Shedd’s Wild Reef exhibition includes a massive floor-to-ceiling habitat containing a variety of sharks, including zebra sharks. “By confirming the lineage of the offspring, we could more soundly make decisions on future breeding efforts to maintain maximum genetic diversity while supporting the Association of Zoos and Aquarium’s Species Survival Plan for zebra sharks.” “As we started to see successful breeding of zebra sharks at Shedd in 2004, we also began genetic testing to confirm which of the sharks were the parents of the offspring,” says Lise Watson, assistant director of animal operations and habitats at Shedd Aquarium and an author of the study. The study, published in the Journal of Fish Biology, focuses on endangered zebra sharks at Shedd Aquarium in Chicago. “This latest paper is just another step in learning why these ‘virgin births’ happen.” “We've known for several years that parthenogenesis occurs in animals like sharks, but some aspects of it remain unknown, like why it occurs and what triggers it,” says Kevin Feldheim, a researcher at Chicago’s Field Museum and the study’s corresponding author. However, a recent study revealed an example of a female zebra shark in an aquarium reproducing via parthenogenesis, even though there were healthy, reproductive males in the same enclosure.This finding has implications for not only the continued care of zebra sharks in zoos and aquariums, but also for conservation efforts focused on their wild counterparts. ![]() ![]() A process called parthenogenesis allows some female animals to fertilize an egg with their own genetic material, producing offspring by “virgin birth.” Scientists have assumed that vertebrates that usually reproduce sexually turn to parthenogenesis as a “hail Mary pass,” a last-ditch effort at reproduction when there aren’t enough mates to go around. view moreĪsexual reproduction is common for animals like starfish, deep-sea worms, and stick insects, but among vertebrates, it’s a rarity. "You lose genetic diversity with generations of asexual reproduction, so we'll be seeing if these offspring can mate sexually themselves," Dudgeon said.Image: An adult zebra shark at Shedd Aquarium's Wild Reef exhibit. The species, which is found in the western Pacific and Indian oceans, is listed as endangered on the International Union for Conservation of Nature's (IUCN) Red List of Threatened Species.ĭudgeon plans to monitor Leonie's pups to find out if these asexually produced sharks can have pups of their own with a male partner. If parthenogenesis is indeed an evolutionary adaptation to a lack of suitable mates, that could have implications for the survival of zebra sharks. It might be happening in the wild, but it's never been recorded in this species before." "What we want to know now is, 'Could this occur in the wild?' and, if so, 'How often does it?' One reason why we haven't seen it before could be because we haven't been looking for it. "Leonie adapted to her circumstances, and we believe she switched because she lost her mate," Dudgeon said in a statement. (Scientists have reported similar cases in a boa constrictor and an eagle ray.) ![]() ![]() That makes Leonie one of the rare individuals known to have had babies by sexual reproduction only to switch to asexual reproduction later on. In most of these previous parthenogenesis cases, the females were from captive environments and never had any exposure to male mates during their reproductive prime, Dudgeon and her colleagues wrote.
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