Bugs are rhombic-shaped bony plates formed as a result of the fusion of ganoid scales. They are located on the body of sturgeon fish in five longitudinal rows: one dorsal, two lateral and two ventral. Between the rows of bugs, smaller bony plates are embedded in the skin.

Sturgeons have no scales as such. The body of sturgeon and sterlet is covered with rows of bony plates - bugs with a tooth protruding in the middle. The bugs of sturgeon fish are several merged and modified ganoid scales, which are older than the bony scales. Real ganoid scales in sturgeons are preserved only on the upper lobe of the caudal fin.