Ovogenese in yamú, Brycon siebenthalae (Teleostei: Characidae), in captivity

Abstract

Monthly, during two serial reproductive cycles, were collected and studied ovaries of yamú Brycon siebenthalae, with the purpose of relate the morphological changes and microscopic changes and suggest the maturation scale. The ovary is an organ saccate of the type cistovarie with synchronous oogenesis for groups and spawn total. With an annual cycle of five phases of development of the oocytes, contained in two stages: in the first (of primary growth or pre-vitellogenic), the nuclear-to-cytoplasm ratio decreases, multiple nucleoli appear, visualization of the corpuscle of Balbiani and appearance of the covers membranes (theca, granulose and zone pellucid). The oocytes in this stage were presented along the whole cycle and they constituted the reservation lot (oocyte chromatin nucleoli and oocyte perinucleolari). In the second stage (of secondary growth or vitellogenic), there are engrossments the membranes follicular and quick increase of the cellular size for yolk vesicles deposit. The oocytes recruited for this stage (of the reservation lot), constitute the maturation lot and they are those that ovulated in the following reproduction (oocyte cortical alveoli, oocyte vitellogenic and mature oocyte). A phase of atresic oocyte is recognized. The maturation scale is defined in four stadiums: immature or spent, maturation, mature and regression o spawned.