Mandarinfish are a marine fish referred to specifically by the genus species name, Synchiropus splendidus. They belong to the dragonet family of Callionymidae, making them one of approximately 188 members. These fish are from the tropical Indo-Pacific, like the Philippines, Indonesia, Hong Kong, the Ryukyu Islands, Australia and New Guinea. They enjoy temperate ranges of 24 to 26°C and live on coral reefs and shallow lagoons. They can be found roaming the bottom or hidden under foliose and dead coral at depths as shallow as 1-18 meters. Mandarinfish are slow, shy and passive in nature most of the time.
They have a broad, depressed head, 4 dorsal spines, 8 dorsal soft rays and no anal fins. The first dorsal spine is more elongated on the male. The females also reach at most 6 cm in length, while the males reach 3 in. Their large fan-like pelvic fans let them walk along the bottom. Mandarinfish are not covered with scales, but instead a layer of mucus composed of two different layers of cells. The first layer protects them from their immediate surroundings and potential parasites. The second layer consists of sacciform cells on their skin which produce and release substances with some toxins. This creates a foul odor and bitter taste most likely used to deter predators. The most striking feature of mandarinfish is their vibrant coloration. Their body is primarily blue in color with orange, red and yellow wavy line accents. It’s unclear the purpose of these stand-out colors, but two possibilities are for mating aesthetics and for warning predators of their toxins.
Because there are fewer active females, the males do compete with one another for mating rights. Larger and stronger males tend to mate more frequently, indicating that is the sexual preference of the females. They are pelagic spawners and provide no parental care to their eggs or young. The babies thus develop fairly quickly, with the eyes becoming pigmented and the mouth becoming well-developed only 36 hours after fertilization. The adult color pattern will not develop though until the second month, or when the fish reaches about 10-15 mm in length. While their appearance makes them desirable aquarium fish, mandarinfish can be difficult to maintain because of their different dietary requirements compared to wild mandarinfish. What’s more, mandarinfish in captivity only live to be 2-5 years at most while wild mandarinfish can live up to 10-15 years. Currently there has been no conservation status given to mandarinfish by the IUCN (International Union for Conservation of Nature).