![]() “We don’t exactly know why they have shorter lifespans,” Feldheim tells Popular Science. Offspring born from parthenogenesis often die young, and the shark pups in this study only survived for a few months. But they did match the female that laid the eggs,” says Kevin Feldheim, a biologist and researcher at the neighboring Field Museum and co-author of the study, in a statement. “These pups didn’t match any of the mature males that were in the enclosure. This showed that they were getting DNA strands from their mother rather than two different parents. They had identical copies of some alleles, or alternative versions of a gene. The pups didn’t have any genetic markers with any of the potential fathers. In 2008, Watson and her colleagues moved a clutch of eggs to a baby shark nursery behind the scenes, where they could safely hatch beyond the limelight of an aquarium tank.Īn analysis of the newly hatched shark pups’ DNA revealed seemingly impossible results. This research focuses on a female zebra shark-a dark fish with yellowish stripes found in the Pacific and Indian Oceans-that lived in Shedd’s Wild Reef exhibition. While previous studies have detailed parthenogenesis in zebra sharks at other aquariums, the report published in December 2022 in the Journal of Fish Biology is another step in understanding why these births happen. One thing that we’ve noticed is sometimes the females are not very receptive to males at certain times, or at all.” “From observing our population for 20 years, we have a long history with them. ![]() “This changes what we think we know about parthenogenesis and why it occurs,” says Lise Watson, assistant director of animal operations and habitats at Shedd Aquarium and a co-author of the study, in reference to the biological phenomenon behind these partner-less births. ![]() This process is usually reserved as a last resort for sharks if there aren’t any mates to go around, but a recent study revealed that female zebra sharks at Shedd Aquarium in Chicago, Illinois, reproduced by themselves, even though there were healthy males in the same enclosure. Through a process called parthenogenesis, some female animals in the order elasmobranch that includes sharks, rays, and skates can fertilize an egg using their own genetic material. While this form of sex isn’t typically associated with reproduction, generating offspring without a partner is common in small, spineless animals like sea stars and stick insects, but it is more rare in vertebrates. The species is capable of parthenogenesis, a process where females give birth without sperm. An adult zebra shark at Shedd Aquarium in Chicago.
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