arrangement was used by Galtsoff and Arcisz 

 (1954) in their work on the effects of known con- 

 centrations of Escherischia coli on oysters. 



For observations intended to last several days 

 or weeks it is convenient to use a slow-motion 

 kymograph, rotating at the speed of about 1 inch 

 per hour. A time marker of 1-hour or K-hour 

 intervals can be made by mounting a Incite disk 

 on a Telechron type motor making one revolu- 

 tion per hour. A piece of copper wire attached 

 to the periphery of the disk acts as a contact 

 which slides over the two poles of an electric 

 circuit and activates a small signal magnet. Using 

 these methods it was possible to record the ventila- 

 tion of the gills for 26 consecutive days with only 

 occasional brief interruptions for cleaning the 

 tank and for the removal of feces accmnulated 

 inside the apron. An excerpt of such a record 

 is reproduced in figure 171. 



2 



Centimeters 



Figure 172. — Electric drop counter. 



Shell movement 



rm n 



Open 



Closed 



Discharge of water- each stroke corresponds to 250ml 



i iii i I l l i iiii ii iii i i i iiHiiiii ii iiii iiii iii ii mi i i i ii i iiiiiiMi 



Figure 171. — Typical record of the shell movements 

 (upper line) and rate of transport of water by the gills 

 (second line) of an adult C. virginica kept in running 

 sea water at the fishery laboratory in Woods Hole at 

 the temperature of 21° to 22° C, Each vertical stroke 

 corresponds to the discharge of a dumping vessel of 

 250-ml. capacity. Time interval, 1 hour. 



An electric drop counter (fig. 172) may be used 

 instead of a dumping vessel or water wheel if the 

 volume of water passed through the gills is small, 

 as for instance in juvenile American oysters or in 

 Ostrea lurida. The drop counter is made of a 

 short section of glass tubing with two platinum 

 wires sealed opposite each other. Each time a 

 drop of water falls between the wires the contact 

 is completed and electric current from a trans- 

 former or a battery activates the signal magnet 

 and makes a mark on the kymograpli drum. The 

 counter works satisfactorily in water of liigli 

 salinity but is not suitable for brackish water. 

 The number of drops per unit of time is counted 

 from the kj-mograph record shown in figure 173. 



190 



Current indicators. — The relative velocity of gill 

 current can be studied by recording on a kymo- 

 graph drum the deflections of a shallow cone 

 placed in front of the cloacal opening (Hopkins, 

 1933). The cone C (fig. 174) about 5 cm. in 

 diameter at its open end is made of lightweight 

 paper waterproofed by dipping in a dilute solution 

 of gum damar in xylene. The cone is mounted 

 on the lower end of vertical rod F^, which rotates 

 on horizontal a.xis A and moves the horizontal 

 lever F which indicates the cm'rent. The entire 

 system is very light, since lever and rod are made 

 of straw, and it is accurately balanced by con- 

 necting the vertical rod F' by a hair to a simple 



I I I I I I I I I I I I I I I I I I I I I I I I 



— \ \ — \ — I — \ — I I I I I 



(— I — \ — I — I — I — I — \ — \ — I — \ — I — h 



I I I 



I I I 



I I I I I I I I I I I I I I I I I I I I I I I 



Figure 173. — Four parts of a record of the rate of water 

 transport by the gills of a 2-year-old C. virginica ob- 

 tained with an electric drop counter. Upper lines — 

 each stroke corresponds to one drop of water discharged 

 by the oyster; lower lines — time intervals of 1 sec. 

 Temperature of water 22.2° C. 



FISH AND WILDLIFE SERVICE 



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