Wax esters, which function as reserve fuels, account for 25 to 40 % of the lipid of the pelagic eopepod Calanus helgolandicus (Copepoda, Calanoida). In laboratory experiments with these crustaceans, diatoms (Lauderia borealis, Ghaetoteros curvisetus, and Skeletonema costatum) and dinoflagellates (Gymnodinium splendens), which contained no wax esters, were used as food. Changes m the food concentration affected both the amount of lipid and the composition of the wax esters. Since the fatty acids of the triglycerides and wax esters of C.helgolandicus resembled the dietary fatty acid composition, it appeared that eopepods incorporated their dietary fatty acids largely unchanged into their wax esters. The polyunsaturated alcohols of the wax esters did not correspond in carbon numbers or degrees of unsaturation to the dietary fatty acids. We postulate two different metabolic pools to explain the origin of these long chain alcohols. The phospholipid fatty acids were not affected by changes in the amount or type of food, probably because of their structural function.
High-speed cinematography was used to observe adult female copepods feeding in pure cultures of roughly spherical algal cells ranging from 4.5 to 22.0 pm in diameter. Eucalanus pileatus and Puraculunus puruus detect and handle individual cells as small as 12 pm. Continuous low amplitude movement of the second maxillae and combing of the appendages is used by E. pileutus to capture cells smaller than the 12qm sensitivity threshold. Different energetic costs are probably associated with capturing small and large cells, and the probability of copepods encountering large cells should be greatly increased due to remote detection. The above suggests that descriptions of selective feeding in grazing trials using Coulter Counter data are influenced by the size above which the copepods can detect individual cells and by the proportions of the pregrazing particle spectrum larger and smaller than this threshold.
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