A single female eagle ray switched from sexual reproduction to producing a pup asexually less than one year after being separated from the male9. The presence of sexually produced litters captured from the same regions and time periods as parthenogenetic offspring suggest that complete isolation from males during a female's reproductive lifetime may not be a requirement or even a driver.Ī recent study on a captive eagle ray Aetobatus narinari suggests that relatively short periods of separation from a potential mate may trigger a shift in reproductive strategy9. This genetic signature in vertebrates is mostly attributed to the mechanism of terminal fusion automixis, the restoration of diploidy by fusion of the egg with a polar body12, although gametic duplication also leads to elevated homozygosity and in most cases cannot be disregarded as the potential mechanism3. Parthenogenetic offspring in these populations were identified among sexually produced offspring based on their unusually high levels of genetic homozygosity. In particular, parthenogenesis has been demonstrated in wild vertebrate populations: pit viper snakes15 and sawfish8. Novel lines of evidence can help elucidate the prevalence and function of parthenogenesis in vertebrates. This raises questions regarding the adaptive strategy of facultative parthenogenesis in these isolated incidences or whether parthenogenesis in most vertebrates is accidental14. Most documented cases of facultative parthenogenesis in vertebrates have been recorded from females in captive environments that have had no exposure to male conspecifics during their entire reproductive lifetime3,6. Mammals are an exception as facultative parthenogenesis does not naturally occur in this group due to intracellular processes such as genomic imprinting during gametogenesis13. Facultative parthenogenesis, the occurrence of asexual reproduction in otherwise sexually producing species, is found more widely across major vertebrate groups including reptiles, birds, bony fish and six species of sharks and rays1,3-12. Obligate parthenogenesis, where all individuals within a species reproduce asexually, is restricted to the Squamate reptiles2'3. ![]() ![]() Occurrences of parthenogenetic reproduction in vertebrate organisms have been increasingly documented (recorded from >0.1% of extant vertebrate species)1. Parthenogenesis is a natural form of asexual reproduction in which embryos develop in the absence of fertilisation. 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. A co-housed, sexually produced daughter zebra shark also commenced parthenogenetic reproduction at the onset of maturity without any prior mating. 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. Most commonly found in plants and invertebrate organisms, an increasing number of vertebrate species have recently been reported employing this reproductive strategy. Dudgeon1, Laura Coulton2, Ren Bone2, Jennifer R. Received: 05 August 2016 Accepted: 28 November 2016 Published: 16 January 2017Ĭhristine L. ![]() Parthenogenetic reproduction in a zebra shark
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |