Ultrastructure of the spermatozoon of the Chinese water snake, Myrrophis (Enhydris) chinensis (Reptilia: Homalopsidae)

Identifying the polymorphism of the spermatozoon ultrastructure of squamates is vital for improving the accuracy of phylogenic analyses. Multiple studies have been conducted to distinguish the similarities and differences among the sperms of squamates, but these studies have mainly focused on lizards. Thus, there is a need to update the database of the ultrastructure of snake spermatozoa. Myrrophis chinensis is a protected snake in China because of its economic and scientific value. In this study, we examined the ultrastructure of the M. chinensis epididymal spermatozoon. The ultrastructure of the M. chinensis spermatozoon was found to have the following characteristics: dense collar, multilaminar membranes, extracellular microtubules and extraordinary elongation of the midpiece, all of which are typical sperm characteristics of the synapomorphies of Serpentes. Although no unique trait was identified, the current findings could still provide valuable data for phylogenetic analysis.