Juvenile hormone
Juvenile hormone (JH) is a hormone in insects that regulates the development of larval characteristics and determines the product of the moult . There are different types of JH (JH0 to JHIII, 4-methyl-JHI, 12′-OH-JHIII, 8′-OH-JHIII, 4′-OH-JHIII). JHIII is the only one to be found in all insect orders, JHI, II and 0 only in butterflies .
Biological function
While the hormone ecdysone triggers a periodic moult, the concentration of juvenile hormone decides whether larval moulting or pupation occurs in holometabolic insects or adult moulting in hemimetabolic insects . In the presence of JH, larval moults occur. However, if the concentration falls below a certain threshold value, a pupa is created the next time it sheds . From this the imago finally hatches .
In adult insects, JH also stimulates the synthesis of vitellogenin and its storage in the egg cells .
Excessive doses lead to developmental disorders in the form of excess larval moults. Malformations often occur, and the animals can no longer shed their skin completely and die before they have reached the reproductive adult stage. Many plants use this effect by producing juvenoids to ward off their predators (e.g. juvabion in the balsam fir or farnesol in the lily of the valley). Analogues of the juvenile hormone (e.g. fenoxycarb or methoprene ), which can be used as an insecticide in agriculture, work on the same principle . The disadvantage is the lack of species specificity and the hydrophobic properties of the juvenile hormones.
If the juvenile hormone is removed from an insect larva early on, it will pupate, but will not grow to its full size.
biosynthesis
JH is formed in the corpora allata (singular: corpus allatum) located behind the brain, usually in pairs , and released directly into the hemolymph , where it binds to certain transport proteins. Storage of YH does not take place. The synthetic activity of the corpora allata is controlled by inhibiting (allatostatin) and activating (allatotropin) factors.
Others
Chemically speaking, juvenile hormones are sesquiterpenes .
See also
literature
- Hans Piepho : Juvenile hormone and behavior in the wax moth . Springer, Berlin a. a. 1967
- Gerhard Seifert: Entomological internship . 3. Edition. Georg Thieme Verlag, Stuttgart 1995, ISBN 3-13-455003-2 .
- David A. Schooley, Fred C. Baker: Juvenile hormone biosynthesis . In: Gerald A. Kerkut, Lawrence I. Gilbert (Eds.): Comprehensive insect physiology, biochemistry and pharmacology, Vol. 7: Endocrinology 1 . Pergamon Press, Oxford 1985, ISBN 0-08-030808-2 , pp. 363-389.
- Eric Darrouzet, Bernard Mauchamp, Glenn D. Prestwich, Lucien Kerhoas, Istvan Ujváry, Franck Couillaud: Hydroxy Juvenile Hormones. New Putative Juvenile Hormones Biosynthesized by Locust Corpora Allata in Vitro . In: Biochemical and Biophysical Research Communications , Vol. 240 (1997), pp. 752-758, ISSN 0006-291X .