Variation in growth rate in the landsnail Cepaea nemoralis

Abstract

SummaryIn a number of experimental populations of the landsnail Cepaea nemoralis living under natural conditions a variation in growth rate has been observed both within and between populations. Usually it takes two years for newly hatched snails to become adult, but sometimes it takes only one and sometimes three years. The differences between populations had large effects on the differences in number of individuals in these populations.Under experimental conditions in the laboratory it has been shown that there is a large variation in growth rate, part of which is genetic. The genes affecting polymorphism in Cepaea do not seem to be involved in the genetic variation in growth rate. Large eggs produce faster growing juveniles. No effect of the size of the parents on growth rate of the juveniles could be detected. Faster growing snails become larger adults. This may result in faster growing snails having a larger fecundity as larger snails produce on the average more and larger clutches of eggs. Some suggestions were obtained that slow growing individuals have a lower chance of survival.A descriptive model is used to illustrate the increase of complexity of the dynamics of Cepaea populations because of the variation in growth rate.