Tuesday, June 4, 2013

Shark Week: Nurse Shark.

This is a weird shark week. That means we'll be going off the beaten path, looking at sharks you never knew existed. Not every shark can be Jaws, so how about we switch to something more docile, yes?

This is a nurse shark (Ginglymostoma cirratum). Nurse sharks are fond of shallow, warm waters in the Pacific and Atlantic Oceans. They aren't dangerous to humans unless you disturb them, in which case prepare for a nasty bite from thousands of needle teeth. Small stuff on the bottom, be it fish, crustacean, or mollusc, is not so lucky. Their barbs function much like the whiskers on a catfish, meaning that stuff beneath the sand is not safe.

Nobody really knows why these sharks are called nurse sharks. They don't take particularly good care of their (!live) babies. The name could come from the shark's docile nature or how it "nurses" the sea bottom with its mouth, but the most likely explanation is the Old English "hurse," meaning this particular type of bottom-dwelling sea shark. In other words, name change via spell check. We've all been there.

Now, here's a puzzle: How do bottom-dwelling sharks, well, stay on the bottom? Most sharks need to swim constantly to circulate water across their gills.Nurse sharks circulate water by pumping it through their mouths. These sharks do rest a lot, sometimes on top of each other. They can be seen sleeping in masses of up to 30-40 members in one spot, meaning that these are relatively social sharks. How far removed is that from a terrifying great white?

In many ways, nurse sharks are the "Burmese pythons" of the saltwater aquarium trade. People see a cute juvenile, don't think it'll get very big, then wind up with a 10+ foot shark that no tank will hold. Good luck finding a home for a shark; most aquariums will not take them. Please do your homework before taking home any animal, especially a shark!

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