Structure and Function of Gill Cover and Branchiostegal Rays in Teleostei

— A comparative analysis of the diversity in structure of gill cover and branchiostegal rays in Teleostei is presented. The variants of these bony structures are systematized according to the special features of their function during feeding and respiration. The morphology of the main opercular muscles is described. The special features of working m. levator operculi are discussed. The functional causes underlying the trend of decreasing size of the operculum and formation of a muscular gill cover are described. Possible factors influencing the changes in the shape and location of the opercular bones and branchiostegal rays are outlined.