Copepods

The second pair of antennae are the main source of propulsion, beating like oars to pull the animal through the water.
Many of the smaller copepods feed directly on phytoplankton, catching cells singly. Some of the larger species are predators of their smaller relatives. Many benthic copepods eat organic detritus or the bacteria that grow in it, and their mouth parts are adapted for scraping and biting. Herbivorous copepods, particularly those in rich cold seas, store up energy from their food as oil droplets while they feed in the spring and summer plankton blooms. These droplets may take up over half of the volume of the body in polar species.