QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online June 12, 2009
Journal of Experimental Biology 212, 1995-1999 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.026344

This Article Figures Only Full Text Full Text (PDF) Supplementary Material Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Caro, S. P. Articles by Visser, M. E. PubMed Articles by Caro, S. P. Articles by Visser, M. E. Social Bookmarking                         What's this?

Temperature-induced elevation of basal metabolic rate does not affect testis growth in great tits

Samuel P. Caro^1,2,* and Marcel E. Visser¹

¹ Netherlands Institute of Ecology (NIOO-KNAW), PO Box 40, 6666 ZG Heteren, The Netherlands
² Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA

^* Author for correspondence (e-mail: s.caro{at}nioo.knaw.nl)

Accepted 8 April 2009

The timing of reproduction varies from year to year in many bird species. To adjust their timing to the prevailing conditions of that year, birds use cues from their environment. However, the relative importance of these cues, such as the initial predictive (e.g. photoperiod) and the supplemental factors (e.g. temperature), on the seasonal sexual development are difficult to distinguish. In particular, the fine-tuning effect of temperature on gonadal growth is not well known. One way temperature may affect timing is via its strong effect on energy expenditure as gonadal growth is an energy-demanding process. To study the interaction of photoperiod and temperature on gonadal development, we first exposed 35 individually housed male great tits (Parus major) to mid-long days (after 6 weeks of 8 h L:16 h D at 15°C, photoperiod was set to 13 h L:11 h D at 15°C). Two weeks later, for half of the males the temperature was set to 8°C, and for the other half to 22°C. Unilateral laparotomies were performed at weeks 5 (i.e one week before the birds were transferred to mid-long days), 8 and 11 to measure testis size. Two measures of basal metabolic rate (BMR) were performed at the end of the experiment (weeks 11 and 12). Testis size increased significantly during the course of the experiment, but independently of the temperature treatment. BMR was significantly higher in birds exposed to the cold treatment. These results show that temperature-related elevation of BMR did not impair the long-day-induced testis growth in great tits. As a consequence, temperature may not be a crucial cue and/or constraint factor in the fine-tuning of the gonadal recrudescence in male great tits, and testis growth is not a high energy-demanding seasonal process.

Key words: energy expenditure, respirometry, gonadal cycles, timing of reproduction, seasonal reproduction, phenology, supplemental factors, environmental cues, captive experiments, predictability, day length

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?