Louisiana: A baby swell shark named Yoko has baffled experts after hatching in a Louisiana aquarium where no male sharks were present. The rare birth has sparked excitement and curiosity, with scientists exploring two possible explanations—parthenogenesis or delayed fertilization.
A Shark Birth Without a Father?
Shreveport Aquarium announced that baby shark Yoko was born in early January from an egg laid by one of two female sharks. However, neither female had been in contact with a male for over three years, making the birth a scientific mystery.
Aquarium officials believe there are two possible explanations:
- Parthenogenesis – a rare form of asexual reproduction where an embryo develops from an unfertilized egg.
- Delayed Fertilization – a phenomenon where sperm remains stored in the female’s body for an extended period before fertilization occurs.
The Science Behind Parthenogenesis
Parthenogenesis has been observed in several shark species, including zebra sharks and white-spotted bamboo sharks. In some cases, it even occurs when males are present, but the triggers remain unknown.
Kevin Feldheim, a shark expert from the Pritzker Laboratory, noted that parthenogenesis often occurs when females are isolated from males. He believes it could be a survival strategy to ensure the species continues in extreme conditions.
“We think this is a last-ditch effort by the female to pass on her genes,” Feldheim stated.
Could It Be Delayed Fertilization?
Another possibility is that one of the female sharks stored sperm from a previous mating encounter. Some shark species can retain sperm for years, with one case documenting a female storing sperm for at least 45 months before fertilization. However, little is known about how long this process can last in different species.
DNA Testing Will Reveal the Truth
To determine the true cause of Yoko’s birth, scientists at the Shreveport Aquarium will conduct genetic testing once the pup is old enough. This will confirm whether Yoko was born through parthenogenesis or delayed fertilization.
Greg Barrick, the aquarium’s curator of live animals, expressed excitement over the discovery.
“This situation is incredible and shows the resilience of this species,” Barrick said. “It really proves that life… finds a way.”
With ongoing scientific research, Yoko’s birth may help uncover new insights into the fascinating world of shark reproduction.
