On some aspects of the behaviour of Oithona plumifera (Copepoda: Cyclopoida)

Individual adult females of the cyclopoid copepod Oithona plumifera were continuously observed for up to 60 min to evaluate their motion and feeding behaviour. These females move only about five times per minute, each time with a brief relocation jump. They sink rather slowly while mainly in a horizontal position, which enhances the probability of encountering suitable food particles. They perceive food particles hydrodynamically via the setae on their first antennae, their prosome appendages and their abdomen. They appear to be able to obtain sufficient food even at tropical open ocean food abundances. A comparison with the calanoid Clausocalanus furcatus reveals notable differences in behaviour between these two species, which dominate the copepod assemblages in oligotrophic environments.