Famine and feast in a common freshwater calanoid: Effects of diet and temperature on fatty acid dynamics of Eudiaptomus gracilis
Limnol. Oceanogr., 59(3), 2014, 947-958 | DOI: 10.4319/lo.2014.59.3.0947
ABSTRACT: We investigated the effects of temperature (4°C, 8°C, and 12°C) on structural and storage dynamics, as measured by changes in fatty acids (FA) associated with cell membrane phospholipids (PL) and triacylglycerols (TAG), respectively, as well as on body weight and survival of a freshwater calanoid copepod (Eudiaptomus gracilis) during fasting (10 d) and refeeding (10 d) with two algae of differing nutritional quality (Cryptomonas ozolinii and Scenedesmus obliquus). Fasting led to 50% loss in body weight, a near total depletion of TAG, and a drastic decrease of the polyunsaturated FA (PUFA) in TAG and PL, indicating their preferential utilization and alterations in membrane function, respectively. Higher temperatures accelerated the decrease of body weight and of PUFA in PL and TAG, and decreased survival. After 10 d of refeeding, copepods partially recovered their initial lipid stores and cell membrane composition. The effects of food quality were temperature dependent: Cryptomonas promoted better recovery (i.e., return to or close to the levels at the beginning of the experiment) of both body weight and TAG at only the two higher temperatures (8°C and 12°C), whereas no recovery was observed at 4°C. Higher temperatures and refeeding on Cryptomonas also had a positive, but minor, influence on the recovery of membrane FA composition. Survival differed among treatments but was lowest at the intermediate temperature (8°C) for both diets. We conclude that temperature changes on the order of 4–8°C significantly influence TAG and PL during fasting periods and interact with food quality to determine the extent of recovery in copepod lipids.