![]() ![]() However, the fertility of these male snakes was not determined 3, 17. In three other cases, captive female pythons have produced parthenogenetic offspring after having been observed copulating with male conspecifics. Genetic analyses demonstrated that these were comprised of parthenogenetic offspring despite what appeared to be potential mating opportunities 16. After a four year period of isolation she was housed with other male conspecifics during which she produced two litters. A captive Boa constrictor imperator produced a litter through a sexual encounter with a co-housed male B. Only one other published study demonstrates this switch within an individual vertebrate. ![]() A single female eagle ray switched from sexual reproduction to producing a pup asexually less than one year after being separated from the male 9. 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 strategy 9. 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 body 12, although gametic duplication also leads to elevated homozygosity and in most cases cannot be disregarded as the potential mechanism 3. 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 snakes 15 and sawfish 8. 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 accidental 14. 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 lifetime 3, 6. Mammals are an exception as facultative parthenogenesis does not naturally occur in this group due to intracellular processes such as genomic imprinting during gametogenesis 13. 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 rays 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12. Obligate parthenogenesis, where all individuals within a species reproduce asexually, is restricted to the Squamate reptiles 2, 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. ![]()
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