Growth and Metabolism of Ostrea edulis Larvae

Abstract

ONLY a fraction of the plant food captured by zooplankton is converted into growth ; the rest is lost through incomplete assimilation, excretion and metabolism. The net growth efficiencies, K2 (percentage of assimilated food converted into growth) for haloplanktonic animals such as Calanus and related copepod species are generally lower than the percentage of assimilated food lost in metabolism (100-K2. In terms of calories, values of K2 quoted in a recent review by Corner and Davies1 range from 23–58 for C. hyperboreus, from 6–55 for C. helgolandicus, and from 14–29 for Acartia clausi. There are few comparable estimates of growth efficiencies for meroplankton species, such as molluscan larvae, but the data that does exist suggests that the values of K2 are considerably higher than those for copepods. Jorgensen calculated a value for K2 of 73% for Mytilus larvae and values of 62% and 63% for two gastropod veligers2, and from short-term feeding experiments with Ostrea edulis Walne estimated that 68–80% of the total food assimilated by the larvae is utilized for growth3. During larval development the daily level of assimilated food declined from 56% to 29% of the body weight.