Abstract
The Chinese soft-shelled turtle, Pelodiscus sinensis (Reptilia: Trionychidae) is a typical seasonal breeding species and its spermatogenesis pattern is complex. In this study, the process of sperm cell development was studied using histology. The process of sperm cell development may be divided into six stages based on a combination of different cell types in the seminiferous epithelium. A close examination revealed two patterns of sperm cell development in the seminiferous tubules during the breeding season. The first is a normal sperm cell development pattern, in which the process of sperm cell development and maturation are completed in the seminiferous epithelium without round spermatozoa in the lumen. The second is rapid sperm cell development, in which the first batches of round spermatozoa fall off the seminiferous epithelium before they mature, thus beginning a second batch of sperm cell development. The round sperm cells are shed into the lumen and further mature in the seminiferous tubules and epididymis. This rapid sperm cell development process of the Chinese soft-shelled turtle is rare in other vertebrate species and may be an adaptation to cope with seasonal breeding. The results of this study provide insight into the theory of seasonal reproduction in reptiles.