Escorting Beakworm

The escorting beakworm evolved from the multicolor beakworm. Unlike its ancestor, it doesn't live in shoals, but follows big creatures like the strainbean and snark. They remove all parasites, like the strainbeansuckers, and keep the skin clean. In return, they're safe and won't be eaten by its host, and they can eat the rest, which the host lets fall down. No matter where they are on the skin, their top is always directed towards their host, so that they can pick things with their bent beak from the skin. In conclusion, the fin at the top degenerated, while the fins at the bottom became larger.