2023-06-07 15:55:00
“Life always finds a way” said Jeff Golblum in the movie Jurrasic Park and the American crocodile can only confirm this adage. In Costa Rica, scientists have announced the first case of a “single birth” observed in a Crocodylus acutus (American crocodile). Indeed, a female crocodile, in captivity for 16 years, has laid eggs. One of the eggs contained a fetus which was incidentally a female like its mother.
In the study, published Wednesday, June 7, in the journal Biology Letters, researchers said that seven of the 14 eggs produced by the crocodile in Costa Rica were viable. Zookeepers incubated these eggs, but they did not hatch. After three months, they opened the eggs to study them. The contents of six of the eggs were “indiscernible” except for one. The latter contained a fully formed fetus. Genetic analysis showed that he was almost identical to the mother.
Could dinosaurs reproduce by parthenogenesis?
Genetic analyzes later revealed that the crocodile produced these eggs without any male input, in a process called parthenogenesis, which literally means “virgin creation.” Although the eggs didn’t hatch, it’s a stunning discovery in a new branch of the animal kingdom that would show how far back this unusual reproductive strategy might go.
Crocodiles and birds are members of a branch of reptiles called archosaurs which once also included dinosaurs and flying reptiles. Now that “pristine creations” have been documented in crocodiles and birds, findings suggest that their ancient ancestors, the dinosaurs, may have shared this singular reproductive ability.
« Discovery offers tantalizing insight into possible reproductive abilities of extinct archosaur relatives, crocodilians and birds, including members of Pterosauria and Dinosauria“, says the team of researchers led by biologist Warren Booth of Virginia Tech.
Parthenogenesis would be a trait “probably possessed by a common ancestor distant from these lines”. However, further research is needed to “fully test the evolutionary distribution and dynamics (of parthenogenesis) across deeper evolutionary time,” say the Virginia Tech scientists.
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Parthenogenesis: a means of reproduction more present than we thought
Parthenogenesis has been observed in lizards, snakes, birds and now crocodiles. Credit: Biology Letters
Sexual reproduction is the most common mode of reproduction in animals. Unlike parthenogenesis, it involves the meeting of an egg and a sperm, each of which provides half of the genes needed to create a new individual.
Parthenogenesis, on the other hand, is a form of asexual reproduction where female animals that would usually need a male’s sperm to reproduce, can do so without mating. Indeed, females can fuse two of their cells to form a viable embryo that has only one parent.
Once thought to be rare, scientists have realized that parthenogenesis is more common in vertebrate animals than they first thought. The proof with this crocodile.
>> Read also: An unknown prehistoric reptile living with dinosaurs discovered
Crocodiles and many other species
“Virgin creations” have since been observed in more than 80 species of vertebrates, including lizards, snakes, sharks and rays. But mainly in captive animals.
Since then, scientists have begun to find examples of parthenogenesis in some wild animals. This would be a survival strategy that females adopt when they cannot find a male mate, especially in sparse populations and on the verge of extinction, but not only.
A study on captive-bred Californian condors suggested that these critically endangered birds can reproduce independently even when females are in regular contact with perfectly fertile males.
However, pathogenesis does not appear to be a viable long-term solution for creating offspring. The latter would lack genetic diversity, which both parents bring, to perpetuate the species optimally.
Source : LiveScience / Biology Letters / Oxford Academy / Trends in Genetic
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