PHYSIOLOGY OF CHEMORECEPTION 263 



nervous systems. The toxic material produces immediate locomotory symp- 

 toms, which commonly lead to the death of any animal ingesting them. The 

 role of these poisons in the normal environment of the crabs has yet to 

 be specified, and repellent or toxic actions on normal predators, although 

 suspected, remain to be determined. As with most toxicology studies, the 

 effects of the active molecules on sensory systems, particularly chemo- 

 receptors, are unknown but could prove to be extremely interesting. 



The few naturally occurring shark repellents described thus far probably 

 represent only a beginning in the investigation of a promising area. It will 

 be especially interesting to discover whether and how other marine animals 

 may have solved the problems of protecting themselves against shark attack. 

 Realistically, investigations in this area are no more likely than any past 

 studies to identify a repellent capable of incapacitating a frenzied shark. 

 However, it is quite reasonable to anticipate discovery of natural repellents 

 that significantly lower the probability of attack or ingestion by sharks. A 

 combination of basic natural history studies, including the taxonomy, 

 ecology, and behavior of suspected producers of natural repellents and 

 toxins, as well as detailed pharmacological analyses of their secretions, 

 might advance knowledge in particularly interesting and valuable ways at 

 this time. 



ACKNOWLEDGMENTS 



Original investigations of the chemical senses of sharks have been supported 

 by Office of Naval Research contract Nonr 552 (07) with the American 

 Museum of Natural History and contract N00014-76-0943 with Tufts Uni- 

 versity. Field studies were carried out at the Lerner Marine Laboratory, 

 Bimini, Bahamas, and at the Heron Island Marine Station, Queensland, 

 Australia. The autoradiographs of olfactory receptors of sharks were pre- 

 pared in the laboratory of Dr. Arland Carsten, at the Medical Department 

 of the Brookhaven National Laboratory, New York. Dr. Carsten also col- 

 laborated in all the tracer studies at Bimini. It is a pleasure to express our 

 indebtedness and thanks to many helpful staff members at these various 

 laboratories who contributed to the progress of the studies. The color 

 prints of photographs illustrating this work were prepared by Boris Color 

 Laboratories, Boston, under the supervision of Mr. Irving Rubin, whose 

 interest and care have also been most helpful. 



REFERENCES 



Adrian, E. D., and C. Ludwig. 1938. Nervous discharges from the olfactory 

 organs of fish. J. Physiol. (London) 94:441-460. 



Attaway, D. H., and L. S. Ciereszko. 1974. Isolation and partial characteri- 

 zation of Caribbean palytoxin. Pages 497-504 in Proceedings of the 2nd 

 international symposium on coral reefs, vol. 1. Edited by A. M. Cameron, 

 B. M. Campbell, A. B. Cribb, et al. The Great Barrier Reef Committee, 

 Brisbane, Australia. 



