In a groundbreaking discovery, scientists unveiled the first observed instance of a remarkable event known as a “virgin birth” in crocodiles. This extraordinary occurrence took place when a female crocodile, who had been kept isolated for an extended period of 16 years, was found with a batch of eggs.
The particular crocodile involved in this exceptional case is the American crocodile (Crocodylus acutus). At age 2, she was taken into captivity in 2002 and placed in an enclosure within Parque Reptilandia, located in Costa Rica.
For the following 16 years, she remained solitary in her habitat. However, in January 2018, an astonishing discovery was made within her enclosure — 14 eggs had materialized.
Virgin births or facultative parthenogenesis
Virgin births, scientifically referred to as facultative parthenogenesis (FP), pertain to a form of asexual reproduction occurring in species that would normally reproduce through sexual means.
Researchers have previously documented this phenomenon in captive birds, sharks, lizards, snakes, and various other creatures. Intriguingly, until now, no such instances had ever been observed within Crocodilia—the taxonomic order encompassing crocodiles, alligators, caimans, and gharials.
Details of the research
In a research paper released on June 7 in the scientific journal Biology Letters, a group of scientists reported their findings on the eggs laid by the aforementioned crocodile in Costa Rica. Out of the total of 14 eggs, seven were deemed to be capable of developing into viable offspring.
Caretakers at the zoo took charge of these eggs and placed them in an incubation environment. However, despite their best efforts, the eggs did not successfully hatch. Consequently, after a period of three months, the caretakers decided to open the eggs to investigate their contents.
Results of the examination
Upon examination, it was discovered that the contents of six of the eggs were indiscernible, making it impossible to determine their nature or stage of development. However, one egg was found to contain a fetus that was fully formed, but unfortunately incapable of survival.
Through genetic analysis, it was revealed that this fetus was nearly identical to its mother, further supporting the hypothesis of a “virgin birth” scenario.
Crocodile who made herself pregnant identified at a Costa Rica zoo.
She produced a foetus 99.9% genetically identical to herself.
Phenomenon of "virgin birth" found in species of birds, fish & other reptiles never in crocodiles.
Trait might be inherited fm evolutionary ancestor pic.twitter.com/9wt610yzwh
— Rita Rosenfeld (@rheytah) June 7, 2023
The research team, led by Warren Booth, an entomologist from Virginia Tech, expressed their disappointment in the study regarding the unsuccessful hatching of the discovered egg. They noted that it is not uncommon for offspring from “virgin births” to exhibit abnormalities and struggle to survive.
Moreover, the researchers suggested that facultative parthenogenesis (FP) may be more prevalent among species that face the threat of extinction. They proposed that further investigations conducted on wild populations could uncover additional instances of FP.
Additionally, the team highlighted the significance of the crocodile’s virgin birth in terms of evolutionary connections. They emphasized that the discovery of FP occurring in both birds, descendants of dinosaurs, and a crocodilian species, indicates a shared evolutionary origin.
Birds and crocodilians serve as the remaining representatives of archosaurs, a group that also encompassed dinosaurs and pterosaurs. This finding contributes to our understanding of the interconnectedness between these ancient lineages.