WASHINGTON: Scientists have documented in Florida a series of “virgin births,” reproduction without mating, in a critically endangered sawfish species pushed to the brink of extinction by over-fishing and habitat destruction. The scientists said on Monday it marks the first time the phenomenon called parthenogenesis has been seen in a vertebrate in the wild. Some females may be resorting to asexual reproduction because smalltooth sawfish numbers are so low mating opportunities may not exist, they said.
“There have been a number of cases in reptiles, birds and sharks of ‘virgin birth’ in captivity,” Stony Brook University marine biologist Andrew Fields said. “This raises many questions about how common this mode of reproduction is in the wild.”
In parthenogenesis, 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.
The one that eventually becomes the egg cell retains key cellular structures and the gel-like cytoplasm. The other three hold extra genetic material.
In parthenogenesis, one of those cells essentially acts as a sperm cell and fuses with the egg. This “fertilized” egg possesses about half the mother’s genetic diversity, a trait allowing parthenogenesis to be detected through genetic testing.
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