Tvåskalsiga

Tvåskalsiga is a Swedish term that translates to "bivalve" in English. It refers to a class of marine and freshwater mollusks belonging to the phylum Mollusca, characterized by a shell composed of two hinged parts, or valves. These valves are typically symmetrical and are connected by a flexible hinge ligament, which allows the shell to open and close.

The two valves of a bivalve shell serve to protect the soft-bodied animal within. The shell can be opened to allow the animal to feed, respire, and move, and then clamped shut for defense against predators. Many bivalves are filter feeders, drawing water into their mantle cavity and extracting food particles. Others are deposit feeders or even predatory.

Examples of common bivalves include oysters, mussels, clams, and scallops. They inhabit a wide range of aquatic environments, from shallow coastal waters to the deep sea, and from freshwater lakes and rivers. Bivalves play important ecological roles, such as filtering water and serving as a food source for other organisms. Their shells have also been used by humans for various purposes, including as food, tools, and decorative items. The term "tvåskalsiga" specifically emphasizes the defining characteristic of having two shells.