The Order Amphipoda belongs to the class Crustacea, and is a group of small, shrimplike, freshwater or marine animals. Amphipods are a diverse group, with over 7,000 species known. They can be found in almost all aquatic environments, including the deep sea, and play an important role in food webs. The Order Amphipoda is sometimes referred to as the "scuds" or "side-swimmers" due to their characteristic swimming behavior. Other synonyms for the Order Amphipoda include the suborder Gammaridea and the family Talitridae. Amphipods are important to monitor environmental changes because they are sensitive to pollution and other environmental stressors.