PREFACE 



Different areas of science characteristically enjoy "peak" periods, during 

 which curiosity and concern about unsolved problems, availability of re- 

 search support, and emerging new results and insights combine to yield eras 

 of exceptional productivity. Shark research is enjoying such a peak phase at 

 the present time. This makes it an especially exciting, as well as a useful, 

 time to take stock of what is known (and what is not known) in this area of 

 sensory physiology and animal behavior. 



People are interested in sharks, skates, and rays for many reasons. At 

 some point in their studies, virtually all biology students encounter diagrams 

 or preserved specimens of sharks, the anatomical features of which provide a 

 good starting point for understanding the basic body forms of backboned 

 animals, including man. Marine biologists, dealing with living elasmobranchs 

 in the sea, are fascinated by the many and superb adaptations of these 

 animals that account for their long evolutionary success. People whose work 

 or recreation takes them into the sea are concerned about the possibilities of 

 being attacked by sharks; thus they are interested in the work of sensory 

 physiologists and ethologists who attempt to understand the behavioral 

 patterns, with their underlying mechanisms, in predatory species. Most 

 recently, engineers and technologists have recognized that some sense organs 

 of elasmobranchs far exceed the capacities of our human sensory apparatus 

 and therefore might provide clues or prototypes for better instrumentation 

 to assist human probings of the sea. 



Two brief examples illustrate the latter types of interest. The olfactory 

 receptors of sharks are highly efficient detectors of waterborn chemicals. In 

 some cases, only a few molecules contacting these chemoreceptors can trigger 

 powerful responses from sharks, well before any analytical methods now 

 used by chemists can signal the presence of the molecules. In an age when 

 man's needs to sample and monitor the chemistry of the seas (and the effects 

 of human activities upon them) are increasing, it is not unreasonable to 

 anticipate that our chemical detecting systems might profit from better 

 understanding of those that already serve the sharks so well. 



In other cases, the sharks, skates, and rays have sensing mechanisms that 

 are completely absent in ourselves. Recent research has shown that sharks 

 use bioelectrical cues from their prey to guide close-range attacks. The 

 stingray, for another example, has a sensory mechanism for detecting weak 

 magnetic forces and regularly uses this sense for orienting to the geomagnetic 

 field of the earth. What a convenience such an inborn sense would be to 

 human navigators! 



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