de informações básicas a esse respeito,

especialmente para espécies ocorrentes no limite sul da distribuição da ordem

(sul do Brasil, Uruguai e Argentina) sendo um obstáculo para o melhor

conhecimento destes peixes.

No estado do Rio Grande do Sul a ausência total de estudos a respeito do

gênero Brachyhypopomus tem levado a subestimativa da diversidade do mesmo

e a falta de subsídios para sua conservação e de seus habitats.

Objetivos

Este trabalho tem como objetivos:

- definir a diversidade de espécies do gênero Brachyhypopomus no Rio

Grande do Sul através da descrição de novas espécies;

- estudar a reprodução das espécies B. bombilla e Brachyhypopomus

“G” n. sp., analisando o período reprodutivo, fecundidade, proporção

sexual, tamanho de primeira maturação gonadal e tipo de desova,

além de estabelecer possíveis relações entre o ciclo reprodutivo das

mesmas e aspectos abióticos e alimentares;

- descrever, através de análises histológicas, o desenvolvimento

gonadal de machos e fêmeas das espécies B. bombilla e

Brachyhypopomus “G” n. sp. ao longo das diversas fases do período

reprodutivo;

- descrever a ultraestrutura e a morfologia de espermatozóides das três

espécies de Brachyhypopomus ocorrentes no Estado, além das

espécies Eigenmannia trilineata e Gymnotus aff. carapo utilizando os

métodos de microscopia eletrônica de transmissão (MET) e

microscopia eletrônica de varredura (MEV);

- comparar a ultraestrutura e a morfologia dos espermatozóides das

espécies de Brachyhypopomus, família Hypopomidae, com a das

espécies E. trilineata, família Sternopygidae, e G. aff. carapo, família

Gymnotidae, verificando possíveis padrões e/ou variações

morfológicas;

- reunir estas informações com as já disponíveis para outras espécies, a

fim de avaliar a evolução das características reprodutivas em um

contexto filogenético e de fornecer subsídios para estudos

sistemáticos em gimnotiformes.

Literatura Citada

Agostinho, A. A. & H. F. Júlio Jr. 1999. Peixes da bacia do alto Rio Paraná. Pp.

374-400. In: Lowe-McConnell, R. H. (Ed.). Estudos ecológicos de

comunidades de peixes tropicais. São Paulo, Edusp, 535p.

Albert, J. S. 2001. Species diversity and phylogenetic systematics of American

knifefishes (Gymnotiformes, Teleostei). Miscellaneous Publications of the

Museum of Zoology, University of Michigan, 190: 1-127.

Albert, J. S & R. Campos-da-Paz. 1998. Phylogenetic sistematics of

Gymnotiformes with diagnosis of 58 clades: a review of available data. Pp.

419-446 In: Malabarba L. R., R. E. Reis, R. P. Vari, Z. M. Lucena & C. A. S.

Lucena (Eds). Phylogeny and classifacation of Neotropical fishes. Porto

Alegre, Edipucrs, 603p.

Albert, J. S. & W. G. R. Crampton. 2003. Seven new species of the neotropical

electric fish Gymnotus (Teleostei, Gymnotiformes) with a redescription of G.

carapo (Linnaeus). Zootaxa, 287: 1-54.

Albert, J. S. & W. G. R. Crampton. 2005. Diversity and Phylogeny of Neotropical

eletric fishes (Gymnotiformes). Pp.360-409. In: Bullock, T. E., C. D. Hopkins,

A. N. Popper & F. R. Fay (Eds.). Electroreception. Ithaca, Cornell University

Press, 472p.

Alves-Gomes, J. A. 1997. Informações preliminares sobre a bio-ecologia de

peixes elétricos (Ordem Gymnotiformes) em Roraima. Pp. 509-555. In:

Barbosa, R. I., E. J. G. Ferreira & E. G. Castellón (Eds.). Homem, Ambiente e

Ecologia no Estado de Roraima. Manaus, INPA, 613p.

Alves-Gomes, J. A. 2001. The evolution of electroreception and

bioelectrogenesis in teleost fish: a phylogenetic perspective. Journal of Fish

Biology, 58: 1489-1511.

Alves-Gomes, J. A., G. Ortí, M. Haygood, W. Heiligenberg & A. Meyer. 1995.

Phylogenetic analysis of the evolution of the south american electric fishes

(order Gymnotiformes) and the evolution of their electrogenic system: a

sinthesis based on morphology, electrophysiology, and mitochondrial

sequence data. Molecular Biology and Evolution, 12(2): 298-318.

Barbieri, G. & M. C. Barbieri. 1982. Fecundidade e tipo de desova de Gymnotus

carapo (Linnaeus, 1758), na represa do Lobo, Estado de São Paulo (Pisces,

Gymnotidae). Spectrum: Jornal Brasileiro de Ciência, 2(7): 25-29.

Barbieri, G. & M. C. Barbieri. 1983a. Dinâmica da reprodução de Gymnotus

carapo na represa do Lobo, Estado de São Paulo. Influência de fatores

abióticos. (Pisces, Gymnotidae). Tropical Ecology, 24(2): 244-259.

Barbieri, G. & M. C. Barbieri. 1983b. Growth and first sexual maturation size of

Gymnotus carapo (Linnaeus, 1758) in the Lobo reservoir (state of São Paulo,

Brazil) (pisces, gymnotidae). Revue d’Hydrobiologie Tropicale, 16(2): 195-

201.

Barbieri, M. C. & G. Barbieri. 1984a. Reprodução de Gymnotus carapo

(Linnaeus, 1758) na represa do Lobo (SP.). Morfologia e histologia de

testículo. Variação sazonal. (Pisces, Gymnotidae). Revista Brasileira de

Biologia, 44(2): 141-148.

Barbieri, G. & M. C. Barbieri. 1984b. Crescimento de Gymnotus carapo

(Linnaeus, 1758) na represa do Lobo, Estado de São Paulo, pelo método da

distribuição da freqüência de comprimento (Pisces, gymnotidae). Revista

Brasileira de Biologia, 44(3): 239-246.

Barbieri, M. C. & G. Barbieri. 1985. Reprodução de Gymnotus carapo (Linnaeus,

1758) na represa do Lobo (SP.). Morfologia e histologia de ovário. Variação

sazonal. (Teleostei, Gymnotidae). Revista Brasileira de Biologia, 45(1/2): 3-

12.

Begon, M., J. Harper & C. R. Townsend. 1987. Ecologia: individuos, poblaciones

y comunidades. Barcelona, Ediciones Omega, 886p.

Burns, J. R., S. H. Weitzman, K.R. Lange & L. R. Malabarba. 1998. Sperm

ultrastructurein characid fishes (Teleostei, Ostariophysi). Pp.235-244. In:

Malabarba L. R., R. E. Reis, R. P. Vari, Z. M. Lucena & C. ª S. Lucena (Eds).

Phylogeny and classifacation of Neotropical fishes. Porto Alegre, Edipucrs,

603p.

Campos-da-Paz, R. 1997. Sistemática e taxonomia dos peixes elétricos das

bacias dos rios Paraguai, Paraná e São Francisco, com notas sobre espécies

presentes em rios costeiros do leste do Brasil (Teleostei: Ostariophysi:

Gymnotiformes). Unpublished Ph. D. Thesis, Universidade de São Paulo,

São Paulo, 314p.

Cognato, D. De P. & C. B. Fialho. 2006. Reproductive biology of a population of

Gymnotus aff. carapo (Teleostei: Gymnotidae) from southern Brazil.

Neotropical Ichthyology, 4(3): 339-348.

Costa, W. J. E. M. & R. Campos-da-Paz. 1992. Description d’une novelle espèce

de poisson eléctrique du genre néotropical Hypopomus (Siluriformes:

Gymnotodei: Hypopomidae) du sudest du Brésil. Revue Française

d’Aquariologie, 18(4): 117-120.

Crampton, W. G. R. 1996. Gymnotiform fish: an important component of

Amazonian floodplain fish communities. Journal of Fish Biology, 48: 298-301.

Crampton, W. G. R. 1998. Electric signal design and habit preferences in a

species rich assemblage of Gymnotiform fishes from the upper Amazon basin.

Anais da Academia Brasileira de Ciências, 70(4): 805-847.

Fernández-Yépez, A. 1972. Análisis ictiológico del complejo hidrográfico (04)

“Río Yaracuy”. Direccion de Obras Hidraulicas, Ministerio de Obras,

Republica de Venezuela. 25 p., 41pl.

Ellis, M. M. 1913. The gymnotid eels of tropical America. Memoirs of the

Carnegie Museum. 6(3): 109-195.

França, G. F. 2006. Ultraestrutura da espermiogênese e dos espermatozóides

da ordem Gymnotiformes (Teleostei, Ostariophysi) com considerações

filogenéticas. Unpublished MsC. Thesis, Universidade Estadual de Campinas,

Campinas. 89p.

França, G. F., C. Oliveira & I. Quagio-Grassiotto. 2007. Ultrastructure of

spermiogenesis and spermatozoa of Gymnotus cf. Anguillaris and

Brachyhypopomus cf.pinnicaudatus (Teleostei: Gymnotiformes). Tissue &

Cell, 39 (2): 131-139.

Giora, J. & C. B. Fialho. (in press). Reproductive biology of weakly electric fish

Eigenmannia trilineata López & Castello, 1966 (TELEOSTEI, Sternopygidae).

Brazilian Archives of Biology and Technology.

Hagedorn, M. 1988. Ecology and behavior of a pulse-type electric fish,

Hypopomus occidentalis (Gymnotiformes, Hypopomidae), in a fresh-water

stream in Panama. Copeia, 1988(2): 324-335.

Hopkins, C. D. 1974a. Electric communication: functions in the social behavior of

Eigenmannia virescens. Behaviour, 50: 270-305.

Hopkins, C. D. 1974b. Electric communication in the reproductive behavior of

Sternopygus macrurus (Gymnotoidei). Zeitschrift fur Tierpsychologie, 35: 518-

535.

Hopkins, C. D. 1991. Hypopomus pinnicaudatus (Hypopomidae), a new species

of gymnotiforme fish from French Guiana. Copeia, 1991(1): 151-161.

Jamieson, B. G. M. 1991. Fish Evolution and Systematics: Evidence from

Spermatozoa. Cambridge, Cambridge University Press, 319p.

Kirschbaum, F. 1975. Environmental factors control the periodical reproduction of

tropical electric fish. Experientia, 31: 1159-1160.

Kirschbaum, F. 1979. Reproduction of the weakly electric fish Eigenmannia

virescens (Rhamphichtyidae, Teleostei) in captivity. Behavioral Ecology and

Sociobiology, 4: 331-355.

Kirschbaum, F. 1984. Reproduction of weakly electric teleosts: just another

example of convergent development? Environmental Biology of Fishes,

10(1/2): 3-14.

Kirschbaum, F. 1995. Taxonomy, Zoogeography and general ecology of South

American knifefishes (Gymnotiformes). Pp. 446-464. In: Moller, P. (Ed.).

Electric Fishes. History and Behavior. London, Chapman & Hall, 584 p.

Kirschbaum, F. 2000. The breeding of tropical freshwater fishes through

experimental variation of exogenous parameters. Breedin through simulation

of high and low water conditions. Aquageografia, 20: 95-105.

Kirschbaum, F. & C. Schugardt. 2002. Reproductive strategies and

developmental aspects in mormyrid and gymnotiform fishes. Journal of

Physiology - Paris, 96: 557-566.

Kramer, B. 1983. Electrocommunication in fish: stimulus waveform-dependent

responses in Eigenmannia (Gymnotiformes, Teleostei) – a model for

intraspecific communication?. Verhandlungen der Deutschen Zoologischen

Gesellschaft, 170.

Kramer, B. 1985. Jamming avoidance in the electric fish Eigenmannia: harmonic

analysis of sexually dimorphic waves. Journal of Experimental Biology, 119:

41-69.

Loureiro, M. & A. Silva. 2006. A new species of Brachyhypopomus

(Gymnotiformes: Hypopomidae) from Northeast Uruguay. Copeia, 2006(4):

665-673.

Mago-Leccia, F. 1978. Los peces de la familia Sternopygidae de Venezuela.

Acta Cientifica Venezolana, 29 (suppl. 1): 1-89.

Mago-Leccia, F. 1994. Electric fishes of the continental waters of America.

Caracas, Fundacion para el Desarrollo de las Ciencias Fisicas, Matematicas

y Naturales. Electric Fishes: 1-206.

Malabarba, L. R. 1989. Histórico sistemático e lista comentada das espécies de

peixes de água doce do sistema da laguna dos Patos, Rio Grande do Sul,

Brasil. Comunicações do Museu de Ciências da PUCRS (Sér. Zool.), 2(8):

107-179.

Mattei, X. 1991. Spermatozoon ultrastructure and its systematic implication in

fishes. Canadian Journal of Zoology, 69: 3038-3055.

Nikolsky, G. V. 1969. Theory of fish population dynamics. Edinburg,Oliver &

Boyd Ltda, 323p.

Parenti, L. & Grier, H. 2004. Evolution and Phylogeny of Gonad Morphology in

Bony Fishes. Integrative & Comparative Biology, 44: 333-348.

Provenzano, R. F. 1984. Aspectos de la reproduccion en peces Gymnotiformes

del Bajo Llano de Venezuela. Unpublished PhD. Thesis, Universidade Central

de Venezuela, Caracas. 68p.

Quintana, L., A. Silva, N. Berois & O. Macadar. 2004. Temperature induces

gonadal maturation and affects electrophysiological sexual maturity indicators

in Brachyhypopomus pinnicaudatus from a temperate climate. The Journal of

Experimental Biology, 207: 1843-1853.

Regan, C. T. 1914. Fishes from Condoto River, Colômbia, collected by Dr. H. G.

F. Spurrel. Annals and Magazine of Natural History, 14(79): 31-33.

Reis, R. E., S. O. Kullander & C. J. Ferraris, Jr. 2003. Check list of the freshwater

fishes of south and central america. Porto Alegre, Edipucrs, 742p.

Schultz, L. P. 1944. Two new species of fishes (Gymnotidae, Loricariidae) from

Caripito, Venezuela. Zoologica, 29(1): 39-44.

Schwassmann, H. O. 1976. Ecology and taxonomic status of different geographic

populations of Gymnorhamphichthys hypostomus, Ellis (Pisces,

Cypriniformes, Gymnotoidei). Biotropica, 8: 25-40.

Steindachner, F. 1868. Abhandlung über die Gymnotiden des Wiener Museums.

Anzeiger der Akademie der Wissenschaften in Wien, 5(20): 176-177.

Sullivan, J. P. 1997. A phylogenetic study of the Neotropical hypopomid electric

fishes (Gymnotiformes: Rhamphichthyoidea). Unpublished Ph. D.

Dissertation. Duke University, Durham, North Carolina, 336p.

Triques, M. L. & D. K. Khamis. 2003. Brachyhypopomus jureiae, a new species

of freshwater Neotropical electric fish (Teleostei: Gymnotiformes:

Hypopomidae) from a coastal stream of southeastern Brazil. Lundiana, 4(1):

61-64.

Vazzoler, A. E. A. de M. 1996. Biologia da reprodução de peixes teleósteos:

teoria e prática. Maringá, Editora da Universidade, 169p.

Westby, G. W. M. 1988. The ecology, discharge diversity and predatory

behaviour of gymnotiforme electric fish in the coastal stream of French

Guiana. Behavioral Ecology and Sociobiology, 22: 341-354.

Capítulo I

Brachyhypopomus draco, a new sexually dimorphic species

of Neotropical electric fish from southern South America

(Gymnotiformes: Hypopomidae)

Brachyhypopomus draco, a new sexually dimorphic species of Neotropical

electric fish from southern South America (Gymnotiformes: Hypopomidae)

Julia Giora*, Luiz R. Malabarba*, ** and William Crampton***

* Universidade Federal do Rio Grande do Sul, IB, Departamento de Zoologia, Av.

Bento Gonçalves, 9500, bloco IV, prédio 43435, 91501-970 Porto Alegre, RS,

Brazil.

[email protected]; [email protected]

** Museu de Ciências e Tecnologia, PUCRS, Av. Ipiranga, 6681, P. O. Box.

1429, 90619-900 Porto Alegre, RS, Brazil.

*** Department of Biology, University of Central Florida, Orlando, 32816-2368,

USA. [email protected]

Brachyhypopomus draco, new species, is described from central, southern and

coastal regions of Rio Grande do Sul state, Brazil, and Uruguay. It is diagnosed

from congeners by, among other characters, the shape of the distal portion of the

caudal filament in mature males, which during the reproductive period forms a

distinct paddle shape structure.

Brachyhypopomus draco, espécie nova, é descrita para as regiões central, sul e

costeira do estado do Rio Grande do Sul, Brasil, e Uruguai. Ela é diagnosticada

de seus congêneres, entre outros caracteres, pelo formato da porção final do

filamento caudal de machos maduros durante o período reprodutivo, que forma

uma estrutura distinta em forma de remo.

Key words: Electric Organ Discharge, EOD, rio Uruguay, laguna dos Patos, rio

Tramandaí.

Introduction

The family Hypopomidae, proposed by Mago-Leccia (1978), is widespread

in South American countries, except Chile, and distributed from the río de la

Plata in Argentina (35°S) to northern Panama (8°N) (Albert, 2001). The genus

Brachyhypopomus was described by Mago-Leccia (1994) to comprise six

species that previously belonged to Hypopomus and that share the characters:

short snout, absence of mesocoracoid bridge, short and crescent-shaped

maxillary bone, and posterior nares closer to eyes than to snout tip. Later, Albert

(2001) redefined the genus based on four synapomorphies: premaxilla gracile

with a curved anterior margin and forming a distinct angle with the maxilla in

lateral view, dentary gracile, body cavity with 16-17 precaudal vertebrae, single

transitional vertebra. Albert (2001) maintained the same six species cited by

Mago-Leccia (1994) in the genus. Additionally he listed seven undescribed

species and recognized five clades within Brachyhypopomus that were

previously proposed by Sulivan (1997).

The six Brachyhypopomus species recognized as valid by Mago-Leccia

(1994) and Albert (2001) are: B. brevirostris (Steindachner, 1868), which occurs

in Eastern South America from the Orinoco to la Plata drainages; B. occidentalis

(Regan, 1914), which occurs in Panama, and in several trans-Andean drainages

of north eastern South America, including the Magdalena, Atrato, Catatumbo and

Pacific slope rivers; B. beebei (Schultz, 1944), which is widespread through

tropical areas east of Andes; B. diazi (Fernández-Yépez, 1972), which is

restricted to the Caribbean littoral of Northwest Venezuela, from the río Tocuyo to

río Alpargaton and also the northern Llanos in the Orinoco basin; B.

pinnicaudatus (Hopkins, 1991), which is widespread through cis-Andean South

America, including the Guianas, the Orinoco and Amazon basins, and much of

the rio Paraná-Paraguay-Uruguay drainage as far south as the río de la Plata;

and B. janeiroensis (Costa & Campos-da-Paz, 1992), which is known only from

the São João and Paraíba do Sul river basins in Rio de Janeiro state (Albert &

Crampton, 2003).

Subsequently, Triques & Khamis (2003) described B. jureiae, which is

known to occur in the Una do Prelado river system in southern Brazil, and also

from Ribeira de Iguape drainage, near Iguape, São Paulo (Triques & Khamis,

2003; F. Lima & W. Crampton pers. obs.). Loureiro & Silva (2006) described B.

bombilla, which is distributed throughout the middle rio Uruguay tributaries and

the laguna dos Patos and lagoa Mirim systems in eastern Uruguay.

In Rio Grande do Sul state, southern Brazil, there have been no previous

studies of the species diversity of Brachyhypopomus, excepting the occasional

mention of the genus in checklists and reviews. The oldest citation was by Ellis

(1913), based on specimens identified as Hypopomus brevirostris

(=Brachyhypopomus brevirostris) collected by Herman von Ihering in the laguna

dos Patos drainage (Malabarba, 1989). Brachyhypopomus pinnicaudatus, B.

beebei and an undescribed species have been quoted as widely distributed in

cis-Andean South American basins by Sullivan (1997), including material from

Rio Grande do Sul state. Brachyhypopomus brevirostris and B. pinnicaudatus

have been cited to occur in the rio de la Plata drainage (Campos-da-Paz, 1997;

Albert & Crampton, 2003), and B. beebei from laguna dos Patos drainage

(Campos-da-Paz, 1997).

Based upon extensive sampling in Rio Grande do Sul, our studies

revealed the presence of three Brachyhypopomus species in this region: B.

bombilla; a second species that has been largely identified as B. pinnicaudatus in

the literature; and a third and new species that is widespread in the rio Uruguay,

laguna dos Patos and rio Tramandaí drainages in southern Brazil and Uruguay.

This latter species is described herein.

Materials and Methods

Comparative data from B. pinnicaudatus, B. bombilla and B. jureiae were

taken directly from the type specimens (see Comparative Material). Data from B.

brevirostris, B. occidentalis, B. beebei, B. diazi and B. janeiroensis were

compiled from original descriptions. Morphometric data were taken as point-to-

point linear distances using digital calipers to the nearest 0.1 mm.

Measurements were analyzed as percentage of length to the end of the anal fin

(LEA), measured as the distance from tip of the snout to posterior end of anal fin

base, or as percentage of head length (HL), measured from tip of snout to

posterior margin of bony operculum. Total length was not used as a numerator in

morphometric body relationships because of the high number of specimens with

a damaged and/or regenerated caudal filament. Regenerated parts of the body

were not measured and their meristic data were not recorded. The other

measurements used were: caudal filament length, measured from the end of

anal fin base to the tip of caudal filament; snout to anal-fin origin, from tip of

snout to origin of anal-fin base; depth of caudal filament, measured at the

posterior end of anal-fin base; longest anal-fin ray, from base to tip of the longest

ray; pectoral-fin length, from the dorsal border of the fin base where it contacts

the cleithrum to tip of the longest ray; body depth, measured at anal-fin origin;

snout length, from tip of snout to anterior margin of orbit; gape width, between

lateral margins of mouth gape; orbital diameter, between anterior and posterior

margins of the orbit; interorbital distance, shortest distance between margins of

orbits; posterior nare to eye, from posterior margin of posterior nare to anterior

margin of orbit; branchial aperture, from posterodorsal to anteroventral extent of

branchial fold; head width at operculum, largest width measured at bony

operculum; head width at eyes, head width measured at center of eyes. Pectoral

and anal-fin ray counts were taken directly from ethanol preserved specimens

under a stereo-microscope. Vertebrae were counted from radiographed

specimens including the four vertebrae of the Weberian Apparatus. Apparently,

Albert (2001) did not include the vertebrae of the Weberian Apparatus in the

precaudal counts; therefore, four vertebrae were added to Albert’s (2001) counts

for comparison. Osteological data were taken from cleared-and-stained

specimens following Taylor & Van Dyke (1985). Sex and the stage of sexual

maturity were determined by dissection, following Cognato & Fialho (2006).

Fish specimens belong to the collections of Departamento de Zoologia,

Universidade Federal do Rio Grande do Sul, Porto Alegre (UFRGS), Museu de

Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande do Sul,

Porto Alegre (MCP), Universidade Federal de Minas Gerais, Belo Horizonte

(DZUFMG), Museu de Zoologia, Universidade de São Paulo, São Paulo

(MZUSP), Museu Nacional, Rio de Janeiro (MNRJ), Faculdad de Ciências

Naturales, Montevideo (ZVC-P), Academy of Natural Sciences of Philadelphia,

Philadelphia (ANSP), National Museum of Natural History, Washington D.C.

(USNM), California Academy of Sciences, San Francisco (CAS), University of

Michigan Museum of Zoology, Ann Arbor (UMMZ).

Electric Organ Discharge (EOD) recordings were taken from fishes

obtained from rio Uruguay, rio Tramandaí and laguna dos Patos drainages.

Specimens were held in water from the capture locality at 27ºC +/- 0.5 ºC for at

least 12 hours before the recording. All recordings were made in an aquarium

maintained at 27ºC +/- 0.1 ºC, containing water from the capture locality (or

nearby). Each specimen was allowed 10 minutes to acclimate before recording.

Signals were picked up from silver/silver-chloride electrodes placed posterior

and anterior to the fish and with a ground contact in the center. Individual fish

were placed within a nylon-mesh sock. The electrodes were connected to a

custom-built AC-coupled differential amplifier with a frequency response of +/- 3

dB from 0.2 Hz-110 kHz (Wells & Crampton, 2006). EODs were digitized using

an Edirol UA5 A-D converter at a sampling rate of 96 kHz and resolution of 24

bits. Recordings of resting repetition rate were taken during daylight hours

between 1000 and 1400 from fish held in nylon-mesh socks under subdued

lighting. Recordings of nocturnal activity were taken from 1-3 hrs after sunset

from single specimens held in 10 l buckets containing water from the source

locality, and water hyacinths. An electrode was placed in the center of this tank

and the fish was allowed unrestricted movement before and during the

recording. All signal analyses were conducted using custom-written MATLAB or

Java software designed by W. Crampton. EOD durations were calculated with

the beginning and end of the EOD taken at a 1% threshold of the amplitude of

the dominant positive phase (P1) following normalization to the P1 amplitude.

EODs recorded from specimens with more than 10% damage to the caudal

filament were not included for waveform analyses.

Calculations of EOD repetition rate were taken by measuring all

successive inter-pulse intervals over one minute recordings. The EOD rate for

each fish was characterized by three parameters. 1. The mean pulse rate in Hz

calculated as the reciprocal of the mean of all IPIs (in seconds). 2. The standard

deviation (SD) around the mean pulse rate in Hz. This measure of variance

indicates the stability of the EOD repetition rate. 3. The coefficient of variance

(CV) calculated as a percentage (mean/SD*100). Because the CV is weighted

by the mean, it is used for standardized comparisons of the relative stability of

the pulse rate over a wide range of rates. The mean and SD of these three

measures were then calculated among all recorded adult or post-larval

specimens, and are presented here to summarize diurnal and nocturnal EOD

activity.

Results

Brachyhypopomus draco, new species

(Figs. 1, 2)

Holotype. MCP 41540, 1 (male, 137.39 mm LEA), Brazil, Rio Grande do Sul,

Parque Estadual de Itapuã, lagoa Verde (30°22’52.4”S - 51°01’25”W), 12 Jan

2004, D. Cognato, L. R. Malabarba, C. E. Machado, R. Q. Carvalho.

Paratypes. All from Brazil, Rio Grande do Sul. Laguna dos Patos drainage:

MCP 41539, 1 (male, 147.12 mm LEA), collected with the holotype. UFRGS

8888, 1 (male, 126.43 mm LEA), same locality of the holotype, 18 Jan 2006, J.

Giora, A. P. Dufech & J. Ferrer. MNRJ 30916, 2 (1 male, 151.87 mm LEA, 1

female, 128.42 mm LEA), same locality of the holotype, 9 Feb 2004, D. Cognato,

M. Azevedo, A. Schaan & C. Hiroshi. MCP 41538, 2 (1 male, 88.49 mm LEA, 1

female, 91.76 mm LEA), same locality of the holotype, 30 Jun 2004, D. Cognato

& A. Schaan. MNRJ 30917, 1 (male, 150.27 mm LEA), MZUSP 94429, 1 (male,

139.13 mm LEA), same locality of the holotype, 9 Sep 2004, D. Cognato, M.

Schossler & A. Schaan. MCP 41537, 1 (female, 108.40 mm LEA), same locality

of the holotype, 10 Oct 2003, D. Cognato & A. Schaan. MNRJ 30918, 1 (male,

138.20 mm LEA), same locality of the holotype, 11 Nov 2003, D. Cognato, J.

Giora, J. Anza & A. P. Dufech. UFRGS 732, 1 (female, 78.02 mm LEA), Viamão,

arroio Alexandrina (30°06’00”S - 50°57’00”W), 7 Sep 1980, L. R. Malabarba.

UFRGS 820, 1 (male, 93.77 mm LEA), Guaíba, açude near BR290 highway

(30°07’00”S - 51°20’00”W), 4 Nov 1979, L. R. Malabarba, C. F. M. Santos & P. A.

Buckup. UFRGS 822, 1 (male, 92.56 mm LEA), Guaíba, açude in BR290

highway, near junction with BR116 highway (30°03’00”S - 51°21’00”W), 18 Jan

1980, P. A. Buckup & C. Souto. UFRGS 6526, 1 (male, 102.21 mm LEA),

UFRGS 6525, 1 (male, 100.69 mm LEA), Eldorado do Sul, artificial canal near

BR290 highway (30°02’55”S - 51°23’34”W), 10 Dec 2003, W. Crampton & L. R.

Malabarba. UFRGS 4317, 1 (male, 50.01 mm LEA), Viamão, arroio Itapuã

(30°15’00”S - 51°02’00”W), 01 Mar 1988, F. Becker & L. R. Malabarba. Rio

Tramandaí drainage: UFRGS 6486, 1 (male, 85.37 mm LEA), UFRGS 6488, 1

(male, 98.12 mm LEA), UFRGS 6489, 1 (male, 100.80 mm LEA), UFRGS 6490,

1 (female, 95.54 mm LEA), UFRGS 6491, 1 (male, 80.94 mm LEA), Capão da

Canoa, creek parallel to Estrada do Mar road (29°43’09”S - 50°56’00”W), 20 Nov

2003, L. R. Malabarba, J. Giora, J. Anza & D. Cognato. MNRJ 30915, 2 (1 male,

69.93 mm LEA, 1 female, 85.29 mm LEA), Cidreira, lagoa Fortaleza (30°08’58”S

- 50°14’30”W), 11 Jul 2003, L. R. Malabarba. UFRGS 6671, 3 (2 males, 85.75-

107.03 mm LEA, 1 female, 96.37 mm LEA), Terra de Areia, creek into rio Três

Forquilhas, along the road RS486 (29°33’22”S - 50°04’19”W), 20 Nov 2003, L. R.

Malabarba, J. Giora, J. Anza & D. Cognato. Rio Uruguay drainage: UFRGS

6748, 1 (male, 90.84 mm LEA), Rosário do Sul, Sanga do Jacaré, BR290

(30°12’04”S - 55°03’17”W), 18 Jun 2004, D. Cognato, W. Crampton, J. Giora &

D. Rocha. MZUSP 94428, 8 (2 males, 95.64-126.77 mm LEA, 6 females, 51.97-

103.94 mm LEA), UFRGS 6753, 1 (male, 88.35 mm LEA), Rosário do Sul,

stream tributary of arroio Gueromana, BR290 (30°01’00”S - 55°23’18”W), 19 Jun

2004, D. Cognato, W. Crampton, J. Giora & D. Rocha. UFRGS 6785, 4 (2 males,

79.31-105.13 mm LEA, 2 females, 84.54-85.32 mm LEA), UFRGS 6494, 1 (male,

92.56 mm LEA), UFRGS 6497, 1 (male, 90.12 mm LEA), Rosário do Sul, sanga

do Jacaré, BR290 (30°12’42”S - 55°03’17”W), 26 Nov 2003, L. R. Malabarba, J.

Giora, D. Cognato, G. Neves & J. Ferrer. UFRGS 6789, 4 (2 males, 106.52-

126.36 mm LEA, 2 females, 71.58-80-06 mm LEA), Rosário do Sul, stream

tributary of arroio Gueromana, BR290 (30°01’00”S - 55°23’18”W), 26 Nov 2003,

L. R. Malabarba, J. Giora, D. Cognato, G. Neves & J. Ferrer. UFRGS 6507, 1

(male, 92.94 mm LEA), UFRGS 6509, 1 (male, 92.56 mm LEA), UFRGS 6511, 1

(male, 98.32 mm LEA), São Gabriel, stream tributary of arroio Piraí, BR290

(30°18’56”S - 54°24’22”W), 26 Nov 2003, L. R. Malabarba, J. Giora, D. Cognato,

G. Neves & J. Ferrer.

Non-type material. The following specimens were used to record the distribution

of the new species, but are not used in the species description and are not part

of the type series. However, they do not differ in morphometric or meristic

characteristics from the type specimens. Brazil, Rio Grande do Sul: MCP

20215, 5, and MCP 20217, 3, Eldorado do Sul; MCP 20711, 1, Osório; UFRGS

7686, 30, Viamão, and UFRGS 7707, 3, Viamão; UFRGS 8475, 4, Pantano

Grande - Rio Pardo; UFRGS 8938, 1, rio Tramandaí; UFRGS 6780, 11, São

Gabriel; UFRGS 6750, 14, Rosário do Sul - Alegrete; UFRGS 8263, 28,

Charqueadas. Paraguay: USNM 181483, 5, Pueblo Ybytymi, Departamiento

Paraguarí; ANSP 170412, 1, Deparatamiento Missiones; ANSP 175180, 1,

Departamiento Missiones. Uruguay: ZVC-P 2727, 1, Departamiento Artigas,

lagoa Redonda.

Diagnosis. Brachyhypopomus draco can be distinguished from all described

congeners by the extreme broadening of the distal portion of the caudal filament

in males during the reproductive period to form a distinct paddle shaped structure

(vs. moderately broadened distally in B. pinnicaudatus and B. brevirostris into

paddle-shaped structures, and versus broadened along most of the length of the

caudal filament in B. occidentalis, B. diazi, B. beebei, B. janeiroensis, and in

several undescribed species of the genus). Brachyhypopomus draco can be

further diagnosed from other species of the genus by the following characters:

caudal filament length 17.3-35.2% of LEA (vs. 36.5-50.0% in B. jureiae; 33.0-

50.0% in B. janeiroensis, and 13.3-20.0% in B. bombilla); pectoral fin ray length

4.1-5.8% of LEA (vs. 6.7-7.9% in B. pinnicaudatus); body depth 8.8-12.2% of

LEA (vs. 12.1-16.2% in B. pinnicaudatus); snout length 20.7-30.0% of HL (vs.

31.7-32.2% in B. jureiae); gape width 9.5-16.5% of HL (vs. 17.8-23.1% in B.

pinnicaudatus); interorbital distance 22.7-35% of HL (vs. 14.9-20.5% in B.

bombilla); branchial aperture 16.5-26% of HL (vs. 24.9-31.0% in B.

pinnicaudatus); head width at operculum 48.4-65% of HL (vs. 60.0-73.0% in B.

pinnicaudatus); head width at eyes 31.3-45.6% of HL (vs. 24.7-31.7% in B.

bombilla); number of anal fin rays 155-198 (vs. 188-211 in B. jureiae; 251-295 in

B. brevirostris; 214-228 in B. beebei, and 200-240 in B occidentalis); upper jaw

equal to lower jaw (vs. upper jaw slightly longer than lower jaw in B. bombilla, B.

occidentalis, B. diazi, B. brevirostris and B. jureiae).

Description. Morphometric data are presented in Table 1. Head conical, nearly

triangular in lateral view, snout short, eyes small, mouth terminal with upper jaw

equal to lower jaw, no teeth in both jaws. Body slender, slightly laterally

compressed. Dorsal profile straight from snout to supraoccipital, slightly convex

posteriorly to caudal filament. Ventral profile gently convex from lower jaw to

anal-fin origin, slightly convex to nearly straight along anal-fin base. Highest body

depth located posterior to anal-fin origin. Body depth increasing smoothly from

head to body region near the 30th anal-fin ray, clearly gradually decreasing from

that point to caudal filament. Caudal filament moderately short, slender and

laterally compressed in females, juveniles and males in non-reproductive period;

caudal filament paddle-shaped in sexually mature males (see sexual

dimorphism, below). Cycloid scales covering uniformly the body, except head

and fins. Scales smaller on all anterior quarter portion of body; posterior scales at

dorsal and medial body regions two to four times larger in diameter than anterior

ones; smallest scales covering region of anal-fin pterygiophores. First anterior

perforated scale of lateral line above pectoral fin origin and lateral line extending

to caudal filament tip, hardly discernible. Branchial aperture small and slightly

anterior to pectoral fin origin. Anus with the presence of urogenital papilla in

males and females, although less developed in juveniles. Pectoral fins rounded

with pigmented rays and perpendicular insertion; pectoral-fin rays i-ii + 13-15 (15-

17 total pectoral-fin rays, n = 47, median = 16). Anal fin relatively long with vii-xii

+ 148-186 rays (155-198 total anal-fin rays, n = 41, mean = 181.3) which are

pigmented. Anal-fin origin located posterior to posterior edge of pectoral fin.

Precaudal vertebrae 21-23 (20-22 anterior, 1-2 transitional; n= 6).

Coloration in life. General body color brownish varying from dark brown to

yellowish brown, dark brown near dorsal midline and clearing ventrally. A highly

variable number of dark brown bands, well delineated or not, nearly

perpendicular or oblique to longitudinal body axis, running posterodorsally from

base of anal-fin rays to nearby lateral line and occurring from head to tip of

caudal filament. Anal and pectoral-fin rays speckled brown, with hyaline inter-

radial membranes. Adults and juveniles exhibit the same coloration pattern.

Secondary sexual dimorphism. During reproductive period, established

through monthly variation analysis of male and female gonads in a B. draco

population, males undergo hypertrophy of the distal portion of caudal filament.

This has been observed between August and December in a population studied

from the type-locality (A. Schaan, J. Giora and C. Fialho, in preparation).

Extremely vertical broadening and lateral compression give the caudal filament a

paddle-like shape. After the reproductive period, this structure regresses until the

caudal filament resembles those of females and juveniles. In addition, adult

males are significantly larger than females.

Electric organ discharge. Brachyhypopomus draco generates a continuous

train of pulse-type EODs. Adult specimens (with developing or fully developed

gonads) (72.6-105 mm LEA) exhibited the following EOD parameters. The mean

EOD repetition rate (per individual) during the day ranged from 15.7-24.6 Hz

(mean among all specimens, 19.6 Hz, SD 2.5, n = 11 individuals fishes), with a

standard deviation (SD) of 0.4-1.2 Hz (mean 0.7, SD 0.3, n = 11), and coefficient

of variance of 1.8-7.0 % (mean 3.9 %, SD 1.88, n = 11). The lowest and highest

absolute pulse rates recorded from all diurnal recordings were 13.7 and 29.2 Hz

respectively. During the hours of peak foraging activity, 1-3 hours after sunset,

the mean EOD repetition rate (per individual) ranged from 34.2-45.8 Hz (mean

among all specimens 38.6 Hz, SD 5.2, n = 6) with a standard deviation of 2.8-

10.8 Hz (mean 2.9, SD 1.1, n = 6) and a coefficient of variation of 8.3-27.3 %

(mean 20.7 %, n = 6). The lowest and highest absolute pulse rates recorded from

all nocturnal recordings were 8.4 and 80.2 Hz respectively.

In sum, adult specimens of B. draco exhibited a distinct increase in pulse

rate from the resting day-time state (mean 19.6 Hz) to the nocturnal active state

(mean 38.6 Hz). The coefficient of variation of pulse rate during nocturnal activity

(mean 20.7 %) was considerably higher than during the day (mean 3.9%)

reflecting the greater variability in pulse rate during foraging. Disturbances such

as minor vibrations provoked novelty responses, sudden increases in the resting

pulse rate from the baseline rate (Fig. 3). The approximately stable resting

diurnal EOD punctuated by novelty responses results in a right-skewed

distribution of inter-pulse intervals in a histogram (Fig. 3). Some specimens of B.

draco displayed spontaneous complete cessations of the EOD for periods of up

to 1 minute. Normal EOD activity was resumed after these interruptions.

The EODs waveforms of adult specimens of B. draco comprised two

components of alternating polarity (P1 and P2) sensu Crampton & Albert (2006),

and varied in duration from 1.172-1.992 ms (mean 1.578, SD 0.147, n = 23) (Fig.

4). The Peak Power Frequency (PPF) (see Fig. 4) of these EODs varied from

0.6958-0.8942 kHz (mean 0.7707, SD 0.0534, n = 23).

We did not encounter evidence for obvious sexual differences in the EOD

waveforms of B. draco, despite evidence for this phenomenon in other species of

Brachyhypopomus (e.g. B. occidentalis, Hagedorn, 1985, Shumway & Zelick,

1988; B. pinnicaudatus Stoddard et al., 2003; B. brevirostris, Kawasaki &

Heiligenberg, 1989, Crampton, 1996). Where a sexual difference exists, this is

manifest as an elongation of the second negative waveform phase, P2 and a

corresponding reduction in the PPF of the EOD. We observed no consistent EOD

waveform shape differences. Likewise, we observed no significant difference

between the PPF of five sexually mature males (0.7504-0.8942 kHz, mean

0.8178, SD 0.0675) and 2 sexually mature females (0.7385-0.7949 kHz, mean

0.7667, SD 0.0399) (2-sample T-test, df = 5, n = 7, P = 0.38). The observation of

a lower PPF in mature females than males contrasts with cases of sexual EOD

differences in Brachyhypopomus, where sexually mature males invariably display

lower PPFs. Nonetheless, we did note that the Spectral Power Densities of the

two sexually mature females exhibited a more rapid decline from the PPF than in

the five sexually mature males (Fig. 4). Males and females with developing

gonads also exhibited no obvious difference in waveform shape, and no

significant difference in the PPF (males: 0.6958-0.8362 Hz, mean 0.7518, SD

0.0460, n = 10; females: 0.7111-0.8194 kHz, mean 0.7642, SD 0.0422, n = 6) (2-

sample T-test, df = 14, n = 16, P = 0.59). All recorded specimens had been held

in social isolation for several days before they were recorded. This is known to

minimize the hormonally-induced modulation of the P2 phase in sexually mature

males (Stoddard et al., 2003). Further investigation is required to explore whether

EOD differences emerge in males that are exposed to normal social stimuli (i.e.

the presence of sexually mature conspecifics).

All recordings presented here were made during the southern summer

(December) when ambient water temperature is typically in the range 24 – 30º C.

During the winter, water temperatures in Rio Grande do Sul decline to as low as

10º C. We noted that these seasonal temperature changes have a significant

impact on the waveform duration and shape of the EODs of B. draco. The PPF of

the EOD declines substantially, and the P2 phase becomes diminished in relative

amplitude. We will present detailed observations on this phenomenon elsewhere.

Loureiro & Silva (2006) discuss the effect of temperature on the EODs of B.

bombilla.

Distribution. Brachyhypopomus draco is widely known from central, southern

and coastal regions of Rio Grande do Sul state, Brazil, and Uruguay. It is known

from three drainages: laguna dos Patos, rio Uruguay and rio Tramandaí, and was

also found at two localities in Paraguay (USNM 181483; ANSP 170412; ANSP

175180).

Habitat. Brachyhypopomus draco inhabits river edges, slow-moving creeks,

lagoons and flooded areas with muddy or sandy bottom and abundant emergent

or floating vegetation. The species was particularly abundant in the type locality,

a lagoon (30°22’52, 4”S e 51°01’25”W) inside a state preserved area, Parque

Estadual de Itapuã in Rio Grande do Sul, Brazil. The lagoon is approximately 4

hectares in area and reaches 1 meter in depth. It has a muddy bottom, abundant

macrophytes and vegetal material in various stages of decomposition, and is

surrounded by psammophilous forest with strong vegetational influence from

Atlantic forest formations (Fig. 6). At the type locality, B. draco was found

occurring together with Gymnotus aff. carapo. At other collecting sites throughout

Rio Grande do Sul state the species was collected along with the gymnotiforms

Eigenmannia trilineata, B. bombilla and another undescribed Brachyhypopomus

species (see Comparative Material).

Etymology. Name “draco”, from the Greek “drakon” meaning dragon, in

reference to the shape of distal portion of caudal filament in mature males,

similar to that illustrated in these imaginary creatures.

Discussion

The new species is referred to the genus Brachyhypopomus, since it

conforms to diagnoses of the genus proposed by Mago-Leccia (1994) and Albert

(2001). The new species lacks a mesocoracoid bridge, presents a short snout, a

short and crescent-shaped maxillary bone, and posterior nares closer to eyes

than to snout tip, as proposed in Mago-Leccia’s (1994) diagnosis.

Albert (2001) considered the characters used by Mago-Leccia (1994)

ambiguous in his analysis, and proposed four other characters to diagnose the

genus. Brachyhypopomus draco possesses two of these: the premaxilla gracile

with a curved anterior margin and forming a distinct angle with the maxilla in

lateral view, and the dentary gracile. The two other characters used by Albert

(2001) were the presence of a single transitional vertebra and body cavity with

16-17 precaudal vertebrae (20-21, with the addition of C1-C4).

We observed 21-23 precaudal vertebrae in B. draco (20-22 anterior, 1-2

transitional; n= 6). The number of transitional vertebrae exhibited variability, with

three of six specimens bearing one transitional vertebra; two bearing one

transitional vertebra, and one vertebra associated to a rib (but not completely

developed, and not attached to the vertebra); and one bearing two transitional

vertebrae. Variability in the number of precaudal and transitional vertebrae has

also been observed in B. bombilla (Loureiro & Silva, 2006).

From a study of both morphological and molecular sequence data,

Sullivan (1997) diagnosed five species groups within Brachyhypopomus,

discussed later by Albert (2001): the B. brevirostris group, consisting of B.

brevirostris and one undescribed species; the B. beebei group, including B.

beebei, B. pinnicaudatus, B. janeiroensis, and two undescribed species, and the

B. occidentalis group, including B. occidentalis and B. diazi. Within the B. beebei

species group, two subgroups were established: one clade consisting of two

undescribed species, and another consisting of B. beebei and B. pinnicaudatus.

Brachyhypopomus draco can be included in the B. beebei species group, sharing

all the group characteristics: lower jaw equal to upper jaw; ventral ethmoid

reduced; fourth supraorbital lateral line pore close to vertical through posterior

nares; and supraorbital lateral line canal not attached to frontal rostral to the

orbit. Nevertheless, B. draco cannot be included in any of the B. beebei

subgroups because it does not share any of their characteristics.

Although B. draco is more closely related to B. beebei, B. pinnicaudatus,

and B. janeiroensis, included in the B. beebei group, it can be easily

distinguished from these species. In addition to the presence of the paddle-

shaped tail in mature males and the morphometric and meristc characters

presented in diagnosis, the coloration pattern of B. draco also differs from these

Brachyhypopomus species. According to the diagnoses presented by Sullivan

(1997), B. beebei has a narrow depigmented stripe running along the posterior

half of upper dorsum, B. pinnicaudatus has a nearly solid dark brown pigment

over the dorsum broken by fine unpigmented reticulations, and B. janeiroensis

lacks lateral bands along sides of the body in mature individuals. All these color

patterns diverge from B. draco that presents a dark brown dorsal surface with a

variable number of darker bands, nearly perpendicular or oblique to the

longitudinal body axis. Moreover, the clade consisted of B. beebei and B.

pinnicaudatus is diagnosed by the presence of a tiny hook-like ossification medial

to first branchiostegal ray (Sullivan, 1997; Albert, 2001), which is absent in B.

draco.

The undescribed species referred herein as occurring in Rio Grande do

Sul can also be diagnosed from B. draco by the lack of a paddle-shaped distal

portion of caudal filament in mature males, and by the coloration pattern,

showing dorsal surface of the body with chocolate-brown stains that form a

reticulated drawing contrasting with a yellow background. Furthermore, B. draco

has the anal-fin origin located posterior to posterior edge of the pectoral fin

(versus anal-fin origin located at the same line of posterior edge of the pectoral

fin in the undescribed species).

Comparative material. Brachyhypopomus jureiae: DZUFMG 011, 2,

Paratype, Brazil, São Paulo, rio do Descavado, Juréia Ecological Station;

Brachyhypopomus bombilla: ZVC-P 6287, 1, Holotype, Uruguay, Rocha

Departamiento, rio Cuatro Palmas; ZVC-P 5688, 1, Paratype, Uruguay, rio

Quebracho; ZVC-P 5686, 10, 3 CS, Uruguay, Rocha Departamiento, rio San

Luiz; ZVC-P 5685, 1, Uruguay, Tacuarembo Departamiento, rio Batovi; MNHN

3210, 1, Paratype, Uruguay, Rocha Departamiento, rio San Luiz; UFRGS 9282,

15, UFRGS 9273, 18, UFRGS 9284, 17, UFRGS 6741, 1, UFRGS 6742, 1,

UFRGS 6745, 1, UFRGS 6496, 1, UFRGS 6495, 1, Brazil, Rio Grande do Sul,

Rosário do Sul; Brachyhypopomus pinnicaudatus: ANSP 163463, Holotype, 1,

French Guiana; ANSP 163464, Paratype, 1, French Guiana; USNM 301966,

Paratype, 1, French Guiana; USNM 301967, Paratype, 1, French Guiana; USNM

301968, 1, French Guiana; UMMZ 216032, Paratype, 3, French Guiana;

Brachyhypopomus sp.: UFRGS 6520, 1, UFRGS 6524, 1, UFRGS 8932, 1,

Brazil, Rio Grande do Sul, Viamão, Parque Estadual de Itapuã, lagoa Negra;

UFRGS 2219, 2, Brazil, Rio Grande do Sul, Santo Antônio da Patrulha; UFRGS

3844, 2, Brazil, Rio Grande do Sul, Capão da Canoa, lagoa dos Quadros;

UFRGS 6499, 1, UFRGS 6503, 1, UFRGS 6504, 1, UFRGS 6505, 1, Brazil, Rio

Grande do Sul, São Gabriel.

Acknowledgements

We are grateful to David Catania (CAS), John Lundberg and John Sullivan

(ANSP), Marcelo Loureiro (ZVC-P), Zilda Margarete Lucena (MCP), Mauro

Triques (DZUFMG), and Richard Vari and Stanley Weitzman (USNM) for the

loan of specimens. The first author was funded by CAS, ANSP and CAPES to

travel and visit museum collections. This project was supported by CNPq

(process 476821/2003-7; 478002/2006-8). WGRC was funded by National

Science Foundation grant DEB–0614334.

Literature Cited

Albert, J. S. 2001. Species diversity and phylogenetic systematics of American

knifefishes (Gymnotiformes, Teleostei). Miscellaneous Publications of the

Museum of Zoology, University of Michigan, 190: 1-127.

Albert, J. S. & W. G. R. Crampton. 2003. Seven new species of the neotropical

electric fish Gymnotus (Teleostei, Gymnotiformes) with a redescription of G.

carapo (Linnaeus). Zootaxa, 287: 1-54.

Campos-da-Paz, R. 1997. Sistemática e taxonomia dos peixes elétricos das

bacias dos rios Paraguai, Paraná e São Francisco, com notas sobre espécies

presentes em rios costeiros do leste do Brasil (Teleostei: Ostariophysi:

Gymnotiformes). Unpublished Ph. D. Thesis, Universidade de São Paulo,

São Paulo, Brazil.

Cognato, D. De P. & C. B. Fialho. 2006. Reproductive biology of a population of

Gymnotus aff. carapo (Teleostei: Gymnotidae) from Southern Brazil.

Neotropical Ichthyology, 4(3): 339-348.

Costa, W. J. E. M. & R. Campos-da-Paz. 1992. Description d’une novelle espèce

de poisson eléctrique du genre néotropical Hypopomus (Siluriformes:

Gymnotodei: Hypopomidae) du sudest du Brésil. Revue Française

d’Aquariologie, 18(4): 117-120.

Crampton, W. G. R. 1996. The electric fish of the Upper Amazon: ecology and

signal diversity. Unpublished Ph. D Thesis, The University of Oxford, Oxford.

223p.

Ellis, M. M. 1913. The gymnotid eels of tropical America. Memoirs of the

Carnegie Museum. 6(3): 109-195.

Fernández-Yépez, A. 1972. Análisis ictiológico del complejo hidrográfico (04)

“Río Yaracuy”. Direccion de Obras Hidraulicas, Ministerio de Obras,

Republica de Venezuela. 25 p., 41pl.

Hagedorn, M. 1985. Ecology and behaviour of a pulse-type electric fish,

Hypopomus occidentalis (Gymnotiformes, Hypopomidae), in a fresh-water

stream in Panama. Copeia, 1985(2): 324-335.

Hopkins, C. D. 1991. Hypopomus pinnicaudatus (Hypopomidae), a new species

of gymnotiforme fish from French Guiana. Copeia, 1991(1): 151-161.

Kawasaki, M. & W. Heiligenberg. 1989. Distinct mechanisms of modulation in a

neuronal oscillator generate different social signals in the electric fish

Hypopomus. Journal of Comparative Physiology A., 165: 731-741.

Loureiro, M. & A. Silva. 2006. A new species of Brachyhypopomus

(Gymnotiformes: Hypopomidae) from Northeast Uruguay. Copeia, 2006(4):

665-673.

Mago-Leccia, F. 1978. Los peces de la familia Sternopygidae de Venezuela.

Acta Cientifica Venezolana, 29 (suppl. 1): 1-89.

Mago-Leccia, F. 1994. Electric fishes of the continental waters of America.

Caracas, Fundacion para el Desarrollo de las Ciencias Fisicas, Matematicas

y Naturales. Electric Fishes: 1-206.

Malabarba, L. R. 1989. Histórico sistemático e lista comentada das espécies de

peixes de água doce do sistema da laguna dos Patos, Rio Grande do Sul,

Brasil. Comunicações do Museu de Ciências da PUCRS (Sér. Zool.), 2(8):

107-179.

Regan, C. T. 1914. Fishes from Condoto River, Colômbia, collected by Dr. H. G.

F. Spurrel. Annals and Magazine of Natural History, 14(79): 31-33.

Schultz, L. P. 1944. Two new species of fishes (Gymnotidae, Loricariidae) from

Caripito, Venezuela. Zoologica, 29(1): 39-44.

Shumway, C. A. & R. D. Zelick. 1988. Sex recognition and neuronal coding of

electric organ discharge waveform in the pulse-type weakly electric fish,

Hypopomus occidentalis. Journal of Comparative Physiology A., 163: 465-

478.

Steindachner, F. 1868. Abhandlung über die Gymnotiden des Wiener Museums.

Anzeiger der Akademie der Wissenschaften in Wien, 5(20): 176-177.

Stoddard, P. K., M. R. Markham & V. L. Salazar. 2003. Serotonin modulates the

electric waveform of the gymnotiform electric fish Brachyhypopomus

pinnicaudatus.

Journal of Experimental Biology, 206: 1353-1362.

Sullivan, J. P. 1997. A phylogenetic study of the Neotropical hypopomid electric

fishes (Gymnotiformes: Rhamphichthyoidea). Unpublished Ph. D.

Dissertation. Duke University, Durham, North Carolina.

Taylor, W. R. & G. C. Van Dyke. 1985. Revised procedures for staining and

clearing small fishes and other vertebrates for bone and cartilage study.

Cybium, 9:107-119.

Triques, M. L. & D. K. Khamis. 2003. Brachyhypopomus jureiae, a new species

of freshwater Neotropical electric fish (Teleostei: Gymnotiformes:

Hypopomidae) from a coastal stream of southeastern Brazil. Lundiana, 4(1):

61-64.

Wells, K. & W. G. R. Crampton. 2006. A portable bio-amplifier for electric fish

research: design and construction. Neotropical Ichthyology, 4 (2): 295-299.

Table 1. Morphometric data for Brachyhypopomus draco. Length to the end of

anal fin (LEA); Head length (HL).

Character Holotype n Minimum Maximum Mean L1 L2 S.D.

LEA (mm) 137.39 44 50 151.9 96.9 24.559

HL 10.1 44 9.4 14.2 11.4 11.084 11.694 1.004

Caudal filament length 29.1 34 17.3 35.2 25.1 23.324 26.863 5.152

Snout to anal fin origin 18.3 44 17.9 23 20.3 19.93 20.703 1.272

Depth of caudal filament 2.7 44 1.4 3.1 2.1 2.01 2.244 0.386

Longest anal fin ray 3.7 43 2.9 4.4 3.6 3.528 3.739 0.347

Longest pectoral fin ray 4.1 41 4.1 5.8 5 4.852 5.168 0.507

Body depth 9.4 44 8.8 12.2 10.8 10.521 11.085 0.926

Snout length 26.5 50 20.7 30 25.6 25.128 26.086 1.686

Gape width 14.5 50 9.5 16.5 13.7 13.322 14.148 1.454

Orbital diameter 9.5 50 9.4 14.4 12.3 11.903 12.641 1.3

Interorbital distance 23.4 50 22.7 35 28.4 27.602 29.257 2.913

Posterior nare to eye 3.4 49 2.9 5.4 4.2 4.044 4.343 0.526

Branchial aperture 23.3 50 16.5 26 19.9 19.312 20.448 1.999

Head width at operculum 54.1 50 48.4 65 57 55.969 57.962 3.507

Head width at eyes 37.2 50 31.3 45.6 39.9 39.091 40.636 2.718

95% confidence limit

Percents of LEA

Percents of HL

Fig. 1. Holotype (MCP 41540, male, 137.39 mm LEA) (above) and paratype

(MCP 41537, female, 108.40 mm LEA) (below) of Brachyhypopomus draco, from

Parque Estadual de Itapuã, Rio Grande do Sul, Brazil.

Fig. 2. Brachyhypopomus draco, MCP 41540, male, 137.39 mm LEA; a, head; b,

tail.

Fig. 3. a. Resting diurnal Electric Organ Discharge (EOD) repetition rate of a

single specimen of Brachyhypopomus draco (UFRGS 6487). Repetition rate in

Hz (pulses per second) is plotted for a 60 s recording. Each point represents the

distance from an EOD to the preceding one (Inter-Pulse Interval, IPI). Note the

intermittent upward modulations of repetition rate (arrows) in response to

disturbances such as minute vibrations. These ‘novelty responses’ are a normal

part of EOD activity in the wild. b. Histogram of 1218 IPIs for the 60 s recording,

exhibiting a typical right-skewed distribution due to the novelty responses.

Repetition rate (Hz) is the reciprocal of Inter-pulse interval (e.g. 1/20 Hz = 0.05 s)

Fig. 4. Electric Organ Discharge (EOD) waveform (left) and Spectral Power

Density (right) of adult specimens of Brachyhypopomus draco from Rio Grande

do Sul state, Brazil. a: All 23 recorded specimens with developing or fully

developed gonads (86-135 mm). b: 7 adult specimens with fully mature gonads;

5 male (blue) 2 female (red). c: 16 adult specimens with developing gonads; 10

males (blue), 6 females (red). EODs plotted with head positivity upwards,

normalized to the amplitude of the dominant positive phase (P1), and aligned at

the P1 peak. Scale bar = 1 ms. Spectral Power Densities (SPDs) were computed

from a 65, 536-point Fast Fourier Transform and the Peak Power Frequency

(PPF) scaled to 0 dB. Upper and lower ranges of the PPF are marked with

arrows. Note the more rapid decline of the SPDs of the two sexually mature

females versus males (labeled with asterisk in c) but no obvious sexual

difference in EOD waveform shape or PPF.

Fig. 5. Map of Southern Brazil, Uruguay, Argentina and Paraguay with the

distribution of Brachyhypopomus draco. Squares represent non-type specimens.

Empty circle represents the type locality.

Fig. 6. Typical habitat of Brachyhypopomus draco; marshland in the Parque

Estadual de Itapuã, Rio Grande do Sul, Brazil.

Capítulo II

A new species of the Neotropical electric fish genera

Brachyhypopomus from southern South America

(Gymnotiformes: Hypopomidae).

A new species of the Neotropical electric fish genera Brachyhypopomus

from southern South America (Gymnotiformes: Hypopomidae).

Julia Giora*, Luiz R. Malabarba*, **

* Universidade Federal do Rio Grande do Sul, IB, Departamento de Zoologia, Av.

Bento Gonçalves, 9500, bloco IV, prédio 43435, 91501-970 Porto Alegre, RS,

Brazil. [email protected]m; [email protected]

** Museu de Ciências e Tecnologia, PUCRS, Av. Ipiranga, 6681, P. O. Box.

1429, 90619-900 Porto Alegre, RS, Brazil.

A new species of Brachyhypopomus, from central, southern and coastal regions

of Rio Grande do Sul state, Brazil, Uruguay, and Paraguay is described. It is

diagnosed from the congeners on the basis of body coloration, meristic and

morphometric characters, such as the number of anal-fin rays, position of anal-fin

origin in relation to pectoral-fin, distal portion of caudal filament of mature males,

and body proportions. The new species has been formerly identified as B.

pinnicaudatus and is herein distinguished from it.

Uma nova espécie de Brachyhypopomus das regiões central, sul e costeira do

estado do Rio Grande do Sul, Brasil, Uruguai e Paraguai é descrita. Ela é

diagnosticada de seus congêneres baseado em coloração do corpo, caracteres

merísticos e morfológicos tais como número de raios da nadadeira anal, posição

da origem da nadadeira anal em relação à nadadeira peitoral, porção distal do

filamento caudal de machos maduros e proporções corporais. A espécie nova

tem sido identificada como B. pinnicaudatus e é aqui distinguida da mesma.

Key words: Brachyhypopomus, rio Uruguay, laguna dos Patos, rio Tramandaí.

Introduction

The genus Brachyhypopomus was described by Mago-Leccia (1994) to

comprise six species that previously belonged to Hypopomus: B. occidentalis

(Regan, 1914), B. beebei (Schultz, 1944), B. brevirostris (Steindachner, 1868), B.

diazi (Fernández-Yépez, 1972), B. pinnicaudatus (Hopkins, 1991), and B.

janeiroensis (Costa & Campos-da-Paz, 1992). All these quoted species were

described for the northern area of Neotropical region, except for B. janeiroensis,

which occurs in São João and Paraíba do Sul river basins in Rio de Janeiro state

(Albert & Crampton, 2003). Recently, with the increase of studies especially on

southern Brazil and Uruguay, additional species have been described.

Brachyhypopomus jureiae Triques & Khamis, 2003 was described as occurring

only in rio Una do Prelado system in southern Brazil, B. bombilla Loureiro &

Silva, 2006 as distributed throughout middle rio Uruguay tributaries and the

laguna dos Patos and lagoa Mirim systems in eastern Uruguay, and B. draco

Giora, Malabarba & Crampton, in press as widely distributed in Rio Grande do

Sul state, southern Brazil, Uruguay, and also in Paraguay. Nevertheless, the low

number of studies on Gymnotiformes from southern South America still resulting

in the underestimation of the species diversity in this area.

The species B. pinnicaudatus was described by Hopkins (1991) on the

basis of one population from French Guiana; however, the author has considered

the species to be widespread throughout tropical South America. Sullivan (1997),

in an unpublished review, considered B. pinnicaudatus widely distributed in the

Amazon and Paraná/Paraguay drainage basins as well as coastal drainages of

southern Brazil and Uruguay, including material from Rio Grande do Sul state.

Campos-da-Paz (1997) and Albert & Crampton (2003) referred B. pinnicaudatus

as distributed throughout eastern South America from rio Catumbo basin,

Orinoco and Guianas to rio de la Plata basin.

Based upon extensive sampling in Rio Grande do Sul state, our studies

revealed the presence of three Brachyhypopomus species in this region: B.

bombilla, B. draco, and a third species, widespread in rio Uruguay, laguna dos

Patos and rio Tramandaí drainages in southern Brazil and Uruguay, which has

been largely identified as B. pinnicaudatus in the literature. We have compared

this population identified as B. pinnicaudatus with the type series and found it to

be a new species. The misapplication of names and the existence of groups of

species concealed under a unique specific name has been a problem for a better

understanding of the real diversity of species in almost all gymnotiform genera.

The present study aims to describe this new Brachyhypopomus species from

southern Brazil.

Materials and Methods

Comparative data from B. pinnicaudatus, B. bombilla, B. draco and B.

jureiae were taken directly from the type specimens (see Comparative Material).

Data from B. brevirostris, B. occidentalis, B. beebei, B. diazi and B. janeiroensis

were compiled from original descriptions. Morphometric data were taken as

point-to-point linear distances using digital calipers to the nearest 0.1mm.

Measurements were analyzed as percents of length to the end of the anal-fin

(LEA), measured as the distance from tip of the snout to posterior end of anal-fin

base, or as percents of head length (HL), measured from tip of snout to posterior

margin of bony operculum. The total length was not used as a numerator in

morphometric body relationships because of the high number of specimens with

a damaged and/or regenerated caudal filament. Regenerated parts of the body

were not measured and their meristic data were not recorded. The other

measurements used were taken following Giora et al. (in press). Pectoral and

anal-fin ray counts were taken directly from ethanol preserved specimens under

a stereo-microscope. Vertebrae were counted from radiographed specimens

including the four vertebrae of the Weberian Apparatus. Apparently, Albert

(2001) did not include the vertebrae of the Weberian Apparatus in the precaudal

counts; therefore, four vertebrae were added to Albert’s (2001) counts for

comparison. Osteologic data were taken from cleared-and-stained specimens

following Taylor & Van Dyke (1985). Sex and the stage of sexual maturity were

determined by dissection, following Cognato & Fialho (2006).

Fish specimens belong to the collections of the Departamento de

Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre (UFRGS),

Museu de Ciências e Tecnologia, Pontifícia Universidade Católica do Rio Grande

do Sul, Porto Alegre (MCP), Universidade Federal de Minas Gerais, Belo

Horizonte (DZUFMG), Museu de Zoologia, Universidade de São Paulo, São

Paulo (MZUSP), Museu Nacional, Rio de Janeiro (MNRJ), Faculdad de Ciências

Naturales, Montevideo (ZVC-P), Academy of Natural Sciences of Philadelphia,

Philadelphia (ANSP), National Museum of Natural History, Washington D.C.

(USNM), California Academy of Sciences, San Francisco (CAS), University of

Michigan Museum of Zoology, Ann Arbor (UMMZ).

Results

Brachyhypopomus “G” n. sp., new species

(Fig. 1)

Brachyhypopomus pinnicaudatus [in part]. Sullivan (1997: 243-248) [specimens

of Brachyhypopomus “G” n. sp. listed under B. pinnicaudatus].

Brachyhypopomus sp. Giora et al. (in press) [listed in comparative material of B.

draco].

Holotype: UFRGS 9229 (male, 149.03 mm LEA), Palmares do Sul,

chanel connecting lagoa do Casamento and lagoa dos Gateados (aprox.

30°28’S, 50°40’W), 28 Sep 2006, F. Becker.

Paratypes: All from Brazil, Rio Grande do Sul. Laguna dos Patos

drainage: UFRGS 9580, 1 (male, 139.62 mm LEA), Charqueadas, floaded area

near arroio dos Ratos creek (29°57’31.9”S, 51°33’10.1”W), 28 Nov 2005, J.

Giora, D. Roca, A. Ribeiro. UFRGS 9581, 2 (1 male, 128.68 mm LEA, 1 female,

126.36 mm LEA), Charqueadas, floaded area near arroio dos Ratos creek

(29°57’31.9”S, 51°33’10.1”W), 22 Sep 2005, J. Giora, D. Rocha, R. Hirano.

UFRGS 6520, 1 (female, 124.32 mm LEA), UFRGS 6524, 1 (male, 125,82 mm

LEA), Viamão, Parque Estadual de Itapuã, lagoa Negra (30°21’35”S,

50°58’34”W), 11 Nov 2003, J. Anza, D. Cognato, A. Dufech & J. Giora. UFRGS

8932, 1 (female, 133.35 mm LEA), Viamão, Parque Estadual de Itapuã, Lagoa

Negra (30°21’35”S, 50°58’34”W), 6 Jan 2003, D. Cognato, T. Dias & J. Giora.

UFRGS 4240, 5 (3 males, 74.40-97.24 mm LEA, 2 females, 75.04-78.09 mm

LEA), Barra do Ribeiro, along the road between BR 116 and Barra do Ribeiro city

(30°17’00”S, 51°21’00”W), 21 Oct 1987, L. Malabarba, F. Becker & M.

Schneider. UFRGS 5641, 2 (males, 81.73-126.29 mm LEA), Viamão, Parque

Estadual de Itapuã, lagoa do Palácio (30°24’10”S, 50°57’25”W), 26 Nov 2002, J.

Anza, L. Malabarba, T. Gonçalves & T. Hasper. UFRGS 2219, 2 (1 male, 120.87

mm LEA, 1 female, 80.03 mm LEA), Santo Antônio da Patrulha, creek between

BR 290 and Santo Antônio da Patrulha city (29°52’00”S, 50°35’00”W), 3 Mar

1983, L. Malabarba, C. M. Malabarba & R. Reis. Rio Tramandaí drainage:

UFRGS 8933, 1 (female, 101.64 mm LEA), Arroio do Sal, creek parallel to

Estrada do Mar road (29°30’33”S, 49°53’34”W), 11 Mar 2005, J. Anza, J. Giora,

L. R. Malabarba. UFRGS 3844, 2 (1 male, 91.62 mm LEA, 1 female, 83.11 mm

LEA), Capão da Canoa, lagoa dos Quadros (29°42’00”S, 50°06’00”W), 14 Nov

1988, L. Malabarba. Rio Uruguay drainage: UFRGS 6499, 1 (male, 102.13 mm

LEA), UFRGS 6503, 1 (female, 84.12 mm LEA), UFRGS 6504, 1 (male, 123.16

mm LEA), UFRGS 6505, 1 (male, 135.79 mm LEA), UFRGS 6781, 15 (8 males,

59.83-127.17 mm LEA, 7 females, 78.09-127.17 mm LEA), São Gabriel, stream

tributary of arroio Piraí, BR290 (30°18’56”S, 54°24’22”W), 26 Nov 2003, L.

Malabarba, J. Giora, D. Cognato, G. Neves & J. Ferrer.

Non-type material: The following specimens were used to record the

distribution of the new species, but are not used in the species description and

are not part of the type series. However, they do not differ in morphometric or

meristic characteristics from the type specimens. Brazil, Rio Grande do Sul:

MCP 9710, 1, Porto Alegre, Foz do Arroio da Faxina; MCP 14177, 1, Eldorado

do Sul; MCP 14459, 2, Eldorado do Sul; MCP 14606, 2, Guaíba; MCP 15326, 2,

Eldorado do Sul; MCP 11135, 1, Santo Ângelo; USNM 191645, 1, Porto Alegre.

Uruguay: ZVC – P 5002, 1, Paso Manzagano, Rio Negro; ZVC – P 1992, 1,

Paso del Sauce. Paraguay: ANSP 185112, 1, Departamiento Cordillera; ANSP

185116, 5, Departamiento Boqueron; ANSP 185114, 1, Presidente Haynes;

UMMZ 207817, 1, Concepcion; USNM 232235, 3, Presidente Haynes.

Diagnosis: Brachyhypopomus “G” n. sp. is diagnosed from all congeners

by the following combination of features: body depth 11.0-14.1% of LEA (vs.

10.9-11.0% in B. jureiae, 10.1-10.9% in B. janeiroensis); branchial aperture 20.4-

28.1% of LEA (vs. 19.0-19.8% in B. jureiae); caudal filament length 19.6-32.2%

of LEA (vs. 42.3-45.8% in B. jureiae, 34.0-39.6% in B. janeiroensis); anal-fin ray

length 3.6-5.1% of LEA (vs. 3.3-3.4% in B. jureiae); pectoral-fin length 4.9-6.4%

of LEA (vs. 4.3-4.6% in B. jureiae); snout to anal-fin origin 17.0-21.2% of LEA

(vs. 16.1-17.4% in B. beebei); number of anal-fin rays 180-216 (vs. 214-228 in B.

beebei, 200-240 in B. occidentalis, 251-295 in B. brevirostris); upper jaw equal to

lower jaw (vs. upper jaw slightly longer than lower jaw B occidentalis, B. diazi, B.

brevirostris and B. jureiae).

Brachyhypopomus “G” n. sp. is diagnosed from B. pinnicaudatus by the

following characters: caudal filament length 19.6-32.2% of LEA (vs. 32.3-42.3%);

pectoral-fin length 4.9-6.4% of LEA (vs. 6.7-7.9%); head length 10.0-12.7% of

LEA (vs. 12.4-15.6%); number of anal fin rays 180-216 (vs. 176-185).

Brachyhypopomus “G” n. sp. is diagnosed from the syntopic species B.

draco and B. bombilla by the following characters: dorsal surface of the body with

chocolate-brown stains that are connected forming a reticulated drawing

contrasting with the yellow background, vs. dark brown dorsal surface with a

variable number darker bands, nearly perpendicular or oblique to longitudinal

body axis, never being interconnected in B. draco, and body background light

brown with an irregularly scattered darker brown pigmentation more dense in

dorsal half of body in B. bombilla; anal-fin origin located at same line of posterior

edge of pectoral-fin, vs. anal-fin origin located posterior to posterior edge of

pectoral-fin in B. draco; distal portion of caudal filament moderately broadened

vertically and laterally compressed in sexually mature males, vs. extreme

broadened and forming a distinct paddle shaped structure in B. draco, and not

broadened in B. bombilla; body depth 11.0-14.1% of LEA (vs. 8.8-12.2% in B.

draco, 9.4-11.0% in B. bombilla); branchial aperture 20.4-28.1% of LEA (vs. 13.8-

18.3% in B. bombilla); gape 14.4-18.5% of HL (vs. 9.5-16.5% in B. draco); head

width at operculum 52.4-73.2% of HL (vs. 48.4-65.0% in B. draco, 43.6-51% in B.

bombilla); head width at center of eyes 31.1-48.1% of HL (vs. 24.7-31.7% in B.

bombilla); interorbital distance 23.3-30.4% of HL (vs. 14.9-20.5% in B. bombilla);

number of anal-fin rays 180-216 (vs. 155-198 in B. draco); upper jaw equal to

lower jaw (vs. upper jaw slightly longer than lower jaw in B. bombilla); precaudal

vertebrae 20-21, 18-19 anterior and 1-2 transitional (vs. 21-23, 20-22 anterior

and 1-2 transitional in B. draco).

Description: Morphometric data are presented in Table 1. Head conical,

nearly triangular in lateral view, snout short and blunt, eyes small, mouth terminal

with upper jaw length equal to lower jaw, no teeth in both jaws. Body laterally

compressed. Dorsal profile convex from snout to caudal filament, most notably at

anterior half of body. Ventral profile convex from lower jaw to anterior anal-fin

base; nearly straight from that point to caudal filament. Highest body depth

located at anal-fin origin. Body depth increasing from head to anal-fin origin,

remaining nearly same depth to close to the 40th anal-fin ray, sharply decreasing

from that point to caudal filament. Caudal filament moderately short, slender and

nearly cylindrical in females, juveniles and males in non-reproductive period;

caudal filament vertically broadened and laterally compressed in sexually mature

males (see sexual dimorphism, below). Cycloid scales covering body, except

head and fins. Scales smaller on anterior portion of body; five to seven series of

large scales along mid-lateral portion of body, reducing to two or three series

posteriorly. Mid-lateral scales nearly twice larger than dorso-lateral and dorsal

scale and four times larger in diameter than anterior ones; smallest scales

covering region of anal-fin pterygiophores. First anterior perforated scale of

lateral line above pectoral-fin origin; lateral line irregular, not extending to caudal

filament. Branchial aperture small and slightly anterior to pectoral-fin origin. Anus

with the presence of urogenital papilla in males and females, although less

developed in juveniles. Pectoral fins rounded and with perpendicular insertion;

pectoral-fin rays i-ii + 13-15 (15-17 total pectoral-fin rays, n = 38, mean = 15.9).

Anal-fin relatively long with vi-x + 173-206 rays (180-216 total anal-fin rays, n =

38, mean = 196.2). Anal-fin origin located at same line of posterior edge of

pectoral-fin. Precaudal vertebrae 20-21 (18 -19 anterior, 1-2 transitional; n= 5).

Color in Life: General body color varying from light brown to yellow. Head

darker than rest of body. Dorsal surface with chocolate-brown stains that are

connected forming reticulated drawing contrasting with yellow background.

Variable number of brown stripes running from dorsal stains to base of anal fin,

roughly defined in middle of body and occurring from head to tip of caudal

filament. Anal and pectoral fins speckled with dark brown pigment, with hyaline

inter-radial membranes.

Secondary Sexual Dimorphism: The caudal filament of dominant mature

males is laterally compressed, especially on its distal portion, differing from that

of females, juveniles and non-dominant males, which is usually cylindrical (J.

Giora and C. Fialho, in preparation).

Distribution: Brachyhypopomus “G” n. sp. is known from laguna dos

Patos, rio Uruguay and rio Tramandaí drainages in Rio Grande do Sul state,

Brazil, being widely distributed from central, southern and coastal regions of the

state. It also occurs in rio Uruguay basin in Uruguay (ZVC–P 5002; ZVC–P 1992)

and in rio Paraguay basin in Paraguay (ANSP 185112; ANSP 185116; ANSP

185114; UMMZ 207817; USNM 232235).

Habitat: Brachyhypopomus “G” n. sp. inhabits river banks, slow-moving

creeks, lagoons, and flooded areas with muddy or sandy bottom; the occurrence

of the species is always associated with abundant emergent or floating

vegetation. Brachyhypopomus “G” n. sp. is sympatric and commonly syntopic

with B. draco, and more rarely syntopic with B. bombilla. Throughout Rio Grande

do Sul state the species was also collected along with the gymnotiforms

Eigenmannia trilineata and Gymnotus aff. carapo.

Discussion

Brachyhypopomus “G” n. sp. is included in the genus Brachyhypopomus

by sharing the synapomorphies proposed by Mago-Leccia (1994): lack of

mesocoracoid bridge, short snout, short and crescent-shaped maxillary bone,

and posterior nares closer to eyes than to snout tip. Moreover, the new species

shares two of the four diagnostic features defined by Albert (2001) for

Brachyhypopomus: the premaxilla gracile with a curved anterior margin and

forming a distinct angle with the maxilla in lateral view, and the dentary gracile.

Regarding the species-group established by Sullivan (1997) and latter

discussed by Albert (2001), Brachyhypopomus “G” n. sp. can be included in the

B. beebei species group by the presence of lower jaw equal to upper jaw, fourth

supraorbital lateral-line pore close to vertical through posterior nares, and

supraorbital lateral-line canal not attached to frontal rostral to the orbit. The

authors have also described the presence of ventral ethmoid reduced as a

diagnostic character for this group of species; although there is no clear definition

of what “reduced” means, we found the ventral ethmoid small and possibly

comparable to that described condition. The new species cannot be included in

any of the B. beebei subgroups because it does not share any of their

characteristics. Brachyhypopomus pinnicaudatus and B. beebei were quoted by

Sullivan (1997) and Albert (2001) as integrating a clade within B. beebei species

group diagnosed by the presence of a tiny hook-like ossification medial to first

branchiostegal ray (homologous to second brachiostegal ray in species with five

rays). Brachyhypopomus “G” n. sp. does not show this hook-like ossification and

possesses fifth branchiostegal ray differing from the two species mentioned.

Moreover, Albert (2001) states that this character is polymorphic in B.

pinnicaudatus, which can indicate the presence of more than one species

referred to this one.

Sullivan (1997) diagnosed B. pinnicaudatus by the nearly solid dark

brown pigment over dorsum, broken by fine depigmented reticulations, with

narrow yellow streak threaded through reticulated pattern, and by the

posttemporal completely fused to supracleithrum. Brachyhypopomus “G” n. sp.

differs from this diagnosis by presenting the posttemporal completely

independent from the supracleithrum. From the specimens referred by Sullivan

(1997) as B. pinnicaudatus from southern South America, at least two lots of

specimens belong to Brachyhypopomus “G” n. sp. species (UMMZ 207818;

USNM 232235, see non-type material), both from Paraguaian locations.

Brachyhypopomus “G” n. sp. has also been identified as B. pinnicaudatus by

Albert & Crampton (2003), Campos-da-Paz (1997) and many lists of species

from Rio Grande do Sul state river basins (pers. obs.). Nevertheless, the new

species herein described can be easily distinguished from B. pinnicaudatus by

four characters: caudal filament length, pectoral fin length, head length, and

number of anal-fin rays. Through analysis of specimens from Peru, French

Guiana, Guyana, Bolivia, Paraguay, Uruguay, and Brazil – especially southern

and northern Brazilian regions – we have identified a great number of

recognizable morphotypes referred as B. pinnicaudatus. The results point to a

necessity of a review of the species considered to be widespread throughout the

Neotropical region as a matter of avoiding misapplied names and

underestimation of species diversity. Moreover, the description of a new species

with distribution restricted to southern South America reinforces the importance

of continuing taxonomic work on Gymnotiformes species from this region, and

demonstrates that low latitude areas may be more diverse than previously

supposed.

Comparative material: Brachyhypopomus jureiae: DZUFMG 011, 2, Paratype,

Brazil, São Paulo, rio do Descavado, Jureia Ecological Station;