Immaculate Epaulette Shark Conception!
November 03, 2023
Female shark pup born through parthenogenesis (without fertilization)
Brookfield, Ill. — On August 23, an epaulette shark pup hatched at Brookfield Zoo. The hatching wasn’t unusual, but what is, is the way the shark embryo developed. The adult female shark had not been housed with a male since arriving at the Zoo in 2019. At that time, she was only 3 years old, and the species reaches sexual maturity around 7 years of age. Under these circumstances, animal care staff believe the female produced a fertile egg without needing to be fertilized by a male’s genetic material. This reproductive process known as parthenogenesis is when an embryo develops from an unfertilized egg cell.
Beginning in 2022, the adult female shark began laying two to four, typically infertile eggs, each month. One of those eggs was fertile, and following a five-month incubation the pup hatched and has been behind the scenes being monitored by staff. Now at 2 months old, the approximately 5- to 6-inch shark can be seen in one of the habitats just inside the Living Coast’s entrance. Epaulette sharks can reach 2½ to 3 feet in length when fully grown.
Parthenogenesis is a natural occurrence in some invertebrates, but less so in complex vertebrates, including sharks. It is believed this is the second Association of Zoos and Aquariums’ accredited facility to report a potential epaulette shark pup produced by an asexual reproduction. The first was at New England Aquarium, where Brookfield Zoo’s adult females originated.
“We are happy to report that our epaulette pup has been eating well on her diet of finely chopped capelin, minced squid tentacles, and other finely chopped seafood. Our colleagues at New England Aquarium have been a great resource as shark pups produced parthenogenetically can be very delicate,” said Mike Masellis, a lead animal care specialist at Brookfield Zoo. “We are looking forward to guests being able to see the pup.”
Epaulette sharks are mostly nocturnal creatures found in warm, relatively shallow waters over sandy bottoms from the southern coast of New Guinea to the northern coast of Australia. The species is able to tolerate extremely low oxygen environments and has been known to “walk” short distances on the seafloor and even land using its muscular pectoral fins. In order to appear larger than it actually is, the epaulette shark has false eyespots behind its head. These eyespots resemble shoulder decorations on uniforms, which is how the species got its name.