Irregularity of the linear growth of the Margaritifera margaritifera (Bivalvia: Margaritiferidae) population of the Syskyanjoki River, Karelia

Abstract

The interdependence of shell growth in length and height during ontogeny has been studied in the pearl mussel Margaritifera margaritifera, inhabiting the Syskyanjoki River (basin of Lake Ladoga, Karelia). It was shown that by the height-to-length ratio of the shell the population is heterogeneous. The question of whether this is due to the heterogeneity of genetic variability or due to variations in the environmental conditions remains unclear. It was found that during the ontogeny of the M. margaritifera from the population there is a constant change in the relative growth of the shell, leading to lengthening or rounding of the shell. Conventionally, all mussels can be divided into two groups, different by the periods of change in the relative growth. A comparison of the results with the data obtained previously for pearl mussels of the Varzuga River (basin of the White Sea, Murmansk oblast) was performed.