Cyclopoid Copepod Oithona similis
Copepods make up over 70 percent of zooplankton, and this is one of the most abundant, widespread species. As the name suggests, cyclopoid copepods have a single, central eye, which is light sensitive. These arthropods also have a T-shaped, shrimplike body that tapers toward the rear and bears six pairs of swimming limbs. Jerky movements of its limbs sweep food particles efficiently toward the cyclopoid copepod's mouth. Females can be recognized when carrying egg sacs attached to their abdomens.
As part of the zooplankton, copepods of this genus are a vital element of oceanic food chains. They feed on marine algae and bacteria and in turn are an important source of protein for many ocean-dwelling animals. Every night cyclopoid copepods migrate from a depth of about 500 ft (150 m) to the surface layers of the ocean to feed. This daily journey, which is undertaken by many marine creatures, is one of the largest mass movements of animals on Earth.