Scientists have observed the first known “virgin birth” in crocodiles. A female crocodile, kept alone in captivity for 16 years, laid a clutch of eggs that included a fully formed fetus which was genetically identical to its mother. The find reveals that this unusual form of reproduction is possible in more species than we thought – including, perhaps, dinosaurs.
The maternal miracle occurred in a female American Crocodile that’s lived in a reptile park in Costa Rica since 2002, with no access to mates. But in January 2018, keepers discovered a clutch of 14 eggs in her enclosure, seven of which appeared to be fertile. The team artificially incubated them for three months, but none hatched. On closer inspection, a fully formed, but non-viable fetus was found in one.
The researchers took DNA samples from the mother and fetus and compared them, and found that the fetus was essentially genetically identical to the mother. No DNA from a male was present at all.
This kind of spontaneous self-reproduction is known as facultative parthenogenesis (FP), and while it sounds impossible it’s common in insects like cockroaches and bees, and has been recorded in several vertebrates as well. In 2016 a leopard shark in an Australian aquarium hatched three eggs on her own, and in 2021 endangered Californian condors were also found to do away with males on occasion.
But this is the first known example in a crocodilian, a group that includes crocodiles, alligators and gharials. The implications stretch far beyond that group though. Crocodilians and birds are the last surviving members of a clade of animals known as archosaurs, with their last common ancestor existing some 240 million years ago. So now that FP has been detected in both branches, it’s suspected that the phenomenon is an ancient one and may apply to many more species.
Among them is a pretty notable group – the dinosaurs, which along with the pterosaurs that flew overhead during the same time, are all archosaurs. That suggests that they too may have been able to reproduce without males if the need arose, which sure would have helped “life find a way” to cause chaos in Jurassic Park.
The research was published in the journal Biology Letters.