PHYSIOLOGY OF CHEMORECEPTION 



243 



Figure 8 Blinker trail of a lemon shark responding to amine stimulus. Olfactory corridor 

 from stimulus in the far right corner of observation pen is contacted at point S. Shark 

 then swims into strongest current along left side of pen, starting to circle in a different 

 corner from the true origin of the stimulus. 



(e.g., repeated biting at objects in the water near the stimulus release point, 

 milling about near the release point with aggressive behavior toward other 

 sharks or fishes) is indicated by "++." Initial negative responses to the 

 stimulus (turning away from the olfactory corridor, head shaking, and 

 moving away from the stimulus) is indicated by a "0" in the behavioral 

 response column. 



It was particularly difficult to be sure of continued negative responses 

 during the 15 min of testing any single chemical stimulus; sharks that turned 

 away from the stimulus might simply never encounter it again, or they might 

 shift to weak positive responses, suggesting that they were returning to in- 

 vestigate the stimulus after an initial turning away; the latter responses are 

 indicated in the table by "0 -* +." 



Concentrations tested are given in a range from those maximal concentra- 

 tions initially introduced into the test area, to the dilutions obtained by 

 dilution in the laboratory or by tidal flow. In the large pen, dilutions of 

 100 000 or more were found across the length of the test enclosure at some 

 stages of tide. 



