Effects of chilling stress on allatal growth and juvenile hormone synthesis in the cockroach, Dialoptera punctata

During the ovarian cycle of the cockroach, Diploptera punctata, a mitotic w ave occurs in the corpora allata before an increase in gland volume and juv enile hormone (JH) synthesis. Previous studies have demonstrated that the b rain inhibits mitosis and JH synthesis in corpus allatum (CA) cells until a dult females have mated. Herein, we report that chilling stress effectively suppresses mating induced proliferation of CA cells. In mated females, chi lling on melting ice for 0.5-3 hours caused a strong, dose-dependent decrea se in mitotic activity. In insects chilled for 3 hours, although the mitoti c wave in the CA was practically abolished, CA volume and JH synthesis fina lly reached peak levels typical of unchilled insects, despite a 2-day delay . Consequently, oocyte maturation and oviposition were also delayed by 2 da ys, yet in both chilled and unchilled insects, peak values of basal oocyte length were the same. By allowing virgin females to mate on different days after chilling, we found that the chilling effect could be retained in the insect body for at least 2 days. During this period, signals from mating co uld not effectively remove inhibition of CA cell proliferation. Unilaterall y disconnecting the CA from the brain revealed that chilling stress mediate d CA cell proliferation via the brain, and did not directly affect the CA. (C) 2000 Elsevier Science Ltd. All rights reserved.