HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 70/5/1438    most recent biolreprod.103.023002v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Monecke, S. Articles by Wollnik, F. Search for Related Content PubMed PubMed Citation Articles by Monecke, S. Articles by Wollnik, F. Agricola Articles by Monecke, S. Articles by Wollnik, F.

European Hamsters (Cricetus cricetus) Show a Transient Phase of Insensitivity to Long Photoperiods after Gonadal Regression¹

Biological Institute, Department of Animal Physiology, University of Stuttgart, 70550 Stuttgart, Germany

Annual rhythms of body weight and reproduction in the European hamster (Cricetus cricetus) are the result of an interaction between seasonal changes in day length (photoperiod) and seasonal changes in the responsiveness of animals to these photoperiods. The present study demonstrates that under natural conditions European hamsters are not able to perceive long photoperiods (i.e., a 16L:8D cycle) before mid-November. This is an important difference to other hamster species, in which regrowth of the gonads can be stimulated by exposure to long photoperiods at any stage of gonadal regression. The experiments also demonstrate the existence of an annual phase of sensitivity to long photoperiods that starts around mid-November and extends until March/April. During this phase of sensitivity, exposure to a long photoperiod (16L:8D) induced gonadal regrowth within 3 wk. Additional experiments with an accelerated photoperiodic lighting regimen indicated that a photoperiod of approximately 13 h is necessary to stimulate gonadal regrowth. Under natural light conditions in Stuttgart (48.46°N), a photoperiod of 13 h is reached by the beginning of April, which fits well with the finding that the majority of animals kept under a natural light:dark cycle had well-developed gonads by the end of April. Nevertheless, these animals showed a rather variable timing of gonadal regrowth, ranging from early January to late April. This is most likely the result of two processes: first, an endogenous mechanism (photorefractoriness) that induces gonadal recrudescence without any photoperiodic information while the animals are still in their hibernation burrows, and second, a direct stimulatory effect of long photoperiods.

¹ Supported by the German Research Foundation (DFG, Wo354/12-1).

² Correspondence: Franziska Wollnik, Biological Institute, Department of Animal Physiology, University of Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany. FAX: 49 711 685 5090; franziska.wollnik{at}po.uni-stuttgart.de

This article has been cited by other articles:

				S. Monecke, A. Malan, and F. Wollnik Asymmetric Control of Short Day Response in European Hamsters J Biol Rhythms, August 1, 2006; 21(4): 290 - 300. [Abstract] [PDF]