Rare Virgin Shark Birth at Brookfield Zoo

A unique and historic event happened at the Brookfield Zoo in August 2023. An epaulette female shark pup was born without fertilization. The shark was conceived through parthenogenesis, a reproductive process that involves an embryo developing from an unfertilized egg cell. 

This is the second known instance of asexual reproduction by a shark at a U.S. facility in recorded history, with the first being at the New England Aquarium. The baby shark’s mom had not encountered a male since arriving at Brookfield in 2019. Upon reaching sexual maturity, the female shark began laying two to four eggs each month starting in 2022, with the fertile egg hatching an epaulette female shark after a five-month incubation period. 

Parthenogenesis, while rare for sharks, is much more common in birds, fish, insects, and reptiles. The adult epaulette female sharks at Brookfield came from the New England Aquarium, and the Brookfield staff have called on their colleagues in the northeast for their knowledge from the first asexual shark to help care for the new pup. 

The baby shark was kept away from the public eye for two months before being displayed in the zoo’s ‘Living Coasts’ section. It could reach three feet long when fully grown. The shark’s diet consists of finely chopped seafood, including capelin and minced squid tentacles. 

A process called ‘automictic parthenogenesis’ explains how sharks can asexually reproduce. An adult female shark produces an egg along with three polar bodies. Normally, the polar bodies are returned, or reabsorbed, into the female shark. Parthenogenesis happens when one of the polar bodies has the same amount of genetic material as the egg and fertilizes it. 

Photo credit: Jim Schulz/CZS-Brookfield Zoo