Family : Chaetodontidae
Text © Giuseppe Mazza
English translation by Mario Beltramini
The little Eightband butterflyfish (Chaetodon octofasciatus Bloch, 1787) belongs to the class of the Actinopterygii, the ray finned fishes, to the order of the Perciformes and to the colourful family of the Chaetodontidae.
The name of the genus Chaetodon comes from the Greek “χαίτη” (khaite) = hair and “ὀδούς” (odous) = tooth, due to the “bristle-shaped teeth”.
The name of the species octofasciatus means in Latin “with eight bands”, with reference to its black vertical bands.
It is more common in the tropical waters of the Pacific Ocean than in those of the Indian one.
We find it at the Maldives, India, Sri Lanka, Thailand, Malaysia, Australia, Indonesia, New Guinea, Micronesia, New Caledonia, Philippines, Taiwan and China up to southern Japan. Eastwards, it stops at the Solomon Islands.
It lives in the madreporic formations up to 20 m of depth.
The eightband butterflyfish is small and reaches, at the maximum, the 12 cm. The body is flat, more or less squared, with the dorsal profile of the head decidedly concave ending with an unusual mouth, done for tearing off the polyps of the corals.
The dorsal fin has 10-12 spiny rays and 17-19 soft; the anal has 3-4 spiny rays and 14-17 soft; the ventral and the pectoral ones are unarmed and the caudal is more or less blunt. On the background colour, yellowish white, we note seven dark vertical bands starting from the eye up to the caudal peduncle. The eighth one highlights the margin of the dorsal and the anal fins. The caudal fin, close to the translucent part, has also a small dark vertical band.
Usually it lives in pairs nourishing of polyps of various species of madrepores and benthic seaweeds. After the fecundation, the parents entrust the eggs to the currents. The juveniles are then often found under the protecting branches of the madrepores of the genus Acropora.
The populations are in condition to double in less of 15 months, the diet is varied and, furthermore, it is a species little required by the aquarists. Therefore, it is not surprising that their vulnerability index is very low: 11 per 100 only.
Chaetodon octolineatus Gronow, 1854.