First ‘virgin birth’ in crocodile found in Costa Rica
Female crocodile lived in isolation at the Costa Rica zoo for about 16 years before producing an egg with a fully formed fetus.
Scientists have documented the first known case of a “virgin birth” by a crocodile, which lived in isolation at a zoo in Costa Rica for about 16 years, according to a new study.
The female crocodile produced a clutch of 14 eggs in her enclosure in 2018, despite not having had contact with males in about 16 years, researchers said.
While egg production has been documented among captive reptiles, the more puzzling fact came after three months of incubation when one of the eggs was found to contain a fully formed stillborn baby crocodile.
“While it is not uncommon for reptiles to lay eggs in captivity given the period of mate isolation, these are normally considered non-viable and discarded,” the study states.
According to the study published Wednesday in the journal Biology Letters, scientists tested the genetic makeup of the crocodile fetus. They found DNA sequences that showed it was a result of facultative parthenogenesis (FP), or reproduction without the genetic contribution of men.
The research paper contains an image of the mother and fully formed stillborn fetus, which tests later revealed to be female.
The FP phenomenon, which some scientists refer to as “virgin birth,” has also been documented in other species of fish, birds, lizards, and snakes. The scientists said this is the first known specimen in a crocodile.
In FP, a woman’s egg can develop into a baby without being fertilized by a man’s sperm.
When making an egg cell, a progenitor cell divides into four cells: one becomes the egg cell and retains major cellular structures and gel-like cytoplasm, while the others contain additional genetic material.
Then one of those cells essentially acts as a sperm cell and fuses with the egg cell to be “fertilized.”
“These findings therefore suggest that eggs should be assessed for possible viability when males are absent,” the study states.
According to one hypothesis, FP is more common in species on the verge of extinction.
The American crocodile, Crocodylus acutus, is considered vulnerable and in danger of extinction in the wild.
The scientists who conducted the study said the “virgin birth” in Costa Rica could lead to new information about crocodile ancestors that roamed the Earth some 250 million years ago in the Triassic Period.
“This discovery provides tantalizing insights into the possible reproductive capabilities of the extinct archosaur relatives of crocodilians and birds, particularly members of Pterosauria and Dinosauria,” the study said.