A shark pup was born in an all-female aquarium tank. How exactly could that happen?
“This situation is incredible and shows the resilience of this species,” Greg Barrick, curator of live animals at Shreveport Aquarium, said.
A Louisiana aquarium welcomed a new baby shark to its facilities earlier this month, but staff are unsure of exactly where it came from.
On Jan. 3, a swell shark egg hatched at Shreveport Aquarium in Shreveport, Louisiana. The egg was discovered by aquarium staff in a female shark tank about eight months ago, but it may have remained undetected for a month or two before, according to a news release.
What makes the egg's discovery puzzling is that no male sharks reside in the female tank. Furthermore, aquarium staff determined that the two female sharks in the tank with the egg hadn't been in contact with a male since 2014, according to a news release.
So how does a shark egg appear, seemingly out of the blue? Here's what aquarium staff think.
How was the shark egg produced?
There are two possibilities for how the swell shark may have come to be, aquarium staff said.
First, the egg may have been a result of parthenogenesis, a rare form of asexual reproduction.
While asexual reproduction is common among many plants and invertebrates, parthenogenesis, in which an egg develops, is more rare in vertebrates. And scientists are still unsure of exactly why it happens. One hypothesis is parthenogenesis occurs when females lack a male presence, according to the Smithsonian National Museum of Natural History.
Aquarium staff have also predicted that the baby shark was a result of delayed fertilization, where fertilization occurs long after mating. However, because the female and male sharks have been without contact for more than a decade, this seems unlikely, Barrick said.
The current record for delayed fertilization is held by a bamboo shark that was delayed for 45 months, Barrick added.
To confirm the exact cause, aquarium staff will take a blood draw of the baby shark, when it's old enough, to analyze its DNA, according to a news release.
“This situation is incredible and shows the resilience of this species,” Greg Barrick, curator of live animals at Shreveport Aquarium, said in a news release. “We are very excited in the coming months to confirm whether this was indeed a case of parthenogenesis or if it was delayed fertilization. It really proves that life ... uh ... finds a way.”
Baby swell shark is named Yoko
Aquarium staff named the baby swell shark Yoko after the Chumash word for shark, "onyoko," according to a news release.
As aquarium staff continue to study Yoko, the baby shark will remain monitored outside of a public exhibit.
Young sharks born through rare reproductive events often face significant challenges.
While asexual reproduction can be good for rapidly reproducing organisms, it's not ideal for organisms with long reproductive cycles like sharks, as it stunts genetic diversity, according to the Smithsonian National Museum of Natural History.
What is a swell shark?
Swell sharks are native to the eastern Pacific Ocean and are known for their agility to swell their bodies with water or air to deter predators.
Remembering Charlotte stingray
Due to its rarity, asexual reproduction discovered in animals often makes headlines, but sometimes, predictions are made too early.
In late 2023, The Aquarium and Shark Lab by Team Ecco in Hendersonville, North Carolina made waves when it announced that a stingray named Charlotte was pregnant, despite it being the only female stingray in its enclosure.
But after about six months of sharing the news, the now defunct organization said Charlotte wasn't actually pregnant. Rather, she had a "a rare reproductive disease that has negatively impacted her reproductive system."
Initially, Team Ecco thought Charlotte may have experienced parthenogenesis or was a part of a "stingray-shark hybrid," because she resided with male sharks, but these theories were all debunked. It is biologically impossible for stingrays and sharks to cross-match and Charlotte's reported gestation period was too long for the species. Typically, stingrays are pregnant for four to five months, but Charlotte would have been about four months overdue, dependent on the timeline shared by Team Ecco.
Sadly, Charlotte the stingray died in June 2024, not long after her reproductive disease was announced.
Contributing: Mary Walrath-Holdridge, Paste BN
This story was updated to add new information.
Greta Cross is a national trending reporter at Paste BN. Follow her on X and Instagram @gretalcross. Story idea? Email her at gcross@usatoday.com.