Dynamics of Colonization by the Beadlet Anemone,Actinia Equina

Abstract

Colonization of the littoral zone presents many problems to both sessile and relatively sessile invertebrates. These may be especially acute for inhabitants of the upper reaches of this zone, since suitable niches are usually sparsely distributed there, and are often ephemeral in nature. Consequently, both intraand inter-specific competition for space is likely to be particularly intense.The widely distributed and abundant, beadlet anemone,Actinia equinaL., in common with a number of other littoral anthozoans, is apparently capable of both asexual (apomixis or somatic embryogenesis; Polteva, 1963; Gashout & Ormond, 1979; Orr, Thorpe & Carter, 1982) and sexual (Carter & Thorp, 1979) reproduction. The former results in the production of young, which are brooded within the coelenteron and which appear most suited to local dispersal, whilst the latter, if it occurs, is assumed to involve either ovipary or larvipary followed by a planktonic phase. Study of this species therefore affords an opportunity to investigate the dynamics of colonization and dispersal in an heterogeneous environment, in relation to flexibility in reproductive tactics.