226 U, S. BUREAU OF FISHERIES 



sentative data each year, this method can be perfected and more 

 accurate deductions made for the control of oyster-cultural operations 

 in Milford waters. 



PHYSIOLOGY OF THE OYSTER 



Physiological investigations were carried on at the fisheries bio- 

 logical stations at Woods Hole, Mass., and Beaufort, N. C. 



Effect of temperature on the activity of the oyster. — The experi- 

 ments on the effect of temperature on feeding of the oj^ster, carried 

 on by Dr. P. S. Galtsoff since 1926, were completed and two manu- 

 scripts on the subject were submitted for publication. The results 

 of the work prove that feeding is controlled by the temperature. At 

 41° F., and below, the oyster ceases to feed and remains in an inactive 

 state as long as the temperature remains below this critical point. 

 Long exposure to low temperature does not produce adaptation, and 

 oysters taken from cold water in winter begin and cease to strain 

 water at the same temperatures as they do in the summer when they 

 are chilled suddenly. 



A study of shell movements made with self-registering apparatus, 

 based on an analysis of 134 records, has shown that the o^^ster tends 

 to keep its valves open as long as possible — on an average the shell 

 is open 17 hours and 5 minutes in 24 hours. There is no relation 

 between the opening and closing of the shell and the time of day, as 

 has been suggested by some investigators. The experimental study 

 of the effect of temperature on the activity of the ciliary motion con- 

 firms the theory of hibernation advanced 18 years ago by Gorham 

 and Pease. The revision of the methods of sanitary control of 

 oysters, made by the United States Public Health Service, brought 

 up again the question of hibernation; the experimental study on the 

 physiology of the gills settles it ; and as a result of this investigation 

 the committee appointed by the United States Public Health Service 

 has recognized hibernation as an additional safeguard in the sanitary 

 control of oysters. 



Spawning reaction. — Study of the spawning reaction was contin- 

 ued by Doctor Galtsoff during July and August. Attempts were 

 made to isolate the substance (discharged by the male oyster) that 

 produces typical spawning reactions in the female. It has been 

 found that extracts of sperm are as actiye as the live sperm. The 

 active agent is destroyed by heating for 30 minutes at 44'' C 



Green oysters. — Since July, 1927, Drs. P. S. Galtsoff and Samuel 

 Lepkovsky have been engaged in a study of causes that produce the 

 green color that develops in the oysters of certain parts of Long 

 Island Sound and renders them unmarketable. The annual loss to 

 the industry from this cause amounts to many thousands of dollars. 

 The problem of greenness is very complex and, in spite of the exten- 

 sive literature on the subject, not well understood. Undoubtedly the 

 green color of the American oyster is associated with the increased 

 copper content of its body, but the question whether it is due to 

 direct absorption of copper from trade wastes discharged into the 

 water or to such a change in the metabolism of the oyster that re- 

 sults in an accumulation and storage of copper taken from unpol- 

 luted water remain open. In order to devise a method to improve 

 green oysters and make them marketable it is necessary to under- 



