CHEMORECEPTION IN THE MUD SNAIL, NASSARIUS OBSOLETUS. I. PROPERTIES OF STIMULATORY SUBSTANCES EXTRACTED FROM SHRIMP 1 WILLIAM E. S. CARR 2 Department of Zoology, Duke University, Durham, North Carolina Chemoreception is believed to play a role in many aspects of gastropod behavior (Kohn, 1961). Studies have suggested that chemoreceptive mediation is involved with such diverse phenomena as carrion location by scavengers (Copeland, 1918), metamorphosis (Scheltema, 1961), plant recognition by herbivores (Frings and Frings, 1965), predator avoidance (Bullock, 1953), prey recognition by predators (Blake, 1960), sexual differentiation (Coe, 1953), and others. The compilation of a sizable literature on the ecological significance of chemoreception to aquatic gas-tropods and aquatic invertebrates in general (for review, see Hodgson, 1955) is contrasted with the paucity of available information on the molecular aspects of such problems. A satisfactory understanding of aquatic chemoreceptive phenomena can be attained only after insight is gained into the molecular nature of the com-pounds which are involved. Previous studies on chemoreception in marine gastropods have been limited in their scope by the fact that the animals selected for study and/or the techniques em-ployed have denied investigators a chance to progress much beyond the "observa-tion of response" stage of investigation. However, in the present study the mud snail, Nassarius obsoleius, is shown to be an extremely suitable animal for studies of chemoreception. Dimon (1905) noted that this marine gastropod possessed a chemical sense and could detect the "odor or taste" of substances which diffused from dead animals. Submerged individuals were observed by Copeland (1918) to respond to extracts of fish by extending their proboscides. Copeland referred to this response as the proboscis reaction. Prior to the present study no attempt has been made to identify the substances which are stimulatory to this snail. The report which follows has a twofold purpose : ( 1 ) to describe a procedure for studying a chemically mediated response in TV. obsoletus; and (2) to provide the results of experiments which characterized the response-inducing substances ex-tracted from shrimp. 1 This paper is based on a portion of a dissertation submitted to the Graduate School of Arts and Sciences of Duke University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Zoology. These studies were conducted at the Duke University Marine Laboratory, Beaufort, N. C., and were supported by a N.I.H. Physiology Training Grant and by a Bureau of Commercial Fisheries Graduate Education Grant. The author is grateful to Dr. K. M. Wilbur, Department of Zoology, Duke University, fur providing frequent counsel during the course of this research. 2 Present address : Department of Zoology, University of Florida, Gainesville, Florida 32601. 90
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