The first case of a female crocodile reproducing without the help of a male took place at a reptile park in Costa Rica, according to a new study.
The female laid an egg containing a fetus 99.9% genetically identical to her. The phenomenon of the so-called "virgin birth" was observed in species of birds, fish and other reptiles, but never before in crocodiles.
The scientists point out that this trait could be inherited from an evolutionary ancestor, so dinosaurs might also have been able to self-reproduce. The egg was laid by an 18-year-old female American crocodile at Parque Reptilandia in January 2018.
The fetus inside was fully formed but dead, so it did not hatch.
The fetus inside was fully formed but dead, so it did not hatch.
The female who laid the egg arrived at the zoo when she was two years old and stayed away from other crocodiles throughout her life.
For that reason, the park's scientific team contacted scientists from Virginia Polytechnic Institute specializing in virgin births, which is scientifically known as parthenogenesis.
A crocodile coming out of its egg. Photo: Reuters.
The researchers analyzed the fetus and found that it was more than 99.9 percent genetically identical to its mother, confirming that it had no father.
Reasons
It could be that virgin births are more common in crocodiles and have gone unnoticed until now because no instances of them have been sought, note the authors of the study published in the journal Biology Letters of the Royal Society.
It could be that virgin births are more common in crocodiles.
"It's not uncommon for reptiles in captivity to lay clutches of eggs. Given the period of isolation of the pairs, the eggs would normally be considered non-viable and discarded."
"These findings suggest that the potential viability of eggs when males are absent should be assessed," the researchers add.
"Also, since (virgin births) can occur in the presence of potential mates, these cases may be overlooked when reproduction occurs in females cohabiting with males."
It is not clear why parthenogenesis occurs in different species, but cases of this phenomenon are occurring more frequently in the scientific literature, probably because scientists are now looking for them.
One theory is that virgin births occur in species capable of parthenogenesis when the number of individuals declines and the species is on the verge of extinction.
"This new evidence offers tantalizing insights into the possible reproductive capabilities of extinct relatives of crocodiles, especially dinosaurs," the scientists note.