Florida Fish Have Babies by 'Virgin Birth'

Smalltooth sawfish stun scientists with offspring
By Neal Colgrass,  Newser Staff
Posted Jun 1, 2015 7:00 PM CDT
Florida Fish Have Babies by 'Virgin Birth'
A sawfish sifting through the sand.   (AP Photo/Rob Griffith)

Looks like female sawfish don't need the guys so much anymore. Scientists have discovered seven examples in Florida of virgin-birth offspring by smalltooth sawfish, an endangered species whose members grow up to 25 feet in length and have long snouts studded with teeth, LiveScience reports. Their offspring may provide the first strong evidence of vertebrates giving birth in the wild by asexual reproduction, or parthenogenesis: "Rare species, like those that are endangered or colonizing a new habitat, may be the ones that are doing it most often," says Demian Chapman, who co-authored a study on the births. "Life finds a way." Asexual reproduction is common among invertebrates, and is increasingly seen among vertebrates (animals with backbones) like the Komodo dragon, sharks, snakes, and some birds—but only those surviving in captivity, until now.

These sawfish offspring have survived in the wild since 2011, National Geographic reports, and they appear to be in good health. Lead study author Andrew Fields says he stumbled on the "virgin seven," which have genes from just one parent, while combing through a database of 190 tagged smalltooth sawfish. So how does "virgin birth" work? First an egg divides, breaking off a sister cell known as a polar body, which has the same set of chromosomes, the Guardian reports; then the sister cell reconnects with the egg, fertilizing it like sperm. An expert says this amounts to inbreeding, which can help purge bad mutations but also robs populations of genetic diversity. Now it remains to be seen whether the seven, all female, can reproduce, scientists say—and whether parthenogenesis is more common in the wild than anyone knew. (Meanwhile, scientists have found a clue as to why males exist.)

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