Spermatogenesis is seasonal in the large hairy armadillo, Chaetophractus villosus (Dasypodidae, Xenarthra, Mammalia)

Abstract

Very little is known about the distinct reproductive biology of armadillos. Very few studies have investigated armadillo spermatogenesis, with data available only for Euphractus sexcinctus and Dasypus novemcinctus. In the present study, we analysed male germ cell differentiation in the large hairy armadillo Chaetophractus villosus throughout the year, describing a cycle of the seminiferous epithelium made of eight different stages. Evaluation of the testis/body mass ratio, analysis of the architecture of the seminiferous epithelium and the frequency of defective seminiferous tubules allowed identification of a temporal interruption of spermatogenesis during the period between mid-May to July (mid-end autumn) in correlation with very low testosterone levels. Overall, these results suggest that spermatogenesis is seasonal in C. villosus.

Testicular histomorphometry and the proliferative and apoptotic activities of the seminiferous epithelium in Syrian hamster (Mesocricetus auratus) during regression owing to short photoperiod

“…In animals in which tubular sections have been observed in spermatocyte arrest, as in Syrian hamster, only parameters such as tubular thickness (Simeunovic et al, 2000) or variations in the epithelial, tubular, and interstitial areas (Velez et al, 2010) have been studied, although semiquantitatively. All this also applies to mammals and birds in which epithelial atrophy is stronger (Pelletier, 1986;Madekurozwa et al, 2002;Sch€ on et al, 2004;Blottner et al, 2006;Islam et al, 2010;Ara ujo et al, 2013;Luaces et al, 2013). However, these partial results are consistent with those obtained in our work for the final stage of testicular regression.…”

“…Another strategy is spermatogenesis arrest, when tubular sections with spermatogonia and spermatocytes can be observed microscopically, as in deer (Sch€ on et al, 2004), black bear (Tsubota et al, 1997), bank vole (T€ ahk€ a et al, 1997), prairie dog (Foreman, 1997) ( Barnes et al, 1986), or brown hare (Simeunovic et al, 2000). Finally, a third strategy is the much earlier arrest of spermatogenesis, when tubular sections with only spermatogonia and Sertoli cells are observed, as with the hairy armadillo (Luaces et al, 2013), mink (Pelletier, 1986;Blottner et al, 2006) or yellowish myotis (Ara ujo et al, 2013). This third strategy also occurs in birds such as ostrich (Madekurozwa et al, 2002) or jungle crow (Islam et al, 2010).…”

Circannual Testis Changes in Seasonally Breeding Mammals

“…Contrarily, in other species, the regressed seminiferous tubules contain only Sertoli and spermatogonial cells, showing complete absence of meiosis onset in the inactive period. This is true for the white-footed mouse, Peromyscus leucopus [Young et al, 1999], the European starling, Sturnus vulgaris , and the large hairy armadillo, Chaetophractus villosus [Luaces et al, 2013[Luaces et al, , 2014.…”

“…The process of testis regression has been comprehensively studied, including morphological (with both light and electron microscopy), hormonal, ultrastructural, molecular, and functional analyses in 2 mammalian species, the Iberian mole [Dadhich et al, 2010[Dadhich et al, , 2013 and the large hairy armadillo [Luaces et al, 2013[Luaces et al, , 2014. In the mole, a new mechanism of testis regression was reported based on massive desquamation (sloughing, exfoliation) of live, non-apoptotic meiotic and post-meiotic germ cells, which are eliminated through the epididymis and the urethra of males undergoing testis regression ( fig.…”

“…In some species, spermatogenesis is completely arrested, and the animals are unable to breed for several months. This occurs in a variety of species, including hamsters [Bex and Bartke, 1977], deer [Brown et al, 1979;Clarke et al, 1995], brown bears [Tsubota et al, 1997], moles [Dadhich et al, 2010[Dadhich et al, , 2013, and armadillos [Luaces et al, 2013[Luaces et al, , 2014.In mammals, reproduction is a complex feature that is induced and controlled by the hypothalamus-pituitarygonad axis (HPG). The hypothalamic neurons release the decapeptide GnRH (gonadotropin-releasing hormone) in the portal venous system, which in turn causes the release of gonadotrophic hormones LH (luteinizing hormone) and FSH (follicle stimulating hormone) in the anterior pituitary (hypophysis), which activates spermatogenesis and the production of gonadal steroids [Hayes et…”