Juvenile Hormones

Michael E. Adams

University of California, Riverside

Juvenile hormones (JHs), acting in concert with ecdysteroids, orchestrate the expression of larval-specific genes each time the insect molts to a new stage. These morphogenetic effects include determination of an immature body form and internal organs, hardness and color of the cuticle, and accompanying physiology and behaviors. At the conclusion of larval development, juvenile hormone levels drop at critical times, allowing ecdysteroids to program expression of pupal and adult characteristics. Juvenile hormones return in the adult stage, in which they have gonadotropic functions in connection with reproduction. In addition to their morphogenetic and gonadotropic actions, juvenile hormones are involved in dormancy and various types of polyphenisms, including caste determination in social insects.

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