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Inhibition of ecdysteroid production in nymphs of Rhodnius prolixus treated with ethoxyprecocene II
Author(s) -
Garcia Eloi S.,
De Azambuja Patricia,
Feder Denise,
Bowers William S.
Publication year - 1988
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940080206
Subject(s) - ecdysteroid , rhodnius prolixus , prothoracic gland , biology , medicine , endocrinology , rhodnius , nymph , moulting , hemolymph , radioimmunoassay , muda , metamorphosis , hormone , ecdysone , insect , biochemistry , larva , botany
Rhodnius prolixus nymphs fed 7‐ethoxy‐6‐methoxy‐2,2‐dimethylchromene (ethoxyprecocene II, EPII) show a variety of responses, including precocious molting to diminutive adults, severe retardation of molting, or a condition of permanent ecdysial stasis. The latter two conditions are reversible by subsequent treatment with 20‐hydroxyecdysone. Ecdysteroid titers in the hemolymph of individual insects, determined by radioimmunoassay (RIA), show that the ecdysteroid cycle in nymphs undergoing precocious metamorphosis is similar to that of untreated fifth stage nymphs during normal imaginal molting. Nymphs in ecdysial stasis, following EPII treatment, were found to have very low ecdysteroid titers. Analysis of ecdysteroid synthesis by the prothoracic glands (PG), cultured in vitro, showed that: 1) only traces of ecdysteroid were detectable in PG from nymphs treated in vivo with EPII; 2) the PG from untreated nymphs incubated in culture medium with EPII possessed significantly lower ecdysteroid synthesis compared with controls. These studies sought to determine if the inhibition of ecdysteroid biosynthesis observed in Rhodnius , following exposure to EPII in vivo and in vitro, is due to a direct action on the PG or result as an indirect effect perhaps mediated by the neuroendocrine system.