Six previously unknown species of acrocirrid polychaete worms discovered in the depths of the Pacific Ocean. Hypothetical relationships are suggested by the grey lines.
Credit: Karen Osborne
SYDNEY: Marine scientists have discovered worms in the deep ocean, which throw off glowing 'bombs' as a defence mechanism.
"We think they're using them as decoys to avoid predators" said Karen Osborn, evolutionary biologist at the Scripps Institution of Oceanography in California, USA.
"Its exciting both to find a group of animals that we didn't know anything about and to find the bioluminescence," she said. "These are not rare animals. Often when we see them they number in the hundreds. What's unique is that their habitat is really hard to sample."
Seven new species
A total of seven new species of these acrocirrid polychaete worms were described today in the U.S. journal Science, after Osborn and her team spotted them first off the coast of California in 2001 and, then more recently, in the Philippines.
The samples were collected using a robotic submarine known as an ROV (remotely operated vehicles). The worms, which range from two to nine centimetres in size, have been discovered between depths of two and four kilometres below the surface and propel themselves by fanning a series of long bristles.
The first species described in the paper has been dubbed Swima bombiviridis.
What makes these species remarkable is that they produce tiny capsules around their heads that can be thrown away from the body and produce a brief flash of light. These two-millimetre, fluid-filled sacs suddenly burst into light and glow for up to 45 seconds, said the researchers.
Each animal can have up to eight capsules, which are attached to the body like a gill, connected by blood vessels. When harassed, the worm contracts a muscle to release them.
While some other animals, such as brittlestars and squid, are known to be able to detach luminescent structures, this is the first time the trait has been found in a worm. The species also appear to be using different chemicals to produce the glow than detected before, which makes them interesting from an evolutionary standpoint, Osborn said.
"Amazing little animal"
"Its really quite an amazing little animal" commented Pat Hutchings, a marine scientist from the Australian Museum in Sydney, who was not involved in the research. The researchers are "not just describing a new group, but are trying to work out where that group belongs with the other 20,000 odd worms," she said.
The finding highlights just how little we still understand about the deep sea."My guess is that these magnificent worms represent a tiny fraction of the diversity that is hidden within the depths of the ocean," said Lisa Levin, also a marine scientist from the Scripps Institution of Oceanography, but not an author of the paper.
"The study illustrates how modern technology (the ROV), classic systematics approach and new molecular tools can provide novel insight about life in the deep sea, a vast, relatively unexplored part of our planet," she said.
Follow Cosmos on Twitter! twitter.com/cosmosmagazine
