The mechanism of feeding in the oyster.

Abstract

The food of the oyster consists of minute plants, plant detritus, and animals filtered from the water passing through the gills. In turbid waters much sand and other inorganic matter is accumulated along with the food particles. Bivalve molluscs which live in muddy waters possess highly complicated systems of ciliary tracts with the aid of which some separation of food from dirt does occur. In the oyster this mechanism consists partly in the gills, but mainly in the palps. Water borne particles on striking the gills are entangled in mucus and carried by the cilia of the gill epithelium: (a) ventrad to the groove formed by the ventral margins of the gill lamellae; or, (b) dorsad to the dorsal groove which passes along the bases of the gill filaments. In these grooves the mucus covered particles are whipped into slime strings which are then carried anteriorly to the posterior margins of the palps. At this point the material may either pass between the deeply grooved and heavily ciliated faces of the palps, and thence toward the mouth, or failing this is pushed off onto the mantle ventrad the edges of the palps. At intervals the material accumulated here is expelled from the mantle chamber by water forced out by quick contractions of the adductor muscle. When relatively large masses of collected particles are brought to the palps most of these are rejected and pass off onto the mantle as Kellogg has shown. A larger proportion of the material brought to the palps by the dorsal groove is accepted than that which arrives via the ventral groove. Observation shows that the larger particles, chiefly sand grains, are consigned mainly to the ventral groove.