Why luminescent fish scales?

In the real skin layer and above the scales there are many pigment cells and light cells distributed. But if there is only pigment cells, it is impossible to make the fish appear with such brilliant colors.

In the skin of the fish, there is also a type of light cell, in which cells contain bird droppings, turtles are colorless or white crystals, they accumulate in the cell.

When light hits the fish's body, through the reflection and interference of the crystals in the cell, the light that appears before our eyes becomes a sparkling silver light. So fish scales are sparkling, mainly due to the effect of light cells