Diatom – lipid – copepod nexus under threat by global change: Database on copepod size and oil sac volume

This dataset was generated from laboratory experiments investigating the effects of diet and temperature on oil sac development and lipid accumulation in the calanoid copepod Calanus finmarchicus. The dataset contains individual measurements of prosome length (PL, mm) and oil sac area (OSA, mm²) for copepods reared under different experimental treatments. The experiment was initiated with copepods at the C1 copepodite stage. Individuals were maintained under controlled conditions and fed ad libitum with one of three monospecific algal diets: the cryptophyte Rhodomonas salina (RS), the diatom Thalassiosira weissflogii (TW), or the dinoflagellate Heterocapsa triquetra (HT). Experimental treatments were terminated when individuals within a cohort had reached the C4 and C5 copepodite stages. At the conclusion of the experiment, copepods were photographed for morphometric analysis. Prosome length (PL) and oil sac area (OSA) were measured from digital images using ImageJ software (Rasband, 2011). The pixel-to-millimetre conversion was calibrated using images of an appropriate stage micrometer, allowing measurements to be converted to standardized metric units. The resulting dataset provides individual-level records of body size and lipid storage characteristics for each treatment combination.