1Department of Marine Sciences and Coastal Management, Ridley Bulding, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
2Marine Biological Association, Citadel Hill, Plymouth, PL1 2PB, UK.
Many factors potentially affect the choice of substratum for settlement of barnacle cypris larvae. For those barnacle species which show gregarious settlement behaviour, however, chemical cues associated with adult conspecifics are the most important factor. This presentation will describe recent progress on the bioassay-directed isolation of a glycoprotein, termed settlement-inducing protein complex (SIPC), from adult, Balanus amphitrite, tissues which induces cypris settlement. SDS PAGE revealed that the SIPC was composed of three major subunits, of 76, 88 and 98 kDa, each of which contained lentil lectin-binding sugar chains. Each of the subunits was as active as the whole molecule in inducing cypris settlement. Western blots, using a polyclonal antibody against the 76 kDa subunit, have detected SIPC-like activity in all 14 species examined thus far. Differences in intensity of reactive bands and molecular mass were observed and these differences may account, at least in part, for the ability of cyprids to discriminate between con- and allospecific pheromones at settlement.