In 2010, a group studying potential prey species for sperm whales in the Gulf of Mexico hauled in hundreds of them in a net. Among those 3,500 or so creatures was a teeny, tiny pocket shark, one of the most unusual sharks in the world. Only one similar to it has been found, but that was more than 30 years ago, and scientists have yet to determine definitively if they are the same species.
The five and a half inch pocket shark sat frozen for about three years before Mark Grace, a fisheries researcher for NOAA, came across it in October 2013. "I was down to the last gallon bag. I was in the lab by myself and I just couldn't believe it. I had never seen anything like it or read about one," Grace told Newsweek.
In an effort to identify the animal, Grace brought it to Tulane University, which he described as having a "world class fish collection." There, he worked with Michael Doosey, a biologist at Tulane, to identify the fish. "For Mark not to know what it was, he has been doing this for 25 years, we were surprised," Doosey said.
From there, Tulane called in a shark expert. "We spent a year looking at it and comparing it. There are a lot of rare animals but this is two of two, possibly one of one," Doosey said. "Its anatomy is unlike any other."
Indeed: The pocket shark looks a bit like a tiny sperm whale, which many consider adorable, but has a mighty set of chompers. It also has a literal pocket, an orifice behinds its pectoral fin. So it can fit in a pocket and it has its own pocket.
Because the specimen is so rare, the researchers did not want to dissect it. Instead, they focused on DNA sequencing and CAT scans to learn more about the pocket shark. Gavin Naylor, a biologist specializing in the evolution of sharks and rays who has sequenced more than 10,000 sharks, was sent a small piece of tissue to sequence.
"Sure enough, it was distinct," Naylor recalled. Through sequencing, he was able to determine the pocket shark's relatives. "It's related to a cookie cutter shark. That's a very, very strange shark. It has huge teeth and cuts a cookie shape out of fish. You can find tuna and seals with plugs taken out of them. This little Mollisquama, it has some ferocious jaws and perhaps it can do the same thing," Naylor said, using the pocket shark's scientific name.
Another relative is the Euprotomicroides, better known as a taillight shark. "It is really bizarre. It secretes luminous fluid from its anus. And it is closely related to this little pocket shark, so it looks like it has a gland that secretes something as well. We suspect that it secretes a luminous fluid from its pocket in the same way Euprotomicroides does, but we aren't sure why, perhaps to evade predators with luminous fluid."
Because no one has seen the pocket shark alive—in fact only a handful of people have seen it dead—scientists are unsure whether the pocket secretes anything at all, but it is a reasonable hypothesis, the researchers agree.
There has been so little humans interaction with pocket sharks because they dwell in the depths of the ocean. "We know less about the deep sea than the surface of the moon. There are so many unusual organisms down there," Naylor said. "They may have very specific niches on underwater mountains in which they live, and of course they fit in tiny nooks and crannies."
Because of its difficult-to-reach native environment, this specimen, the better preserved of the two known pocket sharks, has been under serious protection. "I couldn't bring myself to put it in the mail. So I carried it on the plane, even though I'm sure it would have been fine. But there is too much riding on this little shark," Grace said of transporting the shark to New York's American Natural History Museum from Tulane. "I'm not worried about him now that he's in New York. We have been very protective of him."
The pocket shark, which Grace lovingly refers to as "the little troublemaker," had to take an even longer trip for a CAT scan, traveling to France with a post-doctoral student. He survived the trip without incident and made it back safely to the U.S.
From New York, the pocket shark will make a stop at the Smithsonian and then it will return to its rightful home in Louisiana, where he may be dissected for further study.
