Zanclus cornutus

The Moorish idol (Zanclus cornutus) is the only existing species of the zanclidae family. It inhabits the coastal waters of tropical seas, and can be found in the Indian Ocean, South Atlantic, Red Sea and Pacific Ocean.

Zanclus cornutus is a very striking species, both for its characteristic shape and its contrasting colors. The body of this species reaches a total length of approximately 20 cm. The mouth is small and is situated in a terminal position at the end of a short tubular snout. The body is strongly compressed laterally, being especially tall. In the vicinity of the eyes, we find small bony protuberances, which give name to the specific epithet of Zanclus cornutus. As for the fins, the dorsal and anal fins are narrow and elongated. The dorsal fin is especially long, extending in the form of a filament backwards. It has 6-7 spiny rays followed by 39-43 soft rays. The anal fin is shorter, lacks filamentous appendages and is formed by 3 spiny rays and 31-37 soft rays. The caudal peduncle is narrow, and from it emerges the truncated caudal fin.

As we mentioned at the beginning, the body of this species adopts very striking colors. The base coloration is white, with a golden yellow spot in the posterior half of the body. It has 3 vertical black stripes that are bordered on the back by a white stripe. The first of the three black vertical stripes is the widest and starts at the anterior height of the eyes, running past the pectoral fins. The second black stripe is narrower and runs from the posterior half of the dorsal fin to the posterior half of the anal fin. Finally, the third black band runs along the back of the caudal fin. Also striking are narrow white stripes that emerge from the eye area and run up the face, as well as a yellow-orange spot at the base of the snout, which is bordered by a thin black line.

This species can be confused with other species of similar shape and coloration. These similar species belong to the genus Heniochus. The differences between these species and Zanclus cornutus, are evident, although they can go unnoticed, and this is the main reason why it is often found misidentified. Species of the genus Heniochus lack the yellowish spot on the back of their bodies, as well as a snout not as narrow and long as that of Zanclus cornutus. Additionally, the yellow spot that Zanclus cornutus has on its head, which is black all around, is absent in the species of the genus Heniochus.

The predominant diet of Zanclus cornutus is based on sponges, occasionally supplemented with small sessile benthic invertebrates such as bryozoans or some ascidians.

It is common to find Zanclus cornutus specimens in small groups of no more than 2 or 3 specimens.