Measurements of Oxygen Consumption 

 by Syringe 



The figures for oxygen consumption of siphonophores 

 presented in table 1 were, with the exception of Experiments 

 8, 11, and 12, * obtained by a simple syringe method. The 

 organisms were placed in 1, 2, or 5 cc syringes filled with 

 seawater without an entrapped gas phase, together with a 

 drop of mercury for stirring. They were placed in water 

 baths at the stated temperature (controlled to ±0. 5°C) for 

 various periods of time. Samples of the same seawater 

 were analyzed for dissolved gases 5 at the start of experi- 

 mental runs. Control syringes, containing seawater with- 

 out organisms, were run alongside those containing sipho- 

 nophores. At the end of the experiment, samples of water 

 from each syringe were analyzed for dissolved gases. 

 Suitable corrections were made for the seawater blanks, 

 and final values were subtracted from starting values to 

 give total oxygen removed from the seawater during the 

 interval in question. 



This procedure assumes a constant rate of oxygen 

 utilization by the siphonophores. In view of the stable 

 temperature, the large volume of water compared to the 

 volume of metabolizing tissue, and, therefore, the large 

 supply of dissolved oxygen, this assumption seems warranted. 



In the case of the fastest metabolizing 10-hour speci- 

 men (Experiment 5), the amount of dissolved oxygen remain- 

 ing at the end of the experiment would have sufficed at the 

 measured level of utilization for more than an additional 

 six hours. The oxygen level, therefore, probably did not 

 become limiting. 



Effects upon respiration of the carbon dioxide evolved 

 are believed negligible because of the large volume of water 

 relative to the siphonophore and also the buffering capacity 

 of the seawater. In a second method described below, where 

 carbon dioxide was absorbed by strong alkali, the measured 

 rates of oxygen consumption were comparable to the syringe 

 values. 



Throughout the report, experiment numbers correspond to those listed in table 1. 



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