CHEMORECEPTION: LOCOMOTION AND ORIENTATION 287 



were categorized by Parker as random movements, so that food localization 

 would be mediated by a combination of osmotropotactic and random move- 

 ments. 



Nearly half a century passed before a further investigation was made of 

 the role of olfaction in the recognition of and orientation toward a food 

 source, by Teichmann and Teichmann (1959) in Scyliorhinus canicula, S. 

 stellare, and Mustelus laevis. The experimental approach differed from that 

 in earlier work in that attempts were made to condition the animals to 

 olfactory cues from synthetic odorants, mostly /3-phenylethyl alcohol. Train- 

 ing was done by first placing odorant-impregnated material (cellulose) and 

 then a piece of food (fish flesh) near the head of an immobile fish. Even- 

 tually, one animal learned to associate the synthetic odor with the food and 

 responded to the conditioned stimulus alone, first with general excitement 

 and then with specific search movements. The authors observed that the 

 duration of the first phase of the response (general excitement, increased 

 respiration, fin movements) became greatly reduced in the companions of an 

 animal that had already become excited and had initiated search movements. 

 The response consisted, therefore, of alarm and orientation phases, but uni- 

 lateral anosmia affected neither these responses nor the turning behavior of 

 S. canicula. Unlike the other two species, Mustelus laevis, excited by the 

 odor, often oriented almost directly to the source once general localization 

 had been achieved. Exact localization, by means of sharp turns, followed. It 

 is of interest that this species responded to unilateral anosmia in exactly the 

 same manner described by Parker (1914) for Mustelus canis, i.e., with search 

 movements in the direction of the functional nostril. 



Tester (1963a, b) made extensive observations on responses to natural and 

 artificial odors in juveniles and adults of various species of sharks (Car- 

 charinus melanopterus, C. menissorah, Sphyrna lewini, and Galeocerdo 

 cuvier). In addition to general locomotion, behavior patterns such as sudden 

 turns, circling, and head-shaking were used as criteria for the behavioral 

 response to the chemical stimuli, which were introduced below the water 

 surface through tubes. 



Based on the activity of the animals during a series of 3-min test periods, 

 with and without olfactory stimulus, numerous responses were defined (no 

 response, sensing only, weak attraction, strong attraction, weak repulsion, 

 strong repulsion, alarm reaction, etc.). Such classification was difficult to 

 interpret because of variability in the responses, and the problem of estab- 

 lishing a reliable bioassay was thereby recognized. In general, the extracts of 

 food substances were attractive to the shark. Even here there was variability 

 in response, making it difficult to compare the attractiveness of the various 

 materials used (flesh of various fish species and invertebrates). Fresh human 

 blood also was "attractive," at concentrations estimated to be at 0.1 to 0.01 

 ppm of seawater, and produced various locomotor responses. Blinded black- 

 tip sharks (Carcharinus melanopterus) were attracted to live fish of various 

 species, presumably by their body odor, as well as to water in which fish had 

 been kept. The response was greatest at the onset of stimulation but then 

 quickly decreased, a result which Tester attributed to habituation. However, 



