The jellyfish and anemones feed on crustaceans and small fish, whereas the corals and hydrozoans feed principally by filtering plankton from the water. This group of common marine worms known as polychaetes is related to the common earthworm. Both belong to the phylum Annelida. The fan and tube worms construct burrows in the sediment or construct rigid limy tubes on the surface of solid objects, including the shells of other animals. Many of these worms possess mucous-covered tentacles which surround the mouth for capturing food.
Polychaete worms feed in many different ways.
Some are filter feeders, others are predators, detritus feeders, scavengers or deposit feeders. Seashells are among the most familiar remains of marine invertebrates. Most mollusks possess hard shells which remain long after the actual animal dies and are the delight of many beachcombers. Gastropods are found in marine waters, fresh water and on land. They may be herbivores, carnivores, scavengers, deposit feeders or filter feeders.