These are nothing more than rays with congenital birth defects. During fetal development, the two "wings" should have merged together and formed a solid disc. Instead, possibly due to water temperature that was too low, too high, some other environmental factor, or premature birth, the development of the disc was delayed or arrested and the ray was born before the two sides of the disc merged into one. It is not genetic, not hereditary, and highly unlikely to be passed on to offspring. And, I might add, certainly not of any value. When there is one visible congenital birth defect, the statistical possibility of other hidden defects is increased.