Scientists have discovered seven examples in Florida of virgin-birth offspring by a rare breed of fish, known as the smalltooth sawfish. Smalltooth sawfish are critically endangered and grow up to 25 feet in length and have long snouts with studded teeth.
Their offspring may provide the first strong evidence of vertebrates giving birth in the wild by asexual reproduction, or parthenogenesis, USA Today reported.
“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 being seen among vertebrates (animals with backbones) such as the Komodo dragon, sharks, snakes, and some birds – but only those surviving in captivity, up until now.
The virgin-birthed smalltooth sawfish have survived in the wild since 2011, National Geographic reports, and they appear to be in good health. Lead study author Andrew Fields said he stumbled on the “virgin seven,” which have genes from just one parent, while combing through a database of 190 tagged smalltooth sawfish.
How does virgin birth work, one might ask. Frist 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 – similar to 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 all seven female smalltooth sawfish are able to reproduce. This also begs the question of whether parthenogenesis is more common in the wild than anyone knew.
Smalltooth sawfish used to be commonly found across the Atlantic, but now the species has dwindled to as low as one percent of what it was in 1900, leading the species to be classified as “endangered” on the US Endangered Species list.