Sea Lamprey, Petromyzon marinus
The sea lamprey is eel-like in shape. Its scaleless body ranges in colour from olive to brown with dark patches in larger individuals. The sea lamprey lacks pectoral and pelvic fins. It has two dorsal fins, the second and largest is continuous with the anal fin. The lamprey does not have opercular openings, but rather has seven gills slits. The absence of true jaws is a key characteristic of the lamprey. Instead, it has a circular oral disc and tongue that are heavily toothed.
The sea lamprey is anadromous spending most of its adult life at sea only returning to spawn. Young lampreys stay in freshwater for up to seven years living in silt and mud. Adult lampreys attach to fish using their toothed disc. When attached the tongue is used to scrap a hole into the body of the fish. The lamprey secretes two substances, one to prevent coagulation and the other to breakdown muscle tissues. It then sucks the fluids from the body. The prey of lamprey include species such as; lake trout, suckers, pike, Atlantic salmon, Atlantic cod, and sturgeon. They will feed until the fish has died, but are sometimes shaken off leaving the fish with a circular scar at the site of attachment. Young lampreys are filter feeders collecting small particles such as algae, detritus, and diatoms.