The juvenile hormone effect of farnesol and some related compounds: Quantitative experiments

Abstract

Farnesol, farnesenic acid, farnesyl pyrophosphate, squalene, farnesyl diethylamine, farnesyl methyl ether, and ‘dendrolasin’ (the furan of farnesal) have been studied. Farnesyl methyl ether is the most effective in preventing metamorphosis in Rhodnius and in inducing yolk formation in the decapitated adult female. A completely larval moult in the fifth-stage larva is induced by 50 μml of farnesyl methyl ether applied to the uninjured cuticle in 10% solution in linseed oil. The active substance so applied is carried by the haemolymph and will act upon a second insect joined to the treated larva in parabiosis. A complete larval moult is induced by the injection of 5 μml in oily solution and a partial larval moult by injection of 2 μml. This small dose is most effective when injected at 8 days after feeding. Deposition of yolk and formation of ripe eggs in the decapitated adult female require the injection of about 1 μml of farnesyl methyl ether per egg. But even a dose of 100 μml leads to the production of only about two-thirds the normal number of ripe eggs produced by the intact female or the female with the brain removed but the corpus allatum present. Farnesyl methyl ether, farnesol, etc. are completely inactive if injected in emulsified form. Problems discussed are the possible relation of farnesol derivatives to the natural juvenile hormone; the minimum requirements of farnesyl methyl ether in comparison with certain hormones in vertebrates; and the form in which the active material is transported in the haemolymph.