Copepoda

noun plural

Co·​pep·​o·​da kō-ˈpep-ə-də 

: a subclass of Crustacea comprising minute aquatic forms abundant in both fresh and salt waters and including one order (Eucopepoda) whose members are chiefly free-living and important as fish food and another order (Branchiura) whose members are parasitic on the skin and gills of fish

copepod

ˈkō-pə-ˌpäd 

noun or adjective