Physical characteristics

All but one species in this suborder have small to medium-size bodies that are compressed and may be deep, disc-like, ovate, or slightly elongated. The spadefishes, or batfishes (Ephippidae), have deep and highly compressed bodies, continuous dorsal fins, and highly elevated dorsal, anal, and pelvic fins. Their scales are small and ctenoid, and their mouths are small and terminal. The scats (Scatophagidae) have deep, compressed bodies, a pronounced forehead, a mouth that is nonprotrusible, and a deeply notched dorsal fin. Fin spines are sharp and reportedly venomous. The rabbitfishes, or spinefoots (Siganidae), have compressed, somewhat elongated bodies; some in the subgenus Lo have a pronounced snout. Siganids are distinguished by the presence of venomous fin spines. Color patterns vary, and some species are quite distinctive. The monotypic louvar (Luvaridae) has a large (up to 78.7 in, or 200 cm, in length) fusiform body that is slightly compressed and quite streamlined. The head is blunt, with a projecting forehead; the mouth is small and somewhat pro-trusible; and the opercular spines are flattened. There is a groove positioned just above the eye. There are no pelvic fins, and the caudal peduncle has a large keel and small accessory keels. The scales are dentroid and quite small. Maximum body sizes range from 6-36 in (15-91 cm) for spadefishes and bat-fishes, 3.5-16 in (9-40 cm) for scats, 8.5-21 in (22-53 cm) for rabbitfishes and spinefoots, and 6.3-39.5 in (16-100 cm) for surgeonfishes. Moorish idols reach about 9 in (23 cm), and louvars reach about 79 in (200 cm) in length.

The Moorish idol (Zanclidae) is also monotypic within its family. This distinctive species has a disc-like body that is strongly compressed and dorsal spines that form an elongated whiplike streamer or filament. The color pattern is a striking arrangement of yellow, black, and white. Surgeonfishes (Acanthuridae) have compressed and disc-like bodies and possess one or more scalpel-like caudal spines or keeled peduncular plates located on each side of the caudal peduncle, which vary in size with species, may be venomous, and are capable of inflicting a painful, if not serious, wound. The caudal fin is strongly lunate, emarginate, or truncate. Many species are quite colorful, whereas others are seemingly drab until close inspection reveals often minute but exquisite details.

Detail of sharp scapel (modified spine) on caudal peduncle of a powder

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