CHEMORECEPTION: LOCOMOTION AND ORIENTATION 



319 



Figure 34 Locomotor track of Negaprion brevirostris under the condi- 

 tions of Fig. 33, but with a flow rate of 0.80 cm/s. After Maynard 

 (1976). 



INTERACTION OF LIGHT AND CHEMICAL STIMULATION 

 IN THE EFFECTS ON THE LOCOMOTOR BEHAVIOR 

 OF THE NURSE SHARK 



In this laboratory, Dorn (1976) exposed nurse sharks to four treatment 

 combinations— (1) light, (2) chemical stimulus, (3) light and chemical 

 stimulus, and (4) control— in the cylindrical monitor (I) and analyzed the 

 interaction of the two stimuli (Steel and Torrie 1960; Ostle 1963). This 

 shark was positively photoactic at a light intensity of 1.87 W/cm 2 , and its 

 behavior clearly demonstrated a significant interaction between the light and 

 chemical stimuli, which means that the response to the combination of the 

 stimuli differs from simple additive responses to the individual stimuli. Sim- 

 ilar interaction phenomena have recently been described in other organisms 

 and for various stimuli (Kleerekoper, Waxman, and Matis 1972; Kleerekoper, 

 Westlake, Matis, and Gensler 1972; Rand et al. 1975; Vernberg et al. 1973), 

 but not in sharks. The significance of such interaction in the orientation of 

 these fish to chemical stimuli remains to be investigated in greater detail. 



