Freshwater true worms (annelid worms) are separated into two kinds of worms which are bristle worms and leeches. Bristle worms, as their name suggests, have bristles on their body segments to help them move. Freshwater bristle worms, like flatworms, have a small number of bristles on each segment (in comparison to most marine bristle worms which have many bristles). Most species of freshwater bristle worms live in mud and vary in size from 2mm to 75mm. Leeches do not have bristles. They move in another way. A leech has suckers front and back and it moves them by ‘looping’. A leech adheres to fish by using its front sucker and then loops its body so that the rear sucker is close to the front one. Then the leech attaches the rear sucker to the fish and releases the front sucker. It then extends its body to a maximum length and re-attaches the front sucker as far as possible from the rear sucker. Leeches usually grow to about eight centimetres in length. Both leeches and bristle worms are fairly common freshwater inhabitants. Some experts have recorded close to 200 different species of leech and bristle worm in England. The Freshwater free-living Flat Worm is commonly found in freshwater environments such as ponds and is described in the pond life section.