The investigator has already demonstrated that a predatory fish, the bluegill, can approach and attack an artificial prey specimen even when it is not visible. When the bluegill's lateral line sense was chemically blocked it still approached the "prey" but did not attack. This suggests that the otolith organs of the inner ear are involved in the animals responses to prey in the water nearby. In this project the phenomenon is being studied in more detail. In one series of experiments the prey is simulated as a moving sphere and in another the bluegill will simply be exposed to a series of low frequency vibrations in the water similar to those that a prey animal would set up. The results will clarify the relation between the lateral line and inner ear sensory systems in fish. This, in turn, bears upon the evolution of vertebrate hearing. It is generally believed that hearing evolved as a mechanism of detecting sound waves originating some distance away; this work may provide evidence that it occurred first as a means of detecting nearby vibrations and later adapted to sound detection.
