Doug Perrine / Salmon shark (Lamna ditropis) female with mating scars and copepod parasites trailing from fins, Port Fidalgo, Prince William Sound, Alaska, USA. Digital composite

Doug Perrine / Parasitic copepods {Copepoda sp.} on snout of Hammerhead shark {Sphyrnidae sp.} Bahamas

Franco Banfi / Greenland shark (Somniosus microcephalus) with parasitic copepod (Ommatokoita elongata), under ice, Lancaster Sound, Nunavut, northern Baffin Island, Canada, Arctic.

Franco Banfi / Greenland shark (Somniosus microcephalus) with parasitic copepod (Ommatokoita elongata), under ice, Lancaster Sound, Nunavut, northern Baffin Island, Canada, Arctic.

Franco Banfi / Greenland shark (Somniosus microcephalus) with parasitic copepod (Ommatokoita elongata), under ice, Lancaster Sound, Nunavut, northern Baffin Island, Canada, Arctic.

Alex Mustard / Whip goby (Bryaninops sp.) with copepod parasites (with characteristic coiled egg mass) on a whip coral. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Franco Banfi / Greenland shark (Somniosus microcephalus) with parasitic copepod (Ommatokoita elongata), under ice, Lancaster Sound, Nunavut, northern Baffin Island, Canada, Arctic.

Doug Perrine / Dorsal fin of Bryde's whale (Balaenoptera brydei / edeni) with copepod parasite near tip, off Cabo San Lucas, Baja California, Mexico (Eastern Pacific Ocean)

Doug Perrine / Porbeagle shark {Lamna nasus} (captive, caught for research) with dorsal fin exposed, showing white patch at rear base of fin that is diagnostic of the species, and copepod parasite (two filaments) at...

David Shale / Deep sea Parasitic copepod {Copepoda} from the mid-Atlantic ridge, depth 100-150m, at night

David Shale / Sand eel {Ammodytes tobianus} from Barents sea, Northern Europe, with parasitic copepods on tail

David Shale / Parasitic copepods on tail of Sand eel {Ammodytes tobianus} from Barents sea, Northern Europe