Interacting Effects of Cell Size and Temperature on Gene Expression, Growth, Development and Swimming Performance in Larval Zebrafish

Cell size may be important in understanding the thermal biology of ectotherms, as the regulation and consequences of cell size appear to be temperature dependent. Using a recently developed model system of triploid zebrafish (which have around 1.5-fold larger cells than their diploid counterparts) we examine the effects of cell size on gene expression, growth, development and swimming performance in zebrafish larvae at different temperatures. Both temperature and ploidy affected the expression of genes related to metabolic processes (citrate synthase and lactate dehydrogenase), growth and swimming performance. Temperature also increased development rate, but there was no effect of ploidy level. We did find interactive effects between ploidy and temperature for gene expression, body size and swimming performance, confirming that the consequences of cell size are temperature dependent. Triploids with larger cells performed best at cool conditions, while diploids performed better at warmer conditions. These results suggest different selection pressures on ectotherms and their cell size in cold and warm habitats.

Intracellular thermometry uncovers spontaneous thermogenesis and associated thermal signaling

Conventional thermal biology has elucidated the physiological function of temperature homeostasis through spontaneous thermogenesis and responses to variations in environmental temperature in organisms. In addition to research on individual physiological phenomena, the molecular mechanisms of fever and physiological events such as temperature-dependent sex determination have been intensively addressed. Thermosensitive biomacromolecules such as heat shock proteins (HSPs) and transient receptor potential (TRP) channels were systematically identified, and their sophisticated functions were clarified. Complementarily, recent progress in intracellular thermometry has opened new research fields in thermal biology. High-resolution intracellular temperature mapping has uncovered thermogenic organelles, and the thermogenic functions of brown adipocytes were ascertained by the combination of intracellular thermometry and classic molecular biology. In addition, intracellular thermometry has introduced a new concept, “thermal signaling”, in which temperature variation within biological cells acts as a signal in a cascade of intriguing biological events.

Data on the body temperature of some ophidians in the Southeast of the Iberian Peninsula

La biología térmica es uno de los aspectos más necesarios para entender la distribución y los patrones de actividad de las especies, sobretodo de los organismos ectotermos. El presente estudio aporta información sobre temperatura corporal de seis ofidios ibéricos y temperatura ambiental para el lugar donde habitan. Para tres de las especies, Coronella girondica (Daudin 1803), Macroprotodon brevis (Günter 1862) y Hemorrhois hip­pocrepis (Linnaeus 1758), estos son los primeros datos publicados en España. En el caso de Natrix maura (Linnaeus 1758) los datos de este estudio incluyen temperatura tanto en medio acuático como en medio terrestre. En total se han obtenido 31 registros de temperatura corporal y 30 registros de temperatura ambiente. También se aportan datos sobre temperatura corporal y ambiental de Malpolon monspessulanus (Hermann 1804) y Zamenis scalaris (Schinz 1822). Thermal biology is one of the most necessary aspects in understanding the distribution and activity patterns of species, above all of ectothermal organisms. The present study provides data on body temperature of six Iberian ophidians and the environmental temperature of the place they inhabit. For three species, southern smooth snake Coronella girondica (Daudin 1803), western false smooth snake Macroprotodon brevis (Günter 1862), and horse-shoe snake Hemorrhois hippocrepis (Linnaeus 1758), these are the first data published in Spain. In the case of Natrix maura (Linnaeus 1758), the present data include its temperature on land as well as in aquatic environments. In total, 31 body temperature records and 30 ambient temperature records were obtained. Additionally, data is given on body and environmental temperature for the ophidian species Malpolon monspessulanus (Hermann 1804) and Zamenis scalaris (Schinz 1822).

The Thermal Biology of Takydromus kuehnei Indicates Tropical Lizards From High Elevation Have Not Been Severely Threatened by Climate Change

Climate change poses different threats to animals across latitudes. Tropical species have been proposed to be more vulnerable to climate change. However, the responses of animals from tropical mountains to thermal variation and climate change have been scarcely studied. Here, we investigated the thermal biology traits of a tropical lizard (Takydromus kuehnei) distributed at high elevations (>950 m) and evaluated the vulnerabilities of T. kuehnei by thermal biology traits, thermal safety margin, and thermoregulatory effectiveness. The average active body temperatures of T. kuehnei in the field were 26.28°C and 30.65°C in April and June, respectively. The selected body temperature was 33.23°C, and the optimal temperature for locomotion was 30.60°C. The critical thermal minimum and critical thermal maximum temperatures were 4.79°C and 43.37°C, respectively. Accordingly, the thermal safety margin (1.23°C) and thermoregulatory effectiveness (1.23°C) predicted that T. kuehnei distributed in tropical mountains were not significantly depressed by environmental temperatures. This study implies that high-elevation species in tropical regions may not be severely threatened by ongoing climate change and highlights the importance of thermal biology traits in evaluating the vulnerability of species to climate change.

Staying warm is not always the norm: Behavioural differences in thermoregulation of two snake species

Thermal biology research compares field with laboratory data to elucidate the evolution of temperature-sensitive traits in ectotherms. The hidden challenge of many of these studies is discerning whether animals actively thermoregulate, since motivation is not typically assessed. By studying behaviours involved in thermoregulation, we can better understand the mechanisms behind body temperature control. Using an integrative approach, we assess thermoregulatory and thermotactic behaviours of two sympatric snake species with contrasting life histories, the generalist Thamnophis sirtalis sirtalis (Linnaeus, 1758) and the semi-fossorial Storeria occipitomaculata occipitomaculata (Storer, 1839). We expected that thermoregulatory behaviours would be optimised based on life history, in that T. s. sirtalis would show higher evidence for thermally-oriented behaviours than S. o. occipitomaculata due to its active nature. Thamnophis s. sirtalis actively thermoregulated, had higher thermal preferences (29.4 ± 2.5 vs. 25.3 ± 3.6°C), and was more active than S. o. occipitomaculata, which showed relatively low evidence for thermotaxis. Our results build on the notion that evaluating movement patterns and rostral orientation towards a heat-source can help ascertain whether animals make thermally-motivated choices. Our data give insight into the thermoregulatory strategies used by snakes with different life histories, and maximise the information provided by behavioural thermoregulation experiments.

The confounding effects of sub-thermoneutral housing temperatures on aerobic exercise-induced adaptations in mouse subcutaneous white adipose tissue

Mice are the most commonly used model organism for human biology, and failure to acknowledge fundamental differences in thermal biology between these species has confounded the study of adipose tissue metabolism in mice and its translational relevance to humans. Here, using exercise biochemistry as an example, we highlight the subtle yet detrimental effects sub-thermoneutral housing temperatures can have on the study of adipose tissue metabolism in mice. We encourage academics and publishers to consider ambient housing temperature as a key determinant in the methodological conception and reporting of all research on rodent white adipose tissue metabolism.

Thermal biology of two sympatric Lacertids lizards (Lacerta diplochondrodes and Parvilacerta parva) from Western Anatolia

Sympatric lizard species differing in morphology present convenient models for studying the differentiation in thermal behavior and the role of morphological differences in thermal biology. Here we studied the thermal biology of two sympatric lizard species which occur together sympatrically in western Anatolia, Frig Valley. These two species differ in body size, with the larger Lacerta diplochondrodes and smaller Parvilacerta parva. Field body temperatures of the individuals belonging to both species were recorded in the activity period. Additionally, several environmental parameters including solar radiation, substrate temperature, air temperature and wind speed were also monitored to investigate the relative effect of these abiotic parameters on thermal biology of the two species. The field body temperature and temperature excess (difference between body and substrate temperature) of two species while being relatively close to each other, showed seasonal differences. Solar radiation, substrate temperature and air temperature were the main effective factors on thermal biology in the field. Additionally, although body size did not have a direct significant effect on body temperature or temperature excess, the interaction between body size and wind were effective on temperature excess. In conclusion, our study partially supports the conservation of thermal biology of related lizard species.