234 CHEMICAL SENSES 



ELECTROPHYSIOLOGICAL CORRELATES WITH 

 CHEMICAL STIMULATION IN ELASMOBRANCHS 



Laboratory Experiments on Curarized Sharks 



Not surprisingly, the first successful electrophysiological recordings from 

 elasmobranch chemosensory systems were obtained from laboratory prepara- 

 tions of sharks immobilized with d-tubocurarine, using crude extracts of 

 biological materials known to evoke feeding behavior (Gilbert, Hodgson, 

 and Mathewson 1964). Three species were studied: bonnet sharks (Sphyrna 

 tiburo), nurse sharks (Ginglymostoma cirratum), and lemon sharks 

 (Negaprion brevirostris). The latter two species were the most extensively 

 studied with these techniques in subsequent experiments. 



Figure 2 shows the locations at which recordings were made from the 

 brain of the lemon shark; recording sites on the brains of the other species 

 were similar, allowing for more species differences in proportions of differ- 

 ent brain lobes. Full technical details have been reported (Gilbert et al. 

 1964). The sites yielding the largest amplitudes of EEG changes, correlated 

 with chemical stimulation from perfusion of the olfactory sac on the homo- 



7 MED 



Figure 2 Brain of lemon shark, Negaprion brevi- 

 rostris. Numbers indicate points for electrophysio- 

 logical recordings. OS — olfactory sac; OB— olfac- 

 tory bulb, OT— olfactory tract, T— telencephalon, 

 CER— cerebellum, MES— mesencephalon, MED— 

 medulla. Numbers indicate positions of electrodes 

 in various experiments; for details, see text. 



