Endangered Sawfish Virgin Births Reported For First Time

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In the strange but true news for Monday category, researchers are reporting female members of a critically endangered species of sawfish are reproducing in the wild without having sex.

There have been a few earlier accounts that vertebrates might sometimes reproduce via a process called parthenogenesis, but these were largely isolated examples of highly stressed captive animals such as birds, reptiles and sharks.

The unusual discovery of sawfish virgin births was reported in the journal Current Biology on Monday, June 1, and marks the first time living offspring from “virgin births” have been discovered a normally sexually reproducing vertebrate in a natural setting, according to the scientists.

Details on sawfish virgin births (parthenogenesis)

The researchers from Stony Brook University and colleagues from the Priztker Laboratory at the Field Museum of Chicago and Florida Fish and Wildlife Conservation Commission were very surprised to discover that vertebrate parthenogens can and do live in the wild. They determined the sawfish virgin births after undertaking some routine DNA fingerprinting of endangered smalltooth sawfish in a Florida estuary. The DNA analyses suggested that nearly 3% of the sawfish in the populations they studied are “parthenogens”.

Parthenogenesis is not uncommon in invertebrates such as bacteria and worms, but it’s very rare in vertebrates. The current theory on vertebrate parthenogenesis is that it occurs when an unfertilized egg absorbs a genetically identical sister cell. However, the resulting offspring have about half of the genetic diversity of their mothers, and often die immature.

More on sawfish

Small-tooth sawfish are a rare species of sawfish, rays known for their long, jagged “tooth” that they use to subdue smaller fish. Researchers have been worried for some time that sawfish could be the first family of marine animals to go extinct because of overfishing and coastal habitat loss. This species of sawfish is mainly found in a handful of locations in southern Florida today, mainly rural areas of the Caloosahatchee and Peace Rivers.

Statement from lead author of study

“We were conducting routine DNA fingerprinting of the sawfish found in this area in order to see if relatives were often reproducing with relatives due to their small population size,” commented the lead author of the study, Andrew Fields, a PhD student at Stony Brook’s School of Marine and Atmospheric Science. “What the DNA fingerprints told us was altogether more surprising: female sawfish are sometimes reproducing without even mating.”

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