This reminded me of Futurama Comic #1 when Fry hatched some sea monkeys and they mutated into giant killer shrimp.
http://cbc.ca/cgi-bin/templates/view.cgi?/news/2001/01/05/killer_shrimp010105
ROGUE SHRIMP TERRORIZES SAN FRAN CHILDREN'S AQUARIUM
WebPosted Fri Jan 5 13:17:51 2001
SAN FRANCISCO The children's section of an aquarium in San Francisco has recently been the scene of more real-life survival of the fittest than intended.
The SplashZone coral reef exhibit at the Monterey Bay Aquarium has become a killing zone as a rogue mantis shrimp has been cutting a swath through the sea snails, barnacles and hermit crabs. A worker at the aquarium said the popping sound of the shrimp attacking the barnacles can be heard near the exhibit.
Two of the 10-centimetre shrimp are thought to have invaded the 5,000-litre tank in the spring, arriving hidden in a shipment of display rock from Florida.
One of the shrimp known as "thumb-splitters" was caught by a worker using tongs. But the other has been elusive, and devastating.