tang (in zoology)
tang, common name for certain members of the Acanthuridae, a family of mostly small, mainly reef-dwelling tropical fishes with compressed bodies and small mouths and teeth. Other members of the family are known as surgeonfishes and unicornfishes. They have sharp spines on either side of the tail, and many are brightly colored. The tangs include the blue-gray to dark-brown doctorfish, several species known as blue tangs, and the larger and more abundant ocean tang of deep waters. The unicornfishes are named after the hornlike projection found in some species; the whitemargin unicornfish is among the largest members of the family, reaching 39 in. (1 m) in length. The allied spadefishes, which include the batfishes of the Indo-Pacific region, are generally large than the tangs and belong to the family Ephippidae. They are barred in black and white. The Atlantic spadefish, also called angelfish or white angelfish, is valued both as a food and a game fish. The tangs and spadefishes are classified in the phylum Chordata, subphylum Vertebrata, class Actinopterygii, order Perciformes, families Acanthuridae and Ephippidae, respectively.