Journal of Thermal Biology 33 (2008) 27–31 Thermal biology of newts (Notophthalmus viridescens) chronically infected with a naturally occurring pathogen Elizabeth Sherman à Natural Sciences, Bennington College, Bennington, VT 05201, USA Received 17 August 2007; accepted 25 September 2007 Abstract 1. Newts chronically infected with an Ichthyophonus-like organism selected warmer temperatures than healthy newts, consistent with prior work on behavioral fever, though the magnitude of the difference was much greater than reported in other studies. 2. The large difference in selected temperature (411 1C) may be a consequence of the chronic nature of the Ichthyophonus infection in newts from the field. 3. Healthy newts exhibited a higher thermal tolerance than infected newts, reflecting the greater morbidity of infected newts. 4. Little is known about the course of Ichthyophonus in newts, and the possible consequences of changes in thermal biology are discussed. r 2007 Elsevier Ltd. All rights reserved. Keywords: Newts; Ichthyophonus; Fungal infections; CTMax; Temperature; Amphibians 1. Introduction I undertook this investigation as a consequence of a serendipitous observation I made while collecting newts for another study. It seemed that a preponderance of the animals that I collected in the hottest parts of the pond had obvious lesions. Newts collected in the cooler parts of the pond appeared healthy. The cause of the lesions was identified by the National Wildlife Health Center in Madison, Wisconsin, as an Icthyophonus-like fungus. My own observations and those of others (Herman, 1984; Mikaelian et al., 2000; Green et al., 2002) suggest that the Ichthyophonus-like organism may have been an endemic pathogen in newts for some time, only now becoming more prevalent. Emerging fungal pathogens have been implicated in worldwide amphibian population declines (Blaustein and Wake, 1990; Daszak et al., 1999; Carey, 2000). Reports suggest that some of the pathogens may have only recently moved into new areas and species while others may have been present in the environment and only just increased in incidence or pathogenicity (Daszak et al., 2001; Green et al., 2002; Rachowicz et al., 2005). While morbidity and mortality associated with Ichthyo- phonus in amphibians have been reported (Mikaelian et al., 2000; Green et al., 2002), the physiological consequences of these infections remain largely unexplored and deserve attention (Wikelski and Cooke, 2006). Moreover, newts are keystone predators in certain ecosystems (Smith, 2006) and their physiological responses to infection may have significant consequences for the composition of those ecosystems. The thermal biology of amphibians is altered as a consequence of infectious agents. Both anurans (Kluger, 1977; Sherman et al., 1991) and salamanders (Parris et al., 2004) treated with pathogens or subunits isolated from pathogens (such as the lipopolysaccharide, LPS, of bacterial cell walls) select warmer temperatures than uninfected control animals. Furthermore, the thermal tolerance of LPS-treated toads was higher than that of controls even though both groups of animals were maintained at the same febrile temperature (Sherman et al., 1991). In all of these prior experiments, however, ARTICLE IN PRESS www.elsevier.com/locate/jtherbio 0306-4565/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jtherbio.2007.09.005 à Tel.: +1 802 440 4466; fax: +1 802 440 4461. E-mail address: sherman@bennington.edu