Second Ever Pocket Shark Specimen Found

Michael Doosey, Tulane University via Science Daily

In 2010, the National Oceanic and Atmospheric Administration caught and froze a collection of fish off the coast of Louisiana to study the feeding habits of sperm whales. Over the past five years, researchers have been sorting through the specimens and recently found what is essentially a diamond in the frozen fish rough: A five and a half inch long juvenile pocket shark, young enough to still have an unhealed umbilical scar.

"Discovering him has us thinking about where mom and dad may be, and how they got to the Gulf," said Mark Grace of NOAA Fisheries' Pascagoula, Miss., Laboratory, lead author of the new study [PDF].

That's because, before this past week, only one pocket shark had ever been seen by humans—a 15 inch female found 36 years ago off the coast of Peru—so not anywhere near Louisiana. Although the species is roughly pocket-sized, they actually get their common name (scientific name: Mollisquama) from their distinctive pocket gland located just above the pectoral fin. Although scientists aren't sure what the "pocket" is for, they speculate that, based on similar species, it might have something to do with the production or excretion of pheromones in an effort to attract potential mates.

Of course, with this being just the second specimen to be studied, very little is known about the diminutive shark. Scientists do know, based on genetic research, that it is a member of the Dalatiidae species, closely related to the kite shark and the nightmare-inducing cookie cutter shark, which feed by taking bites out of much larger animals. Additionally, it's nearly impossible to compare this newer specimen to the earlier-known pocket shark because scientists lack enough information about the animal to know whether age, habitat, or sex are responsible for any differences between the two.

"Comparisons between the holotype and the Gulf of Mexico Mollisquama specimen are complicated by the possibility of undocumented sexual dimorphism and ontogenic allometry," the study says.

Although the new specimen will help scientists fill in some of the questions surrounding the pocket shark, it also serves as a testament to just how much of the ocean's wide array of life still remains a mystery.