Spermatogenic cycle of the African sideneck turtle Pelusios castaneus (Schweigger, 1812) (Reptilia: Testudines)

Abstract

We describe the spermatogenic cycle of the African sideneck turtle (Pelusios castaneus) (Reptilia: Testudines). We further classify the pattern of spermatogenesis in the species, generating new comparative baseline data on the spermatogenic cycle of freshwater turtles in the tropics. Seventy-two adult male P. castaneus collected at different times from various river drainages in Ibadan, Nigeria, were used for the study. The average body weight of the turtles was 723 ± 23.36 g while the curved carapace and plastron lengths of the turtles were 24.4 ± 1.47 cm and 15.7 ± 1.23 cm, respectively. Histology of the testis and epididymis, gonadosomatic index, epididymal mass index, seminiferous tubule diameter and epididymal ductal diameter all suggest the postnuptial pattern of spermatogenesis. Sperm production in P. castaneus starts in May and peaks in September. It is thereafter released into the epididymis, and the degree of sperm packing of the epididymis increases from October, reaching its peak in January. Spermatozoa were found in the epididymis of the turtles all through the year. The study shows that the postnuptial pattern of turtle spermatogenesis is not unique to turtles in the temperate regions of the world and that the spermatogenic cycle of P. castaneus is similar to those of other chelonians with minor variations. This report, the first of its kind for a pelomedusid turtle, therefore serves as baseline information for the family in comparative studies of the spermatogenic cycle of turtles.