Switch from sexual to parthenogenetic reproduction in a zebra shark

Abstract

Parthenogenesis is a natural form of asexual reproduction in which embryos develop in the absence of fertilisation. Most commonly found in plants and invertebrate organisms, an increasing number of vertebrate species have recently been reported employing this reproductive strategy. Here we use DNA genotyping to report the first demonstration of an intra-individual switch from sexual to parthenogenetic reproduction in a shark species, the zebra shark Stegostoma fasciatum. A co-housed, sexually produced daughter zebra shark also commenced parthenogenetic reproduction at the onset of maturity without any prior mating. The demonstration of parthenogenesis in these two conspecific individuals with different sexual histories provides further support that elasmobranch fishes may flexibly adapt their reproductive strategy to environmental circumstances.

Figure 1. Timeline showing the key events of mating and separation, egg production and embryo development of sexual and parthenogenetic zebra sharks.

F1 refers to the primary mature female and M1 to the mature male. F2 is the sexually produced offspring of F1 and M2.