A Rare Phenomenon: Scientists Observe the First Documented Virgin Birth in a Crocodile.
By: Alicia Chen
A female crocodile laid a clutch of eggs after being alone for 16 years. When scientists tested the batch, one egg was
Scientists were shocked at this phenomenon and allowed the egg to mature in an incubator. From it hatched one fully developed baby crocodile. Unfortunately, it was deemed stillborn.
This egg was later identified as a parthenogen, resulting from a virgin birth. While this is the first time researchers have seen this happen with a crocodile, it has been observed in other animals such as king cobras, sawfish, and even California condors. Because crocodiles are closely related to dinosaurs and pterosaurs, this suggests they may have also been capable of pathogenesis, which would indicate that the idea behind Jurassic Park was not entirely incorrect.
Virgin births happen when an egg cell inside a female vertebral organism’s body divides repeatedly, creating half the amount of genetic material needed to create another organism. As a byproduct, polar bodies are formed, which are three smaller cellular sacs containing chromosomes. Normally, polar bodies simply wither away. But during parthenogenesis, one polar body combines with the half-formed egg cell to create a final product that is capable of forming life. This process is known as polar body fusion.
An eye-catching sign of polar body fusion is when the tips of the chromosomes found in the offspring (where DNA was shuffled during the formation of the offspring) differ from that of the parent. Dr. Warren Booth, a professor at Virginia Tech, notes that parthenogenesis happens mostly in birds, lizards, and snakes, indicating that they are all descended from a common ancestor. He claims that “what this tells us is it’s very likely that this also happened in pterosaurs and dinosaurs.”
Though many scientists insist that dinosaurs did indeed do it, we wouldn’t have a way to prove it. To ensure that the offspring really is a result of parthenogenesis and not an instance of a female storing sperm for extended periods of up to six years, a DNA test must be performed. We do not have access to the genetic material of dinosaurs, deeming this hypothesis impossible to confirm.
“We’ll never be able to prove that they could do it, but it suggests that they had the ability,” Dr. Booth said.
The reasons behind why animals produce parthenogens remain a mystery, but scientists think that it may be an essential tool for the survival of a species when there are few to no mates available. Though parthenogens are usually unhealthy, they tend to survive long enough to mate and produce healthy offspring. Another theory is that it is simply not harmful enough to be rooted out by evolution.
In 2020, scientists discovered that lizards often lay clutches of eggs with a mixture of normal and parthenogenic eggs. Dr. Booth states, “It’s an ability that can be switched on or off, and it is perhaps controlled by a single gene.”
There are still many uncertainties surrounding parthenogens, but with DNA testing and other modern resources, scientists may be able to unravel this mystery faster than many expect.