Karmactive Staff
A baby swell shark named Yoko has appeared at Louisiana’s Shreveport Aquarium under extraordinary circumstances – there hasn’t been a male shark in the tank for over three years. This January birth has marine biologists examining two fascinating possibilities in shark reproduction.
“This situation shows the incredible resilience of this species,” says Greg Barrick, the aquarium’s curator of live animals. The tank houses just two female sharks, making this birth particularly notable for shark reproduction research.
The first possibility is parthenogenesis – a reproductive method where females can create offspring without male involvement. During normal egg production, cells called polar bodies carry half the mother’s genetic material. In parthenogenesis, these polar bodies can actually fertilize the egg.
Kevin Feldheim, who manages the Pritzker Laboratory for Molecular Systematics and Evolution, has studied this phenomenon extensively. “In general, we think parthenogenesis is a last-ditch effort by females to pass on their genes,” he explains. He notes that zebra sharks and whitespotted bamboo sharks have shown this ability, though scientists still don’t fully understand what triggers it.
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The second possibility involves sperm storage – female sharks can store sperm for extended periods. In one shark species, scientists have documented a female storing sperm for at least 45 months. This adaptation helps ensure reproduction even when males are scarce.
Swell sharks, known for puffing up with water when threatened, live along the eastern Pacific coast. While Yoko appears healthy, the aquarium notes that sharks born through unusual reproduction often face extra challenges.
The aquarium plans to run DNA tests once Yoko reaches sufficient size for a safe blood draw. “Should Yoko’s time with us be brief,” the aquarium states, “it will still provide invaluable insights into shark reproduction and conservation.”
This case joins other documented instances of unusual shark births, including a 2022 zebra shark birth at Chicago’s Shedd Aquarium, confirmed as parthenogenesis. These events help scientists better understand how sharks adapt to ensure species survival.
