Shell Form and Growth of the Bivalve Scapharca broughtoni

Linear growth rates and age-related changes in shell form are analyzed in the bivalve Scapharca broughtoni from several areas of Peter the Great Bay, Sea of Japan. Mollusks grow fast during the first 4 to 5 years of life; at the age of 10-12 years, the annual growth increment in shell size does not usually exceed 1-3 mm. Irrespective of habitat, the shell valve convexity of S. broughtoni increases with age, but the most significant changes in shell form occur during the first year of life. The peculiarities of growth and age-related changes in shell form of S. broughtoni are discussed from the standpoint of the functional morphology of burrowing bivalve mollusks, which, at the postlarval stage, change from an attached to a free-living mode of life.