Nicola Jones
The discarded mucous houses of tadpole-like sea creatures called larvaceans have been revealed to be a major source of food for seafloor life.
Scientists have long wondered about the origin of the food eaten by creatures that live near the ocean floor. Carbon from the remains of dead fish, plankton and other detritus of marine life is known to trickle down through the water. But measurements have indicated that this slow 'rain' of particulates is not enough to sustain the life below.
So Bruce Robison and his colleagues from the Monterey Bay Aquarium Research Institute in Moss Landing, California, wondered if larvaceans (also known as appendicularians) might make up the difference. These creatures, which can be up to 6 centimetres long, feed themselves by creating a giant filter sack of mucus that can reach up to a metre in length. They pump water through this sack with their tails, and feed on the captured carbon.
When the filters become clogged, the larvacean discards its house and excretes a new one. The old house will sometimes collapse into a ball laden with carbon that plummets through the water. "They become great big, carbon-rich, fast-moving particles the size of your fist that shoot to the deep sea floor," says Robison.
http://www.nature.com/news/2005/050606/full/050606-12.html