14 DAY TRIAL // Some time ago, a shark living in captivity at the aquarium managed by the California Academy of Sciences laid an egg from which, following a normal incubation period, a perfectly healthy pup emerged to greet crowds.
Under any other circumstances, the birth of this brownbanded bamboo shark pup would have gone unnoticed. The reason its arrival is now making headlines is that the egg from which the baby shark was born was years in the making.
That's right, it appears that the female shark that laid the egg had last mated nearly 4 years before it finally mustered up the courage to actually become a mom. Wildlife researchers say that, during this time, the shark simply stored the male gametes in its body.
The birth of the shark pup was kind of, sort of miraculous
In a paper in the Journal of Fish Biology, biologists with the California Academy of Sciences in the US explain that the brownbanded bamboo shark in question was born back in January 2012 from an egg collected from the aquarium’s Shark Lagoon exhibit and placed in a controlled environment.
Seeing how the egg came from a tank populated solely by female brownbanded bamboo sharks and a male belonging to an entirely different species, i.e. a Javanese cownose ray, the birth of this little fellow took biologists quite by surprise, and rightfully so.
“It’s highly unlikely that the bamboo sharks mated with another individual in the aquarium. All the other sharks in the Lagoon are female. There is one male Javanese cownose ray, but mating between sharks and rays is only a very remote possibility,” says researcher Moisés A. Bernal.
Having carried out a series of tests, biologists identified the shark pup's mother to be one of three females that had last enjoyed the perks of a heated love affair in 2007, when living at the Aquarium of the Pacific in Southern California. The identity of the pup's father remains a mystery.
Why female sharks sometimes store male gametes
Wildlife researchers say that the reason female sharks sometimes choose to store male gametes for later use rather than immediately let them to fertilize their eggs is that this helps promote genetic diversity and makes it possible for them to deliver a new generation even in the absence of a male.
Admittedly, some shark species are known to be able to produce pups without having to mate at all, a phenomenon dubbed parthenogenesis, but the fact of the matter is that, when it comes to having babies, mixing and matching genetic information coming from two distinct individuals works best.
“Long-term sperm storage – where a female can delay fertilization for months or even years after mating – is a remarkable adaptation that helps promote genetic diversity. In contrast, asexual reproduction produces offspring with very little genetic variation,” said Dr. Luiz Rocha.
Interestingly enough, word has it that the pup born in January 2012 at the California Academy of Sciences' Steinhart Aquarium represents the longest case of male gametes storage thus far documented in any species of sharks.