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

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.

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.

Exposure to altered nighttime lighting conditions has become common in today's modern world. Light at night disrupts circadian processes that govern feeding patterns, sleep/wake cycles, and metabolic homoeostasis, increasing the risk of developing pathologies associated with cardiometabolic disease. Yet, the underlying mechanism(s) responsible for mediating the resulting physiological outcomes are not clear. Mitochondrial function may provide valuable insight into the physiological costs associated with light at night, given that mitochondria contribute to variation in metabolic performance that underpin human diseases. In this study, 36 male and female wild-derived house mice (Mus musculus) were exposed to continuous light, darkness, or a control light cycle for 6 weeks. We examined animals' bioenergetic capacity at the whole-organism and subcellular level while also measuring changes in body condition and oxidative damage. We found that 6 weeks of constant light and darkness resulted in negligible changes in all our variables of interest. We did not detect strong mitochondrial responses in the liver or skeletal muscle of either sex exposed to constant light or darkness. Furthermore, we did not detect any difference in mitochondrial volume or lipid peroxidation in the liver between treatment groups. Lastly, there was no difference in body condition between treatment groups. Our data indicate that wild-derived mice are able to circumvent challenges of an altered light environment and escape physiological consequences.

Retraction: M. B. Rhouma, M. Venditti, A. Haddadi, L. Knani, L. Chouchene, S. Boughammoura, R. J. Reiter, S. Minucci, and I. Messaoudi, "Melatonin Counteracts Cadmium-Induced Rat Testicular Toxicity via the Mechanistic Target Rapamycin (mTOR) Pathway," Journal of Experimental Zoology - A 341, no. 4 (2024): 470-482. https://doi.org/10.1002/jez.2792. The above article, published online on 04 March 2024 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editor-in-Chief, Randy Nelson and Wiley Periodicals LLC. A third party reported that a version of the DAPI/PNA/CX43 panel in Figure 4b had been copied and rotated as the Cd panel in the same figure. The third party also reported that the CM (-Pr), CMR (+ Pr), and Rapa (+ Pr) panels in Figure 6 A contained similar image elements following image manipulation and rotation. Further investigation by the publisher found the presence of similar cellular sections across the CM panel in Figure 2B and the MLT panel in Figure 3B. This investigation also found that the beta-actin bands had been duplicated between Figures 2A and 4A. The authors responded to an inquiry by the publisher, acknowledged errors in Figures 2B, 3B, 4B and 6A, and stated that these mistakes were made during figure assembly. The authors provided what were labeled as original data for Figures 2, 3, 4, and 6 and supplied corrected images. Upon review of these data, the parties determined that while errors in figure assembly could explain the errors in Figures 2, 3, and 4, the authors did not provide a satisfactory explanation for the errors in Figure 6. The retraction has been agreed to because the number of errors in image assembly, as well as evidence of image manipulation, fundamentally compromises the editors' confidence in the results presented in the article. The authors did not respond to the notice regarding the retraction.

In fish, sex determination and gonadal development are controlled by various genetic and environmental factors. In this study, experiments were conducted on the estuarine mummichog (Fundulus heteroclitus) to investigate gonadal differentiation following exposure to the synthetic estrogen, 17α-ethinylestradiol (EE₂). The period of sensitivity to EE₂ was explored by initiating the exposures at different times post fertilization. In Experiment 1, mummichog embryos were collected within 8 h of fertilization and then continually exposed to increasing concentrations of EE₂ (up to 229 ng/L) for up to 10 weeks. For controls, complete differentiation of the gonad to a testis or ovary in mummichog occurred by 3 weeks post hatch (wph) and there was an equal distribution of males and females. Exposure to all concentrations of EE₂ accelerated female gonadal differentiation as early as 1 wph and contributed to a highly female skewed sex ratio with 80% to 100% of the fish displaying ovaries. Exposure to EE₂ also resulted in a concentration-dependent increase in skeletal abnormalities and mortalities whereas larval lengths were not affected. In Experiment 2, 24 h post-hatch larvae were exposed for 5 weeks to three treatments with measured concentrations (ng/L) of 0.4 (Control), 2.5 ng/L, and 18.0 ng/L). The sex ratio was approximately 50/50 in controls and did not change with EE₂ treatment. EE₂ did not alter the proportion of oocyte stages (chromatin nucleolus, perinucleolar, cortical alveolar) but spermatogenesis was impeded as male fish had greater proportions of spermatogonia, and spermatids were only observed in controls. EE₂ treatment did not change the expression of genes in the ovary implicated in gonadal development including cyp19a1a, foxl2, gdf9, bmp15, dmrt1, and amh. In contrast, testis expression of dmrt1 was decreased and cyp19a1a, foxl2, gdf9, and amh were increased following EE₂ treatment. Overall, by the time of hatching (about 3 weeks post fertilization), sex differentiation was complete, and the sex determination mechanisms were only sensitive to EE₂ during a window of embryonic development before hatch. Early stages of testis differentiation may be more sensitive to exogenous EE₂ exposure than ovarian tissue in the mummichog.

Animals that inhabit high-risk habitats often exhibit morphological and behavioral adaptations to contend with environmental challenges. In arboreal (tree-based) habitats, such adaptations can include corrective behaviors, such as modification of body-limb angles, to avoid dislodgement by perturbations. This study evaluated shifts in limb and tail movements by three arboreal lizard species with different body configurations (variations of limb posture, body height, and tail prehensility) as they experienced simulations of unexpected arboreal perturbations. Animals were placed on a custom-built, laterally sliding perch apparatus, with trials filmed using high-speed video. Effects of different body configuration on restabilization performance were evaluated by comparing center of mass (CoM) displacement, limb angles, and tail behavior that occurred during the recovery from a sudden stoppage of perch movement. Results indicated that both body configuration and tail behavior influenced CoM displacement more than other kinematic factors. Across the three configurations that we compared, the sprawling, prehensile-tailed body configuration showed significantly larger CoM displacement compared to the upright, prehensile-tailed and the sprawling, non-prehensile-tailed configurations, especially when utilizing dynamic tail rotation as a stabilization behavior. These data indicate that a wide range of kinematic behaviors can be employed by arboreal lizards to ensure stability when subjected to potential dislodgement, but specific approaches, may contribute to superior performance for species with particular body designs, as seen with the use of dynamic tail rotation used by sprawling, prehensile-tailed species.