Journal of experimental zoology. Part A, Ecological and integrative physiology最新文献

Steroid-mediated maternal effects are well-studied as a source of phenotypic variation. In bird eggs, the yolk contains various steroids that can influence embryonic development. However, one complicating factor in understanding how yolk steroids affect development is that the embryo metabolizes yolk steroids to regulate exposure. The 5β-reduction of steroids by the enzyme 5β-reductase (AKR1D1) has been identified as a pathway through which yolk progesterone, testosterone, and corticosterone are all metabolized early in avian development. We set out to characterize the mechanism through which AKR1D1 expression is regulated in chickens (Gallus gallus) during embryonic development. We found a synthetic and endogenous ligand (22R-hydroxycholesterol) for Liver X Receptor α (LXRα) induced AKR1D1 expression in the embryo and extraembryonic membranes on Day 2 of development. These results suggest that endogenous ligands of LXRα induce AKR1D1 expression and regulate the metabolism of yolk steroids during development.

Frogs are highly sensitive bioindicators whose skin secretions reflect physiological responses to environmental change. Yet, no study has directly linked amphibian skin metabolomes to quantified habitat parameters across a disturbance gradient. We applied an eco-metabolomics approach to Hylarana erythraea from eight pond sites in northern Peninsular Malaysia, spanning natural to heavily modified habitats. Thirty ecological parameters defined two habitat categories: minimally disturbed and moderately-to-heavily disturbed. Untargeted QTOF LC-MS/MS revealed distinct metabolomic profiles between categories (PERMANOVA, F = 11.78, R² = 0.67, p = 0.001). Frogs from minimally disturbed habitats had higher lysophosphatidylcholines (LPC 18:0, LPC 18:1), consistent with membrane integrity and physiological homeostasis, whereas disturbed sites showed elevated xenobiotic-related compounds (e.g., Triton X-45, Lauramine oxide) and histamine, indicating anthropogenic stress. Generalized linear models identified water clarity, aquatic vegetation, and pond size as the strongest predictors of metabolomic variation (ΔAIC ≤ 2). Our findings provide the first molecular-level evidence linking frog skin metabolites to quantified ecological drivers, demonstrating their value as early-warning biomarkers within amphibian conservation and One Health monitoring frameworks.

Environmental temperatures influence most aspects of ectotherm biology, especially when fluctuating on daily and seasonal scales. The Alligator Snapping Turtle (Macrochelys temminckii) is a species of conservation concern inhabiting temperate latitudes in the southeastern United States. To study the effect of temperature and season on the bite performance of M. temminckii, we used a force transducer and high-speed videography to measure bite force and kinematics, including bite duration, jaw velocity and acceleration, and lunge velocity and acceleration, for 21 captive subadult M. temminckii. We also recorded bite behaviors, including willingness to gape and bite, and pre-bite aggressive displays. We conducted trials at 5°C, 15°C, and 25°C, and repeated our measurements in summer and winter. Maximum bite force varied significantly with temperature, albeit not to an extent likely to be biologically relevant. All bite kinematics varied significantly across at least one of the testing temperatures within seasons, with individuals performing maximally at 25°C. Willingness to bite was more affected by temperature than willingness to gape, with subjects requiring more provocation to gape and bite at 5°C than at higher temperatures and displaying fewer pre-bite aggressive behaviors. There was limited evidence of seasonal acclimation in bite kinematics, with higher summer temperatures yielding maximal performance, and measurements at lower temperatures varying little between seasons. Our findings support the need for rigorous standardization of temperature in studies of ectotherm performance and suggest that care must be taken in selecting the time of year in which temperature studies are conducted.

Humans continue to influence the behavior, physiology and overall status of wildlife, yet how these influences persist over time are not fully understood and likely vary across circumstance and species. Interactions specifically associated with ecotourism and food provisioning have the potential to impact the behavior and physiology of wildlife significantly, especially when it includes the practice of feeding. To better understand whether ecotourism-induced changes in physiology persist over time and the resulting on-going impacts on populations, monitoring across time is needed. We measured immune, energetic, and traditional stress metrics of two Northern Bahamian Rock Iguana (Cyclura cychlura) subspecies (C. c. inornata and C. c. figginsi) across several years in response to body condition and reproductive status, in six insular populations of varying degrees of tourist visitation. We used plasma samples to quantify energy metabolites, immune function, oxidative stress, and plasma corticosterone concentration. Reproductive status in females was a consistently important explanatory factor for oxidative stress, energy metabolites, and bacterial killing ability. For both subspecies, populations with no tourist visitation consistently had lower levels of oxidative stress, bacterial killing ability, and energy metabolites than those that experienced moderate to high levels of tourism, but they also had demonstrated higher levels of corticosterone. Corticosterone and bacterial killing ability varied across years, suggesting that annual differences in physiology are likely to play an important role in long-term population health. Given the impacts of human activity on animal health over time, continual population monitoring of multiple physiological health metrics is needed for greater insight into the long-term impacts of anthropogenic factors on vulnerable species.

Morphofunctional inferences based on anatomical structure often rely on static skeletal features, with limited integration of dynamic locomotor behavior. Although mammalian limb movement exhibits conserved kinematic synergies, to our knowledge no broad comparative data set has quantified how joint poses, angular excursions, and angular range utilization vary across biological factors. A comparative data set of joint motion during the stance phase of walking is presented for 182 terrestrial mammal species spanning 15 orders, classified by limb posture, body mass, top speed, and locomotor habit. Using sagittal-plane video analysis and published sources, joint angles at touchdown, midstance, and toe-off were measured for six major limb joints. From these data, joint angular excursion (JAE), total angular excursion (TAE), and an angular utilization index (AUI% = TAE/∑JAE) expressed as the percentage of summed joint excursion that is realized as net limb excursion during stance, were calculated. Using phylogenetic generalized least squares (PGLS) to account for nonindependence among species, I found that JAE and TAE covaried with the factors considered, with body mass emerging as the dominant predictor. Hindlimb and forelimb TAE decreased with increasing log₁₀ body mass, whereas posture effects were subtle and largely overlapping among categories. Plantigrade, small-bodied and arboreal species tended to display broader angular profiles, whereas unguligrade, cursorial and fast-moving taxa generally used smaller excursions. Quadrant-based comparisons of forelimb and hindlimb AUI further highlighted locomotor strategies aligned with biological factors. Together, these findings indicate that mammals modulate the magnitude and distribution of joint excursions across size and ecological gradients while broadly preserving the proportion of the summed joint excursions range used during stance, providing a reproducible framework for interpreting limb dynamics in extant and extinct mammals.

Animals with seasonal reproductive cycles, as the Roe deer (Capreolus capreolus), have developed mechanisms to synchronize reproduction with the environmental cycle in order to optimize reproductive success through melatonin. Angiogenesis and oxidative stress are key processes in spermatogenesis, contributing to testicular remodeling and recovery after reproductive effort. This study carried out a gene expression analysis on 18 samples of mature male Roe deer testicles, collected during the local hunting season in pre-rut (N = 9) and post-rut (N = 9) periods. A quantitative real-time PCR (qPCR) array targeting 84 genes involved in oxidative stress and 84 in angiogenesis were used, followed by validation through individual qPCR of selected genes and related protein quantification by ELISA assays. Post-rut animals showed upregulation of several antioxidant genes: Peroxiredoxin-4 (PRDX4), Scavenger receptors class A member 3 (SCARA3), Superoxide Dismutase 3 (SOD3). Instead, Leptin (LEP) and Thrombospondin Ⅱ (THBSⅡ), a known angiogenesis inhibitor, are downregulated. A novel insight is represented by the upregulation of Neuropilin (NRP2) in post-rut period that, given to its posttranscriptional silencing too, needs better investigations. The pleiotropic nature of NRP2, including roles in neurodevelopment, immune modulation, and vascular remodeling, makes this gene an interesting candidate for further study, cause its function in reproductive tissues remains poorly understood.

Conditions experienced during early life stages may influence an array of fitness-relevant phenotypes, especially in oviparous ectotherms. The pond slider (Trachemys scripta) has two life stages particularly vulnerable to the influence of ambient conditions: the egg stage and hatchling overwintering stage. We aimed to determine the influence of both incubation temperature and overwinter environment on hatchling turtle performance. In 2019 and 2020, we incubated pond slider eggs at five constant temperatures (24°C, 26°C, 28°C, 30°C, 32°C). After hatching, turtles were distributed to two housing treatments that simulated overwintering in a terrestrial nest or an aquatic environment. In the spring following hatching, we conducted righting response trials, which are frequently used performance measures that may be associated with coordination and neuromuscular function. Our linear mixed-effects models show that incubation temperature, overwinter environment, and their interaction significantly influenced hatchling phenotypes (e.g., shell and tail dimensions, body mass) and righting performance (e.g., total righting response time, latency to right). Aquatically overwintering hatchlings that were incubated at cooler temperatures righted themselves faster than those incubated at warmer temperatures. This relationship did not exist in terrestrially overwintering hatchlings, which had faster overall righting times that were not affected by incubation temperature, suggesting overwintering in the nest may better equip hatchlings for post-emergence dispersals over land.

Depletion of dissolved oxygen (DO; hypoxia) and its influence on sensitive fauna and vulnerable life stages is an emerging concern in lotic freshwater ecosystems. A species particularly vulnerable to hypoxia is the Eastern Hellbender—a large-bodied, fully aquatic salamander which relies on cutaneous respiration and has evolved to thrive in cold, well-oxygenated streams. Adult hellbenders nest in benthic stream microhabitats which are vulnerable to DO depletion caused by loss of riparian forest cover that increases sedimentation and solar radiation. Hellbender populations are experiencing declines characterized by reduced recruitment in areas with low forest cover, but the influence of hypoxia on hellbender embryonic development is unknown. We hypothesized that hellbender embryos are sensitive to hypoxic conditions because of their high degree of habitat specialization. We conducted two experiments where we exposed freshly laid eggs to a range of DO concentrations in the lab (3–10 mg/L). In both experiments we found that hellbender embryos reared in our lowest DO treatments of 3 and 5 mg/L had an average viability 51% and 34% lower than each experiment's 10 mg/L treatment, respectively. In addition, eggs reared in these low DO concentrations had significantly lower hatching success, a higher percentage of premature hatchlings, and produced hatchlings with smaller morphometrics compared to higher DO treatments. In our second experiment, we also continued to track hatchlings at least 14 days post hatching and demonstrated that premature hatchlings had a high probability of dying within weeks of hatching. Our results indicate that hellbender embryos require DO concentrations of > 5 mg/L for proper development, thus placing them on the more sensitive end of the hypoxia tolerance continuum for freshwater taxa. Our experiments confirmed hellbender embryonic sensitivity to environmentally relevant reductions in DO concentrations and identified future research and conservation needs related to the development of hellbender embryos in the field.

Conspecific competitive interactions occur in a variety of contexts, including for resources and territory. These competitive interactions can vary in frequency and duration. The amount of aggression displayed and whether individuals alter their aggressive response during longer competitive bouts may be impacted by individual differences in stress response and behavior. The maternal environment, including maternal stress and the maternal microbiome, can have sex-specific, developmental effects on offspring's physiology and aggressive behavior. We tested whether the maternal environment affects changes to offspring aggressive behavior during long competitive bouts in Siberian hamsters (Phodopus sungorus). We exposed pregnant females to one of four treatments (social stressor, microbiome manipulation, combined social stress and microbiome manipulation, or no treatment) for ten days. Using a resident-intruder behavioral paradigm, adolescent offspring were exposed to a same-sex intruder for 15 min. We assessed differences in offspring behavioral responses during the first and last 5 min of the competitive interaction. All offspring displayed less aggression during the last 5 min compared to the first 5 min, regardless of maternal treatment. Regardless of maternal treatment, both female and male offspring reduced social behavior towards the intruder, while increasing non-social and decreasing anxiety like behavior across the 15-min trial. Our results are consistent with habituation towards an intruder and indicate that early development does not affect habituation during aggression with a conspecific, further confirming the complexity and highly conserved mechanisms involved in habituation.