Developmental stages and chemical composition in embryos of the cockroach, Diploptera punctata, with observations on the effect of diet

Abstract

A developmental time-table has been established for the embryos of viviparous Diploptera punctata. The percentage of gestation time occupied by pre-dorsal closure stages is only 19 per cent compared to 40 or 50 per cent in non-viviparous species. The increase in wet weight of the embryos begins several days before dorsal closure and continues throughout gestation. The increase in dry weight, protein, carbohydrate, and uric acid does not begin until shortly after dorsal closure but thereafter parallels the increase in wet weight. The increase in oöcyte protein during vitellogenesis is tenfold, less than in oviparous or ovoviviparous species. But the increase in embryo protein during gestation is sixtyfold; this characterizes viviparity in D. punctata. Although total lipid increases during gestation, lipid as a percentage of wet weight decreases most rapidly before dorsal closure and less rapidly there-after. It is suggested that before dorsal closure lipid is the major energy source for development. After dorsal closure the embryos are able to drink through their mouths the fluid nutrient provided by the mother. The ultimate source of nutrients required by developing embryos is the maternal diet during gestation. Females starved from ecdysis do not produce young; females fed only sugar from ecdysis produce viable larvae but suffer loss in body weight. Embryos from such females, although normal in length, are deficient in protein.