Red Tail Gills

[kno4te]

For some reason thought this was an acquired thing. Makes sense to be genetic.

 

[thebiggerthebetter]

I don't think missing parts of gill plates is the explanation or the whole explanation because the fish also looks like it's holding a baseball in its mouth... unless I misunderstood the OP who I thought said this wasn't like that until recently.

That's why Ron is saying too that this condition was acquired by the fish, according to the OP.