‘Virgin births’ found in endangered sawfish species

Chuck Bednar for redOrbit.com – @BednarChuck

A critically endangered species of sawfish has made an extreme adaptation in an attempt to fight off extinction, as scientists reported Monday in the journal Current Biology that female members of the sexually reproducing creatures have been observed giving birth… without having sex.

This marks the first time that living offspring from so-called “virgin births” have been found in a type of creature that usually relies on copulation to sire offspring, Dr. Demian Chapman from the Stony Brook University School of Marine and Atmospheric Sciences and his colleagues reported in their new study.

Previous research that vertebrates could occasionally use a process known as parthenogenesis to reproduce originated from isolated examples of captive birds, sharks, reptiles, and other types of animals. In those instances, the creatures surprised their caretakers by giving birth despite not having an opportunity to mate.

Furthermore, scientists recently reported that two free-living female snakes were both pregnant with a single parthenogen, though it was not certain if those embryos would have survived in the wild, and it remains unclear how frequently this phenomenon occurs naturally.

Save the sawfish

In their new study, the Stony Brook-led team found that vertebrate parthenogens can and do live in the wild by analyzing the DNA of smalltooth sawfish living in the wild in Florida. They found that approximately three percent of those sawfish, which face extinction due to overfishing and coastal habitat loss, were born through this unusual form of reproduction.

In parthenogenesis, a process which is common invertebrates but rare in vertebrates, unfertilized eggs absorb genetically identical sister cells in order to produce offspring with far less genetic diversity of their mothers. As a result, creatures produced in this way are unlike to survive, and the general consensus was that parthenogenesis in vertebrates was an oddity that was unlikely to produce viable offspring, the researchers explained in a statement.

Andrew Fields, the lead author of the study and a Ph. D. candidate at the School of Marine and Atmospheric Science, told redOrbit via email that he and his colleagues were surprised by their findings. “While genetically screening some sawfish samples as part of a monitoring effort,” he said, “we came across these fish which are from parthenogenic, or ‘virgin birth,’ origins.”

“Overall this shows that animals from parthenogensis is not just a weird process which happens in an aquarium, but actually in nature as well… Never before have we seen a free-living individual in the wild. Therefore, it is possible that this happens in more species be we just haven’t been looking for it. We certainly were not,” Fields continued.

He concluded that that he hoped their research would help “inspire conservation action for sawfish,” as the creatures are “on the brink of extinction thanks to humans.” Likewise, Kevin Feldheim of the Field Museum of Chicago’s Pritzker Laboratory, where the DNA was analyzed, said the research “should serve as a wake-up call that we need serious global efforts to save these animals.”

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