The female American crocodile laid 14 eggs in 2018 within her
enclosure, a not uncommon phenomenon among captive reptiles. The
more puzzling fact, however, came after three months of
incubation when one egg was found to contain a fully formed
stillborn baby crocodile.
According to the study published in the journal Biology Letters,
scientists tested the crocodile fetus' genetic makeup. They
found DNA sequences showing it was a result of facultative
parthenogenesis (FP), or reproduction without the genetic
contribution of males.
The phenomenon of FP, which some scientists have referred to by
the shorthand of "virgin birth," has also been documented in
other species of fish, birds, lizards and snakes. The scientists
said this is the first-known example in a crocodile.
In FP, a female's egg cell can develop into a baby without being
fertilized by a male's sperm cell.
In making an egg cell, a precursor cell divides into four cells:
one becomes the egg cell and retains key cellular structures and
the gel-like cytoplasm, while the others hold extra genetic
material.
Then, one of those cells essentially acts as a sperm cell and
fuses with the egg to become "fertilized."
The American crocodile is considered vulnerable and at risk of
extinction in the wild. According to one hypothesis, FP may be
more common among species on the verge of extinction, the study
said.
The scientists said the Costa Rica "virgin birth" could lead to
new information about crocodile ancestors that walked the earth
in the Triassic Period some 250 million years ago.
"This discovery offers tantalizing insights into the possible
reproductive capabilities of the extinct archosaurian relatives
of crocodilians and birds, notably members of Pterosauria and
Dinosauria," the study said.
(Reporting by Cassandra Garrison; Editing by David Gregorio)
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