CHEMORECEPTION: LOCOMOTION AND ORIENTATION 



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were significantly affected by the changing location of the stimulus. The 

 effect of flow was tested for individual sharks by comparing the mean re- 

 sponses of the variables in one experiment with flow to the mean responses 

 in another experiment without flow. Interaction between flow effect and 

 stimulus location was determined and a polynomial regression was calculated 

 to establish the significance of that interaction. 



In a representative experiment with continuous flow, the total distance 

 travelled by the shark during 15-min intervals, in the tank as a whole, de- 

 creased for the first 24 h, after which the level stabilized and increased again 

 after the first 48 h, as illustrated in the time series of Figure 23, which 

 indicates along the abscissa the times and places at which stimulation was 

 applied. In Figure 24 these same data are presented for quadrants 1 and 4, as 

 percent of total distance traveled. During the control phase, there is an initial 

 "exploratory" period, recognizable in all four quadrants, during which the 

 shark moves about the whole tank. Whether this "exploratory" behavior has 

 spatial and temporal characteristics similar to those displayed by goldfish 

 (Kleerekoper et al. 1974) has not yet been determined. After this initial 

 period, the animal confined its movement almost entirely to the upstream 



Figure 22 Disposition of the needles in 

 the floor of monitor tank II, used to 

 release for chemical stimulus. The solu- 

 tion or (for control purposes) sea water 

 is kept in a plastic container to which all 

 the needles are connected with surgical 

 tubing. The rate of flow can be adjusted 

 by raising or lowering the container, 

 which is suspended with rope and 

 tackle. Fine adjustments can be made 

 with Hoffmann clamps. The rest of the 

 needle matrix available for stimulation 

 is not shown. Some of the monitor data 

 were analyzed for the tank as a whole, 

 and others for the different quadrants 

 (indicated by circled numbers). 



