Scientists are in possession of the second pocket shark ever found. However, they've had the tiny shark for years — they just didn't realize it.
The specimen was obtained in 2010 nearly 200 miles off the Louisiana coast during a NOAA mission to study sperm whale feeding. The collected fish were then frozen, and scientists have been sorting through them ever since.
NOAA biologist Mark Grace was part of the 2010 mission, and when he came across the 5 1/2-inch shark, he knew he'd found something different because of the "remarkable pocket gland with its large slit-like external opening located just above the pectoral fin," he wrote.
After collecting a tissue sample and consulting the specimen collection at Tulane University's Biodiversity Research Institute, Grace and his colleagues identified the animal as a recently born male pocket shark.
The only other known pocket shark specimen was found 36 years ago off the coast of Peru.
"Discovering him has us thinking about where mom and dad may be, and how they got to the Gulf," Grace said in a NOAA statement.
Scientists are unsure about the purpose of the shark's unique pocket — which makes up about 4 percent of its body — but they think it might be used to release pheromones.
Little is known about the species, but already Grace and his colleagues have added to the body of research on the pocket shark. When comparing the specimen to the taxonomic description from the previously discovered shark, they found a series of light-emitting glands along its abdomen that weren't previously noted.
Genetic analysis of the shark revealed that the animal is closely related to kitefin and cookie cutter sharks, so it's possible that pocket sharks might also feed by removing an oval plug of flesh from large fish and squid.
More research needs to be done on the fish, but Grace says there’s something remarkable about finding the pocket shark at all.
"This record of such an unusual and extremely rare fish is exciting, but it's also an important reminder that we still have much to learn about the species that inhabit our oceans," he said.
Check out more photos of the rare pocket shark below.
Photos: M. Doosey/Tulane University
Related on MNN: