activity. The description of this "feeding frenzy" is suggestive of 

 some of the responses that have been evoked by electrical stimulation 

 of the hypothalamus (inferior lobe) and midbrain in teleosts (Demski 

 and Knigge, 1971; Demski, unpublished observation), in which the stimulated 

 animals swarm around rapidly attacking many different objects which inclu- 

 ded food, gravel, debris, other fish and other inanimate objects. It 

 should be noted that in some stimulations arousal seemed to be less intense 

 and the fish either attacked only another fish or snapped at food objects 

 or gravel. Similar arousal and feeding activity in fishes has been evoked 

 by stimulation of the olfactory tracts (Grimm, 1960), anterior commissure 

 (Fiedler, 1964), and the area near the medial forebrain bundle (Demski, 

 1973). These observations, along with the results of studies that indicate 

 that olfactory cues alone can trigger similar activity in several teleosts 

 (Grimm, 1960; Demski, 1973), suggest that the arousal and snapping activity 

 evoked from the fish hypothalamus may be related to activation of normal 

 forebrain olfactory input to the hypothalamus that runs in the medial 

 forebrain bundle (Demski, 1973). It also seems reasonable to suggest that 

 an analogous situation may exist in sharks which have a similar forebrain 

 bundle input into the periventricular portion of the hypothalamic inferior 

 lobes (Demski, 1974; Ebbesson, 1972), and which are also greatly aroused 

 by olfactory cues. Consistent with this idea are reports of increased 

 electrical activity in the forebrain of nurse, lemon and bonnet head 

 sharks in response to perfusion of the nasal openings with extracts of 

 normal food substances (Gilbert e_t a_l . , 1964). Thus it would be interesting 

 to know if stimulation of the hypothalamus and forebrain olfactory pathways 

 in this group would evoke similar responses to those observed in teleosts. 



In addition to olfactory information, the hypothalamus in various 

 teleosts is reported to receive visual, gustatory and possibly acoustic 

 inputs (see Ariens Kappers e_t al. , 1936; Aronson, 1963; Schnitzlein, 1964; 

 Tuge e_t a_l . , 1968). Thus the hypothalamus may be one of the major sensory 

 integrative centers in the fish brain. Its main output pathways run to the 

 cerebellum, brain stem motor nuclei and possibly spinal cord as well (see 

 above references) ; this suggests that it is likely to strongly influence 

 motor systems. The above anatomical considerations led Herrick (1905) to 

 postulate that the teleost hypothalamus is a sensorimotor correlation 

 center which is involved in feeding activity. As mentioned above, the 

 results of electrical stimulation experiments are consistent with this 

 idea. Internal stimuli such as blood glucose levels may also be important 

 in determining the hypothalamic activity in fishes in a similar manner as 

 proposed for mammalian species (see De Groot, 1967). Thus the study of 

 teleost and shark hypothalamus may give valuable insight into the role of 

 many sensory factors in the determination of predatory behavior of sharks. 



Many shark attacks may be agonistic in nature rather than related 

 primarily to feeding (Baldridge and Williams, 1969; Johnson and Nelson, 

 1973). If this is the case, it is likely that hypothalamic mechanisms 

 similar to those described for feeding are also involved since, in teleosts, 

 electrical stimulation of the hypothalamus frequently evokes both prey 

 catching as well as intraspecif ic aggression (Demski and Knigge, 1971; 

 Demski, 1973). 



Considerable information on the neural mechanisms of feeding and 

 aggression in sharks may be derived by repetition of experiments carried 

 out in teleosts and other vertebrate groups since there are at least 



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