'Mystery' shark pup born at Louisiana aquarium where no males were present
Unlike other sharks that give birth to live young, swell sharks usually release fertilized eggs into the water.
'Mystery' shark pup born at Louisiana aquarium where no males were present
Officials with the Shreveport Aquarium help a swell shark pup hatch from its egg on Jan. 3, 2025. The animal was born in a tank where no males were present for more than 3 years.
Officials with the Shreveport Aquarium recently announced the unusual birth of a swell shark pup in a tank where only two female sharks were present.
Named "Yoko" from the Chumash word "onyoko," meaning "shark," the pup was born on Jan. 3. It hatched out of an egg that was discovered by the aquarium’s husbandry team about eight months ago.
Aquarium officials noted that the two females that were in the tank with Yoko had not had contact with a male swell shark in more than 3 years.
Newborn swell shark pup, Yoko. (Shreveport Aquarium / FOX Weather)
Given that the gestation period of swell sharks is 9-12 months, according to the Aquarium of the Pacific, the math doesn’t add up for the newborn swell shark pup.
Rather, it means that one of two phenomena occurred, officials said. One involves parthenogenesis, a rare form of reproduction without the need for a male, and the other is delayed fertilization, in which fertilization happens well after sharks have mated.
"This situation is incredible and shows the resilience of this species," said Greg Barrick, the curator of Live Animals at Shreveport Aquarium. "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."
Adult swell shark. (Smithsonian Tropical Research Institute / FOX Weather)
The aquarium will determine what happened when Yoko is large enough for a blood draw, allowing the husbandry team to conduct a DNA analysis on the pup.
They noted that sharks born through either parthenogenesis or delayed fertilization tend to "face significant challenges" and live shorter lives. Because of this, Yoko is being closely monitored and kept away from public eyes until it is old enough to move to a larger tank.
Unlike other sharks that give birth to live young, swell sharks usually release fertilized eggs into the water. Sometimes referred to as "mermaid’s purses", the egg cases then attach to features such as rocks or algae, allowing the shark embryo inside to grow and later hatch from the egg.