Originally Posted by SnowySurface
Ok. Now I'm confused.
Is this caused by actively cutting off the tail of a young betta with a knife? Or is it caused by a glitch in DNA not forming the tail in the first place? If it is a genetic problem, then my previous comment is a bit off. I thought the breeder was physically cutting tails off of young fish that were born with healthy tails.
Okay, some quick biology.
1. A mutation was found and the mutated strain was bred over and over until the deformity was established.
2. The fish was cut and shaped during development and it cannot be bred into new generations.
I'd say it's more than likely #1. The fin wraps around cleanly with no scars or anything (if fish get scars). I'd expect it to look more damaged if it was cut up ...