Neuroendocrine roles of the brain in the regulation of 20-hydroxyecdysone responsiveness in two types of diapause pupae of the cabbage armyworm, Mamestra brassicae.
The cabbage armyworm, Mamestra brassicae, has winter-and aestival- diapause pupae (WD- and AD-pupae) showing differences in the strength of diapause. We tried to quantify diapause-strength by measuring the doses of 20-hydroxyecdysone (20-E) required to induce adult development in WD-, AD- and decerebrated non-diapause pupae (ND-pupae). The role of the brain in the regulation of diapause-strength was studied through the decerebration and brain-reimplantation of WD-and AD-pupae. The 20-E doses required for adult development were small within the first 2 days of pupation, and increased thereafter to reach a constant level about 10 days after pupation in AD- and decerebrated ND-pupae. The required 20-E doses in WD-pupae increased for more than 40 days after pupation. When 0-day-old WD- and 0-day-old AD-pupae were decerebrated, required 20-E doses increased after pupation and reached a constant about 10 days later. The required 20-E dose reached a constant level in decerebrated WD-pupae that was smaller than that observed for decerebrated ND- and WD-pupae. Furthermore, the required doses increased when 0-day-old WD-pupal brains were reimplanted into decerebrated WD- and decerebrated ND-pupae. In WD-, AD- and decerebrated ND-pupae, diapause-strength can be represented as the 20-E dose required for adult development. Diapause-strength is weak after pupation, increases thereafter, and reaches a constant about 10 days later in AD- and decerebrated ND-pupae. In WD-pupae, diapause-strength increases for more than 40 days after pupation and reaches a level that is twice that estimated for AD-pupae. Brains of diapausing WD-pupae may secrete a factor that suppresses the 20-E responsiveness of pupal organs, for the purpose of maintaining winter-diapause.
Islam
A T M Fayezul
AT
Biological Institute, Faculty of Science, Yamaguchi University, Yamaguchi, Japan.
Nankaku
Nami
N
Marui
Yukie
Y
Shahjahan
Reza
R
Kong
Weihua
W
Yamanaka
Akira
A
Endo
Katsuhiko
K
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004441:Ecdysterone / Q000494:pharmacology / Q000502:physiology*; D009036:Moths / Q000502:physiology*; D011679:Pupa / Q000502:physiology
D004441:Ecdysterone