舌头上的黑斑就好比人的雀斑，不是健康问题。

有人说舌头上有黑斑的狗狗可能有chow chow的血统，但不是每个人都同意。

"Black spots on a dog's tongue are simply “beauty marks”, similar to freckles on people. They are merely places that have extra pigment than other places on the tongue — that's all! Consider it your dog's own birthmark. So, a black spot on your Labrador's tongue does not mean he's really a Chow mix."

here's something on the website of AKC.

http://www.akc.org/press-center/akc-syndicate/ask-akc/black-spots-on-dog-tongue/