juvenile hormone
[′jü·vən·əl ′hȯr‚mōn]Juvenile Hormone
an insect hormone that regulates the stage-by-stage development of insects. Chemically an isoprenoid, juvenile hormone is a colorless, optically active viscous oil that is insoluble in water.
It was discovered in 1956 by the American entomologist C. Williams in the abdomen of the male Hyalophora cecropia, a butterfly. Its isolation, structural determination, and chemical synthesis were first accomplished by a group of American scientists in the period 1967–69. The hormone occurs in insects with complete as well as incomplete metamorphosis. Its amount in the insect organism is very small, of the order of 10–1 to 10–2 μg/g.
Juvenile hormone is synthesized and secreted by the corpora allatum under the influence of the protein-activating hormone produced by the neurosecretory cells of the brain from the moment the larvae hatch from the ovum. During the larval period, it inhibits the activity of another hormone, ecdysone, which stimulates larval growth and hastens the molting of larva, thus contributing to the normal development of the larva to complete maturity. Inhibition is apparently effected through repression of the genes. With successive moltings, the secretion of juvenile hormone gradually decreases and is drastically reduced in the final larval stage, as a result of which the larva is transformed into a pupa under the influence of ecdysone. Thus, a balanced interaction of juvenile hormone and ecdysone ensures normal development in insects. Juvenile hormone also manifests gonadotrophic activity, influences diapause, and in some insects stimulates production of the sexual pheromones. Other isoprenoids, in particular juvabione, as well as many synthetic analogs, also possess the capability of juvenile hormone.
The use of juvenile hormone and its analogs as insecticides that disrupt the normal developing of insects has proved successful in controlling the larva of the cotton bollworm (Heliothis armígera) and other dangerous pests of agricultural and timber crops. The disadvantage of the insecticides is that their maximum effectiveness is only during the short period of the transformation of an immature individual into a mature one. Antagonists of juvenile hormone, called precocenes (from the English “precocious,” meaning early maturing), which cause premature metamorphosis of larvae, sterility, and anomalous diapause in insects, have been discovered in certain higher plants. Precocenes appear to be promising as “antihormonal” insecticides.
REFERENCES
Pridantseva, E. A., A. A. Drabkina, and Iu. S. Tsizin. “luvenil’nyi gormon nasekomykh.” Uspekhi sovremennoi biologii, 1971, vol. 71, issue 2.Krimer, M. Z., and A. A. Shamshurin. Khimiia iuvenil’nogo gormona i ego analogov. Kishinev, 1972.
Röller, H., and K. H. Dahm. “The Chemistry and Biology of Juvenile Hormone.” In Recent Progress in Hormone Research, vol. 24. New York-London, 1968.
Naturally Occurring Insecticides. Edited by M. Jacobson and D.Crosby. New York, 1971.
Bowers, W. S., et al. “Discovery of Insect Anti-juvenile Hormones in Plants.” Science, 1976, vol. 193, no. 4253.
E. P. SEREBRIAKOV