MECHANISMS OF SUSPENSION-FEEDING IN BIVALVES - RESOLUTION OF CURRENT CONTROVERSIES BY MEANS OF ENDOSCOPY

Controversy concerning the mechanism of suspension feeding in bivalves centers around whether particle capture and transport on the gills (c tenidia) is accomplished via mucociliary or hydrodynamic action. Evide nce for and against these fundamentally different processes has been b ased on examinations of isolated feeding structures and dissected spec imens, techniques that may produce artifactual data owing to the traum a associated with the procedures. In the present study, in vivo observ ations of the ctenidia of undisturbed bivalves, made with a fiber-opti c endoscope and video image-analysis system, revealed that the two mec hanisms are not mutually exclusive. Both mucociliary and hydrodynamic mechanisms function concurrently at different sites on the ctenidia, t hereby minimizing particle loss and optimizing particle transport effi ciency. The importance of mucus in the normal feeding process of bival ves is confirmed. These findings refute results of previous studies th at used surgically invasive techniques and emphasize the importance of making observations on morphologically intact specimens.