Maturation of telotrophic ovary accompanied with ecdysteroidogenic activity and contrastive decrease in ecdysteroids in the whole body of red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae)

Abstract

Ecdysteroids are mainly synthesised in the prothoracic glands, which regulate larval moulting and metamorphosis in insects. After degeneration of the prothoracic gland during pupal–adult metamorphosis, the ovary becomes the source of ecdysteroids in adult females. Here, we demonstrated that the high ecdysteroid level after adult eclosion decreased in the first few days in the eclosed adult red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The ecdysteroids in the freshly eclosed adult might originate from pupae and/or ecdysteroidogenic cells present in the anterior part of the adult body. The ecdysteroid in the haemolymph at the very beginning of adult stage may be important for ovarian development. While ecdysteroid levels decreased in the haemolymph, the ovaries acquired the ability to produce ecdysteroids with increased enzyme gene expression.