Respiration and Metabolism 233 



Rogers-^"- presents an interesting discussion of the decreasing oxygen uptake 

 with age in the small crustacean, Sivtocephahis, measured immediately after 

 hatching et seqiientia, during several larva, nd brood mother stages (Table 

 39). 



Pupating insects present a unique case, with general agreement among 

 investigators on the shape of the curves if not on their interpretation when 

 oxygen uptake is expressed as a function of pupation time. A broad U-shaped 

 curve is usually obtained, the minimum corresponding with the middle of the 



TABLE 39. OXYGEN CONSUMPTION IN SIMOCEPHALUS EXPRESSED IN 



PER CENT OF UPTAKE IMMEDIATELY FOLLOWING HATCHING, 



ALL ADJUSTED TO SAME RELATIVE WEIGHT."" 



Stage Relative Oxygen Uptake 



Hatching (5.6 .\ 10 ' cc. /individual/ min.) 100.0 



3rd instar 96.4 



1st brood mother 52.1 



3rd " " 50.8 



5th " " 41.8 



pupal interval.--' •"'■ ^'■''- -"^•■'' '-^^^ The down slope generally has been represented 

 as the period during which histolytic processes predominate, while the up 

 slope, indicating a rise in rate of oxygen consumption, corresponds to the more 

 constructive phase of dedifferentiation. This, however, seems to be an over- 

 simpliHcation and based on inadequate evidence. As Krogh-'^ has pointed 

 out, "the expenditure of energy required for tissue formation is quite small,' 

 and furthermore the change from catabolic to anabolic processes for the 

 organism as a whole would not be expected to occur all at once. 1 bus the 

 oxygen consumption data on the muscid flies, CaUiphora and Lucilia, for 

 example, do not indicate any sudden change, at least on a weight basis, to 

 account for the abrupt change-over from decreasing metabolic rates. "''• '^''^ It 

 seems more likely that the shift in respiratory exchange results from alterations 

 in the respiratory pattern, involving different substrates and the balance 

 between aerobic and anaerobic processes. 



Among bees, the larger, better-nourished queen outstrips the workers in 

 regard to metabolic activity and growth (Fig. 52). 1 ler relati\e superiority is 

 shown in larval, pupal, and pre-adult stages, calculated on both a weight and 

 an individual basis. -'''^ 



The use of oxidative poisons and of oxygen depri\'ati()n has made it possible 

 to test the relative dependence on oxygen of the various stages of development. 

 In many animals a transition from predominantly anaerobic to aerobic condi- 

 tions is indicated. In the squid, LoHoq pcalei, for instance, an increase in 

 cyanide sensitix'itv can be shown to parallel the increase in owgen consump- 

 tion and carbon dioxide production during development.-^'' A 5-day embrxo 

 withstands exposure to N/1000 NaCN for 20 hours, but older embryos show 

 a graduallv increasing cyanide sensitivity until the stage of the ncv\ly hatched 

 embrvo, which has a tolerance of only 1-2 hours. A Vi-inch squid and the 

 adult have even less— a tolerance of onlv 1 minute. Organisms in the same 



