Mandarinfish

Synchiropus splendidus is a small (6–7 cm), spectacularly colored marine fish of the family Callionymidae (dragonets), found in the western Pacific from the Ryukyu Islands through the Philippines, Indonesia, and Australia to Palau. It is widely regarded as one of the most beautiful marine fishes. The body is small, scaleless, and elongated, with a broad depressed head, large pelvic fins, and a high first dorsal fin (larger in males). The coloration is extraordinary: a vivid psychedelic pattern of wavy blue, orange, green, and yellow lines and spots on a blue-green base, produced by chromatophores containing a rare blue pigment unique among vertebrates—a cellular pigment rather than structural coloration. The skin also produces a thick, foul-smelling mucous coating believed to deter predators and parasites, which may explain its lack of scales. S. splendidus inhabits sheltered lagoons and inshore reefs, typically among rubble and dead coral of Acropora beds, where it moves slowly near the bottom, feeding on tiny benthic crustaceans (copepods, amphipods, isopods) and other invertebrates. Spawning occurs at dusk; pairs rise in the water column and release pelagic eggs. In the aquarium trade, it is highly popular but challenging to keep due to its strict dietary requirements for live microfauna. Wild-caught specimens dominated the trade, but captive breeding has recently become feasible.