No evidence for the involvement of juvenile hormone III and 20-hydroxyecdysone in maternal decisions for embryonic diapause and diapause entry in the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae)

Abstract

Diapause is a programmed stage-specific arrest or delay in reproduction or development and is commonly used to circumvent an adverse season. Some insect species exhibit maternal regulation of diapause, wherein environmental cues are perceived by the mother and subsequently determine the developmental fate of the offspring. Although maternal regulation of diapause is widespread, its endocrinological mechanisms remain largely unknown. In the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae), embryonic diapause is maternally determined. Adult females under long-day conditions lay eggs that develop into nymphs without interruption, whereas those under short-day conditions lay diapause-destined eggs that arrest their development and enter diapause at a very early embryonic stage, the cellular blastoderm. How development is arrested at an early stage is a key area of interest. We hypothesized that juvenile hormone III (JH III) and 20-hydroxyecdysone (20E), the major insect hormones that regulate a wide variety of physiological processes, are involved not only in maternal decisions, but also in diapause entry in D. nigrofasciatus. The results showed that the hemolymph concentrations of JH III and 20E in adult females were lower under short-day conditions; however, the application of JH III and 20E to the mothers did not affect the diapause incidence of offspring. No differences were observed in the amounts of 20E between non-diapause and diapause-destined eggs, and JH III was not detected in these eggs. Thus, we found no evidence for the involvement of JH III and 20E in maternal decisions for embryonic diapause and diapause entry in D. nigrofasciatus.