November 23, 2012
Spearing Mantis Shrimp Uses Muscle Power To Attack Enemy
Lee Rannals for redOrbit.com — Your Universe Online
Spearing mantis shrimp must eat plenty of spinach, because scientists have determined it is their muscle power that thrusts them towards their enemy's doom.
The lobster-sized shrimp stay in their sandy burrow and wait for prey to come by, and then from out of nowhere, shoot out and grab the next meal with their long skinny appendages. Scientists were not sure how these predators were able to unleash their lightning-fast attacks, until now.
Maya deVries from the University of California, Berkeley (UCB) said the shrimp are closely related to smasher mantis shrimps, which pulverize the shells of crustaceans and mollusks with a blow of their claw.
"We thought that the spearers would be just as fast — if not faster — than the smashers because they have a smaller time window in which to capture their prey," deVries said in the statement.
Her team wrote in The Journal of Experimental Biology about their findings after going through some film taken of the shrimp.
When the team analyzed the speed of the attacks, they found that the spearer's harpoon speed was slower than that of their smashing cousin's.
Smasher mantis shrimp store catapult energy in skeletal springs as they unleash their deadly assault. After analysis, the team found that the spearing shrimp were not using the same mechanism.
"The spear has all the same components [as the smashers]", explained deVries, but she also said the shape of some of its structures are subtly different. "If the L. maculata movement is similar to other ambush predators that have muscle-driven strikes, it is possible that these guys are creating strikes with muscle movement," she said.
The team tested the reactions of another, smaller mantis shrimp next to find out whether all spearing shrimps opted for muscle-powered strikes. They filmed the animals grabbing brine shrimp, but found it was obvious that the crustaceans were using a spring-loaded catapult to spear their prey.
The team could clearly see energy-storing deformations in the spring structure before the mantis shrimp unfurled their deadly assaults.
They were puzzled by the spearing shrimp's performance, and found that maybe the lab animals had become too unfit to produce explosive attacks. The team moved their experiment to the wild, and found that the animals' reactions were well within the range of speeds that they had measured in the lab.
"We're trying to get more L. maculata in the lab to look at the complete size range in one species to see how the strike scales and to find out if there is a size threshold above which you can't have a spring-loaded strike anymore," deVries concluded.