Brook lamprey  (Lampetra planeri)

Lampreys are some of the most primitive vertebrates alive today, they are known as cyclostomes, which means 'round mouths' and refers to the fact that they are jawless, having instead a round sucker-like mouth. A further primitive characteristic is that the skeleton consists of cartilage and not bone (2). Lampreys are similar in shape to eels, and have a series of uncovered round gill openings (known as gill pores) on the sides of the head and a single nostril on the upper surface of the head (4). The brook lamprey is the smallest of the British lampreys (4), and has two dorsal (back) fins which are in close contact (2). It is grey-blue to green in colour and during the spawning period the areas around the mouth and the anal opening become rusty red (5). Brook lampreys are also known as 'pride' (6).