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

Abstract

In order to identify components of the Colorado potato beetle (CPB) egg that 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 chromatography followed by radioimmunoassay to identify ecdysteroids. Ecdysteroid titers were relatively low (<300 pg/egg) through day 2 post-oviposition and then increased sharply, reaching concentrations >2,500 pg/egg on day 3 post-oviposition. 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 (metabolic 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. puttleri is relatively high (0-48 h), physiologically-active ecdysteroids (20E and perhaps E are physiologically active) are present at concentrations between 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 eggs. 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 increase in E in day-3 eggs is due, in part, to the breakdown of polar conjugates of E. Nine amino acids were present in significant quantities in eggs sampled at various times between 0 and 48 h post-oviposition. These include histidine, glutamine, proline, asparagine, serine, glutamic acid, threonine, lysine, and tyrosine. The first three amino acids were present at concentrations 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 varied with the age of the eggs from which the extract was prepared, but in general, there was no correlation between the levels at times of maximum parasitization (0 and 30 h) and the levels at the less favored times of parasitization (16 and 48 h). This information should facilitate the development of diets for both parasites and predators of pest species of beetles. Arch. Insect Biochem. Physiol. 44:172-182, 2000. Published 2000 Wiley-Liss, Inc.

Direct and indirect effects of a thrips‐transmitted Tospovirus on the preference and fitness of its vector, Frankliniella fusca

“…In this study, we found that proline increased more than any other amino acid (>190 times), suggesting that it was released probably in response to the water stress induced by TSWV. Incidentally, proline was also found in greater quantities in the eggs of a phytophagous insect than other amino acids (Gelman et al., ) indicating that it could play an important role in egg development. The increase in titers of proline and other amino acids in this study in TSWV‐infected plants/leaflets, probably as an adaptive response to TSWV infection, could have lead to increased thrips oviposition when reared on TSWV‐infected leaflets.…”

“…Earlier studies have shown that virus infection could improve the availability of vital nutrients such as free amino acids in infected plants (Markkula & Laurema, 1964;Ajayi, 1986). Free amino acids have been documented to influence vitellogenesis and oogenesis in insects, and also serve as nutrients for developing eggs in insects (Cohen, 1989;Hurd et al, 1995;Wheeler, 1996;Davey, 1997;Rojas et al, 1998;Gelman et al, 2000;Klowden, 2007). Our study clearly indicated ca.…”

“…In this study, we found that proline increased more than any other amino acid (>190 times), suggesting that it was released probably in response to the water stress induced by TSWV. Incidentally, proline was also found in greater quantities in the eggs of a phytophagous insect than other amino acids (Gelman et al, 2000) indicating that it could play an important role in egg development.…”

Maternal effects and maternal selection arising from variation in allocation of free amino acid to eggs

“…We prepared eggs for analysis following modified methods of Gelman et al. (). We collected 10 eggs from each female and placed them in an Eppendorf tube and pipetted 100 μ L of 75% ethanol into each sample.…”