Mandarinfish

Lore & Background

The mandarinfish has a body shape similar to a goby, though this is the only resemblance. Its vivid coloration sports a bright blue background with swirly orange stripes and a blue-greenish face with bold blue stripes. The large pelvic fins are used for 'walking' on the seafloor, while the real pectorals are nearly transparent. The dorsal fin is exceptionally tall in males. The eyes are usually red with black pupils. Different varieties exist, including a red mandarin and a spotted mandarin. Mandarinfish are reef dwellers, preferring sheltered lagoons and inshore reefs. They are slow-moving and fairly common within their range, but not easily seen due to their bottom-feeding habit and small size (reaching only about 6 cm). They feed primarily on small crustaceans and other invertebrates. In the wild, feeding is continuous during daytime; the fish peck selectively at small prey trapped on coral substrate in a home range of many square meters. The mandarinfish is one of only two vertebrate species known to have blue coloring because of cellular pigment, the other being the closely related psychedelic mandarin (S. picturatus). The name 'cyanophore' was proposed for the blue chromatophores. In all other known cases, the color blue is structural, coming from thin-film interference from piles of flat, thin and reflecting purine crystals.

Reader's Guide

The mandarinfish belongs to the perciform family Callionymidae, the dragonets, which counts 10 genera and more than 182 species. Genus Synchiropus counts 51 species, divided into 10 subgenera; the mandarinfish is in subgenus Synchiropus (Pterosynchiropus) along with S. occidentalis and S. picturatus. In the reef ecosystem, it feeds on small crustaceans and other invertebrates, with a diet determined from gut analyses of seven wild fish that includes harpacticoid copepods, polychaete worms, small gastropods, gammaridean amphipods, fish eggs, and ostracods. Despite its popularity in the aquarium trade, the mandarinfish is considered difficult to keep because its feeding habits are very specific; some fish never adapt to aquarium life, refusing to eat anything but live amphipods and copepods. Individuals that do acclimatize to aquarium food are considered quite hardy and highly resistant to diseases such as marine ich, partly because they do not have the typical skin type affected by this disease. Mandarinfish also have a layer of debatably smelly and bitter slime instead of scales, which blocks out disease and probably also discourages predators, implying their bright coloration is aposematic.

Did You Know?

• Its common name comes from its extremely vivid coloration, evoking the robes of an Imperial Chinese mandarin.
• The mandarinfish has a layer of slime instead of scales, which blocks disease and may discourage predators.
• It appeared on a 39-kip postage stamp from Laos issued in 1987 and a 40-cent stamp of the Federated States of Micronesia issued on 26 August 1993.