Ynghylch

One of the most primitive vertebrates still alive today, the river lamprey is a small, eel-like fish with a toothed, sucker-mouth. It uses this sucker to attach to other fish, rasping away at the flesh and feeding on bodily fluids. It also feeds on carrion. Adult river lampreys live in the sea and return to freshwater to spawn. When they find a suitable breeding place, the male will attach to the female using his sucker and wrap his body around hers, ensuring he fertilises the eggs as she lays them. Females can lay up to 25,000 eggs with a succession of males attached to her. After spawning the adults die; the young hatch, but spend several years buried in the silt. When they finally reach adult stage they will migrate out to sea.