Juvenile hormone
- Pronunciation
- /JOO-vuh-nil HOR-mohn/
- Category
- Physiology
- Singular
- juvenile hormone
- Plural
- juvenile hormones
Definition
A group of acyclic sesquiterpenoid synthesized by the glands in the insect and transported via the haemolymph. Juvenile hormone maintains larval or nymphal characteristics during molting; its titer decline triggers to the stage. Also mediates reproductive maturation, induction, and / determination in social insects.
Etymology
From its role in preserving developmental stages; first isolated and characterized by Vincent Wigglesworth in studies of Rhodnius prolixus.
Example
In the Manduca sexta, high juvenile levels during early larval instars ensure that each produces another caterpillar; the sharp drop in JH titer during the final instar permits the molt to the pupal stage.
Synonyms
- JH
- neotenin
Related Terms
- corpus allatum
- ecdysone
- metamorphosis
- Instar
- diapause
- polyphenism
- Haemolymph
- Complete metamorphosis
- incomplete metamorphosis
Usage Notes
Juvenile is strictly plural in practice (JHs I, II, III, etc.) though often referred to in the singular. Distinguished from , which drive molting itself; JH determines what form emerges from the . Analogous compounds occur in some crustaceans but the term is insect-specific in most usage. Synthetic JH mimics (juvenoids) serve as in pest management.