Who needs a mate? Sawfish are cheating extinction with ‘virgin births’

Scientists say a series of “virgin births”, reproduction without mating, in a critically endangered Florida sawfish species marks the first time the phenomenon has been seen in a vertebrate in the wild. The researchers say the female smalltooth sawfish are resorting to asexual reproduction because their numbers are so low mating opportunities are fewer. They have been pushed to the brink of extinction by over-fishing and habitat destruction. In parthenogenesis, a female’s egg cell can develop into a baby without being fertilised by a male’s sperm cell.

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.

Kevin Feldheim, Pritzker Laboratory for Molecular Systematics and Evolution at Chicago’s Field Museum

In parthenogenesis, a female’s egg cell can develop into a baby without being fertilised by a male’s sperm cell. This “fertilised” egg retains about half the mother’s genetic diversity, a trait allowing parthenogenesis to be traced through genetic testing. The researchers were investigating sawfish inbreeding when they discovered seven, all healthy, born via parthenogenesis. The 'virgin birth’ sawfish amounted to about 3% of all those examined. The sawfish - which grow up to 5.5 metres long - dwell in southwest Florida estuaries and ocean coastal habitats.

Science Sawfish