First Recorded 'Virgin Birth' in Crocodiles Sheds Light on Evolutionary Origins

Scientists have made a groundbreaking discovery, providing evidence that female crocodiles have the ability to lay eggs without mating, employing a reproductive strategy that may have originated during the era of dinosaurs.

Female American Crocodile Laid Eggs Even Without Mating

In 2018, a female American crocodile (Crocodylus acutus) that had been kept in captivity for 16 years laid a clutch of eggs. According to Live Science, genetic analysis conducted by a team of US scientists has now confirmed that the crocodile produced the eggs through parthenogenesis, commonly known as "virgin births," without any contribution from a male.

Although the eggs did not hatch, this remarkable finding sheds light on the evolutionary history of this unusual reproductive strategy within a new branch of the animal kingdom, indicating its ancient origins.

As per Science Alert, the recent documentation of virgin births in crocodiles and birds has raised the possibility that their ancient relatives, the dinosaurs, could have possessed similar remarkable reproductive abilities.

Crocodiles and birds belong to a group of reptiles called archosaurs, which in the past also included dinosaurs and flying reptiles. By exploring the branches of this evolutionary lineage, scientists are now considering the potential reproductive capabilities of the extinct relatives of crocodiles and birds, particularly the members of the Pterosauria and Dinosauria groups.

The research team, led by evolutionary biologist Warren Booth from Virginia Tech, suggests that this discovery provides intriguing insights into the reproductive potential of the ancient archosaurian relatives, shedding light on a previously unexplored aspect of their evolutionary history.

The observation of clone-like similarity in this case of parthenogenesis, similar to what has been seen in birds, snakes, and lizards, suggests that terminal fusion automixis could be the reproductive mechanism involved.

According to Booth and his team, this indicates that parthenogenesis may have been a trait inherited from a distant common ancestor of these lineages. However, further research is needed to comprehensively explore the distribution and dynamics of facultative parthenogenesis across deeper evolutionary time.

How Virgin Births Happen

The New York Times reported that parthenogenesis occurs when an egg cell fuses with a polar body, resulting in a cell with the necessary chromosomes to form an individual. While parthenogens may not always be the healthiest creatures, it allows species to survive in periods when no mates are available.

The ability to reproduce asexually may give them a chance to produce offspring until a mate becomes available for sexual reproduction, which typically produces stronger offspring. Parthenogenesis may not necessarily be a response to stress or lack of mates but rather a trait that persists because it doesn't have significant drawbacks. It is believed to be controlled by a single gene and can be switched on or off.

Confirming parthenogenesis in dinosaurs and pterosaurs is challenging without DNA analysis, which is not feasible with fossil remains. DNA analysis has helped distinguish parthenogenesis from delayed conception, where females store sperm for an extended period before fertilizing eggs.

The discovery of parthenogenesis in crocodiles hints at the possibility of this reproductive strategy in ancient species, but conclusive evidence is currently unavailable without access to DNA from dinosaurs and pterosaurs.

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