The blind "remipede," living in marine caves of the Caribbean, Canary Islands and Western Australia, liquefies its prey -- generally other crustaceans -- with a compound similar to rattlesnake venom, scientists at London's Natural History Museum reported.
That venom -- a mixture of toxins including enzymes and a paralyzing agent -- breaks down body tissues and the remipede sucks out a liquid meal from its prey's exoskeleton.
Similar venoms and similar feeding habits are found in many spiders, the researchers said.
"The spider-like feeding technique of the remipede is unique among crustaceans," researcher Ronald Jenner told the BBC. "This venom is clearly a great adaptation for these blind cave-dwellers that live in nutrient-poor underwater caves."
Crustaceans, which include species such as shrimp, krill, lobsters and crabs, are a large group in the wider category of animals known as arthropods.
"Venoms are especially common in three of the four major groups of arthropods, such as insects," museum researcher Bjoern von Reumont said. "Crustaceans, however, are a glaring exception to the rule.
"This is the first time we have seen venom being used in crustaceans and the study adds a new major animal group to the roster of known venomous animals."