Continuous gametogenesis in the neotropical freshwater teleost, Bryconops affinis (Pisces : Characidae)

The gametogenesis of Bryconops affinis was studied by light, transmission a nd scanning electron microscopy. The spermatogenesis is semi-cystic and spe rmatids are released into the lumen of seminiferous tubules, where spermiog enesis is completed. Spermatozoa have an ovoid head, a rudimentary middle p iece with a small number of mitochondria and long flagellum (primitive sper matozoa). The Sertoli and Leydig cells show secretory activity during sperm atogenesis. By the end of this phenomenon, the Sertoli cells phagocytize th e residual spermatozoa, while the Leydig cells show involuted characteristi cs. With regard to the oogenesis process, the oocyte development was divide d into four stages based on the cytological characteristics of the oocyte a nd its surrounding layers. Ultrastructural analysis revealed that the zona pellucida is formed during the previtellogenic stage. Specializations assoc iated to the outer layer of the zona pellucida may be related to the egg's adherence to the substrata. (C) 2001 Harcourt Publishers Ltd.