A lamprey is a type of jawless fish belonging to the class Agnatha. They have a long, eel-like body and a round mouth filled with sharp, tooth-like structures. Lampreys are found in both freshwater and saltwater environments and are known for their unique feeding habits, which involve attaching to other fish and feeding on their blood and tissues. There are about 38 species of lampreys, and they play important roles in their ecosystems. Some species are considered invasive, particularly in the Great Lakes, where they have negatively impacted local fish populations. Lampreys undergo a complex life cycle, including larval, juvenile, and adult stages.