THE FEEDING BEHAVIOR AND RESPIRATION OF SOME MARINE PLANKTONIC CRUSTACEA

Abstract

1. The respiration rate of twelve species of zooplankton, the majority from oceanic waters and from depths greater than 100 meters, has been measured at temperatures close to that of their environment (4-8° C.). In most cases healthy specimens were brought to the laboratory and their food habits and behavior studied. 2. The following species seemed largely herbivorous: Calanus finmarchicus, C. hyperboreus, and Rhincalanus nasutus. 3. The copepod Paraeuchaeta nor vegica, and the amphipods Euthemisto compressa and Hyperia galba all took animal food readily. Bathycalanus sp., Euchirella rostrata and the euphausids also are believed to be at least partially carnivorous although they demonstrated little or no feeding. 4. The animals studied had a total range in dry weight of nearly four orders of magnitude. When log respiration was correlated with log weight, a positive linear regression coefficient of 0.65 was obtained. This value, which is lower than most previously determined regression coefficients relating size and metabolism in the Crustacea, may result from the lower temperatures used in these experiments compared with those used in the earlier work. 5. As confirmatory evidence, size and metabolism were related by a coefficient of 0.67 at 5° and 0.93 at 13° in the case of Artemia salina. 6. Those zooplankton animals which seemed to be largely carnivorous on the basis of the behavioral studies had a significantly higher respiratory rate than those which seemed to be predominantly herbivorous. 7. Some of the possible explanations and ecological implications of the above-mentioned observations are discussed.