LOACH. The fish known as loaches (CoUtinae) form a very distinct subfamily of the Cyprinidae, and are even regarded by some authors as constituting a family. Characters: Barbels, three to six pairs; pharyngeal teeth in one row, in moderate number; anterior part of the air-bladder divided into a right and left chamber, separated by a constriction, and enclosed in a bony capsule, the posterior part free or absent. They are more or less elongate in form, often eel-shaped, and naked or covered with minute scales. Most of the species are small, the largest known measuring 12 (the European Misgurnus fossilis), 13 (the Chinese Bolia iiariegata), or 14 in. (the Central Asian Nemachilus siluroides). They mostly live in small streams and ponds, and many are mountain forms. They are almost entirely confined to Europe and Asia, but one species (Nemachilus abyssinicus] has recently been discovered in Abyssinia. About 120 species are known, mostly from Central and South-Eastern Asia. Only two species occur in Great Britain: the common Nemachilus barbalulus and the rarer and more local Cobilis taenia. The latter extends across Europe and Asia to Japan. Many of these fishes delight in the mud at the bottom of ponds, in which they move like eels. In some cases the branchial respiration appears to be insufficient, and the intestinal tract acts as an accessory breathing organ. The air-bladder may be so reduced as to lose its hydrostatic function and become subservient to a sensory organ, its outer exposed surface being connected with the skin by a meatus between the bands of muscle, and conveying the thermobarometrical impressions to the auditory nerves. Loaches are known in some parts of Germany as " Wetterfisch."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)