Thermal preference, thermal tolerance and the thermal dependence of digestive performance in two Phrynocephalus lizards (Agamidae), with a review of species studied

Abstract

We reported data on thermal preference, thermal tolerance and the thermal dependence of digestive performance for two Phrynocephalus lizards (P. frontalis and P. versicolor), and compared data among lizards so far studied worldwide. Mean values for selected body temperature (Tsel) and critical thermal maximum (CTMax) were greater in P. versicolor, whereas mean values for critical thermal minimum (CTMin) did not differ between the two species. The two lizards differed in food intake, but not in food passage time, apparent digestive coefficient (ADC) and assimilation efficiency (AE), across the experimental temperatures. Four general conclusions can be drawn from published data. Firstly, thermal preference and thermal tolerance differ among lizards differing in distribution, temporal activity pattern and habitat use. Lizards in thermally more variable regions are better able to tolerate low and high temperatures. Diurnal lizards generally select higher body temperatures than nocturnal lizards, and lizards using habitats with direct sun exposure generally selected higher body temperatures and are better able to tolerate high temperatures. Secondly, CTMax is positively correlated with Tsel. Lizards more likely exposed to extremely high temperatures while active select higher body temperatures than those using shaded habitats. Thirdly, the effects of body temperature on food intake, food passage time, ADC and AE differ among lizards, but it seems to be common among lizards that ADC and AE are less thermally sensitive than food intake and food passage time. Lastly, ADC is dependent on the type of food ingested, with insectivorous lizards digesting food more efficiently than herbivorous lizards.

Environmental temperature alters the overall digestive energetics and differentially affects dietary protein and lipid use in a lizard

“…As enzymatic activity increases and passage time decreases with temperature, often assimilation efficiency is temperature independent (Van Damme et al, 1991;Ji et al, 1996;Du et al, 2000;Chen et al, 2003;Zhang and Ji, 2004). Yet, in several lizard species, measures of assimilation efficiency are higher at intermediate temperatures and reduce at extreme temperatures (Angilletta, 2001;Zhang and Ji, 2004;Luo et al, 2006;Qu et al, 2011), and the thermal optima for assimilation of nutrients can differ from the temperature at which digestion rate is highest (Coggan et al, 2011;Lee et al, 2015). Further, the thermal optima of assimilation may vary between different dietary nutrients (e.g.…”

Differences in Thermal Preference and Tolerance among Three Phrynocephalus Lizards (Agamidae) with Different Body Sizes and Habitat Use

“…Previous studies show that Tp ranges from 16.6 °C in Goniurosaurus kuroiwae to 37.9 °C in Sauromalus ater (Brattstrom, 1965), CTMin from 0.7 °C in Eremias multiocellata (Li et al, 2009b) to 15.4 °C in Liolaemus abaucan , CTMax from 28.9 °C in G. kuroiwae to 49.3 °C in Eremias prezwalskii (Li et al, 2009a), and TTR from 19.7 °C in Eublepharis macularius to 48.3 °C in E. prezwalskii (Li et al, 2009a). Previously published data show that thermal preference and tolerance differ among lizard species that differ in distribution, habitat use and activity pattern, and are affected by a lizard's physiological conditions (Lutterschmidt and Hutchison, 1997;Qu et al, 2011b; and its experience of thermal acclimation (Kour and Hutchison, 1970;Patterson, 1991;Huang et al, 2006;Li et al, 2009b).…”

“…A lizard's thermal preference can be estimated in the laboratory by measuring its preferred body temperature (Tp) in a thermal gradient, and its thermal tolerance can also be determined in the laboratory by measuring the lower (critical thermal minimum, CTMin) and higher (critical thermal maximum, CTMax) survival limits (Lowe and Vance, 1955;Hutchison, 1961;Lutterschmidt and Hutchison, 1997). Exposure of lizards to temperatures outside the thermal tolerance range (TTR, the range between CTMin and CTMax) for prolonged periods of time may lead to death Qu et al, 2011b).…”

Behavioral thermoregulation is highly repeatable and unaffected by digestive status in Agama atra

“…Second, we hypothesized that the repeatability of T set will be higher when T set is examined under a metabolic challenge such as digestion. By selecting higher body temperatures after a meal (Huey 1982;Sievert 1989;Sievert & Andreadis 1999;Gvoždík 2003; but see Wall & Shine 2008;Schuler et al 2011), lizards can release that meal's energy faster and reduce digestion times, thus potentially increasing fitness (although nutrient assimilation does not always follow this pattern, see Qu et al [2011] and Coggan et al [2011] in insects). This second hypothesis is tested by estimating repeatability of T set using high-resolution time-series data as well as parameters derived from the frequency distribution of T set .…”