Search

We determined the ability of blinded mottled sculpin (Cottus bairdi) to determine the distance from the trunk of a vertically oscillating sphere. Sphere distance from the trunk and oscillation amplitude was varied randomly. Fish were trained to respond to a one-cycle oscillation (50 Hz) by attempting to touch the sphere with the mouth in one movement from the fish's initial position. Each of the four fish was tested with both left and right trunk canals intact. Afterward, one canal was blocked with a nylon thread and the other left intact. Precision of distance determination was measured as the correlation coefficient of the distance from the sphere to the fish's trunk before stimulus onset and the response distance. Fish were significantly better at distance determination with intact canals than on the side with the canal blocked (P < 0.001).

The lateral line of adult mottled sculpin, Cottus bairdi, consists of superficial neuromasts (on the skin surface) and canal neuromasts (enclosed in subdermal canals). At hatching, all neuromasts are superficial; some become enclosed in canals as the fish grows. We examined the role of the lateral line in larval feeding and how its role changes as canals form, using prey detection as an indicator of sensitivity. Larval sculpins appear to make excellent use of the lateral line to feed, but canal formation is associated with a decrease in sensitivity.

Blinded Cottus bairdi respond to substrate vibrations from prey and artificial stimuli by placing the mandible on the substrate, turning toward the buried stimulus, moving toward it in a series of “hops,” and biting into the sand at the stimulus. In this study, the accuracy of the initial turning response to a “point” stimulus lo-29 cm away was determined and it was found that C. bairdi accurately turns toward the stimulus in its first hop after stimulus onset. Elimination of lateral line response by either streptomycin or Ca+* free water with Co+* (competitive inhibitor) destroys the ability to locate substrate vibrations, but the fish still respond to stimulus onset by placing the mandibkon the substrate. Placing the mandible on the vibrating substrate may allow transmission of the signal to the mandibular neuromasts, which are the largest neuromasts in this species. ECENT studies of the desert scorpion, Pururoctonus mesaensis (Veajovidae) (Brownell and Farley, 1979) and the lizard, Scincus scincus (Scincidae) (Hetherington, 1989) have shown an ability to locate prey from substrate vibrations. The present study shows similar ability in a benthic fish, the mottled sculpin (Cottus bairdi) (Cottidae). In Lake Michigan, mottled sculpins eat swimming prey from the water column and buried prey, such as burrowing amphipods, oligochaetes, and midge larvae (Hoekstra and Janssen, 1985). Untrained blinded (eye removal) sculpins locate artificially generated substrate vibrations and,respond by biting vigorously and swimming into the substrate (Hock; stra and Janssen, 1985). The primary aim of this study is to describe the response of C. bairdi to live prey and to determine its ability to turn toward an artificial vibrating stimulus buried in lake sand. The effect of pharmacological elimination of the lateral line system on the behavior is also described.

We studied the lateral line receptive field of the mottled sculpin (Cottus bairdi) to live Daphnia magna and to an inert vertically vibrating bead. Both stimuli elicited feeding responses when near the head or trunk but response to stimuli near the trunk extended only as far as the posterior limit of the lateral line (beneath the soft dorsal fin). The sculpin was significantly less responsive to stimuli for the region in front of the snout compared to the side of the head. The region in which the sculpin strikes (strike zone) at prey extended slightly posterior to the mouth and occupied a mean area of 16.0 mm2 for Daphnia, 14.1 mm2 for the bead (both based on four fish). Prey detected outside this region elicited repositioning by the fish so that the prey's original location was in the strike zone.