Spermatogenesis in the yellowtail tetra Astyanax altiparanae: a histological analyses with emphasis to spermatogonial and spermatid types

Abstract

This study aimed at the detailed description of the characteristics of the different germ cell types found in Astyanax altiparanae during spermatogenesis. In this purpose, testes from 25 adult male specimens of A. altiparanae were sampled and submitted to the usual techniques of light microscopy. Based on nuclear shape, chromatin condensation, nucleoli quantity and cell size, four spermatogonial types were identified: type A undifferentiated (A_und.*); type A undifferentiated (A_und.); type A differentiated (A_dif.); and type B spermatogonia. Spermatocytes were observed in different phases of meiosis (leptotene/zygotene/pachytene and diplotene), metaphase I and II and secondary spermatocytes, being distinguish mainly by their chromosomal organization inside the nucleus. It was also identified three different types of spermatids, which were named as initial, intermediate and final, which can be differentiated by increase in nuclear condensation and spacing among cells inside the cysts, possibly by flagella arise and reduction in nuclear diameter. Thus, this study contribute to a better understand of spermatogenesis in this and other fish species.