Meeting Abstract
Animals attaching to a substrate face very different conditions in terrestrial and aquatic environments. We compare both the forces of attachment and the forces acting to detach animals. In the terrestrial environment gravity is commonly understood as the most important detachment force, while under submersed conditions gravity is nearly balanced out by buoyancy and therefore matters little. Moreover, flow forces like drag and lift are more important in an aquatic environment. They can reach much higher values than gravity and vary in magnitude and direction. Attachment mechanisms, such as suction, adhesion including glue, friction, and mechanical principles as hook, lock or clamp and spacer differ when under water compared to terrestrial environment. For example the main principles of dry adhesion, van der Waals forces, which allow a gecko to stick to a wall, are weak in submerged conditions. Capillary forces are very important for wet adhesion e.g. in terrestrial beetles or flies, but do not matter under water. Viscous forces likely contribute to adhesion under water in mobile animals such as torrent frogs and mayflies. Viscous forces and the lack of surface tension also affect frictional interactions in the aquatic environment. Glue is the dominant adhesive mechanism of sessile aquatic animals. However, the aquatic realm presents many challenges to this mode of attachment. Moreover, due to the increasing pressure with water depth, the limitation of suction to the pressure difference at vacuum conditions is ameliorated under water.
