Acanthuroide

Acanthuroide (also Acanthuroidei) is a taxonomic grouping of ray-finned fishes that has been treated in various classifications as either a suborder within Perciformes or as a superfamily, Acanthuroidea, within Percoidei. The name derives from Greek acanthos, meaning spine, and oura, meaning tail, referring to characteristic tail spines found in some members.

Most classifications recognize a core set of families, notably Acanthuridae (surgeonfishes), Ephippidae (spadefishes), and Siganidae (rabbitfishes). Some schemes additionally include Monodactylidae and Drepaneidae, while others place these lineages in separate, adjacent groups. The precise composition has shifted with advances in molecular phylogenetics.

Members are primarily tropical and subtropical marine fishes, most common on or near coral reefs. They tend to have laterally compressed bodies, with a continuous dorsal fin and a small, protrusible mouth adapted for grazing on algae and invertebrates. A hallmark in many surgeonfishes is a pair of sharp, scalpel-like spines on the caudal peduncle used for defense and territorial displays.

Ecology and life history: Acanthuroideans range from herbivorous to omnivorous forms, often forming schools or territory-defending groups. Reproductive modes are diverse, but many species are protogynous hermaphrodites, changing from female to male during life.

Distribution and importance: They are most diverse in the Indo-Pacific, with members also found along Atlantic and eastern Pacific tropical coasts. They play key roles in reef ecosystems through algal control and, in some cultures, as a food source.