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

Individual adult females of the cyclopoid copepod Oithona plumiferawere continuously observed for up to 60 min to evaluate theirmotion and feeding behaviour. These females move only aboutfive 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 foodparticles. They perceive food particles hydrodynamically viathe setae on their first antennae, their prosome appendagesand their abdomen. They appear to be able to obtain sufficientfood even at tropical open ocean food abundances. A comparisonwith the calanoid Clausocalanus furcatus reveals notable differencesin behaviour between these two species, which dominate the copepodassemblages in oligotrophic environments.