copepod

https://doi.org/10.1351/goldbook.14553
Minute marine or freshwater crustacean, usually having six pairs of limbs on the thorax; some are abundant in plankton and others are parasitic on fish, marine mammals, and macro-invertebrates.
Source:
PAC, 2009, 81, 829. (Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)) on page 862 [Terms] [Paper]