Adult zebra shark at Shedd Aquarium. Credit: © Shedd Aquarium/Brenna Hernandez
The study, released in the Journal of Fish Biology, concentrates on endangered zebra sharks at Shedd Aquarium in Chicago.
” As we began to see effective breeding of zebra sharks at Shedd in 2004, we likewise started hereditary testing to verify 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. “By confirming the family tree of the offspring, we could more peacefully make decisions on future breeding efforts to preserve optimal hereditary variety while supporting the Association of Zoos and Aquariums Species Survival Plan for zebra sharks.”
Shedds Wild Reef exhibition includes a massive floor-to-ceiling environment containing a variety of sharks, including zebra sharks. When the shark puppies hatched, Jean Dubach of Loyola University analyzed the sharks DNA to identify their parentage.
” These puppies didnt match any of the fully grown males that were in the enclosure. However they did match the female that laid the eggs,” says Feldheim.
Juvenile zebra shark at Shedd Aquarium. Credit: © Shedd Aquarium/Brenna Hernandez
In addition to having genetic markers in common with their mom but none of the possible fathers, the puppies had identical homozygous copies of some alleles. Believe back to the genetics unit in your high school biology class. You probably made Punnett square grids with different gene types represented by lowercase and upper letters, like B as the dominant allele for brown eyes and b as the recessive allele for blue eyes. You get one allele from each parent, and if theyre the very same (BB or bb), thats called homozygous.
The hereditary markers utilized in these sharks are more complicated than simply B versus b– they have a lot more alleles, to the point that its virtually difficult that they d reveal up precisely the exact same method in 2 various people. So when the shark puppies DNA results came back homozygous, that meant that they had to be getting both of those DNA strands from their mom, instead of from 2 various moms and dads.
” Discovering these puppies were parthenotes was rather a surprise for the team at Shedd, given our previous success in motivating reproducing through sexual recreation,” states Watson.” This news underscored exactly why routine, continuous genetic testing of offspring is very important.”
Pups born by this kind of “virgin birth” sadly tend to have a short life span, as theyre likelier to have unusual recessive genetic conditions. The shark pups in this research study just endured a couple of months. The truth that they were born at all difficulties enduring ideas in biology.
” This is just the 2nd case that we know of where sharks have been born by parthenogenesis even when there were healthy mates readily available,” says Feldheim; the other circumstances was at the Aquarium of Pacific. “This discovery tosses a wrench in what we believed we understood about how and why parthenogenesis takes place, and it highlights an essential element of science: were continually finding out.”
” This study is just the beginning of our understanding of the incident of this hereditary phenomenon in zebra sharks,” states Watson. “Zoos and fish tanks like Shedd have a key role to play in the conservation of species like zebra sharks, which are nearly extinct in some parts of the world. Understanding more about parthenogenesis and confirming the hereditary makeup of our populations in zoos and fish tank is essential to making informed choices that fuel this work.”
Reference: “Parthenogenesis in an elasmobranch in the presence of conspecific males” by Kevin A. Feldheim, Jean Dubach and Lise Watson, 12 November 2022, Journal of Fish Biology.DOI: 10.1111/ jfb.15268.
Shedds Wild Reef exhibit includes a massive floor-to-ceiling environment containing a range of sharks, consisting of zebra sharks. When the shark puppies hatched, Jean Dubach of Loyola University analyzed the sharks DNA to determine their parentage. The shark puppies in this study just survived a few months.” This research study is simply the beginning of our understanding of the event of this hereditary phenomenon in zebra sharks,” says Watson. “Zoos and fish tanks like Shedd have a crucial role to play in the conservation of species like zebra sharks, which are almost extinct in some parts of the world.
An adult zebra shark at Shedd Aquariums Wild Reef exhibit. Credit: © Shedd Aquarium/Brenna Hernandez
Nonsexual recreation prevails amongst animals such as starfish, deep-sea worms, and stick bugs, but it is a rarity amongst vertebrates. Parthenogenesis is a procedure where particular female animals fertilize an egg with their own hereditary product, leading to offspring through “virgin birth”. Researchers have typically thought that vertebrates that normally replicate sexually only resort to parthenogenesis as a last resort when mating partners are scarce.
Nevertheless, a current study has uncovered a circumstances where a female zebra shark in captivity has reproduced through parthenogenesis, despite the presence of healthy, reproductive males within the exact same enclosure. This discovery has substantial ramifications for the management of zebra sharks in captivity and preservation efforts for their wild counterparts.
” Weve understood for a number of years that parthenogenesis happens in animals like sharks, but some aspects of it remain unidentified, like why it takes place and what triggers it,” says Kevin Feldheim, a researcher at Chicagos Field Museum and the studys matching author. “This latest paper is simply another step in learning why these virgin births take place.”
