Rob Jordan / 2020VISION / Close up of Atlantic salmon (Salmo salar) showing signs of sea lice infestation, caught by Tweed Foundation staff netting and tagging migratory fish on the River Tweed, Berwickshire, Scotland, UK, Sep...

Martin Camm / Carwardine / Illustration of Greenland Shark / Sleeper Shark (Somniosus microcephalus), Somniosidae; eye with copepod (Wildlife Art Company).

David Shale / Deep sea Copepod Atlantic ocean

Tony Wu / Newly hatched Japanese horseshoe crab (Tachypleus tridentatus) swimming into murky nutrient-rich water column filled with frenzy of copepods (Copepoda) . Sea of Japan, Yamaguchi Prefecture, Japan.

David Fleetham / Tricolor parrotfish (Scarus tricolor) supermale sleeping at night protected by a mucus cocoon that it secretes, with parasitic copepod caught in it, Tubbataha Reef, Philippines, Pacific Ocean.

David Fleetham / Parasitic copepods just behind the pectoral fin of Trumpetfish (Aulostomus chinensis), Hawaii, Pacific Ocean.

David Fleetham / Bay goby (Lepidogobius lepidus) resting on seabed, with an unidentified female Copepod parasite in its gill with only its paired egg segments visible, British Columbia, Canada, Pacific Ocean.

Kim Taylor / Two Freshwater copepods (Cyclops sp) swimming through pond debris, Surrey, UK, May.

Tony Wu / Hairy frogfish (Antennarius striatus) male resting, lump on head and abdomen resulting from infection by Parasitic copepod (Sarcotaces pacificus). The female parasite resides within the lump where she...

Tony Wu / Hairy frogfish (Antennarius striatus) male resting, lump on head and abdomen resulting from infection by Parasitic copepod (Sarcotaces pacificus). The female parasite resides within the lump where she...

Alex Mustard / Topknot (Zeugopterus punctatus) rests on the seabed, covered in tiny copepod parasites. Swanage, Dorset, England, United Kingdom. English Channel. North East Atlantic