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Seasonal changes in glucocorticoids and their influence on the immune system are widespread in vertebrates, but whether this occurs in lesser studied taxa like turtles is unclear. The purpose of this study was to test for seasonal changes in baseline corticosterone (CORT), innate immunity, body condition, and metabolic factors (triglycerides, uric acid) in free-ranging Eastern Box Turtles ( Terrapene carolina carolina ), a species which is in decline across its range. In addition, the effect of handling and confinement on CORT levels was measured. In both years of the seasonal study, baseline CORT concentrations were significantly higher in fall than in spring, but summer CORT levels differed between the years. The annual variation in CORT levels may be related to weather conditions or associated with opportunistic mating. CORT levels of turtles confined for one hour were higher than turtles bled as quickly as possible, and unlike the seasonal study, females had higher baseline and post-stressor CORT levels than males. Baseline CORT levels were positively correlated with hemolysis titer, indicating a possible immunoenhancing effect of CORT. Triglycerides were positively correlated with body condition and were higher in females than males. The higher triglyceride level in females was likely associated with the energetic demands of reproduction and nesting. Males had a lower body condition in the fall than in both spring and summer, while females exhibited no seasonal differences in body condition. Uric acid and innate immunity measures failed to exhibit significant seasonal or sex related differences. Overall our findings of substantial annual, seasonal, and sexual variation in turtle physiology are consistent with the findings reported for other vertebrates and indicate the importance of incorporating these sources of variation into the design of future studies. [ABSTRACT FROM AUTHOR]

Abstract: Glucocorticoids (GCs) help individuals cope with changes throughout life; one such change is the seasonal transition through life-history stages. Previous research shows that many animals exhibit seasonal variation in baseline GCs and GC responses to stressors, but the effects of season on other aspects of GC regulation have been less studied. Moreover, whether elements of GC regulation covary within individuals and whether covariation changes seasonally has been not been investigated. Evolutionarily, strong linkages among GC regulatory elements is predicted to enhance system efficiency and regulation, however may reduce the plasticity necessary to ensure appropriate responses under varying conditions. Here, we measured corticosterone (CORT), the major avian GC, at baseline, after exposure to a restraint stressor, and in response to dexamethasone (to assess negative feedback capacity) in wild house sparrows (Passer domesticus) during the breeding and molting seasons. We also measured hippocampal mRNA expression of the two receptors primarily responsible for CORT regulation: the mineralocorticoid and glucocorticoid receptors (MR and GR, respectively). Consistent with previous studies, restraint-induced CORT was lower during molt than breeding, but negative-feedback was not influenced by season. Receptor gene expression was affected by season, however, as during breeding, the ratio of MR to GR expression was significantly lower than during molt. Furthermore, MR expression was negatively correlated with CORT released in response to a stressor, but only during molt. We found that individuals that most strongly up-regulated CORT in response to restraint were also most effective at reducing CORT via negative feedback; although these relationships were independent of season, they were stronger during molt. [Copyright &y& Elsevier]

Abstract: In the present study, tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine synthesis) activity was demonstrated in the ovary of the catfish to elucidate the possible physiological role of catecholamines in the gonad. The ovary is innervated by seven pairs of nerves, originating from the paired sympathetic chain lying dorsal to the posterior kidney. Ovarian TH activity showed a significant annual variation (P <0.001, one-way ANOVA), correlating with gonado-somatic index. Activity was low from December to February (resting phase), increased from March to July (recrudescent phase) and then decreased in post-spawning phase (August–November). The annual pattern was similar to that of the brain. An intraperitoneal injection of 100IU hCG/fish induced significant periovulatory changes in TH activity with the peak rise at 16h, and the activity decreased after egg-stripping (P <0.001, one-way ANOVA). Brain TH activity showed similar periovulatory changes. The results suggest that catecholamine synthesis is increased during both ovarian recrudescence and spawning of the annual reproductive cycle, implying a functional role in ovarian growth, maturation and ovulation. [Copyright &y& Elsevier]

Abstract: PPAR isotypes have been previously identified in the teleost brown trout (Salmo trutta f. fario) and their organ distribution pattern established. Being that the liver is a vital metabolic organ presenting expression of all isotypes and also knowing that estrogens/estrogen receptors seem to interact with PPARs, we hypothesized that the latter may very well change seasonally. So, we studied the expression of these receptors in the liver, along the annual reproductive cycle and in both genders. According to real-time RT-PCR, PPARα mRNA expression in females was significantly higher in May and lower in September than in other seasons. No significant variation was observed along the year in males. A significant difference between genders occurred in May, when PPARα expression was higher for females. PPARβ expression showed little variation along the reproductive cycle in females, but in males it was significantly higher in December than in the other seasons. No significant differences existed between genders. PPARγ was more expressed in February than in September and December, for females. As to males, it was more expressed in February than in all other seasons. No significant differences were observed between genders. The study proved our hypothesis that PPARs gene expression varies along the year. Moreover, PPARα expression in females followed the same annual variation pattern as peroxisome volumes and enzyme activities, and an inverse pattern relatively to the salmonid type annual plasma estradiol levels. The data agrees with the idea that PPARα is under estradiol modulation and that cross-talk between this receptor and the estrogen receptor possibly exists. [Copyright &y& Elsevier]

• Hair cortisol concentrations (HCC) positively correlated across body regions. • Individual variation explains highest proportion (44%) of variance in HCC. • HCC captures prey's seasonal and cyclical physiological responses to predation risk. • HCC is an integrative index of long-term adrenocortical activity in wild mammal. Hair cortisol concentration is increasingly used as a convenient, non-invasive, and integrative measure of physiology and health in natural populations of mammals. However, the use of this index is potentially confounded by individual variation in body region-specific differences in cortisol deposition rates. Here we examine correlations in cortisol concentrations in hair collected from the ear, shoulder, and thigh of wild snowshoe hares, Lepus americanus , as well as the influence of sex on cortisol measurements. We further evaluated this technique's ability to capture seasonal and cyclical patterns of snowshoe hare glucocorticoid secretion from 2013 to 2015 in the southwestern Yukon (Canada). We found positive correlations (R2 = 0.20–0.32) in all pairwise comparisons among body regions, and differences among individuals accounted for the greatest proportion of variance (47.3%) in measurements. From 2013 to 2015 the hares' primary predator – Canada lynx – approximately doubled in population abundance. We found a significant increase in hare hair cortisol concentrations across this time period. Cortisol indices were higher in summer than winter pelage, reflecting predicted physiological responses to seasonal variation in food availability and individual risk. Variation in hair cortisol concentrations was more similar to long-term (weeks-months) integrative indices of adrenal capacity than point samples of fecal glucocorticoid metabolite concentrations. Overall, we find that hair cortisol analysis is a simple and useful tool for estimations of population-level stress physiology in wild mammals, and sampling of core body regions with consistent moulting patterns produced the most robust results in this species. [ABSTRACT FROM AUTHOR]