To study the reproductive biology of Moenkhausia intermedia (Eigenmann, 1908) in Itumbiara reservoir, Paranaíba river, Goiás, Brazil, a total of 301 specimens (237 females and 64 males) were captured quaterly from January to December 1993. The gonadosomatic index of females and males were related to morphologic variations of the gonads in different reproductive cycle stages (RCS). Analysis of RCS frequency and variations in the gonadosomatic index showed that M. intermedia reproduces during the whole year with fractional spawning. The smallest standard length at advanced maturity stage was estimated as 6.6 cm for females and 6.0 cm for males. The stomach repletion and coelomic fat indexes of both sexes reached peak values in the rest stage, suggesting that this species probably store energy in this phase and consume its fat reserve during reproduction. In the Itumbiara reservoir there was female predominance (4:1). Males were smaller than females, indicating sexual dimorphism in M. intermedia.
Para estudar a biologia reprodutiva de Moenkhausia intermedia (Eigenmann, 1908) no reservatório de Itumbiara, Goiás, Brasil, capturaram-se, trimestralmente, no período de janeiro a dezembro de 1993, 301 exemplares, sendo 237 fêmeas e 64 machos. O índice gonadossomático de fêmeas e machos acompanhou as variações morfológicas das gônadas nos diferentes estádios de maturação. Através da distribuição de freqüência dos estádios de maturação gonadal e das variações do índice gonadossomático constatou-se que M. intermedia reproduz o ano todo com desova do tipo parcelado. O comprimento padrão de primeira maturação sexual foi estimado em 6,6 cm para fêmeas e 6,0 cm para machos. Os índices de repleção estomacal e de gordura celômica foram maiores no estádio de repouso gonadal indicando que os peixes, provavelmente, acumulam energia nessa fase para ser consumida no período reprodutivo. No reservatório de Itumbiara houve predominância de fêmeas de M. intermedia na proporção de 4:1 e estas foram maiores que os machos indicando dimorfismo sexual para a espécie

The morphology of the ovaries and oogenesis of Pimelodella vittata were studied using anatomical and histological techniques to provide information of its reproductive biology. Eighty adult females were captured trimonthly during the period November 2005 to October 2006. The ovaries are paired, saculiform organs, which are coated with tunica albuginea and contain ovigerous lamellae, where the oocytes develop before being released into the ovarian lumen and following the ovarian duct until reaching the genital papilla. Oogenesis was divided into stages based on the alterations to the nucleus, ooplasm and surrounding follicular layers. Oogonia form groups from the germinal epithelium have asynchronous development and differentiate into initial perinucleolar oocytes. The formation of the zona pellucida is initiated in the advanced perinucleolar oocytes reaching a thickness of 1.46±0.58 μm in the vitellogenic oocytes. The follicular cells are squamous in perinucleolar oocytes, become cubical in the pre-vitellogenic oocytes and prismatic in the vitellogenic oocytes with a height of 11.20±4.74 μm. The histochemical reactions indicate that zona pellucida, cortical alveoli and yolk globules contain neutral glycoproteins and the follicular cells contain neutral glycoproteins in association with carboxylated and sulphated glycoconjugates. Statistical analyses showed significant differences in the diameter of the oocytes and follicular cells height as oocytes matured. This study represents the first data about the ovarian structure and oogenesis of this species.

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