Family : Acanthuridae
Text © Giuseppe Mazza
English translation by Mario Beltramini
The Sailfin tang ( Zebrasoma velifer - Bloch, 1795 ) belongs to the class of Actinopterygii, the ray-finned fishes, to the order of Perciformes and to the famly of Acanthuridae.
The name of the genus “zebrasoma”, comes from “zebra” = zebra, the well known African equine, and from the Greek “soma” = body; it is therefore an anima “with the zebra-shaped body” due to the bands unusually vertical in a surgeonfish.
The name of the species “velifer” comes from the Latin “velum” = sail and “fero” = to carry; it is therefore a fish “carrying the sail”, due to the dorsal and anal fins which may spread, like sails, as in the similar Zebrasoma desjardinii.
It is present in the tropical waters of the Indian Ocean, more or less in the same environments of the Zebrasoma desjardinii, and, farther, we find it in the Pacific, from Indonesia to the Hawaii and to the Tuamotu Islands. As northern limit, it has Japan, and, southward, New Caledonia and Easter Island. It seems to be present also in Florida due to the inadvertent release of aquarium animals.
It lives in the madreporic formations of where are present rocks rich in seaweeds, exploring the bottom in shallow waters, also troubled, up to a maximum of 30 m of depth.
It can reach the 40 cm, but its normal size is of about 30 cm.
The body is flat, more or less oval or roundish when the fins are spread. The dorsal has 4-5 spiny rays and 29-33 soft; the anal 3 spiny rays and 23-26 soft; the ventral ones have a very modest size; the pectoral ones count 23-26 unarmed rays; the caudal is blunt.
The caudal peduncle has the cutting blade typical of the surgeonfishes, evidenced on both sides by a showy blue dot. This is a warning for the importunators, even if not poisonous.
The mouth has relatively bigger teeth than the other Zebrasoma, because it is a fish nourishing of leafy seaweeds.
The body shows 6 wide vertical bands.
The first, longer, crosses the eye and is covered by numerous small white dots, present also in the front part of the snout. The second, close to the small dots which colour of yellow-orange, fades into paler shades and shows already some vertical yellow-orange traits which replace or follow the aligning of the dots. The other 4 vertical bands contain only lines of this colour, more or less forked or interrupted, on a dark brown or bluish grey background.
The first caudal begins as white but then becomes immediately orange, and ends with a blue small margin. Also the sail-shaped fins have several yellow-orange stripes.
They are concentric and parallel to the edge, visible only when they are completely spread out.
The sailfin tang lives solitary or paired. It swims all the day round looking for seaweeds which it nourishes of, and when it feels endangered, like the Zebrasoma desjardinii, it spreads the dorsal and anal fins in order to seem twice as large. This is a way to impress the small opponents or for gaining time and flee.
It reproduces with pelagic eggs.
The juveniles have a simplified livery with vertical yellow and black bands.
It has a vulnerability index of 37 per 100, but the populations may quickly double, in 1,4-4,4 years.
Acanthurus velifer - Bloch, 1795; Zebrasoma veliferum - Bloch, 1795.
The photographic file of Giuseppe Mazza