Adhesion and substrate choice in mussels and barnacles

The force of adhesion of mussel byssus pads appears to be a function of the surface energy of the substratum, increasing with the polarity of the surface. Barnacles at the cyprid stage possess a mechanism for temporary adhesion by an antennulary attachment organ which can withstand a pull per unit surface area of several atmospheres. Associated with temporary adhesion is a capacity for conspecific recognition which can be simulated by spreading adsorbed layers of integumentary protein on a suitable solid surface. The mechanism of recognition is not fully understood and there remain problems in understanding why adsorbates, ubiquitously present in natural sea waters, or thick biofilms, do not appear to interfere with the tactile chemical sense. Both mussels and barnacles show a preference for adherends to which the natural cement will eventually form a stronger bond.