The yellow-tailed para-spiny tailfish, also known as the blue upside-down and pseudo-spiny tail seabream, is the only species of fish in the genus Perciformes suborder Spinytails in the family Spinytails, with no subspecies differentiation. The fish body is brightly colored royal blue, with a distinct palette of black bands, and the larger the fish, the lighter the color. The upper part of the head is scattered with small black spots, and there is a hard spine on each side of the tail stalk. Widely distributed in the Indo-Pacific seas, it is mostly active in coral reef areas, foraging for organic debris, etc., and is a famous ornamental fish.
The body is oval and flattened. The mouth is small, the upper and lower teeth are large, and the teeth are immobile. The dorsal and fins have sharp spines, the ventral fins are only 3 soft strips, and the caudal fins are nearly truncated. The body is blue , the upper half of the body is black from the center of the pectoral fin to the caudal stalk , but there is an oblong oval blue spot behind the pectoral fin ; another black band behind the eye that runs long along the base of the dorsal fin and connects with the black spot of the body ; the dorsal , breech and ventral fins are blue with black margins ; the anterior part of the pectoral fin is blue and the posterior part is yellow; the caudal fin is yellow with a black upper and lower leaf margin. The anterolateral grooves grow toxic glands.
It is an oceanic benthic fish that inhabits clear, sea-facing and tidal reef areas, adults usually congregate in water layers 1-2 meters above the seafloor, and juveniles or juveniles gather near cape corals with staghorns and hide among coral buds as soon as they are frightened. Omnivorous, feeding mainly on zooplankton and sometimes algae. Occasionally alone, mostly swimming in pairs or small groups, the fish also congregates with other fish of the spiny tail family. Gentle temperament, when threatened, it will erect its tail spines to attack enemies.
The spiny tail fish family is a general term for a family of fish belonging to the order Perciformes, with a total of 6 genera. The origin of its family name is that the fish of the family have one or more hard spines on the tail stalk, which is as sharp as a surgical scalpel, and the skin is easily cut and bleed when accidentally touched, so it is called "spiny tailfish". The body is oval or oblong-oval, flattened laterally, and the caudal stalk is thin and powerful. The body is covered with small ctenophores, some of which are fixed in the skin, making the epidermis rough as sandpaper, so it is commonly known as "coarse skin seabream" in Chinese. It is widely distributed in tropical and subtropical waters except the Mediterranean Sea.