Endocrine changes associated with metamorphosis and diapause induction in the yellow-spotted longicorn beetle, Psacothea hilaris.
At 25 degrees C and under a long-day photoperiod, all 5th instar Psacothea hilaris larvae pupate at the next molt. Under a short-day photoperiod, in contrast, they undergo one or two additional larval molts and enter diapause; the 7th instar larvae enter diapause without further molt. The changes in hemolymph juvenile hormone (JH III) titers, JH esterase activity, and ecdysteroid titers in pupation-destined, pre-diapause, and diapause-destined larvae were examined. JH titers of the 5th instar pupation-destined larvae decreased continuously from 1.3 ng/ml and became virtually undetectable on day 13, when JH esterase activity peaked. Ecdysteroids exhibited a small peak on day 8, 1 day before gut purge, and a large peak on day 11, 2 days before the larvae became pre-pupae. The two ecdysteroid peaks are suggested to be associated with pupal commitment and pupation, respectively. JH titers of the 5th instar pre-diapause larvae were maintained at approximately 1.5 ng/ml for 5 days and then increased to form a peak (3.3 ng/ml) on day 11. JH esterase activity remained at a low level throughout. Ecdysteroid levels exhibited a large peak of 40 ng/ml on day 18, coincident with the larval molt to the 6th instar. JH titers of the 7th instar diapause-destined larvae peaked at 1.9 ng/ml on day 3, and a level of approximately 1.1 ng/ml was maintained even 30-60 days into the instar, when they were in diapause. Ecdysteroid titers remained approximately 0.02 ng/ml. Diapause induction in this species was suggested to be a consequence of high JH and low ecdysteroid titers.
Munyiri
Florence N
FN
Laboratory of Applied Entomology, Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan. fmunyiri@hotmail.com
Ishikawa
Yukio
Y
D000818:Animals; D001517:Coleoptera / Q000254:growth & development*; D008401:Gas Chromatography-Mass Spectrometry; D006458:Hemolymph / Q000502:physiology; D007301:Insect Hormones / Q000737:chemistry / Q000502:physiology*; D007605:Juvenile Hormones; D007814:Larva; D008675:Metamorphosis, Biological / Q000502:physiology*; D012717:Sesquiterpenes / Q000737:chemistry
D007301:Insect Hormones; D007605:Juvenile Hormones; D012717:Sesquiterpenes; C055442:juvenile hormone II; C036585:juvenile hormone III