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

Abstract

This study aimed to 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's specimens of A. altiparanae were sampled and submitted to the usual techniques for light microscopy. Based on nuclear shape, chromatin condensation, nucleoli quantity and cell size were identified four spermatogonial types: type A undifferentiated (Aund.*); type A undifferentiated (Aund.); type A differentiated (Adif.); 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. Were 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.Keywords: fish reproduction; germ cells; spermiogenesis; testis morphology ESPERMATOGÊNESE NO LAMBARI-DO-RABO-AMARELO Astyanax altiparanae: UMA ANÁLISE HISTOLÓGICA COM ÊNFASE AOS TIPOS ESPERMATOGONIAIS E ESPERMÁTICO RESUMOO presente estudo teve como objetivo a descrição detalhada dos diferentes tipos de células germinativas encontradas em Astyanax altiparanae durante a espermatogênese. Deste modo, os testículos de 25 espécimes machos e adultos de A. altiparanae foram coletados e submetidos às técnicas usuais para microscopia de luz. Baseado no formato nuclear, condensação da cromatina, quantidade de nucléolos e tamanho celular foram identificados quatro tipos de espermatogônias: indiferenciadas do tipo A (Aund.*); indiferenciadas do tipo A (Aund.); diferenciadas do tipo A (Adif.); e espermatogônia do tipo B. Os espermatócitos foram observados em diferentes fases da meiose (leptóteno/zigóteno, paquíteno e diplóteno), metáfase I e II e espermatócitos secundários, sendo distinguidos principalmente pela organização dos cromossomos nos núcleos. Também foram identificados três diferentes tipos de espermátides, que foram nomeadas como iniciais, intermediárias e finais, que se diferenciaram pelo aumento da compactação nuclear e espaçamento entre as células no cisto, pelo possível surgimento do flagelo, e pelo diâmetro nuclear. Assim, este estudo contribui para um melhor entendimento da espermatogênese nesta e nas demais espécies de peixes.

The efficiency of spermatogenesis and the support capacity of Sertoli cells in Characiformes

“…The types of germ cells in the testicular germinal epithelium of A. altiparanae were morphologically defined [6]. Type A undifferentiated spermatogonia, with nuclear diameter of~8 mm, and the final spermatids at 1 mm were, respectively, the largest and smallest germ cells of the germ cell lineages (Table 1).…”

“…After identification and morphological description of the germ cells present in A. altiparanae spermatogenesis [6], the diameter of the cell nuclei was measured using Motic Images Plus 2.0 software. Nuclei in one-hundred spermatogonia and one-hundred spermatozoa and in 4.500 of each type of spermatocyte and spermatid were measured.…”

“…Much available data regarding the spermatogenesis of A. altiparanae are concerned with morphological aspects [3,6], but interest in morphometric and stereological analysis is increasing [7e10]. Such tools allow elucidation of cellular mechanisms involved in mitotic and meiotic events and the differentiation of germ cells to form hundreds of spermatozoa from a single spermatogonium.…”

Reproductive cycle of the tetra Astyanax bimaculatus (Characiformes: Characidae) collected in Amazonian streams

“…Histology has been used to study reproduction in many fish species such as the tetra Astyanax altiparanae (Rodrigues et al, 2015;Cassel et al, 2017), the Danio Devario aequipinnatus (Chagas et al, 2016; De Jesus-Silva et al, 2018) and some Amazonian species including the Amazonian whitefish Plagioscion squamosissimus (Barbosa et al, 2012) and the 'piranha' Serrasalmus gouldingi (Da Silveira Prudente et al, 2014). This tool is considered one of the most accurate approaches for analyzing reproductive development as it allows the determination of reproductive phases in males and females, defining, for example, time of first maturation, spawning type, reproductive period (Vazzoler, 1996) and fecundity (Mendes et al, 2018).…”

Testicular Structure and Seminal Pathway in the Yellowtail Tetra Astyanax altiparanae (Characiforms: Characidae)

“…Astyanax altiparanae is a tetra species, which presents good livestock characteristics, such as ease of handling, small size, early sexual maturity at 4 months of age and intertidal spawning (Orsi et al., ), which are consolidating it as a fish model in basic studies including the histological evaluation of spermatogenesis (Rodrigues et al., ), morphological characteristics of the testes (Costa et al., ), urogenital papilla (Siqueira‐Silva et al., ), gamete structure and embryonic development (Dos Santos et al., ); and also biotechnological ones, such suppression of spermatogenesis (Siqueira‐Silva et al., ), improvement of semen quality and gametes short‐term storage in laboratory (Yasui et al., ), as a biological indicator (Kida et al., ) among others.…”