EXPERIMENTAL STUDY OF THE OYSTER GILL 



1)9 



EFFECT OF TEMPERATURE ON THE RATE OF FLOW OF WATER 



THROUGH THE GILLS 



SUMMER EXPERIMENTS 



We begin the discussioa of this problem with 

 an analysis of the results of summer experiments 

 The experimental material consists of the data of 

 64 experiments performed during the summers of 

 1925 and 1926, but in the following discussion the 

 data of only 15 experiments, in which the obser- 

 vations were made at not less than five different 

 temperature points, are taken into consideration. 



The following technical procedure was fol- 

 lowed in all the experiments: The first observations 

 were made at room temperature, which in most 

 cases was around 20° C. ; then the water was cooled 

 gradually to 5° and then warmed until the temper- 

 ature of 35° and in a few cases 45° was reached, 

 and cooled again to 20°. In 5 experiments read- 

 ings were made at 2° intervals; in 10 experiments 

 5° intervals were used. Each determination of 

 the rate of flow is a mean of 10 or 20 readings. 

 Altogether 2,470 readings were made. 



All the experiments were made with adult 

 oysters varying in size from 3.5 to 5 inches. There 

 exist considerable individual variations in the rate 

 of flow of water that can not be correlated with 

 the differences in size of the oysters and undoubt- 

 edly depend on the physiological conditions of the 

 organisms. Some of the small oysters proved to 

 be very active and produced very strong currents, 

 while some of the largest ones were very weak. 

 At present it is impossible to determine the cause 

 of such differences. There was nothing in the 

 appearance of the oysters that could be correlated 

 with the efficiency of their gQls. 



The range of individual variations in the rate 

 of flow of water at different temperatures is shown 

 in Table 4 and Figure 4. In Table 4 the experi- 

 mental data are grouped in 14 classes, each at 3° 

 intervals, the figures in the body of the table repre- 

 senting the frequencies ; in Figure 4 the frequency 

 distributions for temperature, ranging from 6° to 

 26.9°, are presented graphically. An examination 

 of the frequency polygons discloses that the individ- 

 ual variations increase with the temperature and 

 reach their maximum between 24° and 26.9° C. 

 93280—28 3 



0.5 1.0 15 2.0 Zb 3.0 15 40 

 LITER PER HOUR. 



FiQ. 4.— Frequency distribution of the rate of 

 flow of water at different temperatures. 

 Cross-hatched areas show the number of 

 oysters that failed to produce any current 



