The crustaceans that live on another animal at its expense. Small, easy to miss, and usually noticed as a lump on a fish rather than as an animal in their own right.
The cymothoid isopods attach to a fish and stay. The tongue-biter enters through the gills, attaches in the mouth and takes the place of the tongue; Anilocra rides on the flank or the head of a cardinalfish or a snapper and is often the first thing seen in a photograph of one. The gnathiid isopods feed only as juveniles, drop off, and are the main thing cleaner shrimps and cleaner wrasses are removing.
The bopyrid isopods live inside a shrimp's gill chamber and show as a bulge on one side of the head. The parasitic barnacle is stranger again: it grows through a crab's body as a network of threads and shows only as a sac under the abdomen, and an infected crab stops moulting and tends the sac as if it were its own eggs.
Every one has a page. They are shown as a list rather than as pictures because nothing has been photographed or logged for them yet, and a species with nothing behind it should not sit in front of one that has.
How many of the 5 carry a record at each destination. A species usually carries several, so these do not add up to 5.
All 1316 species in one index, with filters for destination, rarity and hazard.