Biorhythms of Margaritifera margaritifera (Bivalvia, Margaritiferidae) Freshwater Pearl Mussel Growth: Population of Syuskyuyanioki River (Karelia)

Abstract

It was demonstrated that individual linear growth of the Margaritifera margaritifera freshwater bivalve mollusk in Syuskyuyanioki River is accompanied by natural biorhythms. The periods of biorhythms, as well as growth retardation coefficients, vary widely and differ in different individuals. The periods of biorhythms in individual ontogenesis are approximately constant. Mean values of the growth retardation coefficients and periods do not depend on the biotope and are 0.114 ± 0.003 year^–1 and 3.88 ± 0.06 years, respectively. The possibility of thermodynamic nature of biorhythms is discussed.