Sexless reproduction found among sawfish in Florida estuary

Washington, June 2 (IANS/EFE) Some female sawfish living in a Florida estuary have apparently started to reproduce without mating, marking the first case known of parthenogenesis among vertebrates in the wild, the journal Cell Press reported.

Parthenogenesis is common among invertebrates and has been observed only rarely until now among vertebrates in captivity that cannot mate.

Scientists at Stony Brook University, the Florida Fish and Wildlife Conservation Commission and the Field Museum discovered that some sawfish living in a Florida estuary were apparently the offspring of asexual reproduction.

The finding was a surprise to scientists, who were conducting genetic research on the smalltooth sawfish, now listed as an endangered species.

DNA analyses showed that about 3 percent of the fish studied were born via parthenogenesis.

Sawfish might be the first marine species to become extinct due to overfishing and the loss of coastal habitat, researchers said.

Smalltooth sawfish, one of the five species in the family, are mainly found in a handful of locations in southern Florida, including the Caloosahatchee and Peace rivers.

Parthenogenesis happens when an unfertilised egg absorbs a sister cell called the polar body that is nearly genetically identical and starts dividing in a process thought to be triggered by environmental or chemical factors, or electric shocks.

“Occasional parthenogenesis may be much more routine in the wild than previously thought,” said Kevin Feldheim, of the Pritzker Laboratory at The Field Museum in Chicago, where the DNA fingerprinting was conducted.

It is possible that “parthenogenesis is most often expressed in wild vertebrates when the population is at very low levels and the animals have difficulty finding one another,” Andrew Fields, a Ph.D candidate at Stony Brook University’s School of Marine and Atmospheric Science, said.

“Parthenogenesis could help endangered species like sawfish dodge extinction for a little while, but it should also serve as a wake-up call that we need serious global efforts to save these animals,” Fields said.

Leave a Reply