Respiratory Quotients of Intact Egg, Isolated Embryo and Embryo Homogenate

The problem of the nature and type of chemical compounds utilized during the embryonic development of an organism has been studied for many biological forms and considerable data exist concerning the basic details of such phenomena (Needham, 1942; Spratt, 1952; Cleland and Rothschild, 1952). The terrestrial, cleidoic or closed system egg seems to be rather favorable material for study of this problem since the exchanges of materials from the outside to the inside of the egg and vice versa appear to be at a minimum. The egg of the grasshopper, Melanoplus differentialis, is unusually favorable material for investigating the problem since water, oxygen and carbon dioxide seem to be the only substances passing into and out of the egg during its entire course of development. The fact that the embryo can be completely isolated from the yolk for experimental purposes makes possible detailed quantitative studies of its metabolic activities during various phases of its development. During the normal course of embryonic development there occur periods of mitotic activity (pre-and postdiapause) and block (diapause), thus making possible studies on these phases of the cellular behavior of both the egg and embryo (Bodine and Boell, 1934). Food for the developing embryo is contained within the egg (yolk) and consists largely of lipids and lipid compounds (Slifer, 1930). Previous metabolic studies on the changes of food during the development of this form have indicated that respiratory quotients (R.Q.) are relatively low and suggest that fat conversions or transformations are largely responsible for the chief energy sources of the embryo during its entire developmental cycle (Boell, 1935; Hill, 1945)