A female crocodile that had been in captivity and had not mated for 16 years laid eggs, one of which contained a dead embryo.

The egg was hatched by an 18-year-old female American crocodile at Parque Reptilania in January 2018.

The embryo inside was fully formed but stillborn and thus did not hatch.

As the BBC summarizes citing the relevant publication in the Biology Letters of the Royal Society, the genetic analysis that followed confirmed that the crocodile produced the eggs without the participation of any male crocodile.

The discovery offers unique insight into the potential reproductive abilities of extinct relatives of crocodiles and birds, especially members of the Pterosauria and Dinosauria.

Crocodiles and birds are the living descendants of a group of reptiles called archosaurs related to dinosaurs and flying reptiles.

“Parthenogenesis by female vertebrates was previously thought to be rare, but scientists are discovering that it is more common than previously thought. Parthenogenesis has been observed in over 80 vertebrates now, including lizards, snakes, sharks and other species,” notes a study in Biology Letters.

The genetic analysis of the dead crocodile fetus showed that it had practically the same genotype as its mother, essentially being a clone of her.

The dead fetus was found to be more than 99.9% genetically identical to its mother – confirming that it did not have a father.

Although ‘parthenogenesis’ is therefore a mode of reproduction when males are not available, it is not viable as it lacks the genetic variety that two parents provide.

It is worth noting that the hatching of eggs that came from parthenogenesis in other species is particularly low and only reaches 3%.

BBC