SENSORY STIMULATION OF THE OYSTER, OSTREA 
VIRGINICA, BY CHEMICALS 
J- 
By A. E. Hopkins, Ph. D., Aquatic Biologist, United Stales Bureau of Fisheries 
J- 
CONTENTS 
Page 
Introduction 249 
Material and methods 250 
Experimental observations 250 
Cumarin 251 
Potassium chloride 252 
Sodium chloride 252 
Magnesium chloride 252 
Quinine sulphate 254 
Alkalies 254 
Cane sugar 256 
Discussion 256 
Summary 259 
Bibliography 260 
INTRODUCTION 
Although the adult oyster is immobile it is, like a great many other organisms, 
highly sensitive to environmental changes, both chemical and physical. The obvious 
reaction of the oyster to stimuli is a quick closing of the valves, brought about by 
contraction of the adductor muscle. This may be observed following mechanical 
or chemical irritation or sudden decrease in the intensity of the light; the so-called 
shadow reaction. It is not the purpose of this paper to give a complete account 
of the oyster’s sensitivity to all environmental factors, but it is of interest that the 
only reaction, ordinarily to be observed, to stimuli of various kinds is the shell 
closure. Because of its immobility and its consequently limited number of possible 
reactions the oyster is a favorable object for experiments on sensitivity. 
The sensitivity of invertebrates and lower vertebrates to a wide variety of chemi- 
cal substances has been studied by numerous investigators. It is unnecessary to make 
a complete survey of such works here, but certain of them should be mentioned to 
indicate the scope of the chemical senses. Amphioxus (Parker, 1908) has been 
found to respond to solutions of salts, acids, alkalies, alkaloids, alcohol, ether, chloro- 
form, turpentine, and several essential oils, but not to cane sugar of a concentration 
as high as 2 molar. Kribs (1910) gave the threshold concentrations of a number 
of substances in the stimulation of the Oligochaet, Aelosoma, as follows: Mineral 
acids, N/3,000; organic acids, N/2,000; hydrates, N/1,500; carbonates, N/1,200; 
chlorides, M/80; bromides, M/50; ferric sulphate, M/10,000; copper sulphate, 
M/80,000; zinc sulphate, M/80,000. He stated that increase in temperature or 
exposure to bright light lowered the threshold. 
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