Relative Value of Ten Genera of Micro-organisms as Foods for Oyster and Clam Larvae

Twelve species of micro-organisms, representing ten diffe.rent. genera, were used in feeding experiments t.o determine t.heir relative value as foods for larvae of oysters (C1'a~.Yosft·ea. vll'ginica) and clams (Ventts 1ne1'ce'lUtru,,). booM'ySM galba'na and Monochrysls lutheri were approximately equal in value as foods for either species of larvae, and were the best single foods for oyster larvae. Together with Ch.101'ocoocum. sp. they were also the best single foods for clam larvae. Somewhat more rapid growth of bot.h oyster and clam htrvae was obtained by feeding a mixture of bochrysls galbana, Monockrysis lu.the1'l, DttnaUella eu.chlom, and Pla.tY1nona~ sp. t.han was obtained by feeding equal quantities of any of these foods separately. Growth of larvae of both oysters and clams was comparatively good in each of five concent.rations of I sochl'ysi-s and Monochrysis tested. The rat.e of growt.h did not. fall off rnpidly nor waf; t.here Ilny mortalit.y at t.he higher concent.rations of these foods, as t.here was when equally high concent.rat.ions of (!h.lorella. sp. (Lewin's isolate) were used. The presence, and perhaps thickness, of cell walls and the degree of toxicit.y of t.he metabolites are believed t.o be important factors in determining t.he usabilit.y of micro-organisms as foods for bivalve larvae.