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Odds are even die-hard fans of Shark Week have never heard of the pocket shark, which is so rare one had not been seen for 36 years. That is, until now. The tiny pocket shark, which is the size of a puppy, is extremely rare, but one was found fairly recently in the Gulf of Mexico.
The pocket shark recently found was about 5 and one-half inches in length, Mark Grace of NOAA Fisheries Laboratory in Pascagoula, Miss., reported in a write-up about the find. Grace noted that the male was a newborn, with an unhealed umbilical scar. The discovery had the scientist wondering where the parents may be and, particularly, how the pocket shark got to the Gulf, he added. The last pocket shark seen by humans was a 17-inch female found 36 years ago off of Peru.
The very small and rare species of shark (there are more than 400 known species) has the common name “pocket shark.” It has a scientific name Mollisquamasp., according to the study Grace coauthored and published in the international taxonomy journal Zootaxa. It is part of the same family as dogfish sharks and closely related to the kitefin shark. While it may seem the common name is derived for its size and ability to fit in a pocket, the name was actually attached to the species because it a distinctive opening or orifice just above its pectoral fin that looks like a pocket slit. This is one of creature’s physiological features that scientists are hoping to understand better in the future.
Unfortunately, the baby pocket shark was not swimming in the Gulf when the scientists realized their find. The specimen was collected in a batch of fish gathered in 2010 by the National Oceanic and Atmospheric Administration (NOAA) approximately 190 miles off Louisiana when they were studying sperm whales.
Grace took part in that mission and discovered the shark at the lab three years later when slowly working through the various frozen fish gathered on that trip in the NOAA lab. He knew he had stumbled onto something different when he saw the “pocket gland with its large slit-like external opening located just above the pectoral fin,” according the article.
Grace recruited help in researching his rare find from Tulane University scientists Henry Bart and Michael Doosey, and as well as NOAA’s genetics expert Gavin Naylor. The group examined tissue samples and tapped into the significant specimen collection in Tulane’s Biodiversity Research Institute. They were able to compare data on their new puppy size pocket shark specimen with one found in 1976 near Peru.
One unusual characteristic they found shared between the two specimens, besides the pocket, was a series “ventral abdominal photophore agglomerations” on the shark’s belly. In simple terms, the pocket sharks had light-emitting organs on their undersides. There were other distinctive differences also noted in the specimen, but the scientists are not sure if they exist because the specimens being studied were different sexes or ages.
In a statement, Grace noted that the fact that they found such an unusual and extremely rare fish as the puppy-size pocket shark is exciting. He also pointed out that its unique orifice and belly serve as “an important reminder that we still have much to learn about the species that inhabit our oceans.”
By Dyanne Weiss
Photo courtesy of NOAA/fishwatch.gov