PHYSIOLOGY OF CHEMORECEPTION 



255 





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Figure 12 Lemon shark biting source bottle of TMAO-glycine mixture in reef channel. 



Hobson (1963), based on his study of several shark species in the Pacific. 

 In most cases he found that baits were approached from downstream but 

 that actual feeding required additional stimulation, such as visual cues. 

 Kleerekoper (1978) discusses, elsewhere in this volume, other variables 

 (light, "handedness" of sharks, etc.) that can modify the locomotor activi- 

 ties of sharks. If, to all these important variables integrated by the CNS 

 and controlling locomotor patterns, the individual variable of learned ex- 

 perience by the shark is added, it is clear that what might appear to be a 

 rather simple stimulus-response behavior pattern is actually considerably 

 more subtle and is delicately adjusted to many environmental variables. 



THE TRANSDUCTION MECHANISMS 

 OF CHEMORECEPTORS 



A central consideration in any physiological analysis of chemosensory func- 

 tions is the search for the basic transduction mechanisms, by means of which 

 the chemical energy is, in effect, transformed into the electrical potential 

 across the stimulated chemoreceptor membrane. Only a beginning has been 

 made in approaching this level of analysis with the chemoreceptors of 

 elasmobranchs. At present, it appears that at least several types of chemical 



