You should not worry about this black spot on the tongue of your AKC Purebred Golden Retriever. Because this spot is neither a disease nor a symptom of any other disease. It is simply pigmentation. Not only tongue but also all body of the dog can have some pigments under the hairs. These spots are also called beauty marks or birthmarks.
The pigmentation change of your dogs tongue isn't a big deal. It's comparable to a birthmark in humans. Taking care of a puppy or even dogs in general can really make you worry about simple things. Glad to hear that you're a concerned owner of your dog.
My AKC Golden Retriever developed a black spot on his tongue last year (2008). He will be 3 in Dec. Now I have discovered a new black spot on his tongue, so he now has two. Is this normal? He has a terrible time breathing and I have often wondered if that would have something to do with the black spots
A golden may get allergies.. If she is having trouble breathing see your vet