Investigations on ecdysteroids and juvenile hormones and on morphological aspects during early embryogenesis in the ovoviviparous cockroach Nauphoeta cinerea

Abstract

During early embryogenesis, which is from ovulation (day 0) until dorsal closure (day 19), the quantity of free and conjugated ecdysteroids in the egg cases, as measured by radioimmunoassay (RIA), increases. Thin-layer chromatography (TLC) and high-performance-liquid-chromatography (HPLC) analyses combined with RIA suggest that 20-hydroxy-ecdysone is the predominant ecdysteroid. Hydrolysis of the highly polar products of day-0 and day-17 egg cases by Helix pomatia enzymes indicates the presence of some conjugates of 20-hydroxy-ecdysone, hydrolyzable under these conditions. However, important quantities of RIA-reactive highly polar products are not hydrolyzed particularly in day-17 egg cases. These results demonstrate that the highly polar products of day-0 egg cases are qualitatively as well as quantitatively different from the highly polar products of day-17 egg cases. Morphological investigations show that the peak of 20-hydroxy-ecdysone at the time of the dorsal closure coincides with the synthesis of an embryonic cuticle. Using the Galleria wax test only traces, or no juvenile hormone activity could be detected in embryos during the entire period of early embryonic development. Morphological investigations of the brood sac suggest that this organ is very important to facilitate the initial uptake of water into the eggs. Thereafter the embryos can develop independently of the female when kept in a humid environment.