Dietary change during development in the freshwater calanoid copepod Epischura lacustris Forbes

Abstract:

The diet of the freshwater calanoid copepod Epischarra Iacustris from C2 to adult stage was examined with predation experiments, grazing experiments, and stomach content analyses. There was a transition from an exclusively herbivorous diet in early copepodid stages to an omnivorous diet in adults. Laboratory predation experiments revealed that 62 and 63 were incapable sf ingesting Bosrnina (0.25-0.35 mm), but from 64 to C6 ingestion rate of Bssmina increased with developmental stage. -The order or prey selection for adult Epischura was Bosmina over Diaptsrnus and Cyclops. Grazing rate on small algae (<1 0 ~min)cre ased with developmental stage. Zooplankton remains were only found in the guts of stages older than 62; cladocerans and crustacean eggs were the most common zooplankton food. Algae with longest linear dimensions greater than 10 pm (e.g. Sphaerocystis, Binsbryon, and diatoms) were common in the guts of all developmental stdges of Epischarra. The occurrence of small unicells (<I0 pm) in the guts decreased with developmental stage.