No abstract

Despite many studies demonstrating the effect of acclimation on behavioural or physiological traits, considerable debate still exists about the evolutionary significance of this phenomenon. One of the unresolved issues is whether acclimation to warmer temperature is beneficial at treatment or at more extreme test temperatures. To answer this question, we assessed the effect of thermal acclimation on preferred body temperatures ( T p s), maximum swimming and running speed, and critical thermal maximum ( CT max ) in the Danube crested newt ( Triturus dobrogicus ). Adult newts were kept at 15 ° C (control) and 25 ° C (treatment) for 8 weeks prior to measurements. We measured T p s in an aquatic thermal gradient over 24 h, maximum speeds in a linear racetrack at six temperatures (5-33 ° C), and CT max in a continuously heated water bath. T p s were higher in newts kept at 15 ° C than in those kept at 25 ° C. The maximum swimming speed did not acclimate. The maximum running speed at 30-33 ° C was substantially higher in newts kept at 25 ° C than in those kept at 15 ° C. CT max increased with the treatment temperature. Hence, we conclude that the acclimation response to warm temperature is beneficial not at treatment but at more extreme temperatures in newts.

Sound production is a widespread phenomenon among animals. Effective sound use for mate or species recognition requires some acoustic differentiation at an individual or species level. Several species of caudate amphibians produce underwater sounds, but information about intra- and interspecific variation in their acoustic production is missing. We examined individual, sex, and species variation in underwater sound production in adults of two sympatric newt taxa, Ichthyosaura alpestris and Lissotriton vulgaris. Individual newts produced simple low- (peak frequency = 7–8 kHz) and mid-high frequency (14–17 kHz) clicks, which greatly overlap between sexes and species. Individual differences explained about 40–50% of total variation in sound parameters. These results provide foundations for further studies on the mechanisms and eco-evolutionary consequences of underwater acoustics in newts.