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

First published online February 6, 2004
Journal of Experimental Biology 207, 945-953 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00861

This Article Figures Only Full Text Full Text (PDF) 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 Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by DeNardo, D. F. Articles by Hoffman, T. C.M. Search for Related Content PubMed PubMed Citation Articles by DeNardo, D. F. Articles by Hoffman, T. C.M. Social Bookmarking                         What's this?

Cloacal evaporative cooling: a previously undescribed means of increasing evaporative water loss at higher temperatures in a desert ectotherm, the Gila monster Heloderma suspectum

Dale F. DeNardo^*, Tricia E. Zubal and Ty C.M. Hoffman

Department of Biology, Arizona State University, Tempe, AZ 85287-4501, USA

^* Author for correspondence (e-mail: denardo{at}asu.edu)

Accepted 31 December 2003

The Gila monster Heloderma suspectum is an active forager in an environment that, at times, can be extremely hot and arid. Thus, Gila monsters face extreme thermostatic and hydrostatic demands. For a desert ectotherm routinely risking dehydration, evaporative water loss (EWL) is typically viewed as detrimental. Yet evaporation simultaneously dehydrates and cools an animal. We explored EWL in Gila monsters by measuring cutaneous, ventilatory and cloacal EWL at five ambient temperatures between 20.5°C and 40°C. Our results show that Gila monsters have high EWL rates relative to body mass. Cutaneous EWL underwent a consistent, temperature-dependent increase over the entire range of test temperatures (Q₁₀=1.61, with EWL ranging from 0.378 to 0.954 mg g^–1 h^–1). Ventilatory EWL did not show a significant temperature-dependent response, but ranged from 0.304 to 0.663 mg g^–1 h^–1. Cloacal EWL was extremely low and relatively constant between 20.5°C and 35°C, but rose dramatically above 35°C (Q₁₀ >8.3x10⁷, from 0.0008 at 35°C to 7.30 mg g^–1 h^–1 at 40°C). This steep rise in cloacal EWL coincided with an increasing suppression of body temperature relative to ambient temperature. Dehydration to 80% of initial body mass led to a delay in the onset and an attenuation of the dramatic increase in cloacal EWL. These results emphasize the potential value of EWL for thermoregulation in ectotherms and demonstrate for the first time the role of the cloaca in this process.

Key words: evaporative water loss, temperature, reptile, cloaca, cutaneous evaporation, ventilatory evaporation, lizard, Gila monster, Heloderma suspectum

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

This article has been cited by other articles:

				J. R. Davis and D. F. DeNardo The urinary bladder as a physiological reservoir that moderates dehydration in a large desert lizard, the Gila monster Heloderma suspectum J. Exp. Biol., April 15, 2007; 210(8): 1472 - 1480. [Abstract] [Full Text] [PDF]

				T. C.M. Hoffman, G. E. Walsberg, and D. F. DeNardo Cloacal evaporation: an important and previously undescribed mechanism for avian thermoregulation J. Exp. Biol., March 1, 2007; 210(5): 741 - 749. [Abstract] [Full Text] [PDF]

				G. J. Tattersall and R. M. Gerlach Hypoxia progressively lowers thermal gaping thresholds in bearded dragons, Pogona vitticeps J. Exp. Biol., September 1, 2005; 208(17): 3321 - 3330. [Abstract] [Full Text] [PDF]