EFFECT OF DISSOLVED ORGANIC SUBSTANCES ON OYSTERS 



By Albert Collier and S. M. Ray, Fishery Research Biologists, A. W. Magnitzky, Oceanographer, 



and Joe O. Bell, Fishery Research Biologist 



In the course of prolonged and detailed studies 

 of the effects of industrial wastes on oysters, 

 Crassostrea virginica (Gmelin), continuous record- 

 ings of the activities of several oysters were made 

 simultaneously. We noted that the oysters tended 

 to behave in a parallel fashion which could not be 

 correlated with any of the factors customarily 

 measured. The work reported here presents our 

 efforts to define the cause or causes. A prelimi- 

 nary paper on this subject (Collier, Ray, and 

 Magnitzky, 1950), has demonstrated that an or- 

 ganic substance responding to the test for carbo- 

 hydrates is associated with the activity of oysters. 



There is a large body of information concerning 

 the effect on oysters of those environmental factors 

 which can be readily measured, including temper- 

 ature, salinity, pH, turbidity, and oxygen content. 

 Until recently, however, there have been no ana- 

 lytical estimates of continuous variations in the 

 organic content of sea water and their relation to 

 the activity of oysters. We were fortunate in 

 having at our disposal a technique for estimating 

 certain elements of the organic materials which 

 react to the test for carbohydrates. J. Gordon 

 Erdman suggested the method used here and 

 adapted it to field conditions. The technique is 

 described in the Appendix, page 182. It is impor- 

 tant to note that all carbohydrate values are given 

 in terms of arabinose equivalents, and do not 

 necessarily reflect actual concentrations of carbo- 

 hydrate substances. 



It is our intent not to enter the argument con- 

 cerning the utilization of dissolved organic mate- 

 rials by marine animals — an argument not yet 

 closed (Korringa 1949) — but only to demonstrate 

 the relation between the dissolved carbohydrates 

 of sea water and the activity of oysters. This 

 relation is discussed in the light of previous works 



Note— Albert Oolller, S. M. Ray, and Joe O. Bell, United States Fish 

 and Wildlife Service; A. W. Magnitzky, United States Navy Hydrograpbic 

 Office. 



on oyster physiolc gy, together with some practical 

 and theoretical implications. 



TECHNIQUES 



RECORDING THE ACTIVITY OF OYSTERS 



We chose the simultaneous recordings of shell 

 movements and pumping rates as the best avail- 

 able index of physiological activity, since both 

 lend themselves to uninterrupted recording over 

 long periods of time. The degree of shell gape 

 alone could not be used, because gape is only the 

 prerequisite to the filtration of water, and as long 

 as it exceeds a critical point, the flow of water 

 through the gills may vary considerably. The 

 rate of removal of artificially introduced suspended 

 materials gives a useful index of activity for short 

 periods, for it can be measured quickly and appar- 

 ently without affecting the oyster significantly. 

 The method is not suitable for long-term studies, 

 however, because it does not lend itself to the 

 continued automatic recording of the oyster's ac- 

 tivity in such a way that maximum detail of 

 behavior is discernible in the record at any mo- 

 ment. Also, the carmine-cone and drop-counting 

 techniques (Galtsoff 1928a and 1928b, Galtsoff 

 et al. 1935), have limited value for this type of 

 extended experiment not only because they can 

 be used only for short-term observations, but also 

 because they may seriously interfere with the 

 neurosensory network controlling the water flow 

 through the body of the oyster. In the carmine- 

 cone method, the accumulation of carmine cannot 

 be easily controlled, and its effect on the oyster 

 cannot be measured as the experiment progresses. 



While the pumping rate may not necessarily 

 indicate feeding rate, this is not a legitimate 

 objection to the use of the pumping rate as an 

 index of physiological activity. Because the 

 oyster takes its food from the water, there can 

 be no doubt that the more water it passes through 

 its filtering system, the more food it can get. 



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