The Dotted Butterflyfish, Chaetodon semeion, is a species of butterflyfish (family Chaetodontidae). It is found in the Indian Ocean and Pacific Ocean from the Maldives to the Tuamotu Islands, north to the Ryukyu Islands and south to the Great Barrier Reef. It grows to a maximum of 26 cm (10 in) long. The body is golden yellow. The base of the posterior portions of the dorsal and anal fins is black, a prominent vertical black bar runs across the eye and there are diagonal rows of black dots on the sides. A filament originating from the soft portions of the dorsal fin rays trails posteriorly.
The Dotted Butterflyfish belongs to the large subgenus Rabdophorus which might warrant recognition as a distinct genus. In this group, it appears to represent a distinct lineage, with the Saddle Butterflyfish (C. ephippium) perhaps the only somewhat closely related species. Next closest seems to be a group including the Black-backed Butterflyfish (C. melannotus), Spot-tailed Butterflyfish (C. ocellicaudus) and Yellow-dotted Butterflyfish (C. selene), but these are already so distant that their ancestors must have diverged from the Saddle Butterflyfish’s soon after the Rabdophorus lineage started to diversify.
C. semeion is found at depths between 2 and 30 m. An uncommon species occurring in coral rich areas of clear water lagoon and semi-protected seaward reefs, it is usually found in pairs or small groups and more wary than most species of Chaetodon. (text source: Wikipedia)
Pictures: Misool Islands, Raja Ampat, Papua, Indonesia by Sami Salmenkivi