ON THE ANTENNULAR SECRETION OF THE CYPRID OF BALANUS-AMPHITRITE-AMPHITRITE, AND ITS ROLE AS A SETTLEMENT PHEROMONE

In exploring a substratum, Balanus amphitrite amphitrite Darwin (Crust acea: Cirripedia) cyprids deposit 'footprints' of antennular secretion . The results of in vitro settlement assays suggest that in addition t o serving as a temporary adhesive, the secretion acts as a pheromone, in that its presence induces the settlement of conspecific cyprids. Th is result is in accord with a previous study on Balanus balanoides (L. ) (=Semibalanus balanoides). In settlement assays, the pheromone is li kely to contribute to an observed positive linear relationship between settlement and cyprid density. The density effect should thus be an i mportant consideration in the design of barnacle settlement assays. In the field, cyprid searching behaviour may render a surface more attra ctive to settlement by cypris larvae.