Mechanosensory-based orientation to elevated prey by a benthic fish

Lake Michigan mottled sculpin, Cottus bairdi, respond to both live and artificial (e.g., vibrating sphere) prey with an unconditioned movement towards the source of vibration, followed by a step-by-step approach and final strike at the source. In addition to these well-studied, whole-body movements along the horizontal plane of the substrate, sculpin exhibit a little-studied behavior in which the vertical position of the fish's head can vary from being hush with the substrate to several cm's above the substrate. To test the hypothesis that sculpin can determine source elevation via mechanosensory cues, we measured head elevation of blinded fish as a function of source elevation and distance as fish approached a small (3 mm radius), 50 Hz vibrating sphere. At distances associated with pre-strike positions (< 2 cm), head elevations were positively correlated with source elevation before but not after pharmacological blocking of the lateral line with CoCl2. These results demonstrate that sculpin are able to determine source elevation using mechanosensory cues alone and that in the absence of visual and olfactory cues, vertical orientation of the head towards the source requires the lateral line system.