THE EFFECT OF TEMPERATURE ON REPRODUCTON IN SOME MORPHS OF THE LANDSNAIL CEPAEA NEMORALIS (L.).

Abstract

One way to study evolution is to detect and measure the processes which determine size and genetic constitution of natural populations. In our laboratory a program of population studies of the polymorphic landsnail Cepaea nemoralis (L.) (de Ruiter, 1958; Wolda, 1963; 1964) was started a few years ago, and special attention has been paid to aspects of reproduction. Observations made under more or less natural conditions showed that magnitude, and probably sign, of natural selection through selective egg production depend on environmental factors (Wolda, 1963). Egg clutches produced immediately after a period of warm, dry weather seemed to be relatively large, and a high incidence of such periods seemed to increase oviposition frequency. This influence affected yellow snails more than red ones. These facts suggested some experiments in the laboratory to analyse the possible influence of warm dry weather. Clutch size was correlated positively with temperature at oviposition time. It seemed possible, therefore, that the influence of warm dry weather is in fact an influence of temperature. The results of an experiment designed to test this hypothesis are given in the present paper. Snails originating from different natural populations may behave differently as to migration tendency, mating, and oviposition frequency (Wolda, 1963). Snails from two natural populations were used in the present experiment to test such possible differences.