Scientists have announced the first recorded case of a “virgin birth” of a crocodile after the discovery of a female isolated for 16 years with a clutch of eggs. The discovery provides “tantalizing insights” into the trait’s evolutionary origins, potentially shedding light on the reproductive abilities of dinosaurs, according to a new study.
The American Crocodile (Crocodylus acutus) was taken into captivity in 2002 when she was 2 years old and placed in an enclosure at Parque Reptilandia in Costa Rica. She remained alone for the next 16 years. But in January 2018, a clutch of 14 eggs was found in the pen.
Virgin births, also known as facultative parthenogenesis (FP), are a type of asexual reproduction in species that would normally reproduce sexually. Scientists have documented it in birds, sharks, lizards and snakes in captivity, among other species. Until now, it had never been recorded among the Crocodilia – the order that includes crocodiles, alligators, caimans and gharials.
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In a study published Wednesday, June 7 in the journal Biology Letters, the researchers said that seven of the 14 eggs produced by the crocodile in Costa Rica were viable. The zoo keepers incubated these eggs, but they did not hatch, so after three months they opened the eggs. The contents of six of the eggs were “not discernible”, but one contained a fully formed, but non-viable fetus. Genetic analysis showed that he was almost identical to the mother.
The team, led by Warren Booth, a Virginia Tech entomologist, wrote in the study that it was “disappointing” that the egg did not write, but that it is not unusual for offspring born this way to suffer from abnormalities and does not develop. FP, they added, may be more common in species on the brink of extinction, and studies of wild populations may reveal more cases.
They also said that the discovery of a virgin birth in a crocodile means that FP has now been found in both birds, descended from dinosaurs, and a crocodilian, suggesting a common evolutionary origin. Birds and crocodilians are the remaining representatives of archosaurs – the group that also included dinosaurs and pterosaurs.
“This new evidence offers tantalizing insight into the possible reproductive abilities of extinct archosaur relatives of crocodilians, including Pterosauria and Dinosauria,” they wrote.