. The biology of marine animals. Marine animals; Physiology, Comparative. NUTRITION AND FEEDING MECHANISMS 229 brushed off the basket by the maxillipeds and transferred to the mouth. Finally, we may mention here the parasitic pea'crabs (Pinnotheres), some. Fig. Anterior View of Porcelain-crab Porcellana longicomis while Feeding, to Show the Direction of the Water Currents Drawing Food in Suspension towards the Animal (from E. A. T. Nicol (81).) of which inhabit the mantle cavity of lamellibranchs. These animals collect mucous food-strings from the gills of their hosts with the aid of set
. The biology of marine animals. Marine animals; Physiology, Comparative. NUTRITION AND FEEDING MECHANISMS 229 brushed off the basket by the maxillipeds and transferred to the mouth. Finally, we may mention here the parasitic pea'crabs (Pinnotheres), some. Fig. Anterior View of Porcelain-crab Porcellana longicomis while Feeding, to Show the Direction of the Water Currents Drawing Food in Suspension towards the Animal (from E. A. T. Nicol (81).) of which inhabit the mantle cavity of lamellibranchs. These animals collect mucous food-strings from the gills of their hosts with the aid of setous fringes on their claws (62, 81, 84). Efficiency of Filter-feeding among Invertebrates The food available to filter feeders consists of minute zooplankton, phytoplankton, protozoa, bacteria and organic detritus. This organic matter varies greatly in particle size, from several hundred micra in certain algal cells to sub-microscopic colloidal dimensions in the case of detrital matter. Animals probably differ in the efficiency of their straining appara- tuses: those with structural sieves-—namely sponges, bivalves, copepods and ascidians—retain particles down to 1 // in size; mucous net feeders, on the other hand, filter out material down to 40 A in size. The food intake is a function of the efficiency of the filter, amount of food present in the surrounding sea water and pumping rate. Absolute filtering rates, of course, vary greatly—from less than 100 ml/day in Calanus finmarchicus to 10 in Ostrea virginica. Jorgensen, however, finds that filtration rates of different animals are of about the same order when expressed as litres of sea water per millilitre 02 consumed. Calculated values are as follows— Sponges Echiuroid Lamellibranchs Copepods Ascidians Grantia compressa Halichondria panicea Urechis caupo Ostrea virginica Mytilus edulis Calanus finmarchicus Centropages hamatus Ciona intestinal is \ Molgula manhattensis J 13 14, 31 Oo 20 02
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