Venom complexity in a pitviper produced by facultative parthenogenesis

Facultative parthenogenesis (FP) is asexual reproduction in plant and animal species that would otherwise reproduce sexually. This process in vertebrates typically results from automictic development (likely terminal fusion) and is phylogenetically widespread. In squamate reptiles and chondrichthyan fishes, FP has been reported to occur in nature and can result in the production of reproductively viable offspring; suggesting that it is of ecological and evolutionary significance. However, terminal fusion automixis is believed to result in near genome-wide reductions in heterozygosity; thus, FP seems likely to affect key phenotypic characters, yet this remains almost completely unstudied. Snake venom is a complex phenotypic character primarily used to subjugate prey and is thus tightly linked to individual fitness. Surprisingly, the composition and function of venom produced by a parthenogenetic pitviper exhibits a high degree of similarity to that of its mother and conspecifics from the same population. Therefore, the apparent loss of allelic diversity caused by FP appears unlikely to have a significant impact on the prey-capturing ability of this snake. Accordingly, the pitviper offspring produced by FP retained complex phenotypic characteristics associated with fitness. This result reinforces the potential ecological and evolutionary importance of FP and questions our understanding of the inheritance of venom-associated genes

Virgin birth in a hammerhead shark

Parthenogenesis has been documented in all major jawed vertebrate lineages except mammals and cartilaginous fishes (class Chondrichthyes: sharks, batoids and chimeras). Reports of captive female sharks giving birth despite being held in the extended absence of males have generally been ascribed to prior matings coupled with long-term sperm storage by the females. Here, we provide the first genetic evidence for chondrichthyan parthenogenesis, involving a hammerhead shark (Sphyrna tiburo). This finding also broadens the known occurrence of a specific type of asexual development (automictic parthenogenesis) among vertebrates, extending recently raised concerns about the potential negative effect of this type of facultative parthenogenesis on the genetic diversity of threatened vertebrate species