Intertidal animals of a rocky shore

A line of periwinkles, Nodilittorina unifasciata, at the edge of a mussel bed, Mytilus galloprovincialis, on a rocky shore at Blairgowrie, Victoria. These animals live in the intertidal zone, exposed to wind and sun for several hours at each tide. Each uses a different way to attach to the rock. Periwinkles have a snail-like shell with a horny lid, the operculum. The animal fixes itself to the substrate by means of its foot. In response to drying it produces a mucus that covers the mouth of the shell and hardens to a firm temporary attachment, with the operculum completely sealed.Mussels anchor themselves by means of a byssus - a system of threads that act like guy-ropes, allowing the animal to move with currents whilst attached to the substrate. The picture also shows scattered small limpets, which pull themselves into tight contact with the rock by means of a foot acting as a sucker