Early life exposure to high temperature enhances locomotor performance without alteration in thermal ecology in different populations of Thoropa taophora tadpoles (Anura, Cycloramphidae).

Understanding the intricate relationship between temperature and physiological processes in ectotherm vertebrates is crucial for predicting how these animals respond to environmental changes, including those associated with climate change. This is particularly relevant for the anurans, given their limited capacity for thermoregulation, particularly in larval stages. Herein, we investigated the capacity for thermal acclimatization in Thoropa taophora tadpoles, an endemic species in the Atlantic rainforest of Southeast Brazil, inhabiting distinct thermal environments. These semi-terrestrial tadpoles develop on rocky surfaces, with some populations inhabiting exposed regions near the marine coast where temperatures may reach up to 30°C in sunny conditions, while other populations occupy forested areas near waterfalls that maintain lower temperatures. We aimed to understand the effects of temperature on locomotor performance and on the activity of metabolic enzymes that support performance in tadpoles sampled in four different populations. Moreover, we measured several aspects of thermoregulation, including the critical thermal maximum (CTmax), the body temperature of activity (Tb), the preferred temperature (Tpref) and the effectiveness of thermoregulation (E). Despite differences in body size, tadpoles from warmer environments consistently demonstrated higher locomotor performance, with minimal or no acclimatization seen in other variables. Correlations between habitat temperature and biological endpoints underscore the significance of maximum locomotor performance in shaping physiological responses. Our results show how temperature can impact tadpole behavior and performance, without changes in many organismal measures of thermal acclimatization, providing insights into potential ecological implications, particularly in the context of climate change.

Thermophysiological plasticity could buffer the effects of global warming on a Patagonian lizard.

Ecophysiological plasticity determines, to a great extent, the geographic distribution and the vulnerability of ectotherms to climate change. We studied the relationship between locomotor performance and temperature of Liolaemus elongatus lizards in three populations in northern Patagonia, Argentina, differing in thermal characteristics. We related the thermophysiological and locomotor performance parameters with the environmental conditions currently experienced by these populations and analyzed whether the expected increment of the environmental temperature due to climate change could affect these vital traits. We also determined, for one of the populations, the effects of 30 acclimation days at two temperature treatments (22°C and 30°C) on running speed, thermal preference in the laboratory (Tpref ), panting threshold, and minimum critical temperature. We found that L. elongatus, despite the differences in environmental temperatures among the three sites, exhibited maximum speed at similar temperatures (optimum temperature for locomotor performance; To ). The southern populations currently experience temperatures below that required to reach their maximum locomotor performance while the northernmost population is threatened by peaks of high temperatures that exceed the To . Therefore, global warming could diminish lizards' running performance in northern populations and lizards may spend more time refuging and less time on other activities such as feeding, territory defense, and dispersion. However, we show evidence of plasticity in L. elongatus locomotor performance when acclimated at high temperatures resulting in a potential advantage to cushion the effect of the rising environmental temperatures expected during climate change.

Effects of recent thermal history on thermal behaviour, thermal tolerance and oxygen uptake of Yellowtail Kingfish (Seriola lalandi) juveniles.

This study determined the physiological and metabolic responses of cultivated Yellowtail Kingfish (Seriola lalandi) juveniles in accordance with their recent thermal history. The fish were acclimated at 20, 23, 26, 29 and 32 °C for 21 days to determine the final preferred temperature, thermal tolerance and the effect of acclimation temperatures on their oxygen uptake and aerobic scope. The final preferred temperature of juveniles was established at 26 °C. The critical thermal maximum (CTmax) ranged from 34.2 to 36.9 °C, while the critical thermal minimum (CTmin) ranged from 10.9 to 17.3 °C, depending on acclimation temperature. With the CTmax and CTmin values, the thermal window was determined to have an area of 258°C2, which is characteristic of subtropical organisms. Although, the metabolic rate was relatively constant (ranging 390.6-449.8 mg O2 kg-0.8 h-1) between 20 and 26 °C (Q10 = 1.6, 1.0), an increase to 544.8 mg O2 kg-0.8 h-1 at 29 °C (Q10 = 1.9) and decrease of 478.4 mg O2 kg-0.8 h-1 at 32 °C (Q10 = 0.6) were observed. The maximum value obtained for aerobic scope was 310.9 mg O2 kg-0.8 h-1 at 26 °C. These results suggest that the acclimation temperature of 26 °C is an optimum thermal condition for a physiological and metabolic performance of yellowtail kingfish juveniles. On the contrary, the response observed during the evaluation of critical temperatures, oxygen uptake and aerobic scope indicated that yellowtail kingfish in the juvenile state could be vulnerable when it experiences for long periods (e.g., >21 days) temperatures above 29 °C. According to our results, the thermoregulatory behaviour of yellowtail kingfish in the juvenile stages could be one of the most important mechanisms to maintain its optimal physiological performance by actively selecting a stable thermal environment close to 26 °C. In addition, it was determined the limits of the pejus state of juvenile yellowtail kingfish at 29 °C, where an increase of oxygen uptake to maintain the aerobic energy metabolism was observed, this could certainly affect the growth of juveniles in culture systems if they do not return in a thermal range of 23-26 °C. These results can contribute to infer the different effects of acclimation temperature on the growth, thermal tolerance and respiratory capacity of S. lalandi juveniles on aquaculture systems.

Thermal biology of the sub-polar-temperate estuarine crab Hemigrapsus crenulatus (Crustacea: Decapoda: Varunidae).

Optimum temperatures can be measured through aerobic scope, preferred temperatures or growth. A complete thermal window, including optimum, transition (Pejus) and critical temperatures (CT), can be described if preferred temperatures and CT are defined. The crustacean Hemigrapsus crenulatus was used as a model species to evaluate the effect of acclimation temperature on: (i) thermal preference and width of thermal window, (ii) respiratory metabolism, and (iii) haemolymph proteins. Dependant on acclimation temperature, preferred temperature was between 11.8°C and 25.2°C while CT was found between a minimum of 2.7°C (CTmin) and a maximum of 35.9°C (CTmax). These data and data from tropical and temperate crustaceans were compared to examine the association between environmental temperature and thermal tolerance. Temperate species have a CTmax limit around 35°C that corresponded with the low CTmax limit of tropical species (34-36°C). Tropical species showed a CTmin limit around 9°C similar to the maximum CTmin of temperate species (5-6°C). The maximum CTmin of deep sea species that occur in cold environments (2.5°C) matched the low CTmin values (3.2°C) of temperate species. Results also indicate that the energy required to activate the enzyme complex (Ei) involved in respiratory metabolism of ectotherms changes along the latitudinal gradient of temperature.

Vulnerability to climate warming of Liolaemus pictus (Squamata, Liolaemidae), a lizard from the cold temperate climate in Patagonia, Argentina.

The vulnerability of populations and species to global warming depends not only on the environmental temperatures, but also on the behavioral and physiological abilities to respond to these changes. In this sense, the knowledge of an organism's sensitivity to temperature variation is essential to predict potential responses to climate warming. In particular, it is interesting to know how close species are to their thermal limits in nature and whether physiological plasticity is a potential short-term response to warming climates. We exposed Liolaemus pictus lizards, from northern Patagonia, to either 21 or 31 °C for 30 days to compare the effects of these treatments on thermal sensitivity in 1 and 0.2 m runs, preferred body temperature (T pref), panting threshold (T pant), and critical minimum temperature (CTMin). Furthermore, we measured the availability of thermal microenvironments (operative temperatures; T e) to measure how close L. pictus is, in nature, to its optimal locomotor performance (T o) and thermal limits. L. pictus showed limited physiological plasticity, since the acclimation temperature (21 and 31 °C) did not affect the locomotor performance nor did it affect T pref, the T pant, or the CTMin. The mean T e was close to T o and was 17 °C lower than the CTMax. The results suggest that L. pictus, in a climate change scenario, could be vulnerable to the predicted temperature increment, as this species currently lives in an environment with temperatures close to their highest locomotor temperature threshold, and because they showed limited acclimation capacity to adjust to new thermal conditions by physiological plasticity. Nevertheless, L. pictus can run at 80 % or faster of its maximum speed across a wide range of temperatures near T o, an ability which would attenuate the impact of global warming.

Temperatura óptima y preferencia térmica del camarón de río Macrobrachium tenellum en la costa tropical del Pacífico mexicano / Temperatura ideal e preferência térmica do camarão Macrobrachium tenellum na costa tropical do pacífico mexicano / Optimum temperature and thermal preference of the river shrimp Macrobrachium tenellumin the tropical coast of the Mexican pacific

El objetivo fue determinar la temperatura óptima, la preferencia térmica y la temperatura letal incipiente máxima (TLImax) y mínima (TLImin) para juveniles de langostino Macrobrachium tenellum, bajo condiciones de laboratorio. La determinación de la temperatura óptima se realizo con base en los resultados de crecimiento y supervivencia de juveniles (0.17 ± 0.02 g y 28.56 ± 1.60 mm) bajo tres temperaturas (22, 29 y 36°C) durante 15 días. La preferencia térmica se determinó en una mesa de gradiente térmico con temperaturas ajustadas a 20, 23, 25, 27, 30, 33, 35 y 39°C, mediante el método agudo, en el cual se introdujeron 10 organismos (0.38 ± 0.21 g y 40.38 ± 10.33 mm) aclimatados por 72 h a 23, 30 y 32°C, registrando su porcentaje de aparición por cámara cada 10 min por tres horas. La TLImax y la TLImin se calculó en 10 organismos (0.50 ± 0.20 g y 39.65 ± 0.72 mm)aclimatados por 72 h a 21, 29 y 36°C aumentando o disminuyendo, según el caso, la temperatura del agua hasta lamuerte del 50% de ellos (por triplicado). Los mayores crecimientos se obtuvieron en los organismos a 29ºC (temperatura óptima). La temperatura preferida final fue de 32.25°C, mientras que las TLImax y TLImin a 21°C fueron de 42 y 8.1°C, a 29°C de 43.2 y 10.2°C, y a 36°C de 43.5 y 11.1°C, respectivamente.

O objetivo deste estudo foi determinar a temperatura ideal, a preferência térmica e as temperaturas incipientes letais máxima (TLImax) e mínima (TLImin) para juvenis do camarão Macrobrachium tenellum em condições de laboratório. A determinação da temperatura ideal foi realizada com base nos resultados de crescimento e de sobrevivência de juvenis de M. tenellum (0,17 ± 0,02 g e 28,56 ± 1,60 mm), mantidos em três temperaturas (22, 29 e 36°C) por 15 dias, em triplicata. A preferência térmica foi determinada em mesa de gradiente térmico com temperaturas de 20, 23, 25, 27, 30, 33, 35 e 39°C pelo teste de toxicidade aguda, no qual 10 juvenis foram introduzidos (0,38 ± 0,21 g e 40,38 ± 10,33 mm) e aclimatados por 72 h a 23, 30 e 32°C, registrando-se a porcentagem de ocorrência por câmera a cada 10 minutos por três horas, em triplicata. As TLImax e TLImin foram estimadas em 10 organismos (0,50 ± 0,20 g e 39,65 ± 0,72 mm) aclimatados por 72 h a 21, 29 e 36°C, aumentando ou diminuindo, conforme o caso, a temperatura da água até a morte de 50% dos animais, realizado em triplicata. O melhor crescimento dos organismos foi obtido a 29°C (temperatura ideal). A temperatura final preferencial foi 32,25°C, enquanto TLImax e TLImin foram: a 21°C, 42 e 8,1°C; a 29°C, 43,2 e 10,2°C; e a 36°C, 43,5 e 11,1°C, respectivamente.

The objective was to determine the optimal temperature, thermal preference and maximum incipient lethal temperature (TLImax) and minimum (TLImin) for juveniles of prawn Macrobrachium tenellum under laboratory conditions using the acute method. The determination of the optimum temperature was made based on the results of growth and survival of juvenile M. tenellum (0.17 ± 0.02 g and 28.56 ± 1.60 mm) maintained at three temperatures (22, 29 and 36°C) for 15 days, in triplicate. The thermal preference was determined in a thermal gradient table with temperatures adjusted to 20, 23, 25, 27, 30, 33, 35 and 39°C using the acute method, in which 10 juveniles are introduced (0.38 ± 0.21 g and 40.38 ± 10.33 mm) and acclimated for 72 h at 23, 30 and 32°C, recording the percentage of occurrence per camera every 10 min for three hours (in triplicate). The TLImin and TLImax were estimated at 10 organisms (0.50 ± 0.20 g and 39.65 ± 0.72 mm) acclimated for 72 h at 21, 29 and 36°C by increasing or decreasing the water temperature until the death of 50% of the population. The highest growths in organisms were obtained at 29°C (optimum temperature). The final preferred temperature was 32.25°C, while TLImin and TLImax were: to 21°C, 42 and 8.1°C; to 29°C, 43.2 and 10.2°C; and to 36°C, 43.5 and 11.1°C, respectively.