Introduction

Perhaps the group most familiar to aquarists is the angelfish family, and this seems to be denied by no one. Here I introduce a rare color morph of Centropyge potteri from the Hawaiian Islands that is entirely blue-black on its side. Let's first discuss some background information on the Centropyge genus, and then we'll touch on this recently discovered unusual color morph of Centropyge potteri.

The Genus Centropyge

The Family Pomacanthidae includes seven genera (Randall, 2005) with some 88 recognized species that dwell mainly on Indo-Pacific coral reefs. The family is popularly known as angelfishes (or marine angelfishes) worldwide. Their graceful colors and non-belligerent behavior makes them much sought-after by aquarists and divers everywhere, and they always fascinate not only beginners but veterans, as well as many ichthyologists. Richard L. Pyle has reclassified the group and made some changes. According to the most recent study the genus Paracentropyge was reclassified into the genus Centropyge, and then the species boylei, multifasciata and venusta were shifted from Paracentropyge to Centropyge. Also Frank Schneidewind of Germany wrote a scientific paper describing Centropyge flavicauda and C. acanthops as junior synonyms (= same species) of C. fisheri, which was long thought to be an Hawaiian endemic, and his concept is now widely accepted by most ichthyologists. A new Chaetodontoplus species was described as C. vanderloosi by Allen & Steene, 2004 from Papua New Guinea, and also Centropyge abei was published by Allen, Young & Colin from Sulawesi and Palau in 2006.

Centropyge is probably the most popular genus both in the aquarium trade and in the field, and its species often are called the Pygmy Angels due to their small size, rarely exceeding 10cm. They tend to retire or dash into crevices when danger approaches. They dwell in warm waters of the Indo- west Pacific and the Atlantic Oceans, being absent from only the eastern Pacific. Some species are distributed widely in the Indo-West Pacific, yet some are restricted to very small areas or even to a single island.

Centropyge are commonly mimicked by other fishes. Three species are mimicked by the very similar juveniles of surgeonfishes Acanthurus pyroferus or A. tristis. Also, C. nox is mimicked by the very similar-looking dottyback, Manonichthys paranox. Some species differ in coloration depending on sex, but this difference may be minor, while C. flavissima has an ocellus on its sides in its juvenile stage. Centropyge flavissima has two distinct color morphs; the Pacific variety has a blue eye-ring but those from the Indian Ocean lack it entirely.

Many variations appear among individual species, and we often see such varieties in C. bispinosa, which is red to blue, whitish grey, entirely black or even orange or yellow. Centropyge loriculus also has many variations; typically red with five bars but some (especially those from the Marquesas Islands, southeastern Pacific) completely lack the black except on their fins. The Hawaiian Flame Angelfish is sometimes called the "Ultra Flame" when it is deep red overall, but this case is rare in Hawaii; most of them have a pattern similar to other Pacific populations.

Members of this genus can easily be found at local fish stores and are usually sold at lower prices than larger angelfish species. Many are shipped from the Philippines and Indonesia but some rarities come from the far island group, and they typically command a higher price. Recently, some species have been aquacultured and will be exported to angelfish enthusiasts; these include C. resplendens, C. loriculus, C. interrupta, C. flavissima, C. fisheri, C. multicolor and even C. debelius. Many species of Centropyge are hardy and eat well in captivity, but several species refuse any food offered and are too timid and retiring to thrive in captivity.

The genus now includes 32 species as shown in the following list:

Centropyge debelius was named after a famous diver, Helmut Debelius. Centropyge woodheadi was deleted because of its synonymy with C. heraldi. In addition, a probably undescribed species was found off the coast of Western Australia around the Rowley Shoals. Many natural hybrids have been discovered and one of the most popular is the cross between C. flavissima and C. vrolikii. For further information on the Centropyge genus, the reader is referred to Henry Schultz' article, "What a Darling Little Angel: The Genus Centropyge."

Centropyge potteri

This species is typically yellow-orange with a dark area that covers much of its body and has several dark blue vertical bars on its entire body. It is endemic to the Hawaiian Islands, the area northwest of the Hawaiian Islands (Midway) and Johnston Island (south of Hawaii; rare). It is a shallow water species that can usually be seen at a depth of as little as one meter. The species occasionally forms a harem, usually containing two individuals - one male and its mate, and is also known to form groups of up to three to four individuals in nature. Centropyge potteri has no close relative in the genus and is distinctly colored. It rarely exceeds 10 cm in length and is popularly called the Potter's Angelfish or Russet Angelfish.

I have seen pairs on reefs in Kaneohe Bay several times, southeastern Oahu and a single specimen that was swimming along the wall of a yacht harbor in the bay while I was snorkeling. Four shops in Oahu displayed many individuals of this lovely angelfish at low prices, and most individuals sold at shops are less than 8cm long. Some refuse any kind of food offered in the aquarium, but most learn to accept many artificial foods.

An Unusual Blue Morph

Some five years ago an unusual specimen with a blue-black body was shipped from Hawaii. It was caught at a depth of more than 60 meters off the Kona Coast, Hawaiian Island. Two similarly-colored specimens were captured by divers, and one of them luckily was exported to Tokyo (and another went to the mainland USA). I saw the individual for the first time at a shop in Kyoto in February of 2003. It was not for sale but was displayed in a large reef tank with massive live corals, other invertebrates and a few small, non-aggressive fishes. It was a large, mature fish, some 10 cm long and was eating well. I took several shots, two of which are shown here. It is entirely a brilliant blue with numerous black bars on its side with no yellow area, and some black areas can be seen centrally on its body. It was sold at a price of ¥600000,- at first. The aquarist who got it sold it to his friend, and finally the shop obtained it for display, where it was not offered for sale.

The reason it is this blue color is not known, but such a deep area is very dark, almost black, so it is possible that these specimens' color could have helped them avoid enemies' attacks. But I wonder why it stayed blue in aquariums for over three years…?

Acknowledgements

I greatly appreciate the shop in Kyoto, EARTH, that kindly permitted me to photograph this black beauty there, and also another shop in Osaka, BLUE HARBOR, whose personnel led me to the shop for the first time.

All photos copyrighted and taken by Hiroyuki Tankaka, MD.

Literature Cited:

Allen, G., 1979. Butterfly- & Angelfishes of the World, Volume 2. John Wiley & Sons, USA. Pp. 145-352.

Allen, G., R. Steene & M. Allen, 1998. A Guide to Angelfishes & Butterflyfishes. Odyssey Publ. / tropical Reef Research, USA/Australia. 250pp.

Debelius, H., H. Tanaka, and R. Kuiter, 2003. Angelfishes, a comprehensive guide to Pomacanthidae. TMC-Publishing, UK. 208pp.

Hoover, J., 2003, Hawaii's Fishes (revised edition). Mutual Publishing, USA. 183pp.

Pyle, R., 2003. A Systematic Treatment of the Reef-fish Family Pomacanthidae (Pisces; Perciformes). Ph.D. diss., Univ. of Hawaii, USA. 422pp.

Randall, J., 1996. Shore Fishes of Hawaii. Natural World Press, USA. 216pp.

Randall, J., 2005. Reef & Shore Fishes of the South Pacific. Univ. of Hawaii Press, USA. 707pp.

Schneidewind, F., 1999. Kaiserfische. Tetra Verlag, Germany. 262pp.

Schultz, H. 2003. What a Darling Little Angel: The Genus Centropyge. Reefkeeping Magazine, 2(1).