Ecdysteroid and free amino acid content of eggs of the Colorado potato beetle, Leptinotarsa decemlineata

In order to identify components of the Colorado potato beetle (CPB) egg tha t may be required by Edovum puttleri, a parasitic wasp that parasitizes the CPB egg, to complete development, ecdysteroid and free amino acid content of CPB eggs were analyzed by reversed phase high pressure liquid chromatogr aphy followed by radioimmunoassay to identify ecdysteroids. Ecdysteroid tit ers were relatively low (<300 pg/egg) through day 2 post-oviposition and th en increased sharply, reaching concentrations >2,500 pg/egg on day 3 post-o viposition. Ecdysone (E), 20-hydroxyecdysone (20E), and polar conjugates of E were prominent ecdysteroids present in eggs sampled on days 0 and 1 post -ecdysis, and E, 20E, three peaks containing more polar ecdysteroids (metab olic inactivation products), and polar conjugates of E were present in eggs sampled on day 2. Thus, at a time when parasitization of CPB eggs by E. pu ttleri is relatively high (0-48 h), physiologically-active ecdysteroids (20 E and perhaps E are physiologically active) are present at concentrations b etween 50 and 200 pg/egg. Ecdysone and 20E reached their highest levels in day-3 eggs, indicating that ecdysteroid may direct physiological processes associated with the completion of CPB embryonic development. In day-4 eggs, the concentration of E and 20E fall dramatically and polar metabolites of E and/or 20E are now responsible for the high ecdysteroid content of the eg gs. Interestingly, conjugates of E decrease to relatively low levels in day -3 eggs and are absent in day-4 eggs. Therefore, it is likely that the incr ease in E in day-3 eggs is due, in part, to the breakdown of polar conjugat es of E. Nine amino acids were present in significant quantities in eggs sa mpled at various times between 0 and 48 h post-oviposition. These include h istidine, glutamine, proline, asparagine, serine, glutamic acid, threonine, lysine, and tyrosine. The first three amino acids were present at concentr ations that were approximately 2 to 6 times greater than the concentrations of the last six amino acids. Amounts of most of the free amino acids varie d with the age of the eggs from which the extract was prepared, but in gene ral, there was no correlation between the levels at times of maximum parasi tization (0 and 30 h) and the levels at the less favored times of parasitiz ation (16 and 48 h). This information should facilitate the development of diets for both parasites and predators of pest species of beetles. Arch. In sect Biochem. Physiol. 44:172-182, 2000. Published 2000 Wiley-Liss, Inc.dag ger