Pearlscale butterflyfish

Lore & Background

The pearlscale butterflyfish can grow to a standard length of 15 centimetres with no discernible differences between males and females. Its body is pearly white with black-edged scales, giving the sides a cross-hatched pattern rather than the clear chevrons seen in related species. The hind parts are orangey-yellow, the base of the caudal fin is white, and the head is darker with vertical black eyestripes and a black white-rimmed crown spot.

This species is found on or around reefs of the central Indo-Pacific region from Indonesia and the Philippines north to the Ryukyu Islands. It is diurnal and usually found at depths below 6 metres, in clear coastal to outer reef slopes and drop-offs, often around Acropora staghorn corals. In the wild it is found alone, in pairs, or in small groups, and is territorial towards similar-looking species.

C. xanthurus is one of the "crowned" butterflyfishes, a group of largely allopatric species sharing a color pattern of dark forward-pointing chevrons on silvery hues, a black-and-white crown spot, and yellow to red hindparts. Other members include the Atoll, Eritrean, and Seychelles butterflyfishes, which are more closely related to each other than to C. xanthurus. The relationships among these and other species, such as the Asian Butterflyfish and Blue-striped Butterflyfish, are subject to ongoing taxonomic uncertainty.

Reader's Guide

The pearlscale butterflyfish is a well-known aquarium fish due to its attractive colors. A 50-gallon aquarium is the minimum size recommended, with a water temperature between about 74 and 80°F. Although they can be aggressive at times, they are delicate and require peaceful tankmates to thrive. They may be compatible with other butterflyfishes that have a different color pattern, but there is no guarantee of peaceful relations. When adding more than one to a tank, they must be added simultaneously, and lots of live rock with shelters helps reduce stress.

In the wild, they feed on algae, soft coral polyps, and small benthic invertebrates. Along with other coral-eating Chaetodon species, they can wreak havoc on living corals in the aquarium. They should be fed a variety of foods including mysid shrimp, brine shrimp, krill, spirulina, and foods containing algae.

The species is part of the "crowned" Chaetodon clade, whose further relationships are unclear. They have been placed in the subgenus Exornator or considered a distinct subgenus Rhombochaetodon. DNA sequence studies suggest some older and more singular lineages, but the expanded group's relationship to species like the Speckled Butterflyfish and Four-spotted Butterflyfish remains unresolved. Ultimately, it might be better to merge both Rhombochaetodon and Roaops into Exornator, or if the genus Chaetodon is split up, Exornator might become a subgenus of Lepidochaetodon or a separate genus.

Did You Know?

• The pearlscale butterflyfish is also called yellow-tailed butterflyfish, crosshatch butterflyfish, or Philippines chevron butterflyfish.
• Its scales have black edges that create a cross-hatched pattern rather than clear chevrons.
• It is found in the central Indo-Pacific from Indonesia and the Philippines north to the Ryukyu Islands.
• In the wild it feeds on algae, soft coral polyps, and small benthic invertebrates.