Hormonal regulations in insect metamorphosis: A review

Abstract

Metamorphosis is an obligatory feature in insect physiology mediating to insect evolution, wherein the individual acquires characteristic adult features and stops molting during postembryonic development. Ecdysteroids and juvenile hormones (JHs) are key hormones that are responsible for insect molting and metamorphosis contributing in this process for successful adaptation. To understand the development process of insects, this paper reviews the mechanisms of the major hormones, especially how they control the insect metamorphosis process and their control over gene expression for stage speciation. It also focuses on the source of synthesis of those hormones, their active signalling pathway. This paper is supported by secondary information. According to the literature reviewed, ecdysteroids and Juvenile Hormones (JHs) are key hormones that are responsible for insect molting and metamorphosis, respectively. JH maintains the larval state and its decline along with the increase of ecdysteroid in the hemolymph are crucial to elicit transformation to the pupal stage; therefore, the precise control of JH and Ecdysteroid (ecdysone & 20E), is necessary for normal development and the initiation of metamorphosis. Juvenile hormone signalling pathway with referring to Kr-h1, BR-C and E93 genes have also been described.