The pocket shark is among the rarest species from the family of sleeper sharks (Dalatiidae). So far a single specimen was discovered in the southeast Pacific Ocean in 1984. The female fish was discovered at a depth of 330 meters (1.083 feet) and it was 40 cm long.
According to the journal Zootaxa scientists have now discovered another pocket shark. It was found together with other fish which were collected in a study conducted in 2010 by the National Oceanic and Atmospheric Administration (NOAA). Unfortunately the fish was found frozen, not swimming in the sea. It took Mark Grace, NOAA biologist and lead author of the study, 3 years to sort through many other frozen fish in order to reach the pocket shark.
Grace described the shark saying it was just five and a half inches long male that was born recently. This made scientists wonder where its parents could be and how they ended up in the Gulf. Gavin Naylor, NOAA genetics expert, analyzed a tissue sample from the sharkd and identified it as the Mollisquama genus.
What made Grace be sure that the fish was an unusual one was the fact that it had a pocket gland and just above the pectoral fin the gland had a large external opening resembling a slit. It is not yet sure what is the purpose of the pocket. However research conducted on similar species point at the fact that it may be used to release pheromones or some sort of glowing fluid. Grace also noted that the tiny shark had on its underside a grouping of organs which emitted light.
According to the research conducted by Naylor the closest relatives which the pocket shark has are the cookie cutter sharks and the kitefin. Just like these secies, the pocket shark does not only feed on whole smaller animals, but also on meat plugs from larger animals.
It is surprising that the fish was not thrown away since the lab freezer lost power a couple of times. When the shark was identified it was shipped to France and New York in order to be examined in high-tech labs so the fish would not get pierced.
Grace commented on this discovery:
“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.”
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