Limnetis (unidentifiable). Cyclops is one of the most common genera of freshwater copepods, comprising over 400 species. Liernaeocera (Lernaeocera) is a genus of marine copepods in the family Pennellidae. Lepas is a genus of goose barnacles in the family Lepadidae. Sacculina is a genus of barnacles that is a parasitic castrator of crabs. They are recognized as barnacles because their larval forms are like other members of the barnacle class Cirripedia. Peneus (Penaeus) is a genus of prawns, including the giant tiger prawn (P. monodon), the most important species of farmed crustacean worldwide.