In Vivo Studies of Suspension-Feeding Processes in the Eastern Oyster, Crassostrea Virginica (Gmelin)

Suspension-feeding processes in the eastern oyster Crassostrea virginica (Gmelin, 1791) were examined, in vivo, with an endoscope linked to a video image-analysis system. We found that many of the previously published concepts of particle transport and processing in this species, obtained using surgically altered specimens or isolated organs, are incomplete or inaccurate. In particular, our observations demonstrate that (1) captured particles are transported along the gills by both mucociliary (marginal grooves) and hydrodynamic (basal tracts) processes; (2) the labial palps accept material from the gills both in mucus-bound particle strings (transported in marginal grooves), and suspended in particle slurries (transported in basal tracts); (3) the labial palps reduce the cohesive integrity of the mucous strings and disperse and sort the entrapped particles; (4) particles are ingested in the form of a slurry; and (5) ciliary activity on the labial palps is independent of that on the lips, allowing the oyster to filter particles from suspension and produce pseudofeces without ingesting any particulate matter. Because many ostreids have the same plicate gill structure, we believe that our conclusions are applicable to other oyster species. In addition, the present observations are consistent with other endoscopic examinations recently made on bivalves in different families. We conclude that accepted theories of particle handling in suspension-feeding bivalve mollusks must be modified to accommodate observations made with the endoscope.