THE OCCURRENCE IN VIRGINIA OF GREEN-GILLED OYSTERS 

 SIMILAR TO THOSE OF MARENNES. 



By PHILIP H. MITCHELL and RAYMOND L. BARNEY. 



Contribution from the United States Fisheries Biological Station, Woods Hole, Mass., and the Bio- 

 logical Laboratory of Brown University. 



INTRODUCTION. 



The appearance of green-gilled oysters in Lynnhaven Bay, Va., in such large quan- 

 tities during the fall and early winter of 191 5 that several of the oystermen of the vicinity 

 were unable to sell their product because of the dark-colored gills led to this investi- 

 gation. The problem is of considerable economic interest since the entire oyster industry 

 of Chesapeake Bay was at stake, the green-gilled oysters being found in locations many 

 miles distant from one another. Moreover, if this outbreak could be proved to be 

 an exact reproduction of the greening of the popular Marennes oysters, it might be the 

 basis of oyster culture in Virginia from an entirely new point of view. Further than 

 this, the study offered an interesting scientific problem which narrowed itself down, 

 in the consideration of the writers, to a physiological and chemical study of the pig- 

 ment and the manner in which the oyster re-acted to it. The main purpose, however, 

 in this study has been to find whether or not the greening of the gills in the Lynnhaven 

 oysters is the same as that in the choice Marennes oysters, for a glance at our American 

 oysters shows that they are very similar in general appearance and in the distribution 

 of the pigment to the descriptions and drawings of the Marennes oysters. 



HISTORY. 



In the past there has been considerable work done on the green coloration of oys- 

 ters, especially in Europe. Papers have been written on both the green-gilled and the 

 copper-green oysters. 



The genuine green-gilled oyster was first worked on by M. Gaillon, who published 

 his first paper in 1820. In this paper he explained the French custom of placing the 

 oysters in claires or large reservoirs just within the high-tide mark and allowing them 

 to remain there for a considerable length of time or until the gills and palps showed 

 the green tint. He recognized that if the tanks contained a certain diatom, Navicula 

 osirearia, in large quantities, the oysters would take on the green coloration, but that 

 when the oysters were taken from the tanks and placed in fresh sea water, or allowed 



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