IONS 101 



the beat continued at the normal rate. He therefore placed these 

 ions in the series Li+<Na+<NH4+<K+, the order of their effect 

 on the ciliary beat. 



In general it seems that increase in the concentration of K+ 

 leads to increase in the rate of beat of Mytilus cilia. Not only do 

 the frontal cilia beat fastest in salts of this metal, but the latero- 

 frontal cilia also beat faster and with reduced amplitude in 

 solutions with increased concentration of K+. The lateral cilia 

 of excised gills normally lie quiescent in sea water, an effect which 

 Gray (1926) has attributed to the large concentration of Mg++ in 

 sea water as compared with that in the blood. However, K+ seems 

 to be antagonistic to Mg++, and an increased K+ concentration 

 results in prolonged activity of the lateral cilia. Kinosita (1952) 

 reported that isotonic potassium chloride produces a sudden 

 increase in the angular velocity and frequency of beat of the 

 abfrontal cilia of Mytilus gills. 



The divalent ions Ca++ and Mg++ are important, and lack of 

 either of them leads to irreversible changes in the functioning of 

 the cilia of Mytilus, even if they are replaced by other divalent 

 cations. Changes in the total amount of polyvalent cations 

 upsets the balance between monovalent and polyvalent ions, 

 which is normally fairly steady in any particular environment. An 

 increased concentration of Ca++ has little effect on the ciliary 

 activity of Mytilus, but in the absence of Ca++ the ciliary beat 

 gradually slows down and eventually ceases, although it slowly 

 recovers on return to the normal medium. Gray (1924) has 

 suggested that the absence of calcium upsets the supply of energy 

 to the cilia, particularly the conversion of chemical energy to 

 mechanical energy, without affecting the consumption of oxygen. 

 It is now known that small quantities of both Ca++ and Mg++ are 

 important for the liberation of energy in the reaction breaking 

 down ATP to ADP. 



Wide variations of Mg++ concentration have little effect on the 

 rate of beat of frontal cilia of the Mytilus gill, but the stability of 

 the intercellular matrix is rapidly affected by lack of Mg++. The 

 effect on Mytilus gill lateral cilia is rather different, for these cilia 

 beat most rapidly in a medium from which Mg++ is absent, 

 achieving eventually a fast beat with small amplitude. In higher 

 concentrations of Mg++, even that found in normal sea water, the 



