About the Copepod

It’s plankton. It’s a parasite. It’s a copepod! This tiny but ubiquitous zooplankton plays a superpowered role in the marine ecosystem, competing with Antarctic krill for the title of “most animal biomass on earth.” Copepods are found in nearly every fresh and saltwater habitat, and along with krill, are credited with being the world’s most significant carbon sink. The mere existence of planktonic copepods—which eat carbon-based phytoplankton and release their carbon-based exoskeletons, feces and breath in the deep ocean—removes billions of tons of carbon from the atmosphere each year.

Marine copepods like Calanus finmarchicus are essential players in high-latitude ecosystems, where whales and fish like cod, herring, and redfish (and their larvae) depend on them for food. C. finmarchicus has an “overwintering” strategy, whereby they hibernate in the twilight zone (500-2,500 meters or 1,600-8,200 feet) for six months until phytoplankton blooms at the surface each spring. This species’ relative abundance, high protein content, and omega-3 fatty acids make C. finchmarchicus an attractive target for the dietary supplement industry.

In Latin, “copepod” means “oar-feet” which refers to the crustacean’s method of rowing their frontal appendages through the water to swim. Planktonic species are also able to change the density of the fats in their bodies to travel to the ocean surface at night and sink lower during the day to avoid detection by visual hunters. Most species are transparent, with a minimal circulatory system and a single eye. Lacking gills, copepods absorb oxygen directly through their bodies. Superman can only dream of such powers.


Quick Facts

Common NameCopepod
Scientific NameA subclass of crustaceans comprising over 13,000 species
Other NamesParasitic species may be called “fish lice”
SizeAverage is 1-2 mm (0.04-0.08 inches); polar species are 1 cm (0.39 inches) and parasitic forms have been found up to 32 cm (13 inches)
DiscoveryHenri Milne-Edwards, 1840
Eats what?Phytoplankton like diatoms, marine snow (organic detritus), bacteria, and smaller copepods
Eats how?Varies, but chemical detection of sinking marine snow (organic detritus) is one method; half of copepod species are parasites of fish, marine mammals, mollusks, tunicates and corals.
Is eaten by?Whales, fish (cod, herring, redfish), seahorses, shrimp, krill, filter-feeders