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

Hibernation is an amazing survival skill that some animals use to cope with natural challenges, and cold is the main stimulus. While most hibernation studies focus on long-term cold adaptation mechanisms, the rapid physiological adjustments triggered by short-term cold exposure may also be key components in the initiation of hibernation. This study focused on 20 Chinese Moccasin (Deinagkistrodon acutus), divided into two groups: an active group (n = 10) and a short-term cold exposure group (n = 10). Using serum biochemistry, serum antioxidant measurements, and liver transcriptome technology, the study explored the effects of short-term cold exposure on snake serum lipids, antioxidant capacity, and apoptosis. The results showed that the levels of cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol were significantly lower in cold exposure snakes compared to the active group, whereas total bile acid was higher in the cold exposure group; serum antioxidant indicators glutathione peroxidase, superoxide dismutase, and total antioxidant capacity were lower in cold exposure snakes than in active snakes, whereas the concentration of malondialdehyde was higher in cold exposure snakes. The liver transcriptome revealed that more pro-apoptotic genes were upregulated in active snakes, whereas there were more upregulated anti-apoptotic genes in cold exposure snakes, and the ratio of anti-apoptotic to pro-apoptotic genes was significantly higher in cold exposure snakes than in active snakes. This study not only elucidates the physiological effects of short-term cold exposure on snakes but also advances our understanding of the adaptive mechanisms underlying the transition from activity to hibernation in ectothermic animals.

Chemical communication, typically based on feces, urine, and glandular secretions, often deposited as substrate scent marks, plays a key role in social organization and communication among many mammals, especially carnivores. This study assesses experimentally whether the type of substrate chosen for fecal deposition and the temperature reached by these substrates influence the persistence of volatile compounds in feces of the Iberian wolf (Canis lupus signatus), considering their role in chemical communication. Fresh fecal scats collected in the wild were divided into equal fragments and positioned in an experimental setup on four different types of substrates exposed to the natural environment. Thereafter, we collected small fecal samples from each fragment at seven different time intervals since the initial deposition and analyzed their lipophilic chemical composition using gas chromatography-mass spectrometry (GC-MS). Variations in the temperature of each substrate were also monitored. The number of compounds in feces decreased with time since deposition and depended on the types of substrates. However, substrate temperature only influenced the persistence of some chemical compounds. These results suggest that when wolves select a substrate to deposit feces, enhancing visual cues (i.e., the different visual conspicuity of feces in different substrates) may play a more important role in fecal marking than trying to increase the persistence of the chemical signal. Overall, our study may help to enhance the understanding of fecal marking behavior in the Iberian wolf, especially regarding the interplay between visual and chemical signaling.

The alligator gar, Atractosteus spatula (Lacépède, 1803), is a euryhaline, bimodal breather, occupying a wide range of habitats. The gills and swim bladder are both respiratory organs, creating a potential trade-off for fish inhabiting saline environments where gills must also be used to facilitate osmo- and ionoregulation. Therefore, to understand whether gill adaptations in alligator gar differ from other euryhaline basal fishes and teleosts, alligator gar were acclimated to fresh water (salinity: 0; n = 5) or saline water (salinity: 20; n = 5) for over 4 weeks and gill ultrastructure and localization of the key sodium and proton motive ATPases [Na⁺, K⁺-ATPase (NKA) and vacuolar-type H⁺-ATPase (VHA)] were evaluated. Gills were analyzed by scanning and transmission electron microscopy to evaluate the external surfaces and internal cellular structures of epithelial cells, and by immunofluorescence microscopy to identify ionocyte types. In alligator gar acclimated to fresh water, ionocytes extended beyond pavement cells, contained numerous microvilli and mitochondria, and were generally located on the gill filaments at the base of lamellae. Following acclimation to saline water, ionocytes were recessed compared to adjacent pavement cells, contained numerous mitochondria, and were generally located on the gill filament epithelium at the base of lamellae and in interlamellar spaces. In the gills, there were numerous NKA immunoreactive cells in saline-acclimated fish, with fewer in freshwater-acclimated fish. Notably, VHA-immunoreactive cells were present in both salinity groups and occurred in a separate, less abundant subpopulation than those containing NKA. Therefore, the alligator gar has similar gill adaptations as many teleosts for salinity acclimation, with the presence of VHA resembling other basal euryhaline actinopterygians.

Expression of concern: I. Saha, U. Chatterji, S. Chaudhuri-Sengupta, et al. 2007. "Ultrastructural and Hormonal Changes in the Pineal-Testicular Axis Following Arecoline Administration in Rats." Journal of Experimental Zoology - A 307A, no. 4: 187-198, https://doi.org/10.1002/jez.354. This Expression of Concern is for the above article, published online on 08 March 2007 in Wiley Online Library (wileyonlinelibrary.com), and has been issued by agreement between journal Editor-in-Chief, Randy Nelson and Wiley Periodicals LLC. A third party raised the following concerns: that the image in Figure 3D had been duplicated in another article [Saha et al. 2011 (https://doi.org/10.1016/j.taap.2011.06.010)] and that portions of the image in Figure 2H and portions of the images in Figures 3A and 3B had been duplicated and manipulated in other articles [Saha et al. 2017 (https://doi.org/10.1080/13813455.2017.1352605), Saha et al. 2018 (https://doi.org/10.1080/13813455.2018.1486428), and Cydalima laticostalis 2025 (https://pubpeer.com/publications/1954237BA2AFC72EE913C316CC3BCC)]. All articles included many of the same authors and each described different experimental conditions. An investigation by the publisher confirmed these concerns and also found that the images in Figures 3A, 3C, and 3E had been duplicated in another article by many of the same authors [Saha et al. 2015 (https://doi.org/10.1155/2015/136738)]. The authors did not respond to an inquiry and request for original data by the publisher. The editors and publisher have determined that, while this article represents the earliest known publication of the data in these figures, the re-use and manipulation of data, as well as the representation of data as different samples in future publications, casts doubt on the accuracy of the data reported in this article. The Expression of Concern has been agreed to in order to inform and alert readers about the results of the investigation. The authors were informed about the Expression of Concern.

With climate change, birds will face increasing thermoregulatory demands, which may alter reproductive behaviors such as offspring provisioning. Experimental studies have shown that the provisioning capacity of female tree swallows (Tachycineta bicolor) is limited by their risk of overheating. Given that parental investment strategies may vary between sexes, the thermal environment may have a different impact on males. We experimentally trimmed ventral feathers from male tree swallows to create a "thermal window" through which they could dissipate heat. We remotely monitored provisioning rate and core body temperature of males and their female partners. At high temperatures, all males decreased their nestling provisioning rates irrespective of trimming treatment. In addition, trimmed males maintained core body temperatures similar to those of controls. This suggests that in contrast to previous work with females, males limit provisioning rates to levels below the threshold at which they would overheat. Regardless of male treatment, females adjusted their own activity to match that of their male partners; whether there are costs to females is unknown. Combined, these studies highlight that sex-specific differences in thermal physiology and behavior must be considered when predicting responses to climatic warming.

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.