Clarice Bernhardt Fialho

Reproductive Biology of the Inseminating Glandulocaudine Diapoma speculiferum Cope (Teleostei: Characidae)

Abstract The reproductive period of the inseminating glandulocaudine Diapoma speculiferum was determined through the analysis of 133 males and 158 females obtained from monthly collections in Rio Grande do Sul, Brazil. The reproductive period is highly seasonal, occurring from September to February, which corresponds to the Austral spring and summer. Both male and female gonadosomatic indices were highly correlated with changes in water temperature and day length and, to a lesser extent, food availability. No correlation with rainfall was found. Absolute fecundity (mean 491.1 ± 159.5 oocytes per female) was similar to those found in two externally fertilizing cheirodontine characids but lower than that found in the inseminating glandulocaudine Pseudocorynopoma doriae. Relative fecundities (oocyte number per milligram total body weight) of the inseminating D. speculiferum and P. doriae were found to be lower than that of two externally fertilizing cheirodontines, suggesting that inseminating species may expend a smaller amount of energy in egg production, perhaps as a result of a higher efficiency in fertilization. Gonad histology showed the presence of spermatozoa in ovaries of maturing females, indicating that courtship and insemination take place before the ovaries are mature. Fertilized eggs were not found in the ovaries, suggesting that fertilization may be a very rapid event once oocytes are ovulated. O período reprodutivo do glandulocaudíneo com inseminação, Diapoma speculiferum, foi determinado pela análise de 133 machos e 158 fêmeas obtidos em coletas mensais no Rio Grande do Sul, Brasil. Seu ciclo reprodutivo é sazonal ocorrendo de setembro a fevereiro, correspondendo á primavera e verão na região Austral. Para machos e fêmeas o índice gonadossomático foi altamente correlacionado com as mudanças na temperatura da água e fotoperíodo e, em menor extensão, com a disponibilidade de alimento. Quanto ao índice pluviométrico, não foi verificada nenhuma correlação. A média da fecundidade absoluta (491,1 ± 159,5 ovócitos por fêmea) foi semelhante a observada em dois queirodontíneos de fecundação externa, e menor do que o glandulocaudíneo com inseminação Pseudocorynopoma doriae. A fecundidade relativa (número de ovócitos por miligrama de peso total) dos glandulocaudíneos com inseminação D. speculiferum e P. doriae foi menor do que nos queirodontíneos com fertilização externa, sugerindo que espécies com inseminação tem um menor gasto energético na produção dos ovócitos, talvez como resultado de uma maior eficiência na fertilização. A histologia das gônadas demonstrou a presença de espermatozóides em ovários de fêmeas em maturação, indicando que a corte e inseminação iniciam antes dos ovários estarem maduros. Não foram encontrados ovos fertilizados nos ovários, sugerindo que a fertilização ocorra durante a ovulação.

Comparative dietary analysis of two populations of Mimagoniates rheocharis (Characidae: Glandulocaudinae) from two streams of Southern Brazil

The diet of two populations of Mimagoniates rheocharis, from two freshwater streams of the rio Tramandai, northeastern Rio Grande do Sul, Brazil, are described and compared. The specimens were collected monthly from January 1998 to March 1999, with dip nets and seine nets and preserved in 10% formalin. In laboratory, the standard length of each specimen was measured. The stomachs were removed and dissected for identification of the alimentary items. The data were analyzed using the frequency of occurrence, percent composition and index of alimentary importance methods, being the last two compared among different classes of standard length. Three methods of analysis showed the highest values for allochthonous insects, regardless the locality of collection or body size of the specimens.

Reproductive period, fecundity and histology of gonads of two cheirodontines (Ostariophysi: Characidae) with different reproductive strategies - insemination and external fertilization

The reproductive period and fecundity of the inseminating cheirodontine Compsura heterura and of the externally fertilizing cheirodontine Odontostilbe pequira, from tropical and subtropical regions of Brazil, respectively, are described. The reproductive period of C. heterura lasted from January to April 2002, while O. pequira showed two reproductive periods, the first during September and October 2001 (spring), and the second between January and February 2002 (summer). Smaller classes of SL of females of O. pequira predominated in the second reproductive period, suggesting individuals born in the first period become shortly sexually mature, participating in the second reproductive period. In C. heterura, from a tropical region, temperature showed significant correlations with the variation in the gonadosomatic index (GSI) for both sexes, and rainfall showed significant correlation with the variation in the GSI only for females. In O. pequira, from a subtropical region, photoperiod was the only factor that showed significant correlations with the GSI variation in both sexes. The mean relative fecundity of C. heterura was 0.55 oocytes per milligram of total weight, similar to that of other cheirodontines with external fertilization, refuting the hypothesis, at least in Cheirodontinae, that insemination provides diminishing energy expenditure for the production of oocytes, due to a greater probability of fertilization. The mean relative fecundity of O. pequira was 0.8 oocytes per milligram of total weight, the largest known among cheirodontines. Spermatozoa were found inside the ovaries of maturating, mature and semi-spent females of C. heterura supporting the hypothesis of temporal separation between courtship and spawning. The largest relative weight of testis and the presence of sperm in maturing ovaries outside the reproductive period in C. heterura support the hypothesis that males of inseminating species make a greater investment in gonadal development than those externally fertilized.

Reproductive period and fecundity of Serrapinnus piaba (Characidae: Cheirodontinae) from the rio Ceará Mirim, Rio Grande do Norte, Brazil

Specimens of Serrapinnus piaba were collected monthly from April 2001 to April 2002 in the rio Ceara Mirim, Rio Grande do Norte State, Brazil. The reproductive period, determined through the monthly variation of the gonadosomatic index (GSI) and maturation stages, occurred from January to April. Non-parametric Spearman test was performed in order to test correlation of monthly GSI variation in males and females with water temperature, rainfall and day length. Rainfall and Temperature were correlated with GSI variation in females only and day length showed a negative correlation with GSI variation of males only. It was verified the presence of hooks on the anal fin of mature and maturing males along all the period of study. The absolute fecundity mean was 441 (±178.08) oocytes, determined by the number of yolky oocytes counted in 27 mature female gonads. The relative fecundity, estimated by the number of yolky oocytes divided by milligram of total body weight was 0.74 (± 0.19).

Reproductive biology of a population of Gymnotus aff.carapo (Teleostei: Gymnotidae) from southern Brazil

Sao descritos o periodo reprodutivo e a relacao deste com fatores bioticos e abioticos, a fecundidade absoluta e relativa, o tipo de desova, comprimento de primeira maturacao e proporcao sexual de Gymnotus aff. carapo de um pequeno lago no Parque Estadual de Itapua, Rio Grande do Sul, Brazil. A especie apresentou um periodo reprodutivo relativamente longo, de novembro de 2003 ate marco de 2004. Houve correlacao significativamente positiva entre o IGS dos machos e o oxigenio dissolvido e negativa em relacao a condutividade. O IGS das femeas se correlacionou positivamente com a temperatura e fotoperiodo, e negativamente com o oxigenio dissolvido. A fecundidade absoluta media foi de 915,3 ovocitos e a fecundidade relativa media foi de 0,20 ovocitos por miligrama de peso da femea. A desova foi considerada parcelada e o tamanho de primeira maturacao gonadal foi de 141 mm para femeas e 146 mm para machos. A proporcao sexual no periodo amostrado foi de 1:1, sendo que somente na menor classe de comprimento houve maior abundância dos machos.

Reproductive biology of weakly electric fish Eigenmannia trilineata López and Castello, 1966 (Teleostei, Sternopygidae)

Este trabalho descreve a biologia reprodutiva de uma populacao do peixe eletrico Eigenmannia trilineata do Sul do Brasil. Sao apresentadas informacoes a respeito do periodo reprodutivo, fecundidade, tipo de desova, tamanho de primeira maturacao, morfologia e histologia das gonadas da especie, relacionando estes dados a caracteres alimentares e abioticos. A especie apresentou periodo reprodutivo relativamente longo, com fecundidade relativa de 0,27 ovocito por miligrama do peso da femea e desova do tipo parcelada. O tamanho de primeira maturacao gonadal estimado para femeas foi 80,5 mm e para machos, 63,5 mm de comprimento total. A proporcao sexual, testada pelo teste X2 (Α= 0.01), foi de 1:1 durante todos os meses amostrados; dimorfismo sexual relacionado ao comprimento total foi detectado, possuindo os machos um maior comprimento total. Dos fatores abioticos testados, fotoperiodo e condutividade da agua mostraram correlacao significativa com o IGS das femeas, enquanto somente fotoperiodo apresentou-se relacionado ao IGS dos machos.

Reproductive biology of Bryconamericus stramineus Eigenmann, 1908 (Ostariophysi: Characidae) from the Rio Ibicuí, RS, Brazil

Reproduction of Bryconamericus stramineus was described based on the analysis of 208 females and 166 males collected monthly in the Rio Ibicui, from April 200 1 through March 2002. Reproduction occurred between September and December, with a lower peak in Februa ry. The mean absolute fecundity was 371.3 ( 244.6) oocytes and the mean relative fecundity was 0.35 ( 0.08) oocytes/mg of total weight and the fish was a multiple spawner. A weak correlation between GSI of males and day lengt h was observed. Other parameters (stomach repletion and hepatosomatic index, rainfall and temperature) did not show any correlation with GSI. However, some of these factors might act as “starters” of gonadal maturati on. The presence and frequency of fin ray hooks on the males was compared with the gonadal maturation stages, mo nths and standard length classes. Well-developed ho oks were found mainly in the mature males during the reprodu ctive period and in the largest individuals.

Biologia reprodutiva de Oligosarcus jenynsii (Günther) (Characiformes, Characidae) da Lagoa das Custódias, Tramandaí, Rio Grande do Sul, Brasil

The Custodias lagoon has a great importance in the Tramandai system, because it works as reproduction area, feeding and nursery grounds to several fish species. The aim of this work is the study of aspects related to the reproduction of Oligosarcus jenynsii (Gunther, 1864) as such as reproductive period, sexual ratio, fecundity and size of the first gonadal maturation. The specimens were sampled monthly from October/1994 to October/1995. For each sex, maturation curves were established, based on the monthly variation of the gonadossomatic index mean values, as well as, the relative frequencies of the sexual maturity stages. Breeding seasons took place during the winter and spring. The sex ratio was significanthly different from 1:1, with more females than male in almost all month. The species had a average fecundity of 9.694 ovocytes. The estimated size of first sexual maturation was 114 mm for male and 131 mm for females.

Biologia alimentar de quatro espécies simpátricas de Cheirodontinae (Characiformes, Characidae) do rio Ceará Mirim, Rio Grande do Norte

This study was carried in Ceara Mirim River, State of Rio Grande do Norte, Brazil. At this location, the river shows high water transparency and predominance of aquatic macrophytes in the margins. This study aims to describe the feeding habits and verify the presence of feeding overlap in the diet of four sympatric species of Cheirodontinae: Compsura heterura Eigenmann, 1915 (n= 452), Serrapinnus heterodon (Eigenmann, 1915) (n= 473), S. piaba (Lutken, 1875) (n= 509) and Serrapinnus sp. A (n= 313). The specimens were collected monthly, from April 2001 to April 2002, using seine nets. The stomach contents were analyzed using the frequency of occurrence, percentage composition and an alimentary importance index. The feeding overlap was calculated through the index of Morisita between pairs of species. The species did not showed seasonal variation in the diet. Algae, vegetal matter, microcrustaceans and autochthonous insects were predominant in the species diet. Serrapinnus heterodon and Serrapinnus sp. A presented omnivorous feeding behaviour, while C. heterura and S. piaba showed omnivorous feeding behaviour with tendency to herbivory. In addition, the species showed high feeding overlap due to the consumption of similar items. These results suggest that food resources are abundant and enough to be partioned by these four omnivorous sympatric species.

Biologia populacional de Pachyurus bonariensis Steindachner, 1879 (Perciformes, Sciaenidae), uma espécie alóctone no sistema hidrográfico da laguna dos patos, Brasil

The genus Pachyurus is widely distributed in the large hydrographic systems of South America, being represented only by Pachyurus bonariensis in the southern portion of the continent, in the La Plata drainage (Uruguay, Parana and Paraguay rivers). The occurrence of this species is recent in the Laguna dos Patos system, and most aspects about population biology and distribution of P. bonariensis for this region are unknown. Abundance, constancy of occurrence, sexual dimorphism and sex ratio were analyzed for the species. The establishment of this species in the Laguna dos Patos system is discussed. One hundred and one specimens (82 females, 15 males and four immature) were captured in the Parque Estadual de Itapua, Rio Grande do Sul State, at Praia das Pombas, Lago Guaiba. The species was constant during the studied period, from June 2002 to July 2003. The abundance was higher in January and April 2003. Females were larger and significantly more abundant than males (c2 = 43.12; p < 0.05). These results and the identification of sexually mature females suggest reproductive activity and indicate that P. bonariensis is an allochthonous species that established a successful population in the Laguna do Patos hydrographic system.