Population Densities and Breeding in Eurydice Pulchra and Eurydice Affinis in Britain

Abstract
Despite the widespread occurrence of Eurydice pulchra Leach on sand beaches along the Atlantic coasts of Europe and around Britain (Jones & Naylor, 1967), there has been no detailed work on growth and reproduction in this species until a recent account by Salvat (1966), who carried out investigations on breeding populations of this species and the closely allied E. affinis at Arcachon, south-west France. Apart from this there are some brief generalized observations on the reproductive cycle of E. pulchra in ecological studies upon the fauna of sandy beaches (Watkin, 1941, 1942; Scott, 1960; Lagardère, 1966), and some reference to reproduction in other species of the genus is given by Fage (1933), Bacesco (1948), and Soika (1955). In view of some contrasting accounts given by previous authors and the lack of detailed observations on British material, present investigations were carried out into the reproduction and life cycle of E. pulchra and E. affinis in South Wales. Estimates of the reproductive potential of each species are made and discussed in relation to actual population densities recorded on the beaches.