Diel and seasonal influences in the metabolic rate of the Asiatic clam, Corbicula fluminea (Müller), Bivalvia, Corbiculidae

Oxygen consumption rates were measured at various times throughout the day for the freshwater Asiatic clam, Corbicula fluminea (Müller), at three periods throughout the spring of 1982 (group I collected 31 March, group II collected 22 April and group III collected 10 May). Significant daily variations in metabolic rates (eg. as much as 76% for 2 mg individuals of group I) occur in a rhythmic pat tern with two peaks of high metabolic activity at approximately 1300 and 2000 hours and two periods of low activity at approximately 0900 and 1700 hours. Daily fluctuations in the metabolic rates of Corbicula may be associated with the osmoregulatory activity of energy requiring sodium pumps since variation and rhythmicity of reported rates coincide. It is possible that the daily patterns reported in this study are representative of a portion of the circadian rhythmicity in the physiological functions of Corbicula. Significant differences (95% level) in metabolic rates noted for clams from different collection dates. Group II (collected 22 April 1982) had the highest metabolic rates as well as the greatest daily variations in those rates. Group III had both the lowest absolute rates which were as much as 79% below rates for Group II animals at similar times of the day and the smallest variations in daily metabolic rhythms. Shell length - ash-free dry weight relationships changed during this study with group III having the most tissue weight per unit shell length and group I having the least tissue weight per shell length. It is suggested that this increase in tissue weight might be the result of the Corbicula in this population becoming reproductively active. Therefore, the differences in the rates of oxygen consumption from group to group are probably the result of the clams increasing their reproductive activity as the spring spawning season begins.