Different scientific names and different appearance characteristics.

1. The scientific name of the flatfish is the flatfish, which belongs to the family Plaiceidae, and the scientific name of the opium fish is the family Plaiceidae, which belongs to the order Plaiceidae.

2. The eyes of the flatfish are on the same side of the body, making it look like it has only one eye, while the eyes of the opium fish are distributed on both sides of the body.