ON FOOD AND FEEDING OF LARVAE OF THE AMERICAN OYSTER, C. VIRGINICA

¹ U. S. Fish and Wildlife Service, Milford, Connecticut

1. None of the 13 species of marine bacteria tested to date was utilized as food by oyster larvae.

2. Five species of flagellates, Dicrateria inornata, Chromulina pleiades, Isochrysis galbana, Hemiselmis rufescens and Pyramimonas grossii, were utilized as food by oyster larvae, while another, an unclassified chrysomonad, in addition to the three flagellates previously reported, was not.

3. Chlorella sp. was not utilized as food by young oyster larvae but was utilized during later larval stages.

4. None of the combinations of foods tried gave any evidence of providing a more balanced diet or more rapid larval growth than could be obtained by feeding equivalent quantities of a single food. The effects of all foods tested, including Chlorella, are additive.

5. When equal numbers of cells are fed, different species of flagellates induce different rates of growth of oyster larvae.

6. Species of flagellates also differ in the number of cells needed to induce the maximum rate of growth of oyster larvae.

7. The maximum concentration of food organisms that can be created in water containing oyster larvae without unfavorably affecting the larvae varies with the species.

8. With the number of food organisms equal, the rate of growth of oyster larvae had an inverse relation to the number of larvae per unit volume.

9. Variations between rates of growth of larvae in cultures receiving the same treatment in successive experiments appear to be due to some variable factor in the sea water that affects the ability of the larvae to utilize the food that is present.