Abstract
Barnacles are prominent sessile organisms in marine ecosystem. Larval settlement in sessile organisms is a critical developmental stage for their survival and reproduction. The gregarious settlement of barnacles and its chemical basis was first described in the middle of the 20th century. An overview of studies on barnacle settlement pheromones, especially recent molecular approach, is described in this review. An adult glycoprotein, purified from Amphibalanus amphitrite and named as the settlement-inducing protein complex (SIPC), induces settlement of conspecifc cypris larvae. SIPC is active when adsorbed on the surface of substratum, and is thought to be a leading molecule for the gregarious settlement in barnacles. From immunological studies, it was shown that SIPC is a barnacle specific protein and is involved in both adult-larva and larva-larva interactions. Recent cDNA cloning revealed that SIPC shares a 30% sequence homology with α2-macroglobulins and the cDNA encodes 1, 547 amino acids with a 17-residue signal peptide region. The SIPC may have evolved from an ancestral α2-macroglobulin gene.
