Carcinus maenas

Carcinus maenas, the European green crab, is a shore-dwelling crab native to the northeastern Atlantic and introduced to coastlines worldwide. It tolerates varied habitats and can strongly affect coastal ecosystems.

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Brachyura: Brachyura is the infraorder of true crabs, characterized by a short abdomen tucked beneath the thorax. This is the larger crab group to which Carcinus maenas belongs.
Osmoregulation: Osmoregulation is the control of water and dissolved-ion concentrations within an organism. Its ability to regulate internal salts helps the crab tolerate changing estuarine salinity.
Invasive species: An invasive species is a nonnative organism that spreads and causes ecological, economic, or other harm. Introduced populations of the green crab have become damaging in several coastal regions.
Trophic cascade: A trophic cascade is an ecological chain reaction in which changes at one food-web level affect others. By consuming key grazers and shellfish, green crabs can alter food-web structure.
Crustacean: Crustaceans are arthropods that include crabs, lobsters, shrimp, and barnacles. The green crab's jointed limbs and segmented body place it among crustaceans.
Euryhalinity: Euryhalinity is the ability to tolerate a wide range of environmental salinities. This tolerance lets the green crab occupy both marine shores and brackish waters.
Ballast water: Ballast water is water carried in ships to maintain stability and discharged at ports. Shipping ballast is one proposed pathway for the crab's transoceanic dispersal.
Eelgrass: Eelgrass is a marine flowering plant that forms underwater meadows in shallow coastal waters. Crab predation on grazers can change eelgrass condition, while burrowing and disturbance affect beds.
Decapoda: Decapoda is an order of crustaceans with five pairs of walking legs, including crabs and lobsters. Its five pairs of thoracic appendages identify the green crab as a decapod.
Crustacean molting: Crustacean molting is the shedding of an old exoskeleton to permit growth. The crab must molt repeatedly because its rigid shell cannot expand.