224 INVERTEBRATE PHYSIOLOGY 



increases prior to a molt, and varies in accordance with diurnal, tidal, and 

 lunar cycles as well. The diurnal cycle, at least, corresponds with a cycle 

 of bodily activity. The variation of oxygen consumption in the intermolt 

 cycle, and in some of the shorter cycles as well, is under control of endocrine 

 factors in the eyestalks. One of these may also be a molt-inhibiting factor. 

 Eyestalk removal is followed by an increased frequency of molts, resulting 

 from a decrease in the length of the intermolt period, in most but not all 

 crustaceans. Eyestalkless animals also increase in size following a molt 

 to a greater extent than do normal animals ; the increase results from in- 

 creased uptake of water, and it is not known whether increased tissue for- 

 mation also occurs later in the intermolt cycle. 



A principal function of glucose in some crustaceans appears to be as a 

 precursor of chitin, rather than as a substrate for oxidative metabolism or 

 glycolysis. Glycogen acts either as a direct precursor of chitin or as a stor- 

 age form for glucose. The conversion of glucose to chitin is influenced by 

 an endocrine factor in the eyestalks which may also be the molt-inhibiting 

 factor. This factor is also involved in the regulation of the level of reducing 

 substances, and especially glucose, in the blood. Lipids may serve as energy 

 stores during fasting, and there is some evidence that their metabolism is 

 also under endocrine control. The processes of cellular metabolism in 

 crustaceans are poorly understood, and evidence concerning their endo- 

 crine control is scanty and conflicting. 



The variations in metabolism with sex, the control of such variations by 

 hormones, and the complexity of the hormonal control of events in the 

 intermolt cycle all provide fruitful fields for future investigation. The 

 hormonal control of glucose metabolism offers the most promising oppor- 

 tunity for test of a postulated mechanism of hormone action. Better knowl- 

 edge of the details of intermediary metabolism in crustaceans is essential 

 to our understanding of any of these problems. 



REFERENCES 



Abramowitz, A. A., F. L. Hisaw, and D. N. Papandrea, 1944. The occurrence of a 

 diabetogenic factor in the eyestalks of crustaceans. Biol. Bull. 86, 1-5. 



Abramowitz, R. K., and A. A. Abramowitz, 1940. Moulting, growth and survival after 

 eyestalk removal in Uca pugilator. Biol. Bull. 78, 179-188. 



Ball, E. G., and B. Meyerhof, 1940. On the occurrence of iron-porphyrin compounds 

 and succinic dehydrogenase in marine organisms possessing the copper blood pig- 

 ment hemocyanin. /. Biol. Chcni. 134, 483-493. 



Bauchau, A. G., 1948a. Intensite du metabolisme et glande sinusaire chez Eriocheir 

 sinensis H. M. Edw. Ann. Soc. Roy. Zool. Belg. 79, 73-86. 



Bauchau, A. G., 1948b. Phenomenes de croissance et glande sinusaire chez Eriochier 

 sinensis H. M. Edw. Ann. Soc. Roy. Zool. Belg. 79, 125-131. 



Baumberger, J. P., and J. M. D. Olmsted, 1928. Changes in the osmotic pressure and 

 water content of crabs during the molt cycle. Physiol. Zool. 1, 531-544. 



