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

Abstract

Although there are almost thirty-thousand species of fish living in a great variety of habitats and utilizing vast reproductive strategies, our knowledge of morphofunctional and quantitative aspects of testis structure and spermatogenesis is still incipient for this group of vertebrates. In this review, we discuss aspects that are important to better understanding of testis structure and function, and of the development of germ cells (GC) during spermatogenesis. To achieve this, we have recently completed a number of studies presenting morphometric and functional data related to the numbers of GC and Sertoli cells (SC) per each type of spermatogenic cyst, the number of spermatogonial generations, the SC efficiency, and the magnitude of GC loss that normally occurs during spermatogenesis. We also investigated SC proliferation and the relationship of this important event to early spermatogenic cysts. The available data strongly suggest that SC proliferation in sexually mature tilapia is the primary factor responsible for the increase in testis size and for determination of the magnitude of sperm production. The influence of temperature on the duration of spermatogenesis in tilapia was also evaluated and we have used this knowledge to deplete endogenous spermatogenesis in this teleost, in order to develop an experimental system for GC transplantation. This exciting technique results in new possibilities for investigation of spermatogenesis and spermatogonial stem cell biology, creating also an entirely new and promising scenario in biotechnology-transgenic animal production and the preservation of the genetic stocks of valuable animals or endangered species.

Can Myxosporean parasites compromise fish and amphibian reproduction?

“…In European sea bass, S. testicularis invokes parasitic castration because of the destruction of both testicular germinal cells and Sertoli cells that are essential for normal spermatogenesis (Nó brega et al 2009). The infection starts with a few trophozoites in the lumen of seminiferous tubules (figure 3g).…”

“…In these cases, previtellogenic oocytes are scattered through the testicular tissue, even inside the tubular lumen, and surrounded by spermatozoa. This phenomenon could be owing to a hormonal dysfunction invoked by the destruction of Sertoli cells, since these cells have been described to have steroidogenic functions in several fish species (Nó brega et al 2009). In sequential hermaphrodite fishes, a possible parasitic influence on the sex allocation of its host has been postulated for the protogynous Thalassoma bifasciatum.…”

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

“…The main testicular function is to keep spermatogenesis, one complex and extremely organized process, in which one initial diploid cells, named spermatogonia, undergo proliferation and differentiation to produce spermatozoa, which are haploid cells (GRIER et al, 1980;NÓBREGA et al, 2009;SCHULZ et al, 2010).…”

“…Didactically, spermatogenesis may be divided in three phases: spermatogonial or proliferative phase in which spermatogonia undergo successive mitotic divisions. This phase is specie-specific; spermatocitary or meiotic phase, in which the genetic material is duplicated, recombined and segregated; and spermiogenic phase, characterized by morphological and physiological changes of spermatids, with variation according the species, to originate the spermatozoa (GRIER et al, 1980;RUSSELL et al, 1990;VERÍSSIMO-SILVEIRA et al, 2006;NÓBREGA et al, 2009;SCHULZ et al, 2010;.…”

Histomorphological Assessment of Spermatogenesis in African Catfish Clarias gariepinus with reference to Spermatogonial Proliferation

“…Germ cell degeneration, accompanied by cellular loss, has been reported during spermatogenesis in fish [13; 3] and in domestic fowl Gallus domesticus [15]. The number of spermatids supported per Sertoli cell is a function of the cellular carrying capacity of the Sertoli cell; viz: 100 in Tilapia and guppy [16] 8-10 in rats and mice [17], and approximately 100 in the domestic fowl, Barred Plymouth Rock [18].…”