ESTIMATION OF PHOSPHORUS METABOLIC RATES OF DAPHNIA-GALEATA USING A 3-COMPARTMENT MODEL

A compartment model to estimate the different phosphorus metabolic rat es in Daphnia galeata is presented. The model has three compartments: gut, metabolic pool and structural pool. Existing two-compartment mode ls used for carbon and phosphorus turnover in Daphnia do not allow est imation of ingestion and egestion rates. We extended existing two-comp artment models with one more compartment, the gut, which allowed us to estimate both the ingestion and the egestion rates. Parameters of the model are estimated from a single experiment of feeding unlabelled Da phnia with P-32-labelled Scenedesmus obliquus. Separate experiments wi th juvenile and adult daphnids were carried out in order to compare th eir metabolisms. This model permits a reliable estimation of the diffe rent metabolic rates of Daphnia in a single experiment and discriminat es clearly between animals of different sizes.