Morphometric evaluation of the spermatogenesis in trahira Hoplias malabaricus (Bloch) (Characiformes, Erythrinidae)

Abstract

The Erythrinidae trahira, Hoplias malabaricus (Bloch, 1794), is widespread throughout South America river basins. We determined Sertoli cell supporting capacity (ratio of primary spermatocytes: Sertoli cells and spermatids: Sertoli cells), meiotic index (ratio of spermatids: primary spermatocytes) and the number of spermatogonial mitotic generations of this fish. The fish were captured in the Igarapava reservoir, Grande River, Alto Paraná River basin, Brazil. Testis fragments of three sexually mature trahiras were fixed in 5% buffered glutaraldehyde solution and embedded in glycol methacrylate. Serial sections of 2 and 3 µm in thickness were stained with 0.5% toluidine blue. Histological counts from cysts of primary spermatocytes and spermatids revealed, respectively, 326 ± 99 and 468 ± 73 nuclei of these cells. Sertoli cell supporting capacity was considerably higher for spermatids (113.3 ± 16:1) when compared to primary spermatocytes (71 ± 5:1). Between eight and ten spermatogonial generations were formed to give rise to primary spermatocytes. These values were within the generation range of those already found in freshwater teleosts of external fertilization. Correlation between the number of Sertoli cells and primary spermatocytes per cyst, and Sertoli cells and spermatids per cyst were statistically significant (p < 0.05).

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

“…The reduction in cell numbers is directly related to the support capacity of Sertoli cells and seems to be essential, positively contributing to the quality of the generated spermatozoa [7,9]. A similar observation was reported for H. malabaricus [27].…”

“…This number is species-specific and seems to be related to the phylogenetic position occupied [26]. However, in contrast to the eight spermatogonial generations found in Hoplias malabaricus [27], which belongs to the same order as A. altiparanae, the number of generations in A. altiparanae was the same as that reported for Danio rerio [9] of Cypriniformes, which separated~127 million years ago. Therefore, it is necessary to analyze a larger number of species to infer whether this variation occurs at the specific, family, or order level [26].…”

An overview of functional and stereological evaluation of spermatogenesis and germ cell transplantation in fish

“…Another peculiar characteristic of fish Sertoli cells, in comparison with mammals, is related to the capacity of Sertoli cells to support germ cells (Sertoli cell efficiency). In the few fish species in which this has been investigated, one Sertoli cell is able to support around 100 spermatids, which is approximately ten times higher than in most mammalian species already evaluated (Matta et al 2002;Vilela et al 2003;Schulz et al 2005;Bizzotto and Godinho 2007). This high efficiency is attributed to the ready availability of regulatory factors, and the lower percentage of germ cell apoptosis during spermatogenesis.…”

“…In this regard, stereological investigations have shown there are ten spermatogonial divisions in Anguilliformes, eight in Characiformes, eight or nine in Cypriniformes, six or eight in Salmoniformes, eleven in Gadiformes, seven to ten in Perciformes, ten in Beloniformes, and fourteen in Cyprinodontiformes (Miura 1999;Ando et al 2000;Fishelson 2003;Nóbrega 2003;Vilela et al 2003;Fishelson et al 2006Fishelson et al , 2007Bizzotto and Godinho 2007;Almeida et al 2008).…”

Stereological analysis of spermatogenesis in Brycon orbignyanus (Characiformes: Bryconidae)

“…Sertoli cells are attached to germinal cysts, delimiting them and thus limiting the number of germ cells present in the cyst (Rodrigues et al, 2017). In addition to being responsible for nutrition, they also provide hormonal support (synthesizing steroids, follicle‐stimulating hormone and testosterone; Ando et al, 2000; Schulz et al, 2005) and phagocytization of residues (Bizzoto & Godinho, 2007), this increase was evident across species.…”