Spermatogenic efficiency in the spiny rat, Trinomys moojeni (Rodentia: Echimyidae)

The spiny rat (Trinomys moojeni) is a rodent found in the Atlantic Forest, which is considered one of the most diverse and threatened biomes in the world. Knowledge on reproductive biology and physiology is critical to conservation and species management, allowing the prevention of extinction and the use of males in natural and artificial reproduction programs. The main objectives of the present study were to investigate the testis structure as well as spermatogenic and Sertoli cell efficiency in the spiny rat captured in the Caraça Natural Reserve, a fragment of the Atlantic Forest located in the State of Minas Gerais, Brazil. Ten sexually mature spiny rats were analyzed. Intraperitoneal injections of tritiated thymidine were administered to estimate duration of spermatogenesis. The testes were perfused-fixed in buffered glutaraldehyde and routinely processed for histological and morphometric analyses as well as the characterization of the stages of seminiferous epithelium cycle. Volume density (%) of seminiferous tubules and Leydig cells were 97 +/- 0.3 and 0.3 +/- 0.02, respectively. The duration of one spermatogenic cycle and total duration of spermatogenesis were 8.6 +/- 0.1 and 38.5 +/- 0.5 days, respectively. Due to the very great volume density of the seminiferous tubules, short duration of spermatogenesis, tubule length per gram of testis (approximately 40 m), great Sertoli cell efficiency (approximately 15 spermatids per Sertoli cell) and large number of Sertoli cells per testis gram (53 million), spermatogenic efficiency in the spiny rat (82 million) is by far the greatest of the mammalian species investigated thus far.