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 overfishing and habitat destruction.
The scientists on Monday said it marks the first time that the phenomenon called parthenogenesis has been seen in a vertebrate in the wild. Some females may be resorting to asexual reproduction because smalltooth sawfish (Pristis pectinata) numbers are so low that 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, an egg can develop into offspring without being fertilized by a male’s sperm.
The researchers were investigating sawfish inbreeding when they discovered seven young fish, all healthy, born via parthenogenesis, making up about 3 percent of those examined.
“It really surprised us,” said Kevin Feldheim, manager of the Pritzker Laboratory for Molecular Systematics and Evolution at Chicago’s Field Museum. “It is possible that numbers are so low that females have a hard time finding mates. In such a situation, parthenogenesis can be used as a last-ditch effort for a female to pass on her genes.”
Florida Fish and Wildlife Conservation Commission fish biologist Gregg Poulakis said the sawfish came from the Peace and Caloosahatchee rivers, which feed southwest Florida’s Gulf of Mexico Charlotte Harbor estuary system.
Sawfish, a type of ray, have a flattened body and a long, flat snout with pairs of teeth on the side used to find, stun and kill prey. They grow up to 5.5m long.
Their population collapse follows habitat loss and “unintentional” overfishing, being caught in nets targeting other species. They received US federal endangered species protection in 2003.
The research appears in the journal Current Biology.
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