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

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.

Living organisms face stressful situations and use endocrine mechanisms, such as glucocorticoid production, to maintain homeostasis. Although glucocorticoids are essential for basal function, their secretion increases when organisms face stressful situations. In species with temperature-dependent sex determination (TSD), like Caiman latirostris, an increase in these hormones could also alter the sex ratio. In this study, we applied a dose of exogenous corticosterone (70 ng/egg) at developmental stage 20 to assess its effects on sex determination, incubation period (IP), and morphometric traits -including snout-vent length, total length, and body mass- in embryos and hatchlings. Eggs (n = 184) were incubated at 32°C, a temperature that typically produces both sexes. Corticosterone treatment significantly reduced the IP (CORT: 74  ±  2 days; CONTROL: 78  ±  2; z = -9.91, p < 0.01), without affecting hatching success. Morphometric traits did not differ significantly between treatments in either embryos or hatchlings (all p > 0.05). However, a marked shift in sex ratio was observed: while a 30% male to 70% female ratio was expected, corticosterone treatment reversed this pattern, resulting in 75% males and 25% females (χ² = 6.125, p = 0.013). These results indicate that corticosterone can induce male-biased sex differentiation and accelerate hatching without compromising morphological development or hatchling viability. While this mechanism could confer a advantage at the individual level by allowing earlier hatching, it is crucial to investigate whether it carries long-term costs, both in the growth and survival of the offspring and in population dynamics due to the altered sex ratio.

An optimal glucocorticoid stress response is essential because it allows animals to adjust their phenotype to constantly changing environments. Considerable progress has been made regarding our understanding of how various cellular mechanisms of glucocorticoid action modulate animals' stress response phenotype. However, a potentially overlooked mediator of glucocorticoid production and individual's stress response phenotype is the endoplasmic reticulum (ER) and its unfolded protein response (UPR), given that all steroid hormones are synthesised within the mitochondria and the ER. We hypothesise that UPR regulates glucocorticoid synthesis, and ER stress induction would inhibit glucocorticoid production in the adrenal cortex. We conducted in vivo and in vitro studies using outbred deer mice Peromyscus maniculatus and Y-1 adrenal cell lines respectively to investigate the effects of ER stress and UPR on adrenocorticotropic hormone induced glucocorticoid production. Specifically, we tested if induction and alleviation of ER stress using tunicamycin and tauroursodeoxycholic acid, respectively, would affect corticosterone production in deer mice and Y-1 cells and the protein expression of a steroidogenic enzyme in Y-1 cells. We showed that ER stress and UPR modulate glucocorticoid production at both the cell and whole-organism levels, but this is achieved independent of alteration in protein level of 21-Hydroxylase.

Systematics has become an essential aspect of managing and conserving species from the order Crocodilia. All members of the group are listed in CITES appendices, and to control illegal traffic of animals and subproducts, we must be able to correctly assess the specific identity of the samples. Genetic DNA barcoding is a very efficient tool for species identification in the animal kingdom, based on the sequencing of a region of a mitochondrial gene, the Cytochrome oxidase subunit I (COI). Our principal aims were to design specific primers that allow obtaining this sequence from the genetic material of the caiman species and test the potential utility of barcoding in forensic studies, as well as verify the correct identification of different collections. We successfully obtained barcodes using our designed primers to amplify caiman samples, studying a fragment of 610 bp. We also compared sequences (N = 290) from public databases of all the species included in the Order Crocodilia, obtaining a tree that resulted in a similar current crocodilian phylogeny. The primers designed can be applied to obtain barcodes from samples of other crocodilian species, and this information can contribute significantly to forensic and systematic studies.

Identifying individuals over time and across contexts is essential in many scientific fields. There are a variety of well-established methods for uniquely marking individuals (e.g., visible implant elastomer, barcodes, paint). However, for some species, life history stages, and/or experiments, existing methods are not sufficient. Here, we describe procedures for how two tagging methods-a tattoo ink injection method and a fishing line piercing method - can be used with the youngest, smallest juveniles of the African cichlid fish, Astatotilapia burtoni, which are too small for the methods used with adults. With the tattoo method, we injected tattoo ink into the dorsal muscle. Different colors and injection locations can be used to distinguish among individuals over a period of weeks (up to 4 weeks, average 2.5-3 weeks under our conditions). Because fish this young and small are sensitive to handling and injection, we also include physiological data showing fish recover well from anesthetization and tagging. With the piercing method, very thin fishing line is threaded through the dorsal muscle and tied into a barbell or loop. Unique colors and patterns can be used to distinguish among individuals over a period of months. Because a physical tag might impede normal movement in a very small fish, we also include data from an open field exploration test showing similar behavior between tagged and control (non-tagged) juveniles. We expect these effective and inexpensive methods to be useful for a variety of small species and will facilitate early-life, developmental, and longitudinal research.

Fungal pathogens pose a growing threat to vertebrate biodiversity. In snakes, Ophidiomyces ophidiicola (Oo) has garnered particular concern, although its impact in Europe remains poorly understood. We conducted a season-long, standardized survey of dice snakes (Natrix tessellata) along the northern shore of Lake Como (Italy) to quantify Oo and ophidiomycosis prevalence, identify the circulating strain, and explore the association with environmental, morphological and behavioral traits. Between March and October 2024, we collected 96 N. tessellata samples (23 sheds and swabs from 73 live individuals; scale clips were also collected from 60 out of the 73 live individuals). These samples were analyzed through qPCR, histopathology, and direct field observations. After excluding four recaptures, the dataset comprised 92 N. tessellata samples (23 sheds and swabs from 69 individuals), of which 49 tested positive for Oo (53.3%). Among live individuals, 26 tested positive (37.7%). Of these, 21 showed clinical signs (i.e., skin lesions; 80.8%), and histology confirmed ophidiomycosis in 10 of 20 tested Oo-positive samples (47.6%). Among the five Oo-positive snakes without skin lesions, only one showed histological evidence of ophidiomycosis. This resulted in "at least apparent" ophidiomycosis (i.e., pooling the case-classification categories "Apparent ophidiomycosis", "Ophidiomycosis" and "Ophidiomycosis and Oo shedder") being confirmed in 22 out of 69 live snakes (31.9%), corresponding to an overall disease prevalence of 23.9% (22 out of 92) across the full sample set. All sequenced samples belonged to clade II. Bayesian models revealed that skin lesions predicted both Oo detection and ophidiomycosis, while snout-vent length was inversely related to both pathogen presence and disease, suggesting age-linked susceptibility. Both Oo-positive and diseased snakes had lower body temperatures but showed no clear preference for warmer substrates, suggesting limited or absent behavioral fever. Body-condition index (BCI) did not differ between Oo/disease-positive and Oo/disease-negative snakes, suggesting possible host tolerance. An assessment of antipredator behavior revealed a marked reduction in musking among Oo-positive snakes, potentially compromising antipredator defenses. Our findings identify N. tessellata as a possible model for European ophidiomycosis research and highlight the need for multi-season capture-recapture studies.