Table 28. — R.Q. of C. virginica through the year 

 [Long Island Sound oysters] 



other Ostreidae is difficult because of the different 

 conditions under which the metaboUsm tests were 

 made. In a discussion of the relation between 

 the metabolism and temperature and its zoogeo- 

 graphical significance Sparck (1936) makes the 

 statement that, "0. edulis consumes more 

 oxygen than Gryphaea (Crassostrea) angulata of 

 which it is shown that it is able to supplant 0. 

 edulis in several locahties." This conclusion based 

 on a few single determinations is not well sub- 

 stantiated. 



Pedersen (1947) studied the respiration of 0. 

 edulis living in the small salt-water ponds along 

 the Skagerrak coast in Norway. The summer 

 temperature in these ponds rises to 25° C. and 

 higher, while in winter ice covers the ponds for 

 about 5 months. Prior to making the test 

 Pedersen kept the oysters for a few days in filtered 

 sea water, brushed them, washed the shells with 

 40 percent alcohol, and wrapped them in pieces 

 of gauze to prevent small bits of shell from being 

 broken off. For measuring the oxygen uptake 

 the oysters were placed in hermetically closed 



Table 29. — Effect of dextrose in sea water on R.Q. of C. 

 virginica 



glass containers filled with 2 1. of unfiltered sea 

 water. The containers had to be turned over in 

 order to mix the water. Closing and opening of 

 shells were not recorded. Undoubtedly the turn- 

 ing of vessels caused the oysters to close their shells 

 and discontinue the ventilation of the gills. For 

 control Pedersen used blanks that contained no 

 oysters. The difference between the blanks and 

 the samples taken from the experimental con- 

 tainers was considered equal to the quantities of 

 oxygen consumed and carbon dioxide produced by 

 the oysters. The consumption of oxygen was 

 expressed in mg. of oxygen per 100 g. of total 

 weight or per 10 g. of net weight (presumably 

 the wet weight of the meat) per 24 hours. Under 

 these conditions and at temperatures around 24° 

 to 25° C. the oxygen consumption of the oysters 

 varied from 15.0 to 48.9 mg. of oxygen per 10 g. 

 of weight per 24 hours or from 0.62 to 2.0 mg. 

 per 1 hour. Pedersen's technique had serious 

 drawbacks since the time the oysters were open 

 is not known; the mollusks were disturbed by 

 violent motions (turning over of the containers); 

 and the animals probably were affected by accum- 

 ulation of metabohtes. The reported R.Q. of the 

 Norwegian oysters varied from 0.8 to 1.0, but 

 in some instances it was as low as 0.6 or as high 

 as 2.6 and 3.0. The abnormally high and low 

 values are probably fictitious because of some 

 deficiency in technique. 



In a study of the energy-metabolism of 0. edulis 

 Gaarder and Eliassen (1955) used a closed chamber 

 system (desiccators) of 750-ml. capacity. The 

 shells of the oysters were kept open by glass rods 

 inserted between the valves. The sahnity of 

 water was 32 °/oo, and the temperature was kept 

 constant within ±0.05° C. The results were 

 expressed in ml. of oxygen consumed per 1 g. 

 of wet weight per hour. To facilitate the com- 

 parison I have recomputed the data of the Nor- 

 wegian investigators to mg. of oxygen per 10 g. 

 of wet weight of oyster tissues. At 25° C the 

 oxygen consumption by 0. edulis computed on 

 this basis was about 2.0 to 2.5 mg. of oxygen per 

 hom- per oyster. 



As one may expect from observations on the 

 effect of temperature on ciliary motion of the 

 gill epithelium of the oyster, the oxygen consump- 

 tion increases about 1.5 times for every 10° rise 

 (Qio) of temperature between 10° and 25° C. 

 The max-imum is reached at about 25° C. Below 

 5° C. the oxygen uptake decreases rapidly but 



TRANSPORT OF WATER BY THE GILLS AND RESPIRATION 



213 



