岩豆娘鱼​ yán dòu niáng yú

形态特征

岩豆娘鱼是一条小圆形鱼，身体向侧面压缩。鼻子的每一侧都有一个鼻孔，而不像蝴蝶鱼和刺蝴蝶鱼那样只有两个。口小而末端。上颚很大，咽齿众多，骨骼较重；鳃耙很多，狭窄而长，长满了小牙齿。

岩豆娘鱼的最大长度约为23厘米，最大重量重达0.2千克。身体有两个颜色阶段：浅色阶段是岩豆娘鱼在浅沙底上方或在礁石上游动时观察到的，而深色阶段是岩豆娘鱼藏在礁石中的岩石和缝隙中时可见的。浅色阶段的特征是下半身和整个头部呈灰色，通常带有淡淡的绿色。身体的上三分之一是黄色的，而柔软的背鳍、尾鳍和肛门鳍显得暗淡的。身体上有五个突出的垂直黑条，朝着腹部逐渐变窄。有时在尾状尾巴上会看到一个模糊的第六横条。在胸鳍的上底有一个黑点。在深色阶段中，身体呈深灰色或带蓝色，有时其颜色足以遮盖黑色的垂直身体带。这种颜色也经常在雄性在产卵和护巢活动中观察到。

幼鱼总是处于浅色阶段，与生活在马尾藻群落中的幼鱼除外。有时，幼鱼看起来为纯黑色，但大小不超过20毫米。垂直的黑色横条在很小的个体上可能不清楚，而鳍无色

Rock damselfly fish is a small round fish, with its body compressed to the side. There is a nostril on each side of the nose, unlike the butterfly fish and the barbed butterfly fish, which have only two nostrils. The mouth is small and terminal. The upper jaw is large, with many pharyngeal teeth and heavy bones; Gill rakes are many, narrow and long, full of small teeth.

The maximum length of rock damselfly fish is about 23 cm, and the maximum weight is 0.2 kg. The body has two color stages: the light color stage is observed when the rock damselfly fish swim above the shallow sand bottom or on the reef, while the dark stage is visible when the rock damselfly fish hide in the rocks and cracks in the reef. The light phase is characterized by a gray lower body and entire head, usually with a faint green. The upper third of the body is yellow, while the soft dorsal fin, caudal fin and anal fin appear dim. There are five prominent vertical black strips on the body, which gradually narrow towards the abdomen. Sometimes you can see a fuzzy sixth bar on the tail. There is a black spot on the upper bottom of the pectoral fin. In the dark stage, the body is dark gray or bluish, and sometimes its color is enough to cover the black vertical body band. This color is also often observed in males during egg laying and nest protection activities.

Young fish are always in the light color stage, except for those living in Sargasso communities. Sometimes, the young fish looks pure black, but the size is no more than 20 mm. The vertical black stripes may not be clear on very small individuals, while the fins are colorless