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Mussels are among the most important of the internal filter feeders. Inside the shell, the gills do the job of filtering out food particles, and then the water is discharged through a smaller, oval, excurrent siphon. The food is wiped off the gills by a pair of appendages called palps, and is then transferred to the mouth deep inside the shell. Similar arrangements can be seen in the oysters and scallops. Studies have shown that an individual mussel or oyster can filter over a gallon of water per hour.
In many other bivalves, especially the burrowing ones including all the clams, both siphons are simple tubes, and in some cases they are much longer than the rest of the animal.
This allows the animal to live in safety deep in the mud while the siphons emerge above the surface although those siphons are often nibbled by hungry fish and other carnivores! Bivalves feed on plankton, as well as benthic algae and detritus, and in turn they provide food for echinoderms, fish, birds and other animals. Other filter feeders use an external filter. Some of these live in tubes made of mucus and sand; others make a harder, calcified tube.
They are able to retract and close a door operculum when threatened by low tide or predation. A unique type if filter feeding has evolved in a species called the Fat Innkeeper Worm.
This animal constructs and lives in a U-shaped burrow, and it secretes a net of slime that filters out food as the worm pumps water through the tube. When the net is fully loaded with food, the worm swallows the food along with the net, and then makes a new net.
The regular presence of these guests is what gives the animal its name! This is usually accomplished by fields of waving microscopic tentacle-like structures called cilia.
In some cases a string of mucus is produced by the animal to keep the food in place while it is in transit. One of our local filter feeders takes advantage of wave action to move water over its filters.
This is the Pacific Sand Crab Mole Crab which is very common and familiar on our sandy beaches in summer and has two distinct filter feeding mechanisms. Its legs have hairy margins for filtering food and transferring it to the mouth. But when the crab buries itself in the sand it extends its two antennae on the surface where they filter out food particles brought in by wave action.
After the antennae collect the particles, they transfer them to another pair of appendages, the antennules, and then to the mouth. Home Ocean Facts What is a bivalve mollusk? What is a bivalve mollusk? Bivalve mollusks e.
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