102 FACTORS AFFECTING CILIARY ACTIVITY 



lateral cilia are soon brought to rest. Gray (1926) believes that 

 the concentration of Mg++ in the blood is more important than 

 that of the surrounding sea water in the determination of the 

 activity of these lateral cilia. It is difficult to see v^^hy the concentra- 

 tion of Mg++ should affect one group of cilia differently from 

 another, but, if the beat of lateral cilia is normally controlled by 

 the presence of a substance such as serotonin (p. 110), then the 

 Mg++ may interfere with the action of this substance. 



8. Oxygen, Respiration and Ciliary Activity 



In the absence of oxygen, cilia of Mytilus gills were found by 

 Gray (1924) to gradually slow down and stop, but they would 

 quickly recover in aerated water if the oxygen lack was not 

 prolonged ; the lateral cilia of the gill stop well before the frontal 

 cilia (Aiello, 1960). Similarly, the application of cyanide very 

 quickly reduces the oxygen consumption of Mytilus tissues, and 

 the ciliary activity falls away more slowly (Gray). In an earlier 

 paper Gray (1923) had reported that, in Mytilus, the rate of 

 movement of a small platinum plate over the gill surface was 

 directly proportional to the rate of oxygen consumption of the 

 gill tissues, when the ciliary activity was changed by changes in 

 temperature. He also found (Gray, 1924) that when lateral cilia 

 of Mytilus gill which were quiescent were reactivated by the 

 addition of veratrine, K+ or a mixture of K+ and 0H~, the 

 commencement of activity was accompanied by an increase of 

 between 40 and 50 per cent in the oxygen consumption. It 

 appears then that oxygen is essential for the activity of these cilia, 

 but that they will function anaerobically for a short time in much 

 the same way as many other tissues. Usuki (1956a) and Usuki and 

 Okamura (1956) have found that both aerobic and anaerobic 

 processes are important for the ciliary activity of the oyster gill; 

 some energy may be derived from the anaerobic part of the 

 respiratory sequence. 



Many spermatozoa may be stored under conditions of low 

 oxygen supply and are capable of either aerobic or anaerobic 

 respiration, although normally there is a close relation between 

 sperm motility and the rate of respiration (Mann, 1954). Similarly, 

 some ciliated and flagellated protozoa live in situations that are 

 almost if not completely without oxygen, e.g. the flagellate 



