TEMPERATURE AND THE SHELL MOVEMENTS OF OYSTERS 1 
By A. E. Hopkins, Ph. D., Aquatic Biologist, United States Bureau of Fisheries 
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CONTENTS 
Introduction 
Method 
Experiments with Olympia oysters ( Ostrea lurida) 
Number of hours open per day 
Effect of temperature 
Diurnal variation in shell behavior 
Experiments with eastern oysters ( Ostrea virginica) 
Summary 
Literature cited 
INTRODUCTION 
The influence of temperature on the physiology of feeding in the oyster was studied 
by Galtsoff (1928), who found that the rate at which the gill mechanism pumps 
food-bearing water depends upon the temperature of the water, and that not only 
does this rate of pumping become slower with decreasing temperature, but at about 
6° C. it actually ceases and the oyster is unable to feed. During this hibernation 
period induced by low temperature, it may be that cessation of flow of water through 
the gills is only one of the important changes in behavior. All physico-chemical 
activities are probably slow at this time. 
In the oyster, feeding is limited not only by the rate at which the gill mechanism 
acts but also by the shell movements. Feeding occurs at temperature conditions 
favorable to gill activity only if the shells are open, for obviously water can not enter 
when the valves are pressed tightly together. The question arises as to what environ- 
mental factors may influence shell movements. In a work on the effect of sulphite 
pulp mill waste liquor on oysters by Hopkins (1931), it was shown that the presence 
of this substance in the water caused the Olympia oyster ( Ostrea lurida ) to remain 
closed more of the time than specimens in uncontaminated water. The same sub- 
stance was demonstrated by Galtsoff (1931), to reduce the rate of pumping of water 
by the gills of both 0. lurida and 0. gigas. The mechanisms controlling the activity 
of both the gill mechanism and the adductor muscle appear to be highly sensitive to 
environmental factors. Since both of these mechanisms are directly concerned with 
the feeding habits of the oyster, it is important that they be clearly understood. 
In some experiments on the effect of sulphite liquor on the Olympia oyster, the 
shell movements of the control specimens were recorded by means of kymographs, 
and thermograph records of water temperature were kept. Several such series, each 
of from 5 to 30 days’ duration, were obtained. These records show a significant 
correlation between water temperature and shell activity. In the following pages 
certain of these results are presented and analyzed. That these conclusions are 
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1 Approved for publication Nov. 25, 1930. 
