Scientists have discovered the first case of a crocodile producing offspring without mating.
A female American crocodile that had been isolated for 16 years in a reptile park in Costa Rica laid a clutch of 14 eggs, one of which contained a fully-formed but non-viable fetus.
Genetic analysis showed the fetus was almost identical to the mother, indicating a type of asexual reproduction known as facultative parthenogenesis (FP), in which embryos grow from unfertilized eggs.
The phenomenon has been widely observed in animals like snakes and bees, but researchers say this is the first time the reproductive strategy has been found in a crocodilian – a group of reptiles that includes crocodiles, alligators and gharials.
They hope the discovery will help shed light on why parthenogenesis can be suddenly triggered in some animals, and if it could be a widespread ancestral trait.
“It’s not clear why some animals make the switch, but it is thought to be “a response to when all else fails”” said Warren Booth, an associate professor of urban entomology at Virginia Tech in the US and lead author of the study.
He said that FP may be more common in species on the brink of extinction, and may be triggered by environmental or physiological stressors.
But he also suggested that FP may be an ancient ability that can be switched on when sexual reproduction fails.
Crocodiles are part of the archosaurs, the group that also includes dinosaurs and pterosaurs.
“The archosaurs started with crocodiles and they evolved through different things until we finally saw the evolution of birds within that lineage,” Dr Booth said.
He said that the discovery of FP in a crocodile implies that these extinct animals may have also been capable of parthenogenesis.
“This new evidence offers tantalizing insights into the possible reproductive capabilities of extinct archosaurian relatives of crocodilians, notably the Pterosauria and Dinosauria,” he wrote in the journal Biology Letters.
The finding could also have implications for conservation efforts, as FP could affect the genetic diversity and viability of endangered populations.
Dr Booth said that more research is needed to understand how common FP is among crocodilians, and what factors trigger it. He also said that he would like to test fossilized dinosaur eggs for signs of parthenogenesis.
– ‘Virgin birth’ recorded in crocodile for 1st time ever, Live Science, 6 June 2023
– Scientists Discover a Virgin Birth in a Crocodile, The New York Times, 6 June 2023
– The first ‘virgin birth’ in crocodiles has been discovered, but what triggers some animals to go it alone?, ABC News, 7 June 2023