Here’s a twist in the world of marine biology: a baby swell shark has popped up in a Louisiana aquarium tank that only houses female sharks. Named Yoko, the tiny shark hatched in early January, stunning staff at the Shreveport Aquarium.

What makes this birth so baffling? There hasn’t been a male shark in the tank for over three years. So, how did Yoko come to be? Experts are pointing to two possibilities.

First, there’s parthenogenesis, a rare form of asexual reproduction where an embryo develops without fertilization. It’s occasionally seen in sharks and rays, especially when females are isolated from males. Second, there’s delayed fertilization, where sperm is stored for months or even years before an egg is fertilized.

While parthenogenesis has been observed in species like zebra sharks and whitespotted bamboo sharks, scientists are still figuring out what triggers it. “It’s a last-ditch effort for females to pass on their genes,” one researcher noted. As for delayed fertilization, the record stands at a female shark storing sperm for at least 45 months.

The aquarium plans to conduct genetic testing on Yoko once the pup is old enough to determine the exact cause of its birth. “This is incredible and shows the resilience of this species,” said Greg Barrick, the aquarium’s curator.

Whether it’s parthenogenesis or delayed fertilization, one thing’s clear: life always finds a way.