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

Catch-and-release angling (C&R) is a conservation strategy that assumes released fish survive and contribute to populations. However, C&R stress, particularly during spawning, may impact reproductive females and their offspring, such as changes in maternal offspring investment. Here, we studied the effects of maternal stress on lake trout (Salvelinus namaycush), a heavily targeted C&R species, and their offspring. Females were angled, blood sampled, and either held for 48 h (Bag), or held for 48 h and air-exposed every 12 h to mimic repeated C&R events (Air+Bag). A third group of fish (Control) was not held and sampled immediately after capture only (Control). Females in bagged treatments were again blood sampled after 48 h to determine stress indices (cortisol, glucose, and lactate). Following treatment, fish were euthanised and eggs were collected and incubated for 69 days post-fertilization (DPF). Eggs and larvae were temporally analyzed for cortisol, macromolecular contents (glycogen, protein, water, and lipids), and morphometrics (wet mass, dry mass, and length). Maternal cortisol levels increased in bagged treatments, showing deviation in the stress response. Similarly, in these treatments, egg cortisol was elevated at 3 and 12 DPF, and in larvae at 69 DPF. While there were limited changes in macromolecular contents between treatments, the Air+Bag treatment demonstrated increases in egg and larval mass, as well as longer larvae at 69 DPF. These findings suggest maternal stress impacts the stress axis and morphometric development in lake trout offspring. However, the long-term implications of altered larval stress response and growth on lake trout populations remain unclear and a critical area of future work to develop sustainable recreational fisheries.

The red-eared slider turtle inhabits environments ranging from freshwater to semiterrestrial settings. Understanding the sensory adaptations of this species is crucial, particularly concerning its limb skin, which plays a key role in environmental interaction and survival. This study presents the first detailed identification of scale sensilla and sensory corpuscles in the red-eared slider's limb skin, offering insights into their innervation and distribution. We combined scanning electron microscopy (SEM), light microscopy, and immunofluorescence with ten antibodies to elucidate the sensory architecture and adaptation mechanisms of the turtle's skin. The antibodies include E-cadherin, four neural markers (Nestin, PGP9.5, neuron-specific enolase [NSE], and Synaptophysin), and five additional markers (PDGFRα, CD34, Vimentin, α-SMA, and Tom20) to analyze sensory structures and distribution patterns. SEM revealed scale sensilla resembling artichokes, with concentric layers surrounding a central dome featuring microplicae, grooves, and pores. Light microscopy showed these sensilla as dome-shaped structures elevated above the epidermal surface. Immunofluorescence with E-cadherin highlighted scale sensilla cells, central cells, and dermal papillae, while neural markers confirmed sensory nerves within the scale sensilla, underscoring their sensory role. Three types of sensory corpuscles were identified in the limb skin: Meissner's and Ruffini corpuscles in the dermis, and Pacinian corpuscles in the hypodermis. The four neural markers showed strong expression in sensory nerve fiber endings across all corpuscles, highlighting their roles in detecting pressure, vibration, and tactile stimuli. CD34 and PDGFRα were expressed in perineurial fibroblast-like cells and telocytes within the external capsules and concentric lamellae of Pacinian corpuscles, as well as in the external capsules of Meissner's and Ruffini corpuscles, with telocytes surrounding all three types. Vimentin was found in connective tissue and lamellar cells in all corpuscles, suggesting its role in structural support. α-SMA was strongly expressed in Pacinian corpuscles and minimally in Meissner's and Ruffini corpuscles, indicating its primary role in maintaining structural integrity in Pacinian corpuscles. Tom20 highlighted high mitochondrial activity in the nerve fibers and supporting cells of all corpuscles, with the highest expression in Meissner's corpuscles, reflecting the significant metabolic demands of these sensory structures. This study offers unprecedented insights into the sensory architecture of the red-eared slider turtle's skin. The novel identification and analysis of scale sensilla and sensory corpuscles, combined with 10 antibodies, enhances our understanding of the skin's innervation and its role in environmental adaptation, contributing valuable knowledge to sensory biology and herpetology.

Organisms in changing environments are subjected to environmental perturbations that may exacerbate physiological stress. Under the Cort-Fitness Hypothesis framework, sustained elevations in physiological stress can negatively impact individual fitness. This hypothesis predicts a positive association between stressors and glucocorticoids. Using fecal glucocorticoid metabolite (FGM) concentrations from non-invasively collected fecal pellets, we assessed how physiological condition of an imperiled mammal, the New England cottontail (Sylvilagus transitionalis), correlates with potential stressors, namely a proxy of habitat quality (forest successional stage), the presence of a nonnative competitor (eastern cottontail, Sylvilagus floridanus), and the density of an invasive plant species (Japanese barberry, Barberis thunbergii). Invasive plant prevalence and eastern cottontail presence independently had small effect sizes. Additionally, there was an interaction effect of eastern cottontail prevalence and Japanese barberry stem density on FGM concentrations, wherein increasing barberry stem density was associated with reduced FGM concentrations in patches with high eastern cottontail prevalence. Consequently, use of high-density Japanese barberry by New England cottontails may ameliorate physiological stress where eastern cottontails are prevalent. It follows that preferred patches, such as those with abundant food resources and cover, may reduce the physiological stress associated with competition and habitat degradation.

During hibernation, reduced metabolic activity enables to withstand periods of limited resources and harsh weather. Therefore, animals exhibit reduced activity and decreased feeding, which involves energy savings. Thus, a reduction in both physiological and morphological digestive capacities is expected due to the prolonged metabolic depression of hibernation, which involves phenotypic flexibility of the digestive system at several levels. We studied Dromiciops gliroides a heterothermic marsupial endemic of the temperate rainforests of southern South America, by comparing the morphology and physiology of the small intestine between summer (active) and winter (hibernation) seasons. We collected individuals near Valdivia (Chile) in winter (n = 10) and summer (n = 7) using Tomahawk traps, for extracting small intestines, which were then processed for routine histology and biochemistry analysis. We measured disaccharidase activities (sucrase and maltase) as indicators of carbohydrate digestive capacity and N-aminopeptidase activity as an indicator of protein digestion. Our result showed a 32%–44% reduction in disaccharidase activity and 60% reduction in protease activity in torpid animals. Additionally, aminopeptidase-N activity decreased along the proximal-to-distal intestinal axis. In contrast, small intestine weight and villi length remained unchanged between seasons. These findings suggest that gut remodeling occurs in response to seasonal energetic demands, with greater biochemical changes than morphological ones, possibly reflecting the high energetic costs associated with intestinal shrinking and regrowth after hibernation. We conclude that hibernation triggers gut remodeling and phenotypic flexibility in the digestive systems of D. gliroides, representing a crucial mechanism for coping with seasonal environmental conditions.

Climate change causes substantial alterations in marine environments, including salinity reduction due to glacial melting, increased rainfall, and freshwater influx, which impose stress on marine organisms. Hypoosmotic stress leads to increased production of reactive oxygen species, thereby disrupting physiological processes, such as osmoregulation, oxidative responses, and gut microbial stability, in marine fish. Here, we investigated the responses of Chromis notata, a stenohaline damselfish, exposed to hyposaline conditions (27 and 20 psu), to better understand the effects of hyposalinity on osmoregulation, oxidative stress, and gut microbiota. Plasma osmolality was measured alongside Na⁺/K⁺-ATPase (NKA) activity in gill tissue to assess osmoregulatory changes. The plasma levels of hydrogen peroxide (H₂O₂) and lipid peroxidation (LPO) levels were measured as oxidative stress markers. Furthermore, 16S rRNA sequencing and RNA sequencing were conducted to analyze gut microbial diversity and transcriptomic responses, respectively. Plasma osmolality and NKA activity markedly decreased, whereas H₂O₂ and LPO levels remarkably increased under low-salinity conditions. The gut microbiome in the low-salinity groups exhibited decreased α-diversity and increased abundance of Proteobacteria, including pathogenic genera, whereas Lactobacillus abundance was reduced. Upregulated genes were associated with immune and inflammatory responses, including complement activation, and salt transmembrane transporter activity, whereas downregulated genes were linked to the lateral plasma membrane and mitochondrial membrane. These findings suggest that hyposaline induces oxidative stress and disrupts gut microbiome stability in C. notata, thereby triggering complex physiological and molecular responses. These findings provide insights into the challenges encountered by marine fish in coastal and oceanic ecosystems due to climate change.

Serpulids are an ecologically important group of sessile suspension feeders that play a key role in benthic-pelagic coupling by filtering and transforming suspended organic matter from the water column. Temperature is one of the main abiotic factors influencing marine ectotherm physiology and metabolic responses, including serpulids and their growth, survival and distribution patterns. Thus, the present study objective was to determine thermal acclimation effects on metabolic responses of two serpulid species—Spirobranchus spinosus and S. cf. corniculatus—distributed in the temperate Northern Pacific and tropical Eastern Pacific, respectively. Both adult tubeworm species were collected from the wild and acclimated for 30 days at different temperatures, directly affecting oxygen consumption (OCR) and ammonia excretion (AER) rates of both species. However, OCR decreased for warm-water species S. cf. corniculatus at 33°C. The O:N values of both species were low at all acclimation temperatures (0.5–3.9), indicating that individuals were using protein catabolism to obtain energy. The present study not only provides basic data on these two tubeworm species metabolic responses for the first time but also contributes to understanding how their metabolism is influenced by environmental changes (e.g., ocean warming), which may help assess their capacity to cope with climate change scenarios.