Canon Elan IIe, tripod 380EX flash off-camera Sigma 105 EX Macro w/ 36mm extension tube Fuji Press 400 f16 at 1/125

Sounds in the night

This odd-looking fellow confused me for a bit, after I caught him in the nearby sound. While the size of my finger, and thus appearing to be a crayfish of some kind, my web research showed that there are no species of saltwater crayfish. I was assuming it to be some small species of lobster, but couldn't locate a match.

Then I stumbled upon the name of 'Pistol Shrimp' (Alpheus heterochaelis), and the illustration matched nicely, especially that big misshapen claw. The amusing part was, I was researching something else, the loud and distinct clicks that would emanate from the tank every once in a while, mostly at night. I had eliminated several different species, and after hearing the same sounds while chasing crabs on snorkel trips, I was trying to determine what species of crab in my tank might be the producer. I never suspected this guy, and my limited knowledge didn't connect the body shape with 'shrimp'.

The loud "snap" that they can produce is done with the claw, and rather than it being by the pincers clacking together, it's actually a pop from water pressure, an example of extreme cavitation. It can also produce a burst of light, though I have yet to see this. But I've felt it, an actual tap on my fingers as I disturbed the shrimp -- the snap seems to be largely for territorial warnings, though the pistol-hammer action of the claw is used to break open shellfish for food. Another image of a Pistol Shrimp can be found here.

Meanwhile, this little bugger is rearranging my tank on a regular basis. The sets of fins he has underneath his tail are amazingly powerful, and he uses them to distribute the sand in my tank (and in the bowl he was photographed within) with the force of a mini leaf-blower.