154 THE BIOLOGY OF MARINE ANIMALS 



rate of oxygen consumption is correlated with body weight as an exponen- 

 tial function, 



c.c. 2 consumed = kW x 



where A: is a species constant, W is body weight and x is an exponent rang- 

 ing from 0-66 to unity. Measurements on a wide variety of marine fish and 

 crustaceans show a decrease in metabolic rate with increase in body size. 

 Marine forms examined do not conform closely to the surface law ( x = 



It 4t 



Fig. 4.8. Metabolic Rate of Different Animals Plotted on the 

 Basis of Body Weight 



Curves : 1 , nematodes and polychaetes ; 2, 3, Littorina and Nassarius (gastropods) ; 4, 9, 

 Mytilus (lamellibranch) ; 5, 11, Crustacea; 6, Balamts; 7, Asterias; 8, planarians, anne- 

 lids, and echiuroids ; 10, gastropods; 12, insects; 13, fish; 14, amphibians; 15, reptiles; 

 16-19, birds and mammals. (From Zeuthen (171).) 



0-66). For many small metazoa (eggs, larvae, small marine Crustacea) the 

 value of the exponent relating weight to oxygen uptake lies nearer unity 

 (0-8-0-9). For larger organisms the exponent ranges around 0-7 (41, 44, 

 128, 142, 144, 150, 165, 171, 175). 



Effect of Activity. All body activities are ultimately dependent upon 

 aerobic respiration. Hence, any changes in activity will affect cellular 

 respiration and, if of sufficient magnitude, will result in measurable 

 alterations in oxygen consumption. The condition of standard or basal 

 metabolism derived from human physiology is hardly applicable to lower 

 animals, and recourse sometimes is had to anaesthetics to reproduce non- 

 active metabolism (muscular rest). Such procedures demand a knowledge 

 of the mode of action of the anaesthetic and the optimal dose. Zeuthen 

 (171) makes a brief for relating oxygen consumption to normal activity, 

 i.e. a fair sample of activity characteristic of the animal in nature. In a 

 series of invertebrates he has demonstrated the rise in 2 consumption 



