Following range-wide decline, all remnant populations of the relict leopard frog (Rana onca) in the eastern Mojave Desert of the southwestern USA occupied geothermally influenced hot springs. In recent years, however, several large populations have been established at cold-water sites. There has, however, been little research into the thermal ecology of the species. We monitored body temperature (Tb) of adult frogs at a pair of hot and cold springs using implanted temperature data loggers, and measured body condition across seasons. We determined temperature preference using a thermal gradient, and measured mass-specific oxygen consumption rates to estimate energy demands in the wild. We found that frogs at the two sites had similar temperature preferences, but the thermal profiles in the wild were seasonally 2.5°C to 5.7°C warmer at the hot site. In summer, frogs at the hot site mostly sought the lowest temperatures available, which were still warmer than measured thermal preferences. Frogs at the cold site maintained cooler temperatures at night, but warmed up during the early part of the day, likely moving in and out of cold water. At both sites, frogs in winter used two overwintering strategies, manifested mostly as differences in Tb variability. Frogs with low Tb variability thermally reflected cold water temperatures throughout most of winter and were interpreted as mostly inactive. Frogs with higher Tb and variability were interpreted as mostly remaining active throughout winter. We estimated that the energy demands at the hot site were 1.27-fold higher in summer and 1.14-fold higher in winter than at the cold site. Frogs at the hot site had significantly lower body condition than those at the cold site. We concluded that thermal conditions at the hot site were not favorable to R. onca and required higher energy investment in physiological maintenance, presumably at the expense of growth and reproduction.
Physiological performance is highly temperature sensitive, and enhanced physiological activity (e.g., digestion, reproductive, immune activation) often leads to a thermophilic response that elevates body temperature. Previous studies have shown that the hydration state of the organism may influence the extent of the thermophily, and other studies have shown that hydration state can alter physiological performance. However, it is rare for studies to comprehensively examine the interaction among hydration state, physiological performance, and the thermophilic response. We simultaneously examined the effects of hydration state and an immune challenge on thermophily and plasma-based innate immune responses in Gila monsters (Heloderma suspectum). Our results show that water deprivation led to progressive dehydration and reduction of body temperature. Upon receiving a lipopolysaccharide injection, dehydrated but not hydrated Gila monsters showed a thermophilic response, and multiple reactive immunity metrics were elevated in dehydrated individuals, particularly at 7 days post injection. Interestingly, this reactive immune response and the thermophily were not temporally correlated. Also, the reactive immune response of Gila monsters appears to be more responsive to dehydration than is the constitutive immune response, as enhancement of the reactive response was seen at moderated dehydration whereas previous work has demonstrated that enhancement of constitutive immune function does not occur until more severe dehydration. Future research should further investigate the interrelationship of hydration state, body temperature, and both constitutive and reactive immune function, especially in species where dehydration is a mechanism used to tolerate seasonal drought.
Melatonin-mediated modulation of antioxidant enzyme activity is widely reported; however, the mechanism underlying this indirect free radical combating effect of melatonin remains unclear. In the present study, we explored the role of RORα and RORα dependent NF-κB activation in mediating the effects of melatonin on the activity of antioxidant enzymes. The daily variation in the expression of RORα and NF-κB along with the plasma melatonin level was assessed, and its possible association with the antioxidant enzyme activity in the lymphoid tissues of the Indian squirrel was evaluated during different reproductive seasons. Significant daily variation in the expression of RORα and NF-κB was observed, which was inversely related to circulatory melatonin levels and the activity of antioxidant enzymes. The expression of RORα and NF-κB was downregulated at the night when the plasma level of melatonin and activity of antioxidant enzymes namely superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were at their peak. Tissue melatonin can further act as a complementary factor in counteracting oxidative stress; hence, we also checked the lymphoid melatonin content over 24 h. No temporal variations were noted in the tissue melatonin content over the day. Likewise, no significant daily variation was noted in the total antioxidant status (TAS) of the lymphoid tissues. The absence of daily variation in the TAS can be attributed to the direct free radical scavenging activity of tissue melatonin in the spleen and thymus. The daily rhythms in the activity of antioxidant enzymes can be considered an integral part of the adaptive strategy that is regulated by the endogenous melatonin rhythm. However, the melatonin-mediated regulation of the antioxidant enzyme activity is neither mediated by RORα nor NF-κB dependent pathway.
Marsupials diverged from eutherian mammals 125-160 million years ago. Although evolutionarily distinct, both groups of mammals can produce complex adaptive immune responses to antigens with several key differences. This review analyses the current understanding of the adaptive immune system in marsupials and highlights key differences, including the absence of IgD in marsupial genomes and the presence of an additional T cell receptor. We summarize what is known about T cells and antibodies of marsupials, and their role in marsupial diseases including tuberculosis and sarcoptic mange. We also discuss how the innate immune system interacts with the adaptive immune system. As vaccinology becomes increasingly incorporated into marsupial disease management and conservation, we review key vaccine research within this mammalian clade. Further research is needed to expand and improve our understanding of disease responses in marsupials and help prevent further disease-driven extinctions.
A recent increase in the frequency of extreme heat events has urged researchers to examine physiological responses to hot temperatures. Across species, there is variation in whether the sexes respond the same or differently to extreme temperatures. Accordingly, our study investigated the sex-specific responses to an acute heat exposure. We assigned adult male and female zebra finches to a 5-h control (22°C; female: n = 20, male: n = 19) or a heat treatment (43°C; female: n = 23, male: n = 22). We collected blood samples 2 weeks pre-treatment and immediately post-treatment to measure blood concentrations of corticosterone, glucose, ketones (beta-hydroxybutyrate), and DNA damage. Additionally, we measured the core body temperatures of the birds via PIT tags. Heat exposure significantly increased body temperature, blood glucose, blood ketone, and plasma corticosterone levels. In contrast, we found no significant difference in DNA damage levels in the red blood cells. Finally, we found no sex differences in these physiological measures. To explore systematic interactions, we utilized Gaussian Graphical Models, which indicated that heat stress results in more coupled interactions between variables. Notably, ketones and glucose were positively correlated in the control group but negatively correlated in the heated group, suggesting a shift in metabolic fuel utilization. Our findings suggest that physiological and cellular responses to acute heat stress are consistent across sexes in adult zebra finches. These findings are an important step to better understand the physiological underpinnings of how birds respond to acute heat stress.
In the exciting era of non-invasive tissue sampling and data reuse via open access databases, it is increasingly challenging to ensure comparability of sample types for stable isotope analysis in ecology. According to the theoretical predictions about the changes in the stable isotope values between prey and consumers and tissue turnover rates, the ecological question alone should dictate the choice of the sample type used (single tissue, whole body, or pooled samples). However, the sample types have also been constrained by the body size, availability, or legal status of the study species, and stable isotope data sets are routinely obtained from a variety of sample types. While there is a general agreement that this practice may bias the ecological conclusions of stable isotope studies, the risks incurred have seldom been reviewed explicitly, let alone quantified. With both ethical aspects and open science opportunities arising in the field, the issues around sample types in stable isotope ecology must be tackled explicitly. We illustrate how comparing stable isotope values from different sample types affects niche analyses and diet reconstructions, and detail the consequences of pooling samples on stable isotope variance. We call for (1) a thorough consideration of the adequation between sample types and ecological questions, including in data harvesting from global databases, and (2) for the development of methodological studies around sample type issues and that of a systematic framework that incorporates the known variations between sample types in statistical analyses.
Although large oil spills cause intense ecological damage and receive heavy media and research attention, small spills occur much more frequently and have ecological consequences. Currently, assessment of damage to wildlife after oil spills of any magnitude primarily involves carcass counts and observation of individuals with visible oiling. Such methods do not account for sublethal or non-visible oil exposures that accompany the consumption of contaminated prey or soils. Recent research demonstrates that mild oil exposure can affect time-energy budgeting in birds, as they alter foraging and preening time, and metabolic rates. There is a need to understand how both frequency and length of exposure (duration) to oil spills interact with mechanisms of lethality and sublethality to affect population declines and recoveries. We developed a dynamic energy budget individual-based model to represent a generalized altricial bird and simulate the outcomes of various oiling scenarios. The models revealed that sublethal effects of oil exposure are important to population decline and recovery because they altered trajectories of population recovery through reduced fecundity and embryo survival. Our models also indicate that small oil spills can have significant effects on populations, particularly when spills occur frequently or persist in the environment. Our findings agree with empirical studies showing that sublethal effects of oil exposure in birds are important to population dynamics and indicate that frequent or long-lasting small spills can have significant effects on populations. Minimizing frequency and prioritizing expeditious clean-up of all, including small, spills could result in better conservation outcomes.
Mounting an immune response and locomotor activity are energetically costly processes that can generate trade-offs affecting energy allocation, muscle performance, and activity patterns. The balance between these demands can be modulated by factors such as food availability and ecological conditions, influencing the ability to mount an immune response and maintenance of locomotor activity. In a previous study, we demonstrated that Xenopus laevis subjected to an immune challenge maintained voluntary movement, indicating that behavioral depression did not occur in these animals, contrary to what is observed in most species. We hypothesized that food availability influenced this response, since the animals were captive and fed ad libitum. Here, we investigated the effects of food restriction on the locomotor activity of X. laevis after an immune challenge induced by lipopolysaccharide (LPS). We evaluated locomotor endurance, jump force, and spontaneous voluntary movement in individuals subjected to a progressive, 30-day, food restriction protocol. These results suggest that food restriction alters the energetic prioritization following immune activation, leading to reduced locomotor output and behavioral activity. Furthermore, the reduction in jump force and locomotor endurance was more pronounced in individuals on restricted diet, indicating a direct impact of energy availability on locomotor capacity. These findings reinforce the idea that resource availability influences the immune and locomotor response in anurans, highlighting how nutritional stress may constrain immune-locomotor trade-offs in amphibians, with potential consequences for survival and fitness in resource-limited habitats.
ABSTRACT Stable isotope analysis (SIA) provides essential information toward a better understanding of trophic ecology. However, the interpretation of SIA results relies on assumptions about the trophic discrimination factor (TDF), which aims to improve the accuracy but may lead to bias. In aquatic ecosystems, most biota are poikilothermic organisms, thus temperature is one of the most important parameters affecting all biological processes, including the trophic discrimination of stable isotopes. Therefore, we conducted an experiment to establish TDF for freshwater fish under different temperature regimes (15°C, 25°C, and natural ambient pond temperatures from July to September). We used common carp ( Cyprinus carpio , L., 1758) as a model organism. In the first phase of the experiment (weeks 1–6), all fish were fed a defined fish feed to establish a baseline isotopic signal for all individuals. In the second phase (weeks 7–18), fish were randomly divided into three temperature groups and were all fed different types of fish feed. Results indicated temperature‐dependent TDF, with nitrogen showing higher temperature dependency, where highest TDF were observed in the 15°C treatment and lowest in the 25°C treatment. In contrast, for carbon, an equilibrium of muscle isotopic values was reached only in the natural ambient temperature regime. Presumably, discrimination of nitrogen isotopes was related to metabolic turnover rates, where all values were significant, while for carbon, only significant values were found under natural ambient temperature conditions. These findings highlight the importance of considering environmental thermal conditions in evaluating stable isotope signatures in trophic studies.
The success of invasive species, which pose a significant threat to global biodiversity, hinges on their physiological and ecological adaptive capacities to the environments into which they are introduced. Trachemys scripta elegans (T. scripta elegans), recognized as one of the world's 100 most invasive species, has spread across a wide geographic range and exerts considerable pressure on native ecosystems. To investigate this, we studied the thermal ecology of an invasive population of T. scripta elegans in a wetland located in the province of Manisa, in Western Anatolia. Our objective was to assess the species' level of pre-adaptation to local climatic and habitat conditions and to identify its thermoregulatory strategies. Between March and October 2024, we measured individual body temperatures (Tb) and environmental temperatures (Te) in the study area; concurrently, we recorded data on water temperature (Tw), air temperature (Ta), solar radiation intensity, and wind speed. We also measured preffered body temperatures (Tset) in the laboratory. We found that the thermal quality of the habitat (de) was suboptimal during the species' primary activity period, thereby presenting a thermally challenging environment. Despite this, the invading population exhibited high thermoregulatory accuracy (db), successfully maintaining its body temperatures in close alignment with its preferred temperature range. This resulted in a high index of thermoregulatory effectiveness (E = 0.79) and a positive thermoregulation index value (I = 3.79 > 0). Furthermore, Pearson correlation analysis revealed a strong positive correlation between Tb and Tw, as well as between Tb and Ta. Our results indicate that the invasive T. scripta elegans population prefers an effective thermoregulation option rather than being thermoconformist. This high thermoregulatory capability represents a key pre-adaptation, enabling the species to spread successfully even in thermally suboptimal habitats and providing a competitive advantage over native species. The findings from our study support projections that in the face of a warming climate, thermal stress tolerance and behavioral thermoregulation can facilitate the expansion of invasive species.
Rapid urbanisation has significantly increased nighttime illumination, thereby affecting the photoperiod perception of seasonal-breeding animals. In this study, we investigated the effect of dim light (0.0064 W/m2) combined with an extended photoperiod (15 L:9D/day) on the hypothalamic-pituitary-gonadal (HPG) axis in adult (~ 4 months old) Syrian hamsters (Mesocricetus auratus). Two groups of male animals were used: group one (LD; n = 5) was exposed to long photoperiod (15 L:9D), while group two (dLD; n = 5) experienced the same photoperiod with added dim nocturnal light (0.0064 W/m2) for 4 weeks. No significant change in body mass, testicular volume, plasma testosterone, cholesterol and triglycerides was observed at the end of the study. However, analysis of hypothalamic tissue revealed that nighttime light exposure led to upregulation of the Eya3 transcript and downregulation of genes involved in photo responsiveness and reproduction (Tshβ, Dio2, GnRh, Six1), with concurrent downregulation of epigenetic markers (Tet2, Hat1), and increases in Dnmt1, Dnmt3A, and Hdac3. Additionally, there was a downregulation of steroidogenic transcripts (StAr, Cyp17a1, Esrrb, Ar, Prmt5, Nsdhl) in the testes of dLD animals, while the Hdac3 transcript was upregulated in testicular epigenetic transcripts. The hepatic metabolic and epigenetic gene expression also differed significantly. Genes such as Acc, Fasn, Hmgcr, Srebf1, Srebf2, Tet1, and Hat1 were significantly lower under dim-light exposure, while Dnmt3a, Hdac3, and Hdac5 were upregulated. These findings suggest that dim night light can disrupt the photoperiodic sensing pathway of seasonal reproduction, highlighting the ecological effects of artificial light on wildlife in urban settings.
Environmental pressures shape survival and life-history dynamics partly by triggering the release of glucocorticoids, whose short-term benefits but long-term costs make it essential to understand what drives their levels. Here, we used an experimental manipulation of two environmental stressors-food availability and parasite burden-to directly test how they influence fecal corticosterone metabolites (FCMs) in wild wood mice (Apodemus sylvaticus). To do so, we experimentally altered nutrition via high-quality food supplementation and reduced gastrointestinal nematode infection by anthelmintic treatment, using Heligmosomoides polygyrus as an indicator of treatment efficacy. FCM levels were not impacted by either treatment. However, our results may be mediated by variation in resource availability or masked by other factors that affect corticosterone. For example, FCMs declined seasonally, alongside a decline in the number of reproducing individuals. While we expected higher food availability and lower worm burdens to decrease stress, putatively higher rates of reproduction in food-supplemented areas may offset potential declines in corticosterone. Thus, alleviating some environmental stressors in the wild may have unintended consequences on host fitness.
The hepatotherapeutic agents from plants have become more predominant around the world. Evening primrose oil (EPO) is a popular alternative treatment that contains several phytoconstituents with strong anti-inflammatory and anti-oxidant properties. The current work inspected the potential protective effect of EPO against carbon tetrachloride (CCl4)-induced hepatotoxicity in rats. Twenty-four adult male albino Wistar rats were divided into 4 equal groups: group I received the vehicle only (control rats), group II was treated with EPO at 300 mg/kg/day, group III was treated with CCl4 at 1 mL/kg, twice a week, and group IV was treated with EPO at 300 mg/kg/day, followed 60 min later by CCl4 1 mL/kg, twice a week. All regimens were oral and for 4 weeks. At the end of the work, we assessed body-weight gain, liver functional markers, hepatic histological examination, quantitative histochemistry, and immunohistochemical profiling of tumor necrosis factor alpha (TNF-α). Gas chromatography coupled with triple quadrupole mass spectrometry (GC-MS) analysis was used to detect the fatty acid composition of EPO. CCl4 administration revealed a significant increase in serum liver functions, a disrupted oxidant/antioxidant status, hepatic histological changes, and an increase in H-score of TNF-α immunoexpression. Inversely, EPO pretreatment attenuated all toxic insults of CCl4. GC-MS showed that linoleic acid and its ethyl ester are the most prevalent components in EPO. Our findings showed that EPO could be a potential hepatoprotective agent that can be used in the future to prevent liver injury. Furthermore, the dominant compounds identified in this sample that may have the potential protective effects are fatty acids and their ethyl esters, such as linoleic acid and its ethyl ester.
The cognitive abilities of many non-human animals have been investigated in recent years; however, outside of laboratory rodent strains, it is largely unknown how direct and indirect genetic factors influence the development of cognition. In a previous study, we found no impact of maternal genetic or non-genetic effects on problem solving in the fawn-footed mosaic-tailed rat Melomys cervinipes. However, cognition is multifaceted, and different forms of cognition may not all be influenced by the same factors. Therefore, we investigated whether maternal genetic and non-genetic effects affected the development of multiple, different measures of cognition in the fawn-footed mosaic-tailed rat. We first measured the amount of maternal care mothers provided to their offspring and then tested mothers and offspring as adults in three tests: an associative memory test, a novel object recognition test, and a food extraction task (to assess learning). We assessed whether the maternal care provided by mothers influenced cognition and used parent-offspring regressions to determine whether the cognitive abilities of individuals had a heritable component. Offspring that received more indirect care were significantly more likely to learn the lever task than offspring that received less indirect care, possibly because this task required more neurological processing for successful completion than the other tests. No other measure of maternal care significantly influenced offspring cognition, and offspring cognition did not appear to have a heritable component. This suggests that cognitive development in this species is likely quite flexible, and that maternal direct and indirect genetic effects may not play a significant role in the development of cognition.
The rodent Cerradomys goytaca is endemic to the coastal sandplains (restingas) of Brazil. This study aimed to investigate the renal morphology and physiology of this species to elucidate the possible mechanisms involved in urinary concentrating capacity and renal solute handling. Ten female specimens of C. goytaca werecompared with twenty female Wistar Rattus norvegicus. Feed intake and urinary flow were determined. The following parameters indicative of renal function were evaluated: clearance, fractional excretion, and urinary excretion of creatinine, osmolality, urea, sodium, potassium, and glucose. Additionally, morphological analyses of the kidneys were performed to evaluate cortical and medullary structure. C. goytaca showed a significantly higher renal mass index despite a lower nephron count compared to R. norvegicus. The species demonstrated the ability to produce more concentrated urine, with lower urinary flow and greater water reabsorption. Higher urinary excretion of sodium, potassium, and glucose was also observed. Together, these results suggest adaptive mechanisms for electrolyte and glucose handling, as well as water conservation, that may support the survival of this species in its natural habitat.
Sponges are aquatic animals highly sensitive to environmental changes. They significantly impact silicon cycling by constructing siliceous skeletons. The necessity of better understanding of both biosilification and sponge physiology inspired us to focus current work on how silicon deficiency affects spiculogenesis in the branched Baikal sponges Lubomirskia baikalensis. We employed an original method to detect newly formed silica spicules: staining with a vital fluorescent dye specific to new silica deposition. A significant reduction in spicules formation was observed when silicon levels were decreased from 32 μM (artificial Baikal water) to 10 μM or less, alongside compromised primmorphs integrity. This suggests that low silicon availability may slow sponge growth by limiting spicule production. If such reductions occur naturally, they could alter sponge appearance or abundance, highly affecting Baikal's benthic communities. Our findings, consistent with previous studies, indicate a recent shift in the silicon-to-phosphorus ratio in the coastal Baikal waters, characterized by a decrease in silicon concentration. The notable reduction in siliceous sponges coincides with this trend. Further in vivo experiments are required to test the hypothesis that silicon deficiency affects both the growth and health of sponges in nature, thereby increasing their susceptibility to environmental stressors. Additionally, we examined nitrogen and phosphorus's impact on spicule formation. Seasonal fluctuations in these nutrients are unlikely to directly affect spiculogenesis, though surprisingly, higher nitrogen levels appeared to accelerate spicule growth. Our observations have broader implications, given global and anthropogenic influences on biogenic element levels in the coastal zones of aquatic ecosystems.
The release of waterborne chemical cues is a well-documented anti-predator strategy in teleost fish, allowing individuals to detect, and respond to, predation threats. However, little is known about whether an ancient group of fishes, elasmobranchs, employ similar mechanisms to communicate predation risk. Here, we experimentally investigate the behavioral and physiological responses of Bat rays (Myliobatis californica) following the manipulation of an upstream conspecific. Specifically, we examined whether Bat rays receiving water from an upstream conspecific that had been physically chased with a stick for 30 s, simulating a non-injurious predation disturbance, exhibited changes in activity levels and physiological stress markers. Receiving Bat rays increased their velocity by approximately 3 cm/s (~21%) compared to their pre-exposure state, whereas Control rays showed no significant change. Receivers also exhibited a significant shift toward active swimming behaviors, while Controls spent more time in passive behaviors. This shift was positively correlated with velocity, reinforcing that exposure to waterborne disturbance cues from a distressed conspecific triggered increased activity. Physiological measurements showed no significant differences between groups in glucose, β-HB, lactate, or pH levels. We suggest the activity increase corresponds with a flight-type response to predation risk. These findings reveal a previously undocumented communication mechanism in marine predators, contributing to a broader understanding elasmobranch behavior and physiology.
The current work compared the integumentary architecture and feather microbiomes among three avian species inhabiting different ecological niches: the aerial laughing dove (Spilopelia senegalensis), the terrestrial quail (Coturnix coturnix), and the semi-aquatic Muscovy duck (Cairina moschata). Histological, histochemical, and microbial analyses revealed clear interspecific variations that appear to be associatedwith the distinct lifestyles of the examined species. The laughing dove exhibited the thinnest skin, numerous Herbst corpuscles, and a pigmented epidermis, features related to the aerial mode of life and serving to mitigate the frequent exposure to sunlight. in contrast, the quail showed moderately thick epidermis, non-pigmented skin, and less pronounced dispersal of mechanoreceptors, reflecting its tendency toward the ground-dwelling lifestyle. While the Muscovy duck possessed the thickest skin, characterized by the highest microbial load, which aligns with its semi-aquatic habitat and frequent water contact. Furthermore, the preen secretions of the laughing dove exhibited strong antimicrobial potency, while those of the Muscovy duck were functionally engaged in waterproofing rather than microbial combating. Collectively, these findings highlight how skin architecture and microbial populations modulate in response to the environmental challenges, such as ecological demands and the surrounding microenvironment.
The environment through which animals move is rarely homogenous and requires animals to change their kinematics. Especially for small animals, even seemingly minor variations in substrate characteristics may have strong impacts on their locomotor speed and kinematics. In most quadrupedal animals, obstacles are avoided by adapting the movements of the limbs and body, allowing animals to effectively negotiate a diversity of terrains. However, how limb-reduced animals change their kinematics in function of variation in locomotor substrates remains poorly known. Here we study the limb-reduced skink Ablepharus kitaibelii moving on two different substrates (sand and bitumen) across a range of speeds. Our results show an effect of speed as well as significant differences between substrates in most spatio-temporal gait parameters studied. Moreover, speed modulation differed between the two substrates, suggesting that the kinematic and motor control strategies used by this species are substrate-dependent. Axial movements were strong determinants of overall locomotor speed in A. kitaibelii, suggesting that in limb-reduced species, the axial system drives variation in locomotor speed. Our data provide a baseline for future studies on other limb-reduced and non-limb-reduced species.
Climate change and rising ambient temperatures increasingly challenge sheep production systems in arid and semi-arid regions, particularly during the summer breeding season. This study evaluated the effects of heat stress and direct solar exposure on physiological responses, metabolic profile, and reproductive performance of Barbarine ewes, a fat-tailed breed adapted to harsh environments. A total of 112 non-lactating multiparous ewes were allocated to two groups during summer mating: an indoor group protected from solar radiation (IDGp; n = 58) and an outdoor group exposed to direct sunlight (ODGp; n = 54). Both groups experienced severe to extreme heat stress for more than 65% of the experimental period. Sun exposure significantly increased rectal temperature (+0.2 to +0.6°C), respiratory rate (up to 130 vs 61 breaths/min), and heart rate (up to 95 vs 87 beats/min) in outdoor ewes (ODGp) compared to indoor ewes (IDGp), indicating a higher physiological heat load in sun-exposed animals. The temperature-humidity index (THI) remained comparable between groups (≈24.7), suggesting comparable THI values. Metabolic responses were characterized by increased plasma concentrations of triglycerides (+36%), total proteins (+7.5%), urea (+13%), creatinine (+34%), and potassium (+5%), along with a decrease in cholesterol levels (-15%) in ODGp compared to IDGp. Despite these physiological and metabolic adjustments, body condition score and live weight were maintained in both groups. Reproductive performance was not affected by solar exposure, with estrus occurrence exceeding 94%, an ovulation rate of 1.17, and no significant differences in fertility (79.3% vs 77.8%), prolificacy, or fecundity between groups. These findings indicate that, although direct solar radiation increases physiological strain, it does not impair reproductive function under comparable ambient thermal conditions. Barbarine ewes thus exhibit strong functional resilience to heat stress, highlighting their suitability for extensive production systems in hot and dry environments.
