These are Mexican guppies, and what you see on their upper maxilla is an outgrowth of epidermal filaments, and these filaments basically form a fish mustache, if you will.
这是墨西哥古比鱼 你们可以从它们的上颌骨 看到一个表皮细丝的分支 这些细丝形成了 一个鱼须