Figure 3: Representative tracking patterns of barnacle cypris larvae exploring two zwitterionic surfaces.

The motile cypris larvae of barnacles are 'choosy', that is, they explore the suitability of a surface for eventual adhesion by swimming over it, making 'sampling' contacts. The cartoon illustrates an experiment in which the bottom surface of two transparent dishes was coated with either (a) poly(sulfobetainemethacrylate) (polySBMA) or (b) poly(carboxybetainemethacrylate) (polyCBMA). (Note: The two coatings are actually colourless, but are shown as different colours to aid understanding). The dishes were filled with seawater before introducing the barnacle cypris larvae. The green lines illustrate the representative tracks of an individual larva on each surface, starting at or near the centre of the dish. Behaviour on polySBMA (a) is characterized by broad, sweeping deviations in the recorded track, with occasional contacts with the surface and abrupt changes in direction. This behavior suggests that the larvae are actively exploring this surface. Behaviour on polyCBMA (b) is quite different. Here, the larvae spent little time either swimming over the surface or making contacts with it, swimming immediately to the edge of the dish. Cartoon represents original data in ref. 26.