SIGNALING ASYMMETRY IN THE COMMUNICATION OF THE WATER-STRIDER AQUARIUS-REMIGIS IN THE CONTEXT OF DOMINANCE AND SPACING IN THE NONMATING SEASON

The role of high-frequency ripple signals (HF signals) made by males o f the water strider Aquarius remigis was studied in the contexts of co mpetition for food and general spacing behaviour during the nonmating season. HF signals were played back through the ripple-producing legs of males during dyadic agonistic encounters, using a signal-driven wir e coil to oscillate a magnet glued to a leg. These signals were in add ition to normal signals. The additional signals significantly increase d the number of retreats by non-magneted males, showing that the signa ls increased the dominance of a non-territorial male: Hence, our resul ts increase the number of contexts in which HF signals of A. remigis f unction. Males, but not females, avoided a site occupied by a magneted dead male through which HF signals were played. Thus, the communicati on system used by A. remigis males during competition for food seemed to be ignored by females, suggesting sex-specific signals even in a no n-mating context. Evolutionary models of signalling often assume that contestants have evolved the same repertoire of signals in order to re solve conflicts peacefully. This water strider system thus poses an in teresting challenge for future theoretical and empirical research on c ommunication asymmetry.