Feeding ecology and diet

Most bivalves are suspension feeders, filtering food particles from the water column. The expansive ctenidia, in addition to functioning in gas exchange, are the main feeding organs. Their cilia-covered surface collects and sorts particles from currents flowing through the mantle cavity, conveying them to marginal food grooves, then anteriorly toward the labial palps flanking the mouth.

The most primitive bivalves were probably deposit feeders, collecting detritus from the sediment surface. This method is posterior adductor muscle excurrent siphon incurrent siphon digestive gland stomach


Bivalve anatomy. (Illustration by Patricia Ferrer)

anterior adductor muscle mouth labial palp ganglion

(nervous system) intestine foot

Bivalve anatomy. (Illustration by Patricia Ferrer)

still used by living Nuculoida, using specialized structures known as palp proboscides. Other specialists feed by direct absorption of dissolved organic matter, or DOM (e.g., Sole-myidae), or by active capture of small crustaceans and worms through use of a raptorial incurrent siphon (e.g., Cuspidari-idae). Others possess symbiotic organisms, supplementing their energy reserves with by-products from their inhabitants. Examples of symbiotic relationships include chemoau-totrophic bacteria in Solemyidae and Lucinidae that facilitate habitation of anoxic muds, and zooxanthellae in Cardiidae that provide photosynthetic products in shallow eutrophic waters. The wood-eating Teredinidae are enabled by symbiotic cel-lulolytic (cellulose-digesting) bacteria that are stored in pouches along the bivalve's esophagus.

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