Report: Swellshark Capable of Asexual Reproduction

Scientists use 12 microsatellites to watch as one captive female swellshark produces five pups without fertilization from a male.

Nov 28, 2016
Joshua A. Krisch

WIKIMEDIA, CITY.AND.COLORA female swellshark living in captivity has given birth to five shark pups through parthogenesis, according to a November 11 study in the Journal of Fish Biology. Researchers at the National Aquarium in Baltimore used 12 genetic markers to confirm that the pups, born in 2014, were produced by the mother alone. The team monitored the gestation and birth via 12 microsatellites. 

Parthogenesis is nothing new in the animal kingdom: growth of embryos without fertilization has been described in every vertebrate class besides mammals, including in a handful of shark species. But this is the first time that asexual reproduction has been observed in a temperate-water shark, indicating that asexual reproduction “may be more widespread than we thought before,” coauthor Alan Henningsen, a research specialist at the National Aquarium, told Hakai Magazine.

Swellsharks tend to hide in reef crevices during the day and display bioflourescence, possibly as a form of camouflage. Perhaps it is not surprising, then, that swellsharks are capable of parthogenesis—an adaptation befitting shy species. Indeed, “the ocean is a big place,” Jennifer Schmidt, a molecular biologist at the Shark Research Institute in New Jersey who was not involved in the study, told Hakai Magazine. “If you’re a girl shark you’re not always necessarily going to find a boy shark.”