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Changes in fatty acid patterns, digestive and metabolic enzyme activities and egg production rates (EPR) were studied in the small calanoid copepod Temora longicornis. Female copepods were collected in spring 2005 oV Helgoland (North Sea). In the laboratory one group of copepods was fed with the cryptophycean Rhodomonas baltica for a period of 3 days. Another group of copepods was maintained without food. According to the fatty acid patterns, animals from the Weld were feeding on a more detrital, animal-based and to a minor extent to a diatom-based diet. Under laboratory conditions, females rapidly accumulated fatty acids such as 18:4 (n-3), 18:3 (n-3) and 18:2 (n-6) which are speciWc of R. baltica. Diatom-speciWc fatty acids such as 16:1 (n-7) were strongly reduced. In fed animals the activities of digestive and metabolic enzymes remained constant and egg production rates were highest on day 2. Starving animals, in contrast, showed signiWcantly reduced faecal pellet production and EPR. Proteolytic enzyme activity decreased rapidly within 24 h and remained at a low level until the end of the experiment. Citrate synthase decreased continuously as well. T. longicornis rapidly reacts to dietary changes and food depletion.It has limited energy stores and, thus, strongly depends on continuous food supply.

Large pelagic crustaceans from Greenland Sea waters, the northern krill Meganyctiphanes norvegica (Euphausiacea) and the decapod shrimp Hymenodora glacialis (Caridea), were captured in depths down to 1500 m and studied with respect to their physiological food utilization abilities. Both species showed distinct differences in the amount of total lipids (TLs), lipid class and fatty acid (FA) compositions as well as proteolytic enzyme activities. In M. norvegica, the overall amount of TLs and storage lipids was much lower than in H. glacialis, and triacylglycerols formed the major lipid fraction with a mean of 48% TLs. Major FAs comprised the trophic markers 20:1(n-9) and 22:1(n-11), indicating the ingestion of calanid copepods. Additionally, the FAs 22:6(n-3), 18:1(n-9) and 16:0 prevailed. In H. glacialis, TLs (mean = 44% dry mass) were about twice as high as in krill, with wax esters comprising up to 89% TLs. H. glacialis seems to accumulate these lipids as energy reserves to survive periods of food limitation. Moreover, high lipid levels, particularly wax esters, also help to maintain neutral buoyancy. The major FA in H. glacialis was 18:1(n-9); other dominant FAs were 20:1(n-9) and 22:1(n-11), typical of calanid copepods, as well as the diatom trophic marker 16:1(n-7). Both species showed omnivorous feeding behaviour with a strong tendency towards carnivory. Total proteolytic activities in midgut gland tissue were higher in M. norvegica than in H. glacialis. In M. norvegica, proteinases were dominated by serine proteinases, whereas cysteine proteinases formed the major group in H. glacialis. High proteolytic activity in M. norvegica indicates a high digestive potential for proteins and efficient utilization of prey. The presence of different proteinase classes in both species may be due to different group-specific enzyme expression patterns between euphausiids and caridean decapods. Both species follow highly deviating life strategies, as reflected by their specific lipid and enzymatic characteristics.

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