Carnivorous feeding behavior of the adult calanoid copepod Acartia tonsa Dana

The predatory feeding behavior of adult Acartia tonsa Dana copepods on four species of copepod nauplii, A. tonsa, Scottolana canadensis (Willey), Oithona colcarva Bowman, and Eurytemora affinis Poppe, was investigated. Wild adults prey at significantly higher rates on nauplii of other species than on their conspecifics regardless of prey preconditioning. Naupliar size is also important; smaller sized prey are usually preferred. Predation rates observed in the single prey species experiments are not affected by the presence of an alternate algal food source, Pseudoisochrysis sp. The ingestion rate of algae (10⁶ μm³·adult^-1·h^-1) is correlated with the concentration in parts per million by the volume of algae available, but is independent of the presence of naupliar prey.