Facultative Parthenogenesis in a Zoo-Held Northern Water Snake, Nerodia sipedon.

Over the past several decades, facultative parthenogenesis (FP)-the ability of a sexually reproducing species to reproduce asexually-in vertebrates has been removed from the realm of obscurity and placed firmly in a position where it warrants focused scientific attention. Likely fueled by increased recognition of the trait, the availability of molecular tools capable of disentangling FP from long-term sperm storage, and the availability of potential cases originating from both zoological and private collections, a wealth of papers has been published revealing the diversity of vertebrate systems in which FP occurs. Specifically, cases have been reported in squamate reptiles (lizards and snakes), crocodiles, birds, and elasmobranch fishes (sharks, rays, and skates). Nonetheless, gaps remain in species documentation, and it is important to analyze and report on new cases. In this paper, we provide a DNA-based analysis confirming FP in a zoo-maintained northern water snake, Nerodia sipedon, a viviparous natricine species that is common and widely distributed in North America. Additionally, we provide information on the sexual development and health of the male parthenogen. Encouragingly, zoological institutions, aquaria, university laboratories, and private collections continue to be rich sources for the further study and documentation of FP in vertebrate species, advancing our understanding of this reproductive trait.