We studied the relationship between the morphology of the reproductive system and the reproductive strategies of six neotropical catfishes using macroscopic and microscopic analyses. The reproductive system of the examined Siluriformes showed diversified characteristics, but permitted their being grouped according to three reproductive strategies: pelagic spawning, demersal spawning, and internally fertilizing. The pelagic spawners Pseudoplatystoma corruscans and Conorhynchos conirostris have testes that are characterized by filiform lobes, absence of testicular secretion, full-grown oocytes of small diameter, thin zona radiata, and cuboidal follicular cells. Pimelodus maculatus is morphologically distinct from the other two pelagic spawners catfishes due to the presence of testicular secretion. The demersal spawners Lophiosilurus alexandri and Rhinelepis aspera possess homogeneous testicular secretion, large mature oocytes, and columnar follicular cells. The most specialized reproductive system was observed in the internally fertilizing Trachelyopterus galeatus, which possesses a seminal vesicle accessory to the testes, spermatozoa with elongated nuclei that form spermatozeugmata, and a secretory ovarian lamellar epithelium that is associated with sperm storage. The reproductive system observed in Neotropical catfishes showed a relationship associated with the type of fertilization and the reproductive strategies of the six species studied.

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To analyze the reproductive biology of the peacock bass Cichla piquiti, 361 specimens were collected bimonthly in the Itumbiara Reservoir, southeast Brazil, from December 2004 to November 2005. Males and females in reproductive activity occurred during almost the entire year, with reproductive peak occurring before the beginning of the rains when the water temperature remained low, indicating that these environmental variables do not directly influence in the reproduction of C. piquiti. The long reproductive period, partially spent ovaries contained postovulatory follicles and oocytes in all developmental stages, indicate asynchronous development of oocytes and multiple spawning. The mean total length and body weigth were, respectively, 38.2 ± 7 cm and 965.0 ± 654.0 g for males and 37.4 ± 6.1 cm and 899.0 ± 495.0 g for females, statistically showing no sexual dimorphism in size. The smallest male and female found in advanced maturation stage measured 31.0 cm and 29.0 cm of total length, respectively. The body condition (K) of males and females did not present significant differences during the reproductive cycle and the slope (b) of the length-weight relationship was 3.22, suggesting that reproduction and the annual hydrology cycle do not interfere in the health condition. Cichla piquiti is an exotic piscivore fish that is well adapted to this Neotropical reservoir, which exhibits environmental conditions considerably different from its original habitat. This study indicates that the species presents plasticity in reproduction and in allocation of resources, probably due the aseasonality of the reservoir and the exploitation of native species.Para analisar a biologia reprodutiva do tucunaré Cichla piquiti foram coletados bimestralmente 361 exemplares no reservatório de Itumbiara, sudeste do Brasil, no período de dezembro/2004 a novembro/2005. Machos e fêmeas em atividade reprodutiva ocorreram durante quase todo ano, com pico reprodutivo antes do início das chuvas, quando a temperatura da água permanecia ainda baixa, indicando que estas variáveis ambientais não influenciaram diretamente na reprodução de C. piquiti. O longo período reprodutivo, ovários parcialmente desovados contendo folículos pós-ovulatórios e ovócitos em todos os estádios de desenvolvimento, indicaram desenvolvimento assincrônico dos ovócitos e desova múltipla. A média de comprimento total e peso corporal foram, respectivamente, 38,2 ± 7,0 cm e 965,0 ± 654,0 g para machos e 37,4 ± 6,1 cm e 899,0 ± 495,0 g para fêmeas, estatisticamente não mostrando dimorfismo sexual em tamanho. Os menores exemplares, macho e fêmea, capturados no estádio de maturação avançada mediram 31,0 cm e 29,0 cm de comprimento total, respectivamente. O fator de condição (K) de machos e fêmeas não apresentou diferenças significativas durante o ciclo reprodutivo e o coeficiente angular (b) da relação peso-comprimento foi 3,22, sugerindo que a reprodução e o ciclo hidrológico anual não interferem na condição de saúde. Cichla piquiti é um peixe piscívoro exótico que está bem ad...

The morphology of vitellogenic oocytes and the batch fecundity of five tropical forage species belonging to the family Characidae, were studied in 104 late-maturing ovaries. Significant morphological differences between vitellogenic oocytes and ovarian follicles were found. The lowest batch fecundity values were recorded in Hemigrammus marginatus (480 ± 163) and Orthospinus franciscensis (1701 ± 562), which were the smaller species in terms of total length, body weight and oocyte diameter. The highest batch fecundity value was observed in Tetragonopterus chalceus (8384 ± 3944) having the highest GSI and oocyte diameter. Batch fecundity and gonad weight was highly correlated followed by body weight and total length. Relative fecundity was estimated per unit total length, body weight and gonad weight. The wide variation in fecundity observed between the specimens and the species analysed is possibly related to the multiple spawning reproductive strategy of these fishes. Since T. chalceus have higher values of batch and relative fecundity, it is concluded that this species has a higher reproductive potential than the other forage species studied.