Effects of crowding on fecundity in barnacles: Semibalanus (Balanus) balanoides, Balanus glandula, and Chthamalus dalli

Abstract

Phenotypic plasticity of relative investment in shell, eggs, and somatic tissue was examined with experimental population density manipulations in field populations of the intertidal barnacles Semibalanus (Balanus) balanoides from Massachusetts and Balanus glandula and Chthamalus dalli from Washington State, U.S.A. Individuals of S. balanoides of comparable somatic tissue weights produced larger clutches of eggs when crowded and columnar than when conical and uncrowded. Individuals of C. dalli showed a similar pattern. Individuals of B. glandula showed the opposite pattern: at comparable somatic tissue weights, conical uncrowded individuals made slightly larger clutches of eggs than did crowded, columnar individuals. In all cases the greatest shell investment per unit somatic tissue weight was associated with the greatest clutch investment per unit somatic tissue weight.