Biochemical Changes during the Embryonic Development of the Japanese Beetle (Popillia japonica Newman)

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Abstract
The Japanese beetle egg, at 30[degree]C., increases from an avg. initial wt. of 0.83 mg. to 2.45 mg. at the end of the embryonic period. This increase in wt. is associated with absorption of water, water content increasing from 50% in the newly laid egg to 84.7 in the egg at the end of the embryonic period. The changes in wt. result from changes in water content. Total N content remains constant during embryogenesis, at an avg. value of 0.036 mg. per egg. Glucose content increases during embryogenesis. It has an avg. value of 0.0020 mg. in the newly laid egg. Following the 2d day, glucose content increases rapidly reaching a max. value of 0.0074 mg. in the 3-day egg, decreasing to 0.0050 mg. at 4 days, and increasing gradually but significantly during the remainder of the embryonic period. Glycogen decreases rapidly during the early part of embryogenesis from an initial value of 0.021-0.012 mg. in the 3-day egg. A 2d decrease in glycogen occurs near the end of the embryonic period. Glycogen appears to furnish the material from which the glucose is formed and serves as the main source of energy during the early period when O2 consumption is low. Total lipid remains constant during the early period. Beginning with the 4th day, there is a marked decrease in free lipid, which continues until the time of hatching. The total loss of free lipid amounts to approx. 58% of the available supply. It furnishes the main source of energy during embryogenesis. Bound lipid, on the other hand, remains constant throughout the embryonic period.