Shark Pregnancy: Some Species Can Carry Their Babies for Up to 3 Years

If most humans believe nine months is a long time to be pregnant, they should be thankful they are not sharks.

According to a CNN report, Grunge reported that many species of shark have pregnancies that last 11 to 12 months on average.

What's more, this is not even the longest time a single shark can be pregnant, with some species carrying up their babies for up to three years.

The shark with one of those longest gestational periods is the Pacific spiny dogfish, with pregnancies lasting approximately 22 to 24 months.

Shark Pregnancies

As stated in a Monterey Bay Aquarium, this is one of the longest gestational periods as well, of any vertebrate animal.

Nevertheless, some newer studies suggest that sharks like the frilled shark and the basking shark may have even longer periods of pregnancy.

The Government of Canada said, basking sharks are giving birth to live pups after carrying them for two to three years. Meanwhile, frilled shark pregnancies may last three and a half years.

What's even more interesting about shark pregnancies is that sharks can lay eggs or give birth to live pups according to their species.

3 Types of Shark Pregnancies

Essentially, sharks even have eggs yet still get pregnant and give birth to live pups. In fact, marine biologists have defined three types of shark pregnancies which include oviparous, viviparous, and ovoviviparous.

According to How Stuff Works, about one-third of shark species are oviparous and lay eggs, then "leaving them to develop their own in the ocean."

On the other hand, another one-third of shark species, the viviparous, carry a pregnancy and give birth to live pups as most mammals do.

Finally, other sharks, the ovoviviparous, have the most distinctive pregnancies. Such sharks carry their eggs inside their bodies until the shark babies are ready to be born.

The eggs will hatch inside the mother, where she's continuing to carry the pups until they are completely developed and ready to be born.

Some Species Can be Perpetually Pregnant

While the number of eggs or pups a shark can have at one time relies on the species, some sharks can give birth to large numbers in one litter. For instance, the blue shark has litters of 25 to 50 pups, with some litters as massive as 135 pups.

Such sharks are mostly viviparous, carrying all those live pups in them and giving birth to several live pups.

One more impressive shark pregnancy is the short spine spurdog, a common deep-water shark described in Marine and Freshwater Research.

Such sharks can get pregnant immediately following birth through a belt-like conveyor process whereby formed pulses sit at the bottom of the uterus while eggs sit at the top of the uterus waiting for fertilization.

Additionally, according to Oceana, some deep sea sharks, of which the short spine spurdog is one, have a pair of uteruses, which means they can perpetually be pregnant in both uteruses.

Related information about shark reproduction is shown on BlueWorldTV's YouTube video below:

Check out more news and information on Sharks in Science Times.