96 



FACTORS AFFECTING CILIARY ACTIVITY 



Gray (1920) reported that the gill cilia of Mytilus will not beat 

 below pH 5*5 to 6-0, although the stoppage by acid is readily 

 reversed on return to normal pH. Above a pH of about 9, the gill 

 epithelium breaks up into its constituent cells, but the activity of 

 the cilia does not stop. The effects of pH on the mechanical 

 activity of the frontal cilia of Mytilus gill are shown in Fig. 24. 

 However, all acids do not have an equal effect, for weak acids 

 (especially carbonic acid) act more quickly than the strong 

 mineral acids (Gray, 1922a). Thus Nomura (1932) found that 

 the gill cilia of Pecten are stopped in 1 min at pH 6*15 in carbonic 



o 



2 

 O 



o 



I/) 



a. 



Mi 



Q. 



> 



< 



< 



o 



z 

 < 



X 



u 



LJ 



Fig. 24. 



fe 60 6-4 6-8 7-2 7-6 60 S** 68 9«2 

 Hydrogen Ion Concentration Ph. 



The effect of pH on the mechanical activity of frontal 

 cilia of Mytilus gill (from Gray, 1924). 



acid and at pH 3*7 in hydrochloric acid (at 13°C). Haywood 

 (1925) and Tomita (1935) have reported similar findings in other 

 lamellibranchs, and Jucci (1928) observed the same effect on cilia 

 of the coelenterate Sagartia. 



The reason for this different effect of weak and strong acids is 

 evidently concerned with the ease of penetration of the acids, and 

 this in turn depends on their state of ionization. The penetration 

 effect can be illustrated by Gray's (1924) experiments on the 

 relation of ciliary activity to oxygen consumption. Oxygen 

 consumption and ciliary activity are closely related; in the 

 presence of either weak or strong acids the ciliary beat is stopped 

 and the oxygen consumption falls, but it is only completely 



