Observations are presented to elucidate the complex and highly efficient feeding mechanisms and habits in the common Atlantic slippersnail, Crepidula fornicata. Using a newly designed video system coupled with video endoscopy and microscopic observations, collection of food particles throughout the feeding cycle was documented. The process is described from postcapture particle transport on the gill, to production and consumption of the food cord, and the results were compared with controversial historical records and descriptions of feeding, especially with regard to the roles of the radula, food pouch, and a purported mucus net or filter. The food cord is produced continuously and is the dominant mode of feeding. Capture of food cords is efficient, but often sloppy; more than 10% of food volume production is ultimately expelled to the exterior of shell, making these energy-rich cords available to other benthic feeders. Although it was observed that the ciliated food pouch produces balls of mucus-laden food, these balls account for ∼10% of feeding events, and less than 1% of food volume production and ingestion; in other words, the food pouch contributes little to the feeding process or the production of pseudofeces. Coprophagy was also noted fairly regularly, clearly a function of the position of the anus in relation to the gill and site of production of the food cord. Video endoscopy demonstrated that food particles are captured on the frontal surface of the filaments and moved distally by the frontal cilia of the gill. Immediately after capture, particles are incorporated into fine mucous strings on the frontal surface and carried both distally and obliquely across the filaments. At the distal edge of the gill, the mucous strings enter the neck canal, are incorporated into a food cord, and are pulled anteriorly, resulting in the oblique movement of material on the gill. The overlap of mucous strings (those moving distally and those moving obliquely) often gave the appearance of a "mucous net," as has been described in older studies with less sensitive means of visualization. The results presented clearly demonstrate there is no mucous net formed, and a model is proposed to describe the capture and movement of particles, providing clarification of the process and new interpretations of the suspension-feeding process.
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Vol. 33 • No. 1