Tiny Shrimp Terrorizes Aquarium

Jan. 5, 2001 -- They may be shrimps, but they pack a powerful punch.

The so-called smasher variety of the mantis shrimp attacks by whamming down the lower edge of its dull, calcified claw with such speed, it’s enough to pulverize a snail’s shell, smash out chunks of a rock wall or even break a finger.

Now a smasher mantis shrimp is wreaking havoc in a family exhibit of splash zone species at the Monterey Bay Aquarium in California. Hermit crabs, snails and barnacles, which all help filter algae from the tanks and keep them clean, are disappearing daily by the handful. Two small fire fish also disappeared recently, casting more suspicion on the furtive, 3 ½-inch-long smasher.

First There Were Two

“We’ve seen two, and in November we caught one. So we know there’s one left out there,” says David Snipe, an aquarist at the Monterey aquarium. “It makes a pretty big snapping sound when it’s knocking off the snails or hermit crabs, so we know when it strikes.”

Roy Caldwell, a professor of integrative biology and a mantis shrimp specialist at the University of California at Berkeley has identified the pesky aquarium shrimp as a small variety of a smashing stomatopod. Other stomatopods, known as spearers, attack by using their sharp, formidable claws like blades. These “thumb-splitters” can cut through a person’s finger in milliseconds.

The smasher’s claws may be duller, but Caldwell explains, they’re equally effective — especially when attacking a shelled creature.

“I got a letter from a surgeon once in South Africa who was diving and saw a 10-inch long smasher,” Caldwell recalls. “When he tried to grab it, it so severely damaged his finger that they had to amputate.”

Arrived by Rock

Snipe says the lone mantis shrimp in the Splash Zone exhibit at Monterey Bay Aquarium likely arrived as a hitchhiker early last year within rocks or coral the museum imported from Florida and Figi.

Invasive species, which can attack or use up food resources of native species are a common problem in the wilds of California and other states. But normally, they’re not as much as a problem in the controlled environment of an aquarium. Aquarium workers at Monterey scrub clean any new rocks they introduce to their exhibits, but mantis shrimp can be easy to miss since they make their homes by digging deep holes in the rocks.

“We usually get rid of all unwanted hitchhikers,” says Snipe. “In fact, we pulled off some of the other mantis shrimp, but we just missed these two.”

Unfortunately for Snipe and his colleagues, the smashing mantis shrimp is also known for its cunning. Raymond Bauer, a marine biologist at the University of Louisiana, says the complex behavior of the mantis shrimp suggests the crustacean possesses high intellect. For example, when fighting, the shrimp flips over and curls up its plated, barbed tail. Then it jabs at its foe around the edge of its tail as a fencer might use a shield.

Fast, Fierce and Hard to Catch

Their fighting flair, as well as their ability to swim and scurry about very quickly under and above water, means they’re almost impossible to catch. Even in a small, personal aquarium it can be difficult, says Snipe, so to catch one in the 1,300-gallon tank in Monterey is even more daunting.

“We’re trying to catch it mainly by luck,” explains Snipe. “We have a set of metal tongs and we’ll just grab for it if we see it exposed on a rock.”

Snipe says he and his colleagues are not aggressively hunting for the shrimp since it’s not in an exhibit that’s open for touching by visitors. The shrimp, he says, mainly poses a nuisance since workers have to continually replace the snails, hermit crabs and barnacles that have been smashed to bits.

When and if aquarium workers finally manage to snatch the marauding shrimp, they plan to put it in the same tank where they’re holding the mantis shrimp they snagged last November.

Snipe calls it the “Bad Guy’s Tank.”