A laboratory study of feeding and assimilation in Euchlanis dilatata lucksiana

Abstract

Feeding of Euchlanis dilatata lucksiana, a brachionid rotifer isolated from the Loosdrecht Lakes (The Netherlands), was examined in the laboratory using ¹⁴C-labelled food. The gut-filling time at a food concentration of 9.6 μg C ml⁻¹ was about 15 minutes. Animals which were fed on 3 size fractions of the lake seston (< 7 μm, 7–15 μm, and 15–33 μm) showed a clear preference (Jacobs’ selectivity index) for the largest size fraction. This fraction was composed predominantly of filamentous cyanobacteria. For animals weighing 0.37–0.49 μg C ind.⁻¹ the daily ration (daily food consumption per unit body weight × 100) ranged from 50 to 100% at food levels of 2 mg C 1⁻¹ and below, but increased to 150–250% at food concentrations of 5 mg C 1⁻¹ and above. The assimilation efficiency was 100% up to 5 mg C 1⁻¹ of food, but decreased to about 80% at higher food levels.