Metabolism of [³H]‐ecdysone in embryos and larvae of the tick Ornithodoros moubata

Abstract

The fate of [3H]-ecdysone ([3H]-E) was investigated in hanging drop cultures of embryos and larvae of the tick Ornithodoros moubata using HPLC. The hormone was metabolized more slowly during described periods of increasing endogenous ecdysteroid (ES) titers than during periods of low titers except for young embryos. Three different classes of metabolites were produced: 1) apolar products (AP) corresponding to C-22 fatty acid ester conjugates of E and, in some cases, of 20-hydroxyecdysone (20E), 2) unidentified polar products (PP) more polar than E, one peak of which had the same retention times as 20,26-dihydroxyecdysone, and finally, 3) 20E verified by comigration of cold standards on RP-18 and silica columns. Hydroxylation of E to 20E first became evident in cultures of 2 day old embryos and was present in all cultures of older animals. Highest production of free 20E occurred during increasing endogenous ES titers in embryos and during the ES peak in larvae. Conjugation of E to AP occurred in all stages investigated, but was more pronounced during periods of low endogenous ES titers, and may correspond to a detoxification mechanism. In contrast, PP were produced during high 20E production in embryos and during periods of high and decreasing endogenous titers in larvae.

Effect of dietary lipid levels on growth performance, fatty acid profile and enzymatic activity of juvenile swimming crab,Portunus trituberculatus

“…It has been reported that several nutritional factors can affect the process of moulting performance. Molting in crustaceans is triggered by ecdysteroid (Nakatsuji & Sonobe, ), which is metabolized in conjugation with eicosanoids (Dotson, Connat, & Diehl, ). Eicosanoids are main derived from LC‐PUFA such as ARA, EPA and DHA (Schlotz, Sørensen, & Martin‐Creuzburg, ).…”

Efficacy of various lipid supplements in formulated pellet diets for juvenile Scylla serrata

“…Molting in crustaceans is regulated by ecdysteroids secreted from the Y‐organ, which is released into the haemolymph (Subramoniam 2000). It is shown that ecdysteroids get metabolized in conjugation with eicosanoids (Doston, Connat & Diehl 1993) to control the molting. This again can be related to the important role of 20:5n‐3 and 22:6n‐3 in accelerating the intermolt period and production of greater carapace widths in the first crab stage of S. serrata (Suprayudi et al 2004a) and Portunus trituberculates (Takeuchi, Satoh, Sekiya, Shimizu & Watanabe 1999).…”

Hormonal control of tick development and reproduction

“…Furthermore, embryos could metabolise [ 3 H]ecdysone in vitro into 22-fatty acyl esters, 20,26-dihydroxyecdysone (an intermediate in 26-oic acid formation) and 20hydroxyecdysone. Significantly, 20-hydroxylation first became evident in 2-day-old embryos, with highest activity occurring during increasing endogenous ecdysteroid titres (Dotson, Connat & Diehl, 1993). Although fatty acylation occurred in all stages, it was more pronounced during periods of low endogenous ecdysteroid titres.…”

“…Although fatty acylation occurred in all stages, it was more pronounced during periods of low endogenous ecdysteroid titres. It has been suggested that ecdysteroid fatty acyl ester may represent a detoxification mechanism in O. moubata eggs, although their true significance is uncertain (Dotson et al 1993).…”