CHEMORECEPTION: LOCOMOTION AND ORIENTATION 315 



point in the monitor's floor could be detected within one or two observa- 

 tions after application of the stimulus (Figure 31). Gerald et al. (in press) 

 determined that chemical stimulation caused all 17 variables tested to "get 

 out of control," thus manifesting the shark's response to the stimulus. This 

 forecasting technique appears particularly promising as a highly sensitive 

 diagnostic tool for determing the responsiveness of an animal to experi- 

 mentally induced stimuli and their thresholds. The models are now being 

 extended to the locomotor behavior of other species of elasmobranchs and 

 teleosts, for use in detection of locomotor responses to various environ- 

 mental variables. An important aim of these studies is to construct transfer 

 models in which the input of a stimulus might be stochastically controlled to 

 produce a desired output in the locomotor pattern. This, in turn, may lead 

 to a quantitatively sensitive, cybernetic model of locomotor activity in these 

 animals. 



RESPONSES OF SHARKS TO FLOW 



The important interaction demonstrated above between olfaction and flow 

 in the orientation behavior of sharks, raised questions reqarding the quantita- 

 tive relationship of these stimuli. For example, what are the effects of flow 

 on locomotor behavior, in the absence of chemical stimulation? Do sharks 

 discriminate between flow rates, and, if so, how accurately? What are the 

 behavioral effects? Does the interaction of flow and odor depend on the flow 

 rate? 



In this laboratory, interest in these problems was heightened by the find- 

 ing that short-term exposure to a subacute concentration of an acetyl- 

 cholinesterase-inhibiting organophosphate (parathion) greatly affected the 

 interaction between flow and odor in the orientation of the goldfish (Kleere- 

 koper 1974; Rand et al. 1975; Rand 1976). Consequently, experiments were 

 conducted on various aspects of flow response in nurse and lemon sharks 

 (Gruber 1976; Maynard 1976). In the nurse shark, the average swimming 

 velocity, based on data from 14 experiments, was significantly greater in 

 flowing (1.17 cm/s) than in stagnant water in five of seven animals tested. 

 Similar results were obtained with lemon sharks in two out of three experi- 

 mental animals. The increase resulted from a shift in the frequency distribu- 

 tion of velocities: highest frequencies of high velocity classes in flow, of low 

 velocities in nonflow conditions. 



Regardless of these conditions, in lemon sharks the distribution of veloc- 

 ities depended also on the animal's position in the tank, a characteristic 

 described earlier for normal (Kleerekoper et al. 1970) and blinded (Timms 

 and Kleerekoper 1970) goldfish. For goldfish, it was established that the 

 effect of position on velocity (and angle of turning) is determined by the 

 fish's distance from the tank's walls, which have a significant effect on the 

 locomotor behavior long before their position could interfere with the swim- 

 ming of the fish. The fact that blinded goldfish behaved similarly strongly 



