168 METABOLIC HORMONES 



water balance and response to stress. They will be considered in 

 relation to their main actions, namely, the control of general 

 metabolic rate and fat deposition (§5.1), intermediary metabolism 

 of carbohydrates and protein (§ 5.2), and the balance of monovalent 

 electrolytes and water (§5.3) and of calcium and phosphates (§ 5.4). 



5.1 General metabolic rate 

 Changes in the general metabolic rate are reflected in the 

 respiration rate of resting animals and also, less directly, in the 

 deposition of fat, since the latter tends to increase with reduction 

 in oxygen consumption (Table 18). 



5.11 RESPIRATION 



Hormones that increase respiration, and therefore increase 

 oxygen consumption, are well-established in Insecta and Verte- 

 brata; but are less clear in Crustacea. Hormones that decrease 

 respiration are best known in Arthropoda. 



5.111 Increase in oxygen consumption 



Crustacea. Extracts of brain and nerve cord increase respira- 

 tion in the freshwater crayfish, Cambarus immunis. Injection into 

 eyestalkless crayfish of an extract of as little as one-tenth of a brain 

 in 0-05 ml saline results in an increase of 22-8 per cent in oxygen 

 consumption (Scudamore, 1947). This increase is in addition to 

 that produced in the test animals by eyestalk removal (§ 5.12). 

 Similar injections of an extract of the nerve cord and its ganglia 

 can result in an increase of 29 per cent. Cautery of the eyestumps 

 of eyestalkless crayfish, causing injury or stimulation of the brain, 

 also produces a temporary increase of 56-8 per cent in oxygen 

 consumption. 



Insecta. The corpus allatum secretes a hormone which 

 significantly increases the respiratory rate of insects. 



A series of experiments by E. Thomsen (1949, and Thomsen 

 and Hamburger, 1955) on the blowfly, Calliphora, are noteworthy 

 for the use of extensive controls. Uniformity of material was 

 maintained by using only 7- day-old adults cultured at 25 °C and 

 starved for 24 hr before the males and females were tested 

 separately. Since allatectomy, or removal of the corpus allatum, 



