The Monterey Bay Aquarium briefly displayed a 189-lb prickly shark yesterday. As reported by the Monterey County Herald, Moss Landing Marine Labs captured the shark in the Monterey Canyon Tuesday night. It was on display for just a few hours Wednesday morning, but was released at 1:30 in the afternoon. The species is found in deep water, and the shark seemed to have trouble regulating its buoyancy in the shallow (and hence low-pressure) tank. When he began floating upside down near the top of the tank, he was quickly yanked out and released back into the ocean.
Sharks don’t have a swim bladder, the gas-filled organ that many fish use to regulate their buoyancy. Instead, they use a combination of a large, fatty liver and dynamic lift (à la airplane wings) from their fins to keep from sinking. Which is actually fortunate for this shark, since fish with swim bladders don’t just get disoriented when brought to the surface: they tend to explode from the pressure change if brought up too quickly.
The prickly shark, Echinorhinus cookei, is named for it’s large denticles, the tooth-like scales that cover the skin of all sharks. These denticles are literally tooth-like, not only in shape, but in composition—they are made of dentine, which makes up the middle layer of our teeth. In fact, there is some conjecture that the first fish teeth (and therefore the first vertebrate teeth) may have evolved from dermal denticles, though this isn’t entirely clear.
The Monterey Herald story is found here.