Individual Growth of Planorbarius corneus (Planorbidae, Gastropoda) in Postlarval Ontogenesis

摘要

Individual growth of 15 great ramshorn snail Planorbarius corneus individuals was studied in aquaculture at 20 degrees C starting from 2 weeks after hatching until the death of the animals. It was demonstrated that the weight of mollusks increases throughout the study period by an S-type curve. The linear growth (shell diameter) follows a parabolic (convex) curve. Both weight and linear growth on a specified age range is well approximated by the Bertalanffy equation, while the interdependence between the shell weight and diameter by an allometric equation. The value of Bertalanffy equation coefficients is different in different individuals. The mean values of the growth constants in these equations for the weight and linear growth do not differ. Their value is 0.041 +/- 0.004 weeks(-1). The species lifespan, which is determined by a product of the growth constant into maximal lifespan, is approximate to 4.5.