Ultrastructural analysis of the mature spermatozoon in the copperhead, Agkistrodon contortrix (Linnaeus, 1766)

Abstract

Reptilian sperm morphology studies are continually increasing, and sperm biology is presently being utilized in other areas of study such as sexual selection, evolution, and phylogenetic analysis. The numbers of studies concerning sperm morphology in Squamata, however, are still limited compared to the diversity and number of lizard and snake species and the taxonomic distribution of these studies is widespread and random. Comparisons between closely related taxa are not feasible until further spermatozoal studies investigating designated comparative taxa are completed; therefore, this study aims to add a description of the mature spermatozoa of Agkistrodon contortrix (Linnaeus, 1766) and compare these data to the mature spermatid morphology of its related taxon, Agkistrodon piscivorus (Lacepede, 1789). Although the general architecture of the mature spermatozoa in A. contortrix is consistent with previous reports of mature sperm morphology in snakes, minor differences are noted including the location of the fibrous sheath starting at mitochondrial tier 4, a location that has not yet been reported for snakes. These data further suggest that minute differences in sperm ultrastructure can be observed in closely related taxa and may be beneficial in future phylogenetic and evolutionary analyses.