ACCUMULATION OF PHOTOPERIODIC INFORMATION DURING DIAPAUSE DEVELOPMENTIN THE SPIDER-MITE TETRANYCHUS-URTICAE

Citation
Ds. Koveos et A. Veerman, ACCUMULATION OF PHOTOPERIODIC INFORMATION DURING DIAPAUSE DEVELOPMENTIN THE SPIDER-MITE TETRANYCHUS-URTICAE, Journal of insect physiology, 40(8), 1994, pp. 701-707
Citations number
15
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Entomology
ISSN journal
0022-1910
Volume
40
Issue
8
Year of publication
1994
Pages
701 - 707
Database
ISI
SICI code
0022-1910(1994)40:8<701:AOPIDD>2.0.ZU;2-B
Abstract
Photoperiodic control of diapause development was studied in three str ains of the spider mite, Tetranychus urticae, originating from differe nt latitudes in Europe. Diapause was almost fully maintained by a long -night regime during the first month of diapause, but was terminated r apidly and synchronously by a short-night regime. Diapause termination in continuous light was almost as rapid as in short nights; in contin uous darkness diapause termination proceeded much slower, probably rev ealing the ''spontaneous'' rate of diapause development of these mites . The effect on diapause termination of successive short-night cycles appeared to be accumulated in a way comparable to cycle summation duri ng diapause induction. The threshold for diapause termination by short nights, expressed as the number of cycles required for 50% diapause t ermination, was found to be lower the more southern the origin of the strain of mites. However, considerable differences in the number of cy cles required for diapause termination were also present within strain s: some mites needed only 3-4 short nights to terminate diapause, wher eas others needed more than 10. In contrast with short-night cycles th e effect of long-night cycles was not accumulative. Intensification of diapause under the influence of long-night cycles during its early st ages appeared not to take place. Long nights were capable of maintaini ng the state of diapause if experienced before short-night cycles, but not afterwards. Short and long nights seem to act independently from each other, the former accelerating diapause development (''activation ''), the latter slowing down diapause development (''diapause maintena nce''). No antagonistic effect of long and short nights was found on t he photoperiodic maintenance of diapause, in the sense that the effect of short nights might be diminished or even reversed by long nights, and vice versa, as found in photoperiodic induction of diapause in T. urticae. Therefore diapause maintenance does not seem to involve a pho toperiodic counter mechanism comparable with the counter involved in t he photoperiodic induction of diapause in these mites.