Ultrastructure of spermatogenesis and spermatozoa in agoutis during sexual development

Abstract

The aim was to study the ultrastructure of testicular parenchyma and define the morphological ultrastructure of spermatozoa of agoutis kept in captivity. Segments of testes from eight agouti males at prepubescence, prepuberty, pubescence and sexual maturity were fixed in glutaraldehyde. Laboratory procedures were performed for transmission electron microscopy. Spermatogonial cells of Type A - pale, Type A - dark, intermediate and Type B were found. Spermatocytes in the pachytene phase were abundant among primary spermatocytes. From the prepubertal phase, Sertoli cells exhibited invaginations in the nuclear membrane and lipid inclusions in the cytoplasm due to their phagocytic function. Leydig cells displayed higher metabolic activity during puberty as evidenced by the presence of lipid droplets. Spermatozoa were fully formed morphologically at prepuberty. The centriolar complex had partially degenerated and featured a centriolar space as in rodents. Sperm heads were tapered, without prominence of the acrosome or evidence of the perforatorium, differing from cavies, rats and mice. This is the first study to describe the ultrastructure of agouti spermatozoa. This research may assist as a basis for future work related to fertility and other biotechnologies applied to reproductive biology in agoutis.

Reproduction in agouti (Dasyprocta spp.): A review of reproductive physiology for developing assisted reproductive techniques

“…3). Sperm head is tapered, without prominence of the acrosome or evidence of the perforatorium (Arroyo et al, 2017). Likewise, it has been reported that the base of the head is symmetric and the tail is extended and sharpened (Mollineau et al, 2006;Ferraz et al, 2009).…”

“…Regarding reproductive development in males, Costa et al (2010) observed that the spermatogenic cycle lasts for 9.5 ± 0.03 days, and the total duration of spermatogenesis is 42.8 ± 0.16 days. According to Assis Neto et al (2003a), the period from birth to five months comprises the pre-pubertal period, in which the presence of gonocytes is observed with the absence of tubular lumen in the testicular cords as well as the presence of spermatogonia, spermatocytes, spermatids, Sertoli and Leydig cells (Arroyo et al, 2017); from six to eight months of age is the transition phase (pre-puberty to puberty), in which 40% to 90% of the testicular cords are in the process of tubular lumination, coinciding with the appearance of the first primary spermatocytes and rounded spermatids. Puberty in male agouti is established at around the age of nine months, where it is possible to observe the presence of all cell types and spermatozoa in the testicular lumen after eight stages of the cycle of the seminiferous epithelium (Assis Neto et al, 2003b).…”

“…Puberty in male agouti is established at around the age of nine months, where it is possible to observe the presence of all cell types and spermatozoa in the testicular lumen after eight stages of the cycle of the seminiferous epithelium (Assis Neto et al, 2003b). According to Arroyo et al, (2017), the main changes in the testis of agouti (Dasyprocta spp.) occur between the prepubescent and prepubertal periods, when the germinal epithelial organization occurs and the Sertoli cells undergo morphological and functional changes to form the spermatozoa.…”

Ultrastructure of the spermatozoon of the Chinese water snake, Myrrophis (Enhydris) chinensis (Reptilia: Homalopsidae)

“…The perforatorium also varies among the spermatozoa of mammals. For example, it is found in rats (Breed 2005) and bats (Beguelinia et al 2011), but not in agoutis (Arroyo et al 2015) or tree shrews (Jeong et al 2006). The endonuclear canal characteristic of mammalian spermatozoa (Jamieson 1995a) is absent.…”

“…The proximal centriole is present in all amniote classes but is absent or degenerated in some therian mammals (Jamieson 1995a;Arroyo et al 2015). The distal centriole extends through the midpiece in turtle, tuatara, crocodilians, and ratites, but it is short in squamates, and vestigial in mammals (Jamieson et al 1997).…”