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Cobitidae (loaches; subclass Actinopterygii, order Cypriniformes) A family of mainly small, slender-bodied, freshwater fish, that have tiny scales and toothless jaws. The ventrally positioned mouth bears at least three pairs of barbels. Cobitidae occur in swift-flowing mountain streams as well as in slow-moving rivers. When the oxygen concentration of the surrounding water falls to a low level, loaches can gulp in air and extract oxygen via well-vascularized parts of the gut. Many species are sensitive to changes in atmospheric conditions. Misgurnus fossilis (European weatherfish), growing to at least 20 cm, has been used in the past as a barometer because it becomes more active when a weather depression approaches. There are nearly 150 species, found mainly in Europe and Asia.