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Abstract:
The life cycle of the freshwater copepod Cyclops kolensis in the eutrophic Lake Schierensee is characterized by summer diapause. From June to October C4 and C5 copepodid stages persist in the anoxic sediment. Prior to diapause lipids are accumulated. The seasonal patterns of the total lipids and energy reserve lipids in Cyclops kolensis were examined during a two-year period, and the role of the reserve lipids in the life cycle of the copepod was assessed. Triacylglycerols (TAGs) were the dominant lipid class. The seasonal pattern of this energy reserve lipids resembled the seasonal pattern of the total lipids. Total lipid content of diapausing copepodids was approximately one third of their dry mass and decreased only slightly during the diapause period. A drastic decrease of lipids occurred after termination of diapause in November when copepodids emerged. When egg production started in February, the lipid content of adult females was approximately 20 % of their dry mass. During the four-month long reproductive period a decrease in the lipid content of the females was observed, whereas the lipid concentration of the eggs remained almost constant. The offspring developed during the algal spring bloom and accumulated lipids before they entered diapause in June. Stored lipids are considered to provide energy for reactivation of the copepodids after termination of diapause and for early reproduction.
