Recurrent Alternate Parthenogenesis in the Common Smooth-Hound Shark (Mustelus mustelus) with Additional Cases and Further Evidence for a Putative Adaptive Reproductive Strategy

A new case of parthenogenesis in the common smooth-hound shark (Mustelus mustelus), recorded at the Cala Gonone Aquarium (central-eastern Sardinia, Italy) in April 2024, is described as an extension of previous observations. The event involves the production of two offspring originating from a single parthenogenetic reproductive episode, further expanding the available evidence. Genetic analyses excluded paternal contribution, supporting the occurrence of facultative parthenogenesis. The data confirm the recurrence of parthenogenetic reproduction in M. mustelus under captive conditions and document an alternation between two adult females across successive parthenogenetic reproductive events. This recurring pattern supports the hypothesis of a structured reproductive dynamic and suggests the involvement of individual-specific or environmentally mediated factors. These findings contribute to the current understanding of facultative parthenogenesis in elasmobranchs by providing additional empirical evidence across successive reproductive events. The results also offer further insight into the potential adaptive significance of this reproductive mode under conditions of limited mate availability, with implications for the management and conservation of captive populations.