Female Shark Delays Fertilization for Four Years!

In the longest case ever seen of sperm storage, a female shark at the California Academy of Sciences' Steinhart Aquarium delayed fertilization for an astonishing four years, giving conservationists hope for the future of shark species everywhere, new research shows.

Long-term sperm storage is the ability of a female shark to delay fertilization for months or even years after mating - a phenomenon that scientists have long suspected, but rarely documented in the real world. That is, until now, when an adult brownbanded bamboo shark (Chiloscyllium punctatum) popped out a pup after being isolated from males for nearly 45 months. Experts believe that expecting mothers delay the birth of their offspring to help promote genetic diversity.

"In contrast, asexual reproduction produces offspring with very little genetic variation," researcher Dr. Luiz Rocha said in a press release. "Exploring the bamboo shark's ability to store sperm gives us hope that wild sharks can help protect their population's genetic diversity when mates are scarce and serious threats arise."

While it seems possible that researchers at the Steinhart Aquarium simply made an error, they are highly certain that this is the longest documented case ever of sperm storage. This is because all of the other surrounding sharks in the tank were female, and while there is a male Javanese cownose ray, mating between sharks and rays just isn't plausible.

They were also able to rule out parthenogenesis (a type of asexual reproduction) because the pup displayed less genetic variation compared to its potential bamboo shark mothers.

While the new study results are the first documentation of long-term sperm storage in C. punctatum, this resourceful adaptation has been seen in other sharks, as well as marsupials, insects, and frogs.

"Questions remain," added lead author Moisés A. Bernal. "We know that several species of sharks have reproductive tricks like storing sperm or reproducing by parthenogenesis in the absence of males, but we need to know when and how these alternate techniques are triggered. Understanding these mechanisms - and how they impact genetic diversity - could be vital for the future of shark conservation."

The results were published in the Journal of Fish Biology.

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