§ 5.121 FAT METABOLISM 187 



allata cause a change in metabolism in normal females, from an 

 early phase of fat accumulation in the fat body, to a later phase 

 when the fat body becomes depleted and all the fat is passed into 

 the Qgg yolk (Pfeiffer, 1945). If the corpora allata are removed near 

 the beginning of the adult stage (whether the ovaries are present or 

 not), the fatty acid content of the fat bodies continues to rise at the 

 same rate as before. If adult females retain their corpora allata, the 

 usual depletion of the fat bodies follows, even in castrated speci- 

 mens, showing that the ovary has no effect. Normally the corpora 

 allata begin to secrete sufficiently to cause this change some time 

 after the emergence of the aduh, as they are inhibited during 

 metamorphosis (Part II, § 3). 



Vertebrata. Thyroxine causes decrease in fat stores, at least 

 in mammals. Treatment of rats with thyroxine causes an increase 

 in the synthesis and turnover of phospholipids in the liver and in 

 the secretion of cholesterol in the bile (Rawson et al.y 1955). 

 Conversely, hypofunction, or reduction, of the thyroid is accom- 

 panied by increase in fat deposition, provided the food supply is 

 riot limited. The secretion of the thyroid is stimulated by thyro- 

 trophin from the hypophysis (§ 4.221). 



5.122 Decrease in fat consumption or increase in storage 



Crustacea. A sinus gland hormone seems to help in maintain- 

 ing the amount of fat stored in the body. When the sinus gland or 

 the whole eyestalk is removed, there is a rapid disappearance of 

 fat, as well as an increase in oxygen consumption (§ 5.111), 

 followed by the onset of moulting. It is not known if the same 

 hormone controls all three processes. 



The effects of starvation, with and without sinus gland removal, 

 have been examined in the crab, Hemigrapsus nudus. The sinus 

 glands were removed by drilling through the eyestalk and aspir- 

 ating out the gland tissue. Male and female crabs were compared 

 with normal controls in the same inter-moult stage, but no figures 

 are given for mock-operated animals. Female crabs normally have 

 more fat than males, and 23 days of starvation makes no significant 

 difference ; but sinus gland removal, followed by starvation for 23 

 days, results in the fat content dropping by nearly a half in both 

 sexes (Table 20). 



