Chaetodon citrinellus is one of 88 members of the genus Chaetodon, which together with 11 additional genera make up the butterflyfishes family (Chaetodontidae) in which a total of 129 species are currently described. We find this species in the waters of the Indian and Pacific Oceans, from the Red Sea, East Africa, to Hawaii, the Marquesas Islands, south to northern Japan and south to Australia. It is a coastal fish, associated with reefs and with a preference for waters less than 35 meters deep.
With an oval, laterally compressed body, Chaetodon citrinellus reaches sizes up to 13 cm maximum total length. Its rostrum is relatively short, although slightly pointed, with a small terminal mouth equipped with small teeth. The dorsal fin is continuous and has 13-14 spines and 20-22 soft rays. Among the spiny rays of the dorsal fin are the indentations of the membrane that forms the fin. The anal fin has 3 spines and 16-17 soft rays. The posterior ends of the dorsal and anal fins are much more developed, ending in an angle that directs them towards the caudal peduncle. Behind the caudal peduncle, we find the caudal fin which has rounded margins.
Chaetodon citrinellus has a pale yellow body, with numerous dark spots along the body. Its head is smooth, with a vertical black stripe across the eye. The fins are yellow, and the back of the anal fin has a black stripe.
The diet of Chaetodon citrinellus is omnivorous although conditioned in part by its specialized and small mouth. Among the most common prey we find coral polyps, polychaetes, anemones and other marine invertebrates such as copepods and amphipods. Occasionally it complements its diet with some filamentous algae.
Regarding reproduction, Chaetodon citrinellus has individuals with separate sexes that form monogamous clutches, in which the females lay their eggs in the water column usually at dusk, and the male releases a cloud of sperm to fertilize them. Currents in the area disperse the fertilized eggs.
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