THE HORMONAL CONTROL OF METABOLISM IN 

 DECAPOD CRUSTACEANS 



Bradley T. Scheer 

 University of Oregon 



During the last seven years, I have been concerned with the problem 

 of the mechanism of action of eyestalk hormones in decapod crustaceans. 

 It is widely assumed, on the basis of the fact that hormones are active 

 at extremely low concentrations, that these substances act by some catal}i;ic 

 mechanism. \\'hen I began to work on crustaceans, it seemed that the 

 metabolic actions of crustacean hormones were few and simple, and 

 hence that a study of these actions might lead immediately to the discovery 

 of specific effects on enzyme systems. The state of blissful ignorance which 

 made such an opinion possible did not last very long. By now, I am con- 

 vinced that the metabolic actions of crustacean hormones are just as com- 

 plex and numerous as are those of vertebrate hormones, and that crusta- 

 cean metabolism is no simpler than is vertebrate metabolism. 



In the course of this work, I have become increasingly aware of the fact 

 that we really know very little about metabolism in the crustaceans, and 

 consequently we know even less about its control by hormones. It is my 

 purpose here to review briefly some of the available information about 

 oxygen consumption and the metabolism of organic substances in the de- 

 capods, and to summarize what we know about the action of hormones 

 on this metabolism. 



Oxygen Consumption 



We may begin with oxygen consumption as an index of general meta- 

 bolic activity. Spallanzani, in his memoir on respiration published in 1803, 

 was the first to demonstrate oxygen consumption in crustaceans. The in- 

 formation accumulated since that time has been brought together by 

 Zeuthen (1947) ; it may be summarized by saying that the oxygen con- 

 sumption of crustaceans is not notably different from that of other cold- 

 blooded animals of the same size. 



The most interesting aspect of oxygen consumption in decapods is its 

 variation 'during the intermolt cycle. I shall use the phrase "intermolt 

 cycle" in the sense of Drach ( 1939) to indicate a series of morphological 

 and physiological changes between one molt and the next, such that the 

 animal at the end of the cycle is in the same condition as, though older and 

 usually larger than, when the cycle began. I shall also use Drach's sub- 



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