Zebrasoma desjardinii

Zebrasoma desjardinii, the Red Sea sailfin tang, Desjardin's sailfin tang, Indian sailfin tang or Indian sailfin surgeonfish, is a species of marine ray-finned fish belonging to the family Acanthuridae, the surgeonfishes, unicornfishes and tangs. This fish is found in the Indian Ocean.

Taxonomy
Zebrasoma desjardinii was first formally described in 1836 as Acanthurus desjardinii by the English zoologist Edward Turner Bennett with its type locality given as Mauritius. In the past, this taxon was treated as conspecific or synonymous with Zebrasoma velifer. The genera Zebrasoma and Paracanthurus make up the tribe Zebrasomini within the subfamily Acanthurinae in the family Acanthuridae, according to the 5th edition of Fishes of the World.

Etymology
The specific name of Zebrasoma desjardinii honours the French zoologist Julien Desjardins; he lived for a number of years in Mauritius and donated a collection of fishes to the British Museum of Natural History, including the type of this species.

Description
Zebrasoma desjardinii has a tall dorsal fin that has 4 spines and between 27 and 31 soft rays (the longest of which is around half of the standard length), while these figures for the anal fin are 2 and between 22 and 24 respectively. It has a deep body, with the standard length being 1.8 to 2 times its depth; the maximum published total length of this species is 40 cm. The mouth protrudes with a concave profile on the snout. The spine in the caudal peduncle has a narrow posterior connection to the body, and the caudal fin is truncate. The body is grey, with around 8 dark grey vertical bars; each bar houses 2 to 3 orange or yellow vertical lines, which break up into spots towards the lower body and on the anal fin. There are 2 dark brown bars on the head, with the first one passing through the eye. There is a dense pattern of small, light yellow spots on the head and body, and a similar pattern of spots arranged in bands can be on the dorsal fin. The caudal fin is marked with pale blue spots. The juveniles have slender grey and yellow bars on the body and 2 black bars on the head.

Distribution and habitat
Zebrasoma desjardinii is found in the Indian Ocean. It can be found off the eastern coast of Africa (as south as Sodwana Bay, South Africa ), as well as in the Middle East, including off the coasts of Israel, Saudi Arabia and Yemen. It is also found across the islands of the Indian Ocean (such as Sri Lanka, islands in the Andaman Sea, Sumatra, Java, the Cocos (Keeling) Islands and Christmas Island). In 1999, a pair of this species was recorded in the Atlantic Ocean, off Florida, but this was probably due to aquarium release.

Zebrasoma desjardinii is found at depths between 1 and 30 m in lagoon and seaward reefs, although the juveniles are more typically found in sheltered areas within reefs.

Behaviour
Zebrasoma desjardinii adults usually can be found in pairs, while juveniles are solitary. They feed primarily on filamentous algae, macroalgae and plankton, but individuals in the Red Sea have been regularly observed feeding on jellyfish (Scyphozoa) and comb jellies (Ctenophora) as well. This species may form aggregations while feeding on algae; if they do so within the territory of the predatory slingjaw wrasse, the wrasse may darken its colour so as to match the colour of the tangs. The wrasse then joins in the aggregation and mimics their algae-feeding actions while hunting prey.

Zebrasoma desjardinii is a pair spawner; while this is a typical trait of other fish in its genus, group spawning is more common at the family level.

Utilisation
Zebrasoma desjardinii is used in the aquarium trade.