Testis structure, duration of spermatogenesis and daily sperm production in four wild cricetid rodent species (A. cursor, A. montensis, N. lasiurus, and O. nigripes)

Abstract

Although rodents represent approximately 40% of all living mammalian species, our knowledge regarding their reproductive biology is still scarce. Due to their high vulnerability to environmental changes, wild rodents have become beneficial models for ecological studies. Thus, we aimed to comparatively investigate key functional testis parameters in four sexually mature wild rodent species (A. cursor, A. montensis, N. lasiurus, and O. nigripes). These species belong to the Cricetidae family, which is the most diverse family of rodents in South America, with a total of ~120 species in Brazil. The results found for the gonadosomatic index and the sickled sperm head shape observed strongly suggest that the species here evaluated are promiscuous, prolific, and short-lived. The duration of spermatogenesis was relatively short and varied from ~35–40 days. Both the percentage of seminiferous tubules (ST) in the testis parenchyma (~95–97%) and the number of Sertoli cells (SC) (~48–70 million) per testis gram were very high, whereas a fairly good SC efficiency (~8–13 round spermatids per SC) was observed. In comparison to other mammalian species studied, particularly the rodents of the suborder Myomorpha (i.e. hamsters, rats and mice), the rodents herein investigated exhibited very high (~62–80 million) daily sperm production per testis gram. This impressive spermatogenic efficiency resulted mainly from the short duration of spermatogenesis and quite high values found for the ST percentage in the testis and the SC number per testis gram. We expect that the knowledge here obtained will help conservation programs and the proper management of wildlife.

Sexual selection drives the coevolution of male and female reproductive traits in Peromyscus mice

“…birds [Garamszegi et al, 2005], mammals [Cordeiro et al, 2021;Møller, 1989] and insects [Hayward & Gillooly, 2011]), however, it contrasted with our intraspecific results in which only one of the six focal species, P. gossypinus, showed a correlation between testes size and sperm count across males. Notably, we found that variation in both of these traits is greater across than within species, which can make correlations more likely to be detected (Mincey, 2018) and, thus, may account for the differences between our inter-and intraspecific analyses.…”

“…This pattern has been observed in a number of interspecific comparative studies (e.g. in fish [Stockley et al, 1997 ], reptiles [Friesen et al, 2017 ], birds [Garamszegi et al, 2005 ], mammals [Cordeiro et al, 2021 ; Møller, 1989 ] and insects [Hayward & Gillooly, 2011 ]), however, it contrasted with our intraspecific results in which only one of the six focal species, P . gossypinus , showed a correlation between testes size and sperm count across males.…”

Collective cell dynamics and luminal fluid flow in the epididymis: A mechanobiological perspective

“…Studies estimate that 4-8 × 10 7 spermatozoa are produced per gram of testis in mice. 43,44 Considering that the weight of the murine testis is approximately 0.1 g, 45 roughly 5 million spermatozoa are produced per testis per day. As a significant number of spermatozoa are constantly produced at the closed-end of the male reproductive system, they are expelled from the other open-end of the tract.…”

“…Spermatogonial stem cells located in the seminiferous tubules of the testis continuously give rise to spermatozoa after sexual maturation until death. Studies estimate that 4–8 × 10 7 spermatozoa are produced per gram of testis in mice 43,44 . Considering that the weight of the murine testis is approximately 0.1 g, 45 roughly 5 million spermatozoa are produced per testis per day.…”