There are broadly four ways in which benthic animals gather food; they filter suspended particles from the water, they collect food particles which settle on the surface of the sediment, they obtain nutriment from the organic material which has become incorporated in the deposit, or they prey upon other animals. Many of course take food from several sources. For example, the shrimp Crangon feeds largely on surface debris but also preys on small animals; the edible crab Cancer, is omnivorous, taking a wide variety of plant and animal foods; the squat lobster Galathea, takes large pieces of animal and vegetable matter and also uses the setae on its maxillipeds to filter micro-organisms and debris from the bottom deposit. However, in many other cases the feeding mechanism is adapted to deal with a particular source of food. Suspension feeders include sponges, as-cidians, bryozoans and certain polychaetes (Chaetopterus), crustacea (Balanus), gastropods (Crepidula), many lamellibranchs (Cardium, Venus, Dosinia, Gari), and some holothurians (Cucumaria). Surface deposit feeders include polychaetes (Terebella, Amphitrite), and lamellibranchs (Angulus, Abra). Feeding on organic matter within the sediment are polychaetes (Arenicola), heart urchins (Spatangus, Echinocardium) and holothurians (Leptosynapta). Benthic predators include errant polychaetes (Nephtys, Glycera), the majority of actinians, many crabs, some gastropods (Natica, Scaphander, Buccinum), starfish and ophiuroids (Asterias, Amphiura) and many fish, including most of the commercially fished species.
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