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Personalities, i.e. consistent individual differences in behaviour, have been found in many animal populations. However, the reasons why personalities emerge, how they persist and the consequences they have in a changing environment are poorly understood. Factors influencing personalities include genetic background, prenatal (e.g. hormonal) and postnatal (e.g. environmental) conditions, and the strength of these factors can affect the consistency of personalities over time, and hence their flexibility in a changing environment. In birds, for example, hormones in eggs deposited by mothers can modulate aggressiveness of offspring and environmentally induced nutrition deficits in offspring can reduce neophobia later in life. Hence, investigating the fitness consequences of personalities requires the integration of physiological, behavioural and survival measures. We used the opportunity of a reintroduction project of grey partridge, Perdix perdix , to experimentally explore how multiple pre- and postnatal factors including measures of the hormone corticosterone were related to three behavioural traits. Then, we investigated whether the behaviours were repeatable and related to survival after release into the wild. Grey partridges showed distinct personalities affected by multiple pre- and postnatal factors. Proactive birds had low baseline levels of circulating corticosterone and survived longer after release into the wild compared to reactive and passive personalities. Consequently, the number of survivors after 6 months was substantially higher for proactive than for reactive and passive birds. Integrating data on behaviour, physiology and survival thus allows the investigation of the complex interplay of personality and fitness in a changing environment. • Animals have personalities but what are their fitness consequences in the wild? • We explored factors relating to behaviour of grey partridge bound for release. • Genetic, physiological, individual and social factors affected personalities. • After release, bold birds survived longer than passive and shy individuals. • Integration data on behaviour and physiology can support reintroduction outcome. [ABSTRACT FROM AUTHOR]

Urban areas are characterised by the presence of sensory pollutants, such as anthropogenic noise and artificial light at night (ALAN). Animals can quickly adapt to novel environmental conditions by adjusting their behaviour, which is proximately regulated by endocrine systems. While endocrine responses to sensory pollution have been widely reported, this has not often been linked to changes in behaviour, hampering the understanding of adaptiveness of endocrine responses. Our aim was, therefore, to investigate the effects of urbanisation, specifically urban noise and light pollution, on hormone levels in male urban and forest túngara frogs (Engystomops pustulosus), a species with reported population divergence in behaviour in response to urbanisation. We quantified testosterone and corticosterone release rates in the field and in the lab before and after exposure to urban noise and/or light. We show that urban and forest frogs differ in their endocrine phenotypes under field as well as lab conditions. Moreover, in urban frogs exposure to urban noise and light led, respectively, to an increase in testosterone and decrease in corticosterone, whereas in forest frogs sensory pollutants did not elicit any endocrine response. Our results show that urbanisation, specifically noise and light pollution, can modulate hormone levels in urban and forest populations differentially. The observed endocrine responses are consistent with the observed behavioural changes in urban frogs, providing a proximate explanation for the presumably adaptive behavioural changes in response to urbanisation. • In the field, urban frogs have lower corticosterone levels than forest frogs. • Under lab conditions, urban and forest endocrine phenotypes do not converge. • Sensory pollution increases testosterone and lowers corticosterone in urban frogs. • Hormone responses in urban frogs are associated with adaptive behavioural changes. [ABSTRACT FROM AUTHOR]

Highlights • Traffic noise affects nestling tree swallows through direct, not maternal, effects. • Nestling baseline and stress-induced corticosterone increased with noise exposure. • Nestling body condition was negatively related to noise exposure. • Nestlings from noisier nests had greater telomere attrition during development. • Short-term noise exposure may have long-term consequences for tree swallows. Abstract Anthropogenic impacts, such as noise pollution from transportation networks, can serve as stressors to some wildlife species. For example, increased exposure to traffic noise has been found to alter baseline and stress-induced corticosterone levels, reduce body condition and reproductive success, and increase telomere attrition in free-living birds. However, it remains unknown if alterations in nestling phenotype are due to direct or indirect effects of noise exposure. For example, indirect (maternal) effects of noise may occur if altered baseline and stress-induced corticosterone in mothers results in differential deposition of yolk steroids or other components in eggs. Noise exposure may also alter nestling corticosterone levels directly, given that nestlings cannot escape the nest during development. Here, we examined maternal versus direct effects of traffic noise exposure on baseline and stress-induced corticosterone levels, and body condition (as measured by size-corrected mass) in nestling tree swallows (Tachycineta bicolor). We used a two-way factorial design and partially cross-fostered eggs between nests exposed to differing levels (i.e. amplitudes) of traffic noise. For nestlings that were not cross-fostered, we also investigated the effects of traffic noise on telomere dynamics. Our results show a positive relationship between nestling baseline and stress-induced corticosterone and nestling noise exposure, but not maternal noise exposure. While we did not find a relationship between noise and body condition in nestlings, nestling baseline corticosterone was negatively associated with body condition. We also found greater telomere attrition for nestlings from nests with greater traffic noise amplitudes. These results suggest that direct, rather than maternal, effects result in potentially long-lasting consequences of noise exposure. Reduced nestling body condition and increased telomere attrition have been shown to reduce post-fledging survival in this species. Given that human transportation networks continue to expand, strategies to mitigate noise exposure on wildlife during critical periods (i.e. breeding) may be needed to maintain local population health in free-living passerines, such as tree swallows. [ABSTRACT FROM AUTHOR]

Highlights • Animals engage in social interactions by modifying their behaviour and physiology. • The effects of urbanisation on social strategies remain unexplored in reptiles. • Hormonal and behavioural differences were driven by urbanisation in lizards. • Lizards showed alternative coping styles across the urban-rural habitats. Abstract Animals engage in social interactions with changes in their behaviour and physiology. Environmental challenges, however, can influence social interactions by adding additional stressors. Here, we investigated the effects of urbanisation on the behaviour and hormonal responses of a tropical lizard species, Psammophilus dorsalis , during social interactions. We recorded behaviour of males from suburban and rural areas during controlled encounters with other males and females. We then measured corticosterone and testosterone levels of individuals at 10 min intervals, from immediately after the social encounter to 30 min later and then at 120 min after the interaction period. We found that differences in social behaviours and subsequent hormone levels were largely driven by habitat, and not social context. Overall, we found that fewer suburban males showed behavioural displays compared to rural males during social encounters. For those that displayed, intensity of aggression was similar across populations, but courtship intensity was lower for suburban males compared to rural males. Suburban males also had significantly elevated levels of corticosterone both under control conditions (no social encounter) and following intra- and intersexual interactions, while rural males retained low levels of corticosterone across contexts. Social interactions were associated with an increase in testosterone levels in all males, but only rural males maintained elevated levels for up to 120 min after interactions with females. Thus, lizards from these suburban and rural populations showed key differences in responsiveness to and recovery from social challenges, a pattern that suggests alternative coping styles ('proactive' vs. 'reactive'). These differences in social coping styles could influence consequences of sexual selection in an urbanised world. [ABSTRACT FROM AUTHOR]

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]

Steroid hormone assessment using non-invasive sample collection techniques can reveal the reproductive status of aquatic mammals and the physiological mechanisms by which they respond to changes in their environment. A portion of the eastern North Pacific blue whale ( Balaenoptera musculus ) population that seasonally visits the Gulf of California, Mexico has been monitored using photo-identified individuals for over 30 years. The whales use the area in winter-early spring for nursing their calves and feeding and it therefore is well suited for fecal sample collection. Using radioimmunoassays in 25 fecal samples collected between 2009 and 2012 to determine reproductive state and stress, we validated three steroid hormones (progesterone, corticosterone and cortisol) in adult female blue whales. Females that were categorized as pregnant had higher mean fecal progesterone metabolite concentrations (1292.6  ±  415.6 ng · g - 1 ) than resting and lactating females (14.0  ±  3.7 ng · g - 1 ; 23.0  ±  5.4 ng · g - 1 , respectively). Females classified as pregnant also had higher concentrations of corticosterone metabolites (37.5  ±  9.9 ng · g - 1 ) than resting and lactating females (17.4  ±  2.0 ng · g - 1 ; 16.8  ±  2.8 ng · g - 1 , respectively). In contrast, cortisol metabolite concentrations showed high variability between groups and no significant relationship to reproductive state. We successfully determined preliminary baseline parameters of key steroid hormones by reproductive state in adult female blue whales. The presence of pregnant or with luteal activity and known lactating females confirms that the Gulf of California is an important winter-spring area for the reproductive phase of these blue whales. The baseline corticosterone levels we are developing will be useful for assessing the impact of the increasing coastal development and whale-watching activities on the whales in the Gulf of California. [ABSTRACT FROM AUTHOR]

Tryptophan (Trp) has been associated with the regulation of several behavioral and physiological processes, through stimulation of serotonergic activity. Tryptophan utilization at the metabolic level is influenced by the competitive carrier system it shares with large neutral amino acids (LNAA). This study was carried out using meat-type chicken as a model, to investigate the dose response effects of Trp/LNAA on fear response (tonic immobility; TI) and hormonal responses, including corticosterone (CORT), serotonin (5-HT), triiodothyronine (T 3 ) and thyroxine (T 4 ). A total of 12 cages (48 birds) were assigned to each of the six experimental groups at 29–42 days of age. Experimental diets were formulated to have incremental levels of Trp/LNAA (0.025, 0.030, 0.035, 0.040, 0.045, and 0.050). The results revealed that, Trp/NAA had no significant effect on growth performance and TI of the birds. However, elevation of Trp/LNAA was concurred with a linear reduction in CORT ( P  < .0001, r 2  = 0.819) and linear increases in 5-HT ( P  < .0001, r 2  = 0.945), T 3 ( P  = .0003, r 2  = 0.403) and T 4 ( P  < .0001, r 2  = 0.937) levels. In conclusion, the results from the current study demonstrated that, although incremental levels of Trp/LNAA did not affect bird growth performance or fearfulness, it increased 5-HT, T 3 and T 4, and decreased CORT levels in a linear dose-dependent manner. Manipulation of Trp feeding levels could be applied to manage stressful conditions in birds. [ABSTRACT FROM AUTHOR]

Research into stress physiology of mysticete whales has been hampered by difficulty in obtaining repeated physiological samples from individuals over time. We investigated whether multi-year longitudinal records of glucocorticoids can be reconstructed from serial sampling along full-length baleen plates (representing ∼10 years of baleen growth), using baleen recovered from two female North Atlantic right whales ( Eubalaena glacialis ) of known reproductive history. Cortisol and corticosterone were quantified with immunoassay of subsamples taken every 4 cm (representing ∼60 d time intervals) along a full-length baleen plate from each female. In both whales, corticosterone was significantly elevated during known pregnancies (inferred from calf sightings and necropsy data) as compared to intercalving intervals; cortisol was significantly elevated during pregnancies in one female but not the other. Within intercalving intervals, corticosterone was significantly elevated during the first year (lactation year) and/or the second year (post-lactation year) as compared to later years of the intercalving interval, while cortisol showed more variable patterns. Cortisol occasionally showed brief high elevations (“spikes”) not paralleled by corticosterone, suggesting that the two glucocorticoids might be differentially responsive to certain stressors. Generally, immunoreactive corticosterone was present in higher concentration in baleen than immunoreactive cortisol; corticosterone:cortisol ratio was usually >4 and was highly variable in both individuals. Further investigation of baleen cortisol and corticosterone profiles could prove fruitful for elucidating long-term, multi-year patterns in stress physiology of large whales, determined retrospectively from stranded or archived specimens. [ABSTRACT FROM AUTHOR]

Interleukin-1 beta (IL-1β) is a cytokine linking the neuroendocrine system and metabolic homeostasis. We have previously demonstrated the relevance of IL-1β for maintaining the pituitary ACTH-producing cells by immuno-blocking its effects in pituitary cultures. However, the morphological characteristics and the intimate relationship of the pituitary cells expressing IL-1β and ACTH remain unknown. For determining pituitary variations of immunoreactivity for IL-1β and its relation with ACTH-positive cells under stress situations, we performed an immunohistochemical analysis of the expression of IL-1β and ACTH in the pituitary gland of adult rats, in the absence or presence of corticosterone, by establishing different groups: untreated, sham-operated, and bilaterally adrenalectomized animals. In the rats subjected to surgery, the glucocorticoid was administered on the same day of the intervention and on the third day post-surgery. Interestingly, it was observed that IL-1β was located in the pituitary endothelial cells at the hypophyseal portal vessels, regardless of the treatment schedule. When comparing the pituitary immunoreactive surface to IL-1β expression without corticosterone, adrenalectomized animals displayed a significantly greater area than the sham-operated animals. Corticosterone significantly inhibited the effect of adrenalectomy depending on the time interval it was administered. By in situ hybridization, IL-1β mRNA expression was also correlated with immnunocytochemical expression of pituitary IL-1β. Our results demonstrate that IL-1β is a constitutive element in endothelial portal pituitary vessels and under stress experimental conditions IL-1β increases its expression and its relation with ACTH-positive cells, suggesting that IL-1β could participate in an autocrine-paracrine fashion thereby modulating the pituitary population of ACTH-positive cells. [ABSTRACT FROM AUTHOR]

Studies using wild animals in laboratory-based research require bringing wild-captured organisms into a novel setting, which can have long-lasting impacts on physiology and behavior. In several species, captivity stimulates stress hormone production and can alter immune function. Despite this, there is little consensus on how captivity influences stress hormone regulation, or if captivity-induced changes in stress hormone production and regulation mediate changes in immune function. In this study, we investigate the influence of captivity on the physiology of a wild bird commonly-used in laboratory-based research, the house sparrow ( Passer domesticus ). We tested how captivity influences stress endocrinology, immune responses, and organ mass, and also investigated if the production or regulation of corticosterone, the main stress hormone in birds, correlated with changes in immunity. We found that baseline corticosterone concentrations and maximum capacity of the adrenals to secrete corticosterone increase following captivity and remain elevated after 9 weeks of captivity. A measure of innate immune function, the bactericidal ability of plasma, also increased with time spent in captivity. Wound healing was also influenced by time spent in captivity, with birds taking almost 2 days longer to heal if they were wounded after 3 weeks in captivity when compared with birds that were wounded immediately upon capture. Additionally, captivity caused notable reductions in spleen and liver mass. Together, these results imply that captivity can have long-lasting effects on house sparrow corticosterone release and immune function, and suggest that even after 9 weeks house sparrows do not acclimate physiologically to life in captivity. [ABSTRACT FROM AUTHOR]

Corticosteroids are critical for normal development and for mediating effects of stress during development in all vertebrates. Even though gene knockout studies in mouse and zebrafish have identified a number of developmental roles of corticosteroids and their receptors, the numerous pleiotropic actions of these hormones affecting various aspects of development are understudied. For the most part, neither the endogenous hormone(s) nor their receptor(s) regulating developmental processes during natural development have been determined. Here, we address this issue by elucidating the endogenous regulation of the transcription factor Krüppel-like factor 9 ( klf9 ) across tissues during development by corticosteroid hormones (aldosterone and corticosterone) and their nuclear receptors (type-I and type-II receptors). First, we measured the developmental expression profiles of klf9 and type-I and type-II corticosteroid receptors in key target tissues, brain, lungs, and tail, during larval and metamorphic stages in Xenopus tropicalis . We also studied the corticosteroid regulation of klf9 in these tissues in-vivo using exogenous hormone treatments and receptor antagonists. Klf9 and the corticosteroid receptors were expressed in each tissue and significantly increased in expression reaching a peak at metamorphic climax, except for the type-II receptor in brain and tail whose expression did not change significantly across stages. Both corticosteroid hormones induced klf9 in each tissue , although aldosterone required a five times higher dose than corticosterone to cause a significant induction. The upregulation of klf9 by both corticosteroids was completely blocked by the use of the type-II receptor antagonist RU486 and not the type-I receptor antagonist spironolactone. These results are consistent with previous in-vitro studies and indicate for the first time in-vivo that corticosteroid regulation of klf9 occurs exclusively via corticosterone and type-II receptor interaction across tissues. [ABSTRACT FROM AUTHOR]

The secretory patterns of testosterone (T), androstenedione (A4), dehydroepiandrosterone (DHEA), cortisol (C), and corticosterone (Co) were characterized throughout 28 normal pregnancies until two-months post-partum in eleven killer whales. Effects of fetal sex, dam parity or age, and season were evaluated across either day post-conception (DPC), stage of pregnancy (PRE, EARLY, MID, LATE, POST) or indexed month post-conception (IMPC) using a mixed model linear regression with animal ID and pregnancy number as the random variables. Across DPC, DHEA, A4 and T concentrations were affected ( P < 0.05) by season, with highest concentrations during spring (DHEA, A4, & T) and summer (A4) as compared to the fall. A significant effect of parity on androgen production was observed only for DHEA, with multiparous females having higher ( P = 0.01) concentrations than nulliparous females. All three androgens significantly increased with each successive pregnancy stage and IMPC with peak concentrations occurring during IMPC 10 (DHEA), 13 (A4) and 14 (T), respectively. Cortisol was affected by season ( P = 0.03) with highest concentrations being detected during the months of fall, while Co was only affected by parity ( P = 0.003) with significant increases observed for primiparous females as compared to nulliparous females. Cortisol and Co concentrations peaked ( P < 0.05) during IMPC 17 (i.e., the month prior to parturition). The C to Co ratio during pregnancy was 7.4 to 1, indicating that cortisol is the major circulating glucocorticoid studied to date in pregnant killer whales. The significant increase in concentrations of maternal androgens throughout pregnancy, which were unrelated to fetal sex, indicates that they play an important role during killer whale fetal development. [ABSTRACT FROM AUTHOR]

Sterol 27-hydroxylase (CYP27A1) plays an important role in cholesterol homeostasis by degrading cholesterol to bile acids. Betaine can alleviate high-fat diet-induced hepatic cholesterol accumulation and maternal betaine treatment programs the hepatic expression of CYP27A1 in offspring. Excessive corticosterone (CORT) exposure causes hepatic cholesterol deposition in chickens, yet it remains unknown whether prenatal betaine modulates CORT-induced cholesterol accumulation in chicken liver later in life and whether it involves epigenetic gene regulation of CYP27A1 . In this study, fertilized eggs were injected with saline or betaine at 2.5 mg/egg before incubation, and the hatchlings were raised under the same condition till 56 days of age followed by 7 days of subcutaneous CORT injection. Plasma concentrations of total cholesterol (Tch), HDL- and LDL-cholesterol were significantly increased ( P < 0.05), after CORT challenge, in both control and betaine groups. However, prenatal betaine exposure prevented CORT-induced increase ( P < 0.05) in hepatic Tch content. Hepatic expression of cholesterol biosynthesis genes and ACAT1 protein that esterifies cholesterol for storage, were activated in both control and betaine groups upon CORT challenge. However, betaine-treated chickens were protected from CORT-induced repression ( P < 0.05) in LXR and CYP27A1 expression in the liver. CORT-induced down-regulation of LXR and CYP27A1 coincided with significantly increased ( P < 0.05) CpG methylation on their promoters, which was significantly ameliorated in betaine-treated chickens. These results suggest that in ovo betaine injection alleviates CORT-induced hepatic cholesterol deposition most probably through epigenetic regulation of CYP27A1 and LXR genes in juvenile chickens. [ABSTRACT FROM AUTHOR]

Marsupial research, conservation, and management can benefit greatly from knowledge about glucocorticoid (GC) secretion patterns because GCs influence numerous aspects of physiology and play a crucial role in regulating an animal’s response to stressors. Faecal glucocorticoid metabolites (FGM) offer a non-invasive tool for tracking changes in GCs over time. To date, there are relatively few validated assays for marsupials compared with other taxa, and those that have been published generally test only one assay. However, different assays can yield very different signals of adrenal activity. The goal of this study was to compare the performance of five different enzyme immunoassays (EIAs) for monitoring adrenocortical activity via FGM in 13 marsupial species. We monitored FGM response to two types of events: biological stressors (e.g., transport, novel environment) and pharmacological stimulation (ACTH injection). For each individual animal and assay, FGM peaks were identified using the iterative baseline approach. Performance of the EIAs for each species was evaluated by determining (1) the percent of individuals with a detectable peak 0.125–4.5 days post-event, and (2) the biological sensitivity of the assay as measured by strength of the post-event response relative to baseline variability ( Z -score). Assays were defined as successful if they detected a peak in at least 50% of the individuals and the mean species response had a Z ⩾ 2. By this criterion, at least one assay was successful in 10 of the 13 species, but the best-performing assay varied among species, even those species that were closely related. Furthermore, the ability to confidently assess assay performance was influenced by the experimental protocols used. We discuss the implications of our findings for biological validation studies. [ABSTRACT FROM AUTHOR]

Stress is believed to be an important factor mediating animal behavior. Here we explore the relationship between concentrations of a stress hormone and defensive behavior of a snake. The cottonmouth ( Agkistrodon piscivorus ) is an abundant, large-bodied pitviper that is well known for its intense defensive behaviors. The defensive behaviors and hormonal ecology of cottonmouths have been studied extensively, but the interaction between these is not well understood. We conducted field trials, recording the snake’s behavior and obtaining blood samples to quantify plasma CORT concentrations, both upon first encountering a snake and after a 30 min standardized confinement stressor. We found that snakes with elevated levels of baseline CORT at first encounter were more likely to strike than exhibit a threat display when approached in the field. However, this behavior was not related to the magnitude of the snake’s CORT increase following confinement, suggesting that more stress-prone snakes are not more defensive. Post-stressor antipredator behavior was also not related to any of our CORT measures. This study suggests that baseline CORT levels can be important correlates of defensive behavior. If this is a causative relationship, environmental challenges that increase baseline stress levels of populations may elevate cottonmouth defensive behavior. This would increase costs associated with defensive behavior (energetic, lost opportunity, etc.) and have important consequences for animal-human interactions. [ABSTRACT FROM AUTHOR]

Circulating glucocorticoids (GCs) are powerful regulators of immunity. Stress-induced GC secretion by the adrenal glands initially enhances and later suppresses the immune response. GC targets include lymphocytes of the adaptive immune system, which are well known for their sensitivity to GCs. Less appreciated, however, is that GCs are locally produced in lymphoid organs, such as the thymus, where GCs play a critical role in selection of the T cell antigen receptor (TCR) repertoire. Here, we review the roles of systemic and locally-produced GCs in T lymphocyte development, which has been studied primarily in laboratory mice. By antagonizing TCR signaling in developing T cells, thymus-derived GCs promote selection of T cells with stronger TCR signaling. This results in increased T cell-mediated immune responses to a range of antigens. We then compare local and systemic GC patterns in mice to those in several bird species. Taken together, these studies suggest that a combination of adrenal and lymphoid GC production might function to adaptively regulate lymphocyte development and selection, and thus antigen-specific immune reactivity, to optimize survival under different environmental conditions. Future studies should examine how lymphoid GC patterns vary across other vertebrates, how GCs function in B lymphocyte development in the bone marrow, spleen, and the avian bursa of Fabricius, and whether GCs adaptively program immunity in free-living animals. [ABSTRACT FROM AUTHOR]

Exposure to stressors can affect an organism's physiology and behavior as well as that of its descendants (e.g. through maternal effects, epigenetics, and/or selection). We examined the relative influence of early life vs. transgenerational stress exposure on adult stress physiology in a species that has populations with and without ancestral exposure to an invasive predator. We raised offspring of eastern fence lizards ( Sceloporus undulatus ) from sites historically invaded (high stress) or uninvaded (low stress) by predatory fire ants ( Solenopsis invicta ) and determined how this different transgenerational exposure to stress interacted with the effects of early life stress exposure to influence the physiological stress response in adulthood. Offspring from these high- and low-stress populations were exposed weekly to either sub-lethal attack by fire ants (an ecologically relevant stressor), topical treatment with a physiologically-appropriate dose of the stress-relevant hormone, corticosterone (CORT), or a control treatment from 2 to 43 weeks of age. Several months after treatments ended, we quantified plasma CORT concentrations at baseline and following restraint, exposure to fire ants, and adrenocorticotropic hormone (ACTH) injection. Exposure to fire ants or CORT during early life did not affect lizard stress physiology in adulthood. However, offspring of lizards from populations that had experienced multiple generations of fire ant-invasion exhibited more robust adult CORT responses to restraint and ACTH-injection compared to offspring from uninvaded populations. Together, these results indicate that transgenerational stress history may be at least as important, if not more important, than early life stress in affecting adult physiological stress responses. [ABSTRACT FROM AUTHOR]

Climate change is causing rapid shifts in temperature while also increasing the frequency, duration, and intensity of extreme weather. In the northern hemisphere, the spring of 2013 was characterized as extreme due to record high snow cover and low temperatures. Studies that describe the effects of extreme weather on phenology across taxa are limited while morphological and physiological responses remain poorly understood. Stress physiology, as measured through baseline and stress-induced concentrations of cortisol or corticosterone, has often been studied to understand how organisms respond to environmental stressors. We compared body condition and stress physiology of two long-distance migrants breeding in low arctic Alaska – the white-crowned sparrow ( Zonotrichia leucophrys ) and Lapland longspur ( Calcarius lapponicus ) – in 2013, an extreme weather year, with three more typical years (2011, 2012, and 2014). The extended snow cover in spring 2013 caused measureable changes in phenology, body condition and physiology. Arrival timing for both species was delayed 4–5 days compared to the other three years. Lapland longspurs had reduced fat stores, pectoralis muscle profiles, body mass, and hematocrit levels, while stress-induced concentrations of corticosterone were increased. Similarly, white-crowned sparrows had reduced pectoralis muscle profiles and hematocrit levels, but in contrast to Lapland longspurs, had elevated fat stores and no difference in mass or stress physiology relative to other study years. An understanding of physiological mechanisms that regulate coping strategies is of critical importance for predicting how species will respond to the occurrence of extreme events in the future due to global climate change. [ABSTRACT FROM AUTHOR]

Studies of social stress in adult mice have revealed two distinct defeat-responsive behavioral phenotypes; “susceptible” and “resistant,” characterized by social avoidance and social interaction, respectively. Typically, these phenotypes are observed at least 1 day after the last defeat in adults, but may extend up to 30 days later. The current study examined the impact of peripubertal social defeat on immediate (1 day) and adult (30 day) social stress phenotypes and neuroendocrine function in male C57BL/6 mice. Initially, peripubertal (P32) mice were resistant to social defeat. When the same mice were tested for social interaction again as adults (P62), two phenotypes emerged; a group of mice were characterized as susceptible evidenced by significantly lower social interaction, whereas the remaining mice exhibited normal social interaction, characteristic of resistance. A repeated analysis of corticosterone revealed that the adult (P62) resistant mice had elevated corticosterone following the social interaction test as juveniles. This was when all mice, regardless of adult phenotype, displayed equivalent levels of social interaction. Peripubertal corticosterone was positively correlated with adult social interaction levels in defeated mice, suggesting early life stress responsiveness impacts adult social behavior. In addition, adult corticotropin-releasing factor (CRF) mRNA in the paraventricular nucleus of the hypothalamus (PVN) was elevated in all defeated mice, but there were no differences in CRF mRNA expression between the phenotypes. Thus, there is a delayed appearance of social stress-responsive phenotypes suggesting that early life stress exposure, combined with the resultant physiological responses, may interact with pubertal development to influence adult social behavior. [ABSTRACT FROM AUTHOR]

During spring, increasing daylengths stimulate gonadal development in migratory birds. However, late-stage reproductive development is typically postponed until migration has been completed. The hypothalamic–pituitary–adrenal (HPA) axis regulates the secretion of glucocorticoids, which have been associated with pre-migratory hyperphagia and fattening. The HPA-axis is also known to suppress the hypothalamic–pituitary–gonadal (HPG) axis, suggesting the possibility that final transition into the breeding life history stage may be slowed by glucocorticoids. We hypothesized that greater HPA-axis activity in individuals preparing for migration may foster preparation for migration while simultaneously acting as a “brake” on the development of the HPG-axis. To test this hypothesis, we sampled baseline corticosterone (CORT), stress-induced CORT, and negative feedback efficacy of Dark-eyed Juncos ( Junco hyemalis ) in an overwintering population that included both migratory ( J.h. hyemalis ) and resident ( J.h. carolinensis ) individuals. We predicted that compared to residents, migrants would have higher baseline CORT, higher stress-induced CORT, and weaker negative feedback. Juncos were sampled in western Virginia in early March, which was about 2–4 wk before migratory departure for migrants and 4–5 wk before first clutch initiation for residents. Contrary to our predictions, we found that migrants had lower baseline and stress-induced CORT and similar negative feedback efficacy compared with residents, which suggests that delayed breeding in migrants is influenced by other physiological mechanisms. Our findings also suggest that baseline CORT is not elevated during pre-migratory fattening, as migrants had lower baseline CORT and were fatter than residents. [ABSTRACT FROM AUTHOR]

Anthropogenic noise can have important physiological and behavioral effects on wild animals. For example, urban noise could lead to a state of chronic stress and could alter the development of the hypothalamus–pituitary–adrenal (HPA) axis. Supporting this hypothesis, several studies have found that human disturbance is associated with increased circulating corticosterone (CORT) levels. However, it remains unclear whether increased CORT levels are the result of anthropogenic noise or other anthropogenic factors. Here, we experimentally tested the impact of urban noise on the CORT stress response in an urban exploiter (the house sparrow, Passer domesticus ) by exposing chicks to a traffic noise (‘disturbed chicks’) or not (‘control chicks’). If noise exposure has a negative impact on developing chicks, we predicted that (1) disturbed chicks will grow slower, will be in poorer condition, and will have a lower fledging probability than controls; (2) disturbed chicks will have higher baseline CORT levels than control; (3) the CORT stress response will be affected by this noise exposure. Contrary to these predictions, we found no effect of our experiment on growth, body condition, and fledging success, suggesting that house sparrow chicks were not negatively affected by this noise exposure. Moreover, we did not find any effect of noise exposure on either baseline CORT levels or the CORT stress response of chicks. This suggests not only that house sparrow chicks did not perceive this noise as stressful, but also that the development of the HPA axis was not affected by such noise exposure. Our study suggests that, contrary to urban avoiders, urban exploiters might be relatively insensitive to urban noise during their development. Further comparative studies are now needed to understand whether such insensitivity to anthropogenic noise is a consistent phenomenon in urban exploiters and whether this is a major requirement of an urban way of life. [ABSTRACT FROM AUTHOR]

Songbirds exhibit significant adult neuroplasticity that, together with other neural specializations, makes them an important model system for neurobiological studies. A large body of work also points to the songbird brain as a significant target of steroid hormones, including corticosterone (CORT), the primary avian glucocorticoid. Whereas CORT positively signals the brain for many functions, excess CORT may interfere with natural neuroplasticity. Consequently, mechanisms may exist to locally regulate CORT levels in brain to ensure optimal concentrations. However, most studies in songbirds measure plasma CORT as a proxy for levels at target tissues. In this paper, we review literature concerning circulating CORT and its effects on behavior in songbirds, and discuss recent work suggesting that brain CORT levels are regulated independently of changes in adrenal secretion. We review possible mechanisms for CORT regulation in the avian brain, including corticosteroid-binding globulins, p-glycoprotein activity in the blood–brain barrier and CORT metabolism by the 11ß hydroxysteroid dehydrogenases. Data supporting a role for CORT regulation within the songbird brain have only recently begun to emerge, suggesting that this is an avenue for important future research. [ABSTRACT FROM AUTHOR]

Physiological resonance – where the physiological state of a subject generates the same state in a perceiver – has been proposed as a proximate mechanism facilitating pro-social behaviours. While mainly described in mammals, state matching in physiology and behaviour could be a phylogenetically shared trait among social vertebrates. Birds show complex social lives and cognitive abilities, and their monogamous pair-bond is a highly coordinated partnership, therefore we hypothesised that birds express state matching between mates. We show that calls of male zebra finches Taeniopygia guttata produced during corticosterone treatment (after oral administration of exogenous corticosterone and during visual separation from the partner) provoke both an increase in corticosterone concentrations and behavioural changes in their female partner compared to control calls (regular calls emitted by the same male during visual separation from the partner only), whereas calls produced during corticosterone treatment by unfamiliar males have no such effect. Irrespective of the caller status (mate/non-mate), calls' acoustic properties were predictive of female corticosterone concentration after playback, but the identity of mate calls was necessary to fully explain female responses. Female responses were unlikely due to a failure of the call-based mate recognition system: in a discrimination task, females perceive calls produced during corticosterone treatment as being more similar to the control calls of the same male than to control calls of other males, even after taking acoustical differences into account. These results constitute the first evidence of physiological resonance solely on acoustic cues in birds, and support the presence of empathic processes. [ABSTRACT FROM AUTHOR]

Stress induces cognitive impairments, which are likely related to the damaged dendritic morphology in the brain. Treatments for stress-induced impairments remain limited because the molecules and pathways underlying these impairments are unknown. Therefore, the aim of this study was to find the potential molecules and pathways related to damage of the dendritic morphology induced by stress. To do this, we detected gene expression, constructed a protein–protein interaction (PPI) network, and analyzed the molecular pathways in the brains of mice exposed to 5-h multimodal stress. The results showed that stress increased plasma corticosterone concentration, decreased cognitive function, damaged dendritic morphologies, and altered APBB1 , CLSTN1 , KCNA4 , NOTCH3 , PLAU , RPS6KA1 , SYP , TGFB1 , KCNA1 , NTRK3 , and SNCA expression in the brains of mice. Further analyses found that the abnormal expressions of CLSTN1 , PLAU , NOTCH3 , and TGFB1 induced by stress were related to alterations in the dendritic morphology. These four genes demonstrated interactions with 55 other genes, and configured a closed PPI network. Molecular pathway analysis use the Database for Annotation, Visualization, and Integrated Discovery (DAVID), specifically the gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG), each identified three pathways that were significantly enriched in the gene list of the PPI network, with genes belonging to the Notch and transforming growth factor-beta (TGF-B) signaling pathways being the most enriched. Our results suggest that TGFB1 , PLAU , NOTCH3 , and CLSTN1 may be related to the alterations in dendritic morphology induced by stress, and imply that the Notch and TGF-B signaling pathways may be involved. [ABSTRACT FROM AUTHOR]

Both maternal exposure to stressors and exposure of offspring to stressors during early life can have lifelong effects on the physiology and behavior of offspring. Stress exposure can permanently shape an individual’s phenotype by influencing the development of the hypothalamic–pituitary–adrenal (HPA) axis, which is responsible for the production and regulation of glucocorticoids such as corticosterone (CORT). In this study we used captive zebra finches ( Taeniopygia guttata ) to examine the effects of matching and mismatching maternal and early post-natal exposure to one of two types of antigens or a control on HPA axis reactivity in adult offspring. Prior to breeding, adult females were injected with lipopolysaccharide (LPS), keyhole limpet hemocyanin (KLH) or a control. Offspring of females in each of the three treatments were themselves exposed to LPS, KLH or a control injection at 5 and 28 days post-hatch. When offspring were at least 18 months of age, standardized capture and restraint stress tests were conducted to determine the impact of the treatments on adult stress responsiveness. We found significant interaction effects between maternal and offspring treatments on stress-induced CORT levels, and evidence in support of the environment matching hypothesis for KLH-treated birds, not LPS-treated birds. KLH-treated offspring of KLH-treated mothers exhibited reduced stress-induced CORT levels, whereas LPS-treated or control offspring of KLH-treated mothers exhibited elevated stress-induced CORT levels. Although the treatment effects on baseline CORT were non-significant, the overall pattern was similar to the effects observed on stress-induced CORT levels. Our results highlight the complex nature of HPA axis programming, and to our knowledge, provide the first evidence that a match or mismatch between pre and post-natal antigen exposure can have life-long consequences for HPA axis function. [ABSTRACT FROM AUTHOR]

In the oil sands of Alberta, Canada, toxicology research has largely neglected the effects of air contaminants on biota. Captive Japanese quail (Coturnix c. japonica) and American kestrels (Falco sparverius) were exposed to mixtures of volatile organic compounds and oxidizing agents (benzene, toluene, NO2 and SO2) in a whole-body inhalation chamber, to test for toxicological responses. Hepatic biotransformation measured through 7-ethoxyresorufin-O-dealkylase (EROD) tended to be increased in exposed kestrels ( p =0.06) but not in quail ( p =0.15). Plasma corticosterone was increased in the low dose group for quail on the final day of exposure (p =0.0001), and midway through the exposure period in exposed kestrels ( p =0.04). For both species, there was no alteration of T and B-cell responses, immune organ mass, or histology of immune organs ( p >0.05). This study provides baseline information valuable to complement toxicology studies and provides a better understanding of potential health effects on wild avifauna. [ABSTRACT FROM AUTHOR]

Glucocorticoid (GC) hormones are important mediators of responses to environmental conditions. Accordingly, differences in GC physiology may contribute to interspecific variation in response to anthropogenically-induced patterns of climate change. To begin exploring this possibility, we validated the use of fecal cortisol/corticosterone metabolites (FCM) to measure baseline glucocorticoid levels in two species of co-occurring chipmunks that have exhibited markedly different patterns of response to environmental change. In Yosemite National Park, the alpine chipmunk ( Tamias alpinus ) has undergone a significant upward contraction of its elevational range over the past century; in contrast, the lodgepole chipmunk ( T amias speciosus ) has experienced no significant change in elevational distribution over this period. To determine if GC levels in these species vary in response to external stimuli and to assess whether these responses differ between species, we compared FCM levels for the same individuals (1) at the time of capture in the field, (2) after a short period of captivity, and (3) after adrenocorticotropic hormone (ACTH), (4) handling, and (5) trapping challenges conducted while these animals were held in captivity. Our analyses indicate that T. alpinus was more responsive to several of these changes in external conditions. Although both species displayed a significant FCM response to ACTH challenge, only T. alpinus showed a significant response to our handling challenge and to captive housing conditions. These findings underscore the importance of species-specific validation studies and support the potential for studies of GC physiology to generate insights into interspecific differences in response to environmental change. [ABSTRACT FROM AUTHOR]

Determining the physiological mechanisms underpinning life-history decisions is essential for understanding the constraints under which life-history strategies can evolve. In long-lived species, where the residual reproductive value of breeders is high, adult survival is a key contributor to lifetime reproductive success. We therefore expect that when adult survival is compromised during reproduction, mechanisms will evolve to redirect resources away from reproduction, with implications for reproductive hormones, adult body mass, nest attendance behaviour and breeding success. We investigated whether manipulating corticosterone, to simulate exposure to an environmental stressor, affected the secretion of prolactin and breeding success in the black-legged kittiwake Rissa tridactyla . We used implanted Alzet® osmotic pumps to administer corticosterone to incubating kittiwakes at a constant rate over a period of approximately 8 days. Manipulated birds were compared with sham implanted birds and control birds, which had no implants. There was no significant difference in the body mass of captured individuals at the time of implantation and implant removal. Corticosterone-implanted males showed lower nest attendance during the chick rearing period compared to sham-implanted males; the opposite pattern was found in females. Corticosterone treated birds showed a marginally significant reduction in breeding success compared to sham-implanted individuals, with all failures occurring at least 1 week after implant removal. However, prolactin concentrations at implant removal were not significantly different from initial values. We were unable to measure the profile of change in corticosterone during the experiment. However, our results suggest a delayed effect of elevated corticosterone on breeding success rather than an immediate suppression of prolactin concentrations causing premature failure. [ABSTRACT FROM AUTHOR]

The developmental environment can affect the expression of sexually selected traits in adulthood. The physiological mechanisms that modulate such effects remain a matter of intense debate. Here, we test the role of the developmental environment in shaping adult mitochondrial function and link mitochondrial function to expression of a sexually selected trait in males (bird song). We exposed male zebra finches (Taeniopygia guttata) to corticosterone (CORT) treatment during development. After males reached adulthood, we quantified mitochondrial function from whole red blood cells and measured baseline CORT and testosterone levels, body condition/composition, and song structure. CORT-treated males had mitochondria that were less efficient (FCR L/R) and used a lower proportion of maximum capacity (FCR R/ETS) than control males. Additionally, CORT-treated males had higher baseline levels of CORT as adults compared to control males. Using structural equation modelling, we found that the effects of CORT treatment during development on adult mitochondrial function were indirect and modulated by baseline CORT levels, which are programmed by CORT treatment during development. Developmental treatment also had an indirect effect on song peak frequency. Males treated with CORT during development sang songs with higher peak frequency than control males, but this effect was modulated through increased CORT levels and by a decrease in FCR R/ETS. CORT-treated males had smaller tarsi compared to control males; however, there were no associations between body size and measures of song frequency. Here, we provide the first evidence supporting links between the developmental environment, mitochondrial function, and the expression of a sexually selected trait (bird song). • The developmental environment affects the expression of sexually selected traits • We tested development effects on mitochondrial function and song production • Developing males exposed to corticosterone (CORT) had less efficient mitochondria • CORT-exposed males had higher baseline CORT and high frequency songs • Changes in mitochondrial function and song were driven by changes in CORT [ABSTRACT FROM AUTHOR]

Abstract: Exposure to excess glucocorticoids (GCs) during embryonic development influences offspring phenotypes and behaviors and induces epigenetic modifications of the genes in the hypothalamic–pituitary–adrenal (HPA) axis and in the serotonergic system in mammals. Whether prenatal corticosterone (CORT) exposure causes similar effects in avian species is less clear. In this study, we injected low (0.2μg) and high (1μg) doses of CORT into developing embryos on day 11 of incubation (E11) and tested the changes in aggressive behavior and hypothalamic gene expression on posthatch chickens of different ages. In ovo administration of high dose CORT significantly suppressed the growth rate from 3weeks of age and increased the frequency of aggressive behaviors, and the dosage was associated with elevated plasma CORT concentrations and significantly downregulated hypothalamic expression of arginine vasotocin (AVT) and corticotropin-releasing hormone (CRH). The hypothalamic content of glucocorticoid receptor (GR) protein was significantly decreased in the high dose group (p<0.05), whereas no changes were observed for GR mRNA. High dose CORT exposure significantly increased platelet serotonin (5-HT) uptake, decreased whole blood 5-HT concentration (p<0.05), downregulated hypothalamic tryptophan hydroxylase 1 (TPH1) mRNA and upregulated 5-HT receptor 1A (5-HTR1A) and monoamine oxidase A (MAO-A) mRNA, but not monoamine oxidase B (MAO-B). High dose CORT also significantly increased DNA methylation of the hypothalamic GR and CRH gene promoters (p<0.05). Our findings suggest that embryonic exposure to CORT programs aggressive behavior in the chicken through alterations of the HPA axis and the serotonergic system, which may involve modifications in DNA methylation. [Copyright &y& Elsevier]

Highlights: [•] Urinary corticosterone enzyme-immunoassay was validated for male Great Barred Frogs. [•] First study of amphibian baseline glucocorticoid physiology at different altitudes. [•] Significant (P <0.001) increase in urinary corticosterone with altitude. [•] Associations between glucocorticoids, high altitude and life history variables. [Copyright &y& Elsevier]

Highlights: [•] The glucocorticoid stress response (GCSR) promotes homeostasis. [•] Global change is associated with changes in the regime of stressors. [•] Global change may disrupt the efficiency of the GCSR to maintain homeostasis. [•] The GCSR might be adjusted to new stressors through different mechanisms. [•] Studying the GCSR helps understanding how global change affects different species. [Copyright &y& Elsevier]

Abstract: Androgens play a major role in the regulation of sexual signal expression of male vertebrates. In this study we assessed the prevalent, yet largely untested, assumption that signal honesty is maintained through condition-dependent androgen regulation by experimentally manipulating body condition of male red-backed fairy-wrens (Malurus melanocephalus) through trimming several flight feathers before the prenuptial molt. In their first reproductive season males of this species exhibit androgen-regulated plasticity in plumage coloration, ranging from red/black (high androgens) to brown (low androgens). Red/black plumage is preferred by females and might be constrained by a negative relationship between body condition and androgen levels. We also evaluated whether corticosterone changes to altered conditional state mediate the relationship between condition and androgens. While we predicted that males with trimmed feathers would expend greater energy and thus be in poorer condition at the time of molt, they were counter-intuitively in better condition compared to control birds, likely as a consequence of subtle behavioral changes. These birds in better condition molted a greater proportion of red/black plumage, as predicted, and also molted more heavily. However, experimental and control birds did not differ in their androgen or corticosterone concentrations. Furthermore, analysis of long-term data from the same population revealed no correlation between condition and androgen levels. Collectively, these results challenge the notion that condition-dependent androgen regulation alone is responsible for maintaining the honesty of sexual signals and highlights the necessity of considering alternate explanations. [Copyright &y& Elsevier]

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: Chronic stress generally inhibits the activity of the reproductive system. Acute stress also is often inhibitory, but the mechanism involved and its persistence of action once animals are no longer exposed to the stressor are poorly understood. We investigated the effect of capture and restraint stress on plasma testosterone (T), luteinizing hormone (LH), and corticosterone (CORT) in free-ranging male rufous-winged sparrows, Peucaea carpalis. Stress decreased plasma T between 10 and 30min after capture and restraint but did not influence plasma LH, the main hormone that controls T secretion, suggesting that stress did not decrease plasma T by inhibiting LH secretion. The stress-induced decrease in plasma T was associated with elevated plasma CORT, but there was no evidence that these effects were functionally related. Plasma stress-induced T was positively related to plasma initial T measured within 2min of capture. This relationship was, however, complex as plasma T decreased proportionally more in response to stress in sparrows with high than low plasma initial T. The relative sensitivity to the same stressor was, therefore, individually variable and this variation was related to initial plasma T. Birds caught and restrained for 30min, and then released on their breeding territory before recapture up to 6h later, maintained depressed plasma T, indicating that the effect of acute stress on this hormone persists after the stressor removal. These studies provide new information on the effects of acute stress on plasma T in free-ranging birds. In particular, they are among the first to characterize the time course and to describe the persistence of these effects. The findings also contribute to identifying factors that are associated with individual differences in plasma hormone levels. [Copyright &y& Elsevier]

Abstract: Glucocorticoids (GCs) affect the development of both the immune and nervous systems. To do so, GCs bind to intracellular receptors, mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). In addition, GCs bind to membrane-associated corticosteroid receptors (mCR). Two well-known GCs are corticosterone and cortisol. Whereas corticosterone is the primary GC in zebra finch plasma, cortisol is the primary GC in zebra finch lymphoid organs and is also present in the brain and plasma during development. Here, we characterized binding sites for corticosterone and cortisol in plasma, liver, lymphoid organs, and brain of developing zebra finches. In tissues, we examined both intracellular and membrane-associated binding sites. For intracellular receptors, there were MR-like sites and GR-like sites, which differentially bound corticosterone and cortisol in a tissue-specific manner. For mCR, we found little evidence for membrane-associated receptors in immune organs, but this could be due to the small size of immune organs. Interestingly, cortisol, but not corticosterone, showed a low amount of specific binding to bursa of Fabricius membranes. For neural membranes, corticosterone bound to one site with low affinity but a relatively high B max, and in contrast, cortisol bound to one site with high affinity but a lower B max. Our results indicate that intracellular and membrane-associated receptors differentially bind corticosterone and cortisol suggesting that corticosterone and cortisol might have different roles in immune and nervous system development. [Copyright &y& Elsevier]

Abstract: Fledging is a major life transition for birds, when juveniles move from the safety of a nest into an environment where they must find food and avoid predators. The timing of fledging within a season can have significant effects on future survival and breeding success. Proximate triggers of fledging are unknown: though wing development is likely a primary factor, other physiological changes, such as elevated plasma corticosterone (CORT), may affect fledging behavior. Laysan Albatross (Phoebastria immutabilis) chicks have an extended post−hatching period during which they reach 150% of adult mass. However, approaching fledging, chicks fast for days to weeks and lose mass while still putting energy into feather growth. We evaluated chick morphology and physiology to elucidate proximate triggers of fledging. As in some other species, CORT increased as chicks fasted and lost body mass. At the same time, corticosteroid binding globulin (CBG) declined, thus amplifying free CORT prior to fledging. Once chicks reached a morphological threshold, free CORT levels predicted how long they stayed at the colony: chicks with higher free CORT fledged sooner. To perturb the relationship between body condition, endocrine physiology, and fledging behavior, we supplementally fed chicks for the month before fledging. Fed birds had a slower decrease in body mass, slower decrease in CBG, slower increase in free CORT, and stayed at the colony longer after reaching a morphological threshold. Our study suggests that as chicks lose mass, free CORT acts as a signal of energetic or nutritional state to adjust the timing of fledging. [Copyright &y& Elsevier]

Abstract: Stress is thought to be a potent suppressor of reproduction. However, the vast majority of studies focus on the relationship between chronic stress and reproductive suppression, despite the fact that chronic stress is rare in the wild. We investigated the role of fasting in altering acute stress physiology, reproductive physiology, and reproductive behavior of male zebra finches (Taeniopygia guttata) with several goals in mind. First, we wanted to determine if acute fasting could stimulate an increase in plasma corticosterone and a decrease in corticosteroid binding globulin (CBG) and testosterone. We then investigated whether fasting could alter expression of undirected song and courtship behavior. After subjecting males to fasting periods ranging from 1 to 10h, we collected plasma to measure corticosterone, CBG, and testosterone. We found that plasma corticosterone was elevated, and testosterone was decreased after 4, 6, and 10h of fasting periods compared with samples collected from the same males during nonfasted (control) periods. CBG was lower than control levels only after 10h of fasting. We also found that, coincident with these endocrine changes, males sang less and courted females less vigorously following short-term fasting relative to control conditions. Our data demonstrate that acute fasting resulted in rapid changes in endocrine physiology consistent with hypothalamo–pituitary–adrenal axis activation and hypothalamo–pituitary–gonadal axis deactivation. Fasting also inhibited reproductive behavior. We suggest that zebra finches exhibit physiological and behavioral flexibility that makes them an excellent model system for studying interactions of acute stress and reproduction. [Copyright &y& Elsevier]

Abstract: Co-species housing of mice and rats is common practice at most breeding facilities and research laboratories, neglecting the possible effects on the animals. We investigated physiological as well as behavioral stress-reactivity in mice and rats which were either derived from a co-species or species-separated housing condition at the breeding facilities. The animals were kept under the housing condition they were used to or assigned to the opposite one. Co-species housing had a significant impact on acute stress reactivity in mice and rats but only if they were used to this housing condition throughout their lives. Moreover, the stress-effects appeared to be long lasting. Assigning animals, derived from a species-separated housing condition, to co-species housing led to chronic stress in mice and affected experimental behavior of rats. Our findings led to the conclusion that co-species housing in mice and rats should be avoided, supporting the recommendations by the U.S. National Institutes of Health (NIH) and the Dutch Ministry of Health, Welfare and Sport (VWS). In order to support the interpretation, facilitate the reproducibility and comparability and subsequently the generalizability of experimental results, breeding facilities should at least provide detailed information about their housing conditions. [Copyright &y& Elsevier]

Glucocorticoids act throughout life to regulate numerous physiological and behavioral processes. Their levels are therefore highly labile, reacting to varying conditions and stressors. Hence, measuring glucocorticoids (and other steroids) in wildlife is challenging, and devising methods that are unaffected by the stress of capture and handling should be explored. Here we use the tip of free-ranging chameleons’ claws that were cut to allow individual identification, and report a steroids extraction and quantification method. Claw steroids present an integrated level representing the period of claw growth. We found that we could measure corticosterone in small amounts of chameleon claw matrix using commercial EIA kits. Using this method, we learned that in wild male chameleons, claw corticosterone levels were associated with body size. We suggest that claw-testing can potentially provide an ideal matrix for wildlife biomonitoring. [ABSTRACT FROM AUTHOR]

Abstract: The specific role of the glucocorticoid hormone corticosterone in regulating the migratory stages of flight and refueling in free-living migrants is as yet poorly studied, because these stages are difficult to identify in the field. Night-migrating songbirds provide an excellent model to investigate how corticosterone correlates with behavior and physiology because they fly during the night and rest and forage during the day. We measured baseline corticosterone and the adrenocortical response to restraint in 9 free-ranging songbird species: 3 night-migrating species, 3 day-migrating species, and 3 day-migrating irruptive species. Baseline corticosterone of night migrants was higher in birds caught out of nocturnal migration than in birds resting and foraging, and on the same level as in day migrants, suggesting that a rise in circulating corticosterone may facilitate the heightened metabolic processes of active flight, in particular protein breakdown. Stress-induced corticosterone levels increased in both actively flying birds and birds resting and foraging. The increase was highest in landing birds, which are possibly most sensitive to stress when arriving at an unfamiliar place. Migratory endurance flight is thus characterized by corticosterone concentrations that are lower than those associated with acute stressful and life-threatening episodes. In addition, the responsiveness to stress increased with decreasing fat score in a night-migrating species. Corticosterone approaches therefore stressful concentrations only when fat depots are nearly depleted, possibly to promote protein catabolism and to trigger a change in behavior, i.e., a switch to landing and searching for food. [Copyright &y& Elsevier]

Abstract: Combined exposures to maternal lead (Pb) and prenatal stress (PS) can act synergistically to enhance behavioral and neurochemical toxicity in offspring. Maternal Pb itself causes permanent dysfunction of the body''s major stress system, the hypothalamic pituitary adrenal (HPA) axis. The current study sought to determine the potential involvement of altered negative glucocorticoid feedback as a mechanistic basis of the effects in rats of maternal Pb (0, 50 or 150 ppm in drinking water beginning 2 mo prior to breeding), prenatal stress (PS; restraint on gestational days 16–17) and combined maternal Pb+PS in 8 mo old male and female offspring. Corticosterone changes were measured over 24 h following an i.p. injection stress containing vehicle or 100 or 300 μg/kg (females) or 100 or 150 μg/kg (males) dexamethasone (DEX). Both Pb and PS prolonged the time course of corticosterone reduction following vehicle injection stress. Pb effects were non-monotonic, with a greater impact at 50 vs. 150 ppm, particularly in males, where further enhancement occurred with PS. In accord with these findings, the efficacy of DEX in suppressing corticosterone was reduced by Pb and Pb+PS in both genders, with Pb efficacy enhanced by PS in females, over the first 6 h post-administration. A marked prolongation of DEX effects was found in males. Thus, Pb, PS and Pb+PS, sometimes additively, produced hypercortisolism in both genders, followed by hypocortisolism in males, consistent with HPA axis dysfunction. These findings may provide a plausible unifying biological mechanism for the reported links between Pb exposure and stress-associated diseases and disorders mediated via the HPA axis, including obesity, hypertension, diabetes, anxiety, schizophrenia and depression. They also suggest broadening of Pb screening programs to pregnant women in high stress environments. [Copyright &y& Elsevier]

• Use of skin mucus swabs to measure immunoreactive glucocorticoids (cortisol and corticosterone) for three species of cephalopods. • These results demonstrate the first instance where cortisol is measured in a cephalopod. • Stress hormones fluctuate when introduced to a new habitat. • Younger individuals have higher cortisol concentrations compared to older individuals. To better comprehend the physiology of cephalopods, we used a minimal invasive technique of skin mucus swabs to measure immunoreactive corticosteroids in three cephalopod species commonly kept in captivity and promoted as new model organisms: Euprymna berryi , Sepia bandensis , and Octopus chierchiae. We compared results between sexes and age classes and then evaluated their stress responses during acclimation to a new habitat. To better understand glucocorticoid production, we conducted an adrenocorticotropic hormone, using Cosyntropin (an adrenocorticotropin (ACTH) analogue) challenge with a saline control and swabbed their mantles at 15-minute intervals for 2 h. Results showed cortisol was higher for younger individuals. Additionally, cortisol and corticosterone concentrations decreased by 2-fold after 2 to 4 days of acclimation to a new habitat. We were able to successfully measure 2-fold increase in immunoreactive corticosteroids which reacted with cortisol and corticosterone assays for all the species following ACTH injection, although not all individuals responded similarly. With further investigation, this technique can increase our understanding and management of cephalopods in captivity. [ABSTRACT FROM AUTHOR]

Abstract: To better understand the biology of tameness, i.e. tolerance of human presence and handling, we analyzed two lines of wild-derived rats (Rattus norvegicus) artificially selected for tameness and defensive aggression towards humans. In response to a gloved human hand, tame rats tolerated handling, whereas aggressive rats attacked. Cross-fostering showed that these behavioral differences are not caused by postnatal maternal effects. Tame rats were more active and explorative and exhibited fewer anxiety-related behaviors. They also had smaller adrenal glands, larger spleens and lower levels of serum corticosterone. Blood glucose levels were lower in tame rats, whereas the concentrations of nine amino acids were higher. In the brain, tame rats had lower serotonin and higher taurine levels than aggressive rats. Our findings reinforce the notion that tameness is correlated with differences in stress response and will facilitate future efforts to uncover the genetic basis for animal tameness. [Copyright &y& Elsevier]

Abstract: Elevated levels of circulating corticosterone commonly occur in response to stressors in wild vertebrates. A rise in corticosterone, usually in animals of subordinate rank, results in a variety of effects on behavior and physiology. Behavioral and physiological responses to short-term increases in corticosterone are well studied. In contrast, the effects of chronic elevated levels of corticosterone are poorly understood, particularly in lizards. Here, we examined the long-term effects of exogenous corticosterone on locomotor performance, resting and active metabolic rate, and hematocrit in male side-blotched lizards Uta stansburiana. Corticosterone implantation resulted in higher levels of stamina relative to sham-surgery controls. In addition, lizards with elevated corticosterone exhibited lower resting metabolic rates relative to controls. Corticosterone had no effect on peak activity metabolism but did result in faster recovery times following exhaustive exercise. We suggest that elevated levels of corticosterone in response to dominance interactions promote enhanced locomotor abilities, perhaps as a flight response to avoid agonistic interactions. Furthermore, stressed lizards are characterized by lower resting metabolic rates, which may serve as strategy to conserve energy stores and enhance survival. [Copyright &y& Elsevier]

Abstract: For decades, demands associated with the predictable life-history cycle have been considered stressful and have not been distinguished from stress that occurs in association with unpredictable and life-threatening perturbations in the environment. The recent emergence of the concept of allostasis distinguishes behavioral and physiological responses to predictable routines as opposed to unpredictable perturbations, and allows for their comparison within one theoretical framework. Glucocorticosteroids (GCs) have been proposed as important mediators of allostasis, as they allow for rapid readjustment and support of behavior and physiology in response to predictable and unpredictable demands (allostatic load). Much work has already been done in defining GC action at the high concentrations that accompany life-threatening perturbations. However, less is known about the role of GCs in relation to daily and seasonal life processes. In this review, we summarize the known behavioral and physiological effects of GCs relating to the predictable life-history cycle, paying particular attention to feeding behavior, locomotor activity and energy metabolism. Although we utilize a comparative approach, emphasis is placed on birds. In addition, we briefly review effects of GCs at stress-related concentrations to test the hypothesis that different levels of GCs play specific and distinct roles in the regulation of life processes and, thus, participate in the promotion of different physiological states. We also examine the receptor types through which GC action may be mediated and suggest mechanisms whereby different GC concentrations may exert their actions. In conclusion, we argue that biological actions of GCs at “non-stress” seasonal concentrations play a critical role in the adjustment of responses that accompany predictable variability in the environment and demand more careful consideration in future studies. [Copyright &y& Elsevier]

Abstract: Glucocorticoids, the adrenal steroid hormones secreted during stress, are essential to homeostasis and metabolism in the human body. An impaired glucocorticoid signaling due to dysfunction of the glucocorticoid receptor (GR) by synthetic chemicals can cause diseases and disruptions of the homeostasis and metabolism. Here we demonstrate the development of a method for screening endocrine-disrupting chemicals and potent risk factors of human diseases based on the nuclear trafficking of the GR. We constructed a new assay using a pair of genetic indicators with the full length of the GR, split Renilla luciferase (RLuc), and split DnaE (a protein splicing element). The GR-containing fusion protein with C-terminal halves of DnaE and RLuc is localized in cytosol due to the cytosolic character of the GR, whereas the fusion protein with N-terminal halves of DnaE and RLuc stays in the nucleus due to the cofused nucleus localization signal. On being stimulated with a ligand, the GR is translocated into the cellular nucleus. Thus, a protein splicing occurs in the nucleus by an interaction between the splicing junctions of each DnaE fragment. The enzymatic activities from the reconstituted RLuc allow the ligand-dependent luminescence intensities. The feasibility of the method was evaluated by quantifying the hormonal activities of 20 different kinds of steroids and synthetic chemicals using the NIH 3T3 cells carrying the pair of indicators. The hormonal activities of tested ligands are discussed based on the chemical structure–activity relationship. We found that androgens, testosterone, and 19-nortestosterone weakly induce the nuclear transport of the GR. The current assay allows high-throughput screening of risk chemicals and drug candidates influential to a signal transduction pathway of the GR. [Copyright &y& Elsevier]

Abstract: Plasma corticosterone increases during the period of spring migration in a variety of bird species. Long-distance migrants show elevations in corticosterone specifically in association with the stage of flight, suggesting that corticosterone may support flight-related processes, for example, locomotor activity and/or energy mobilization. The pattern of corticosterone secretion as it relates to migratory flight has hitherto not been clearly described in migrants that frequently interrupt flight to refuel, for example, the Gambel''s white-crowned sparrow (Zonotrichia leucophrys gambelii). The Gambel''s white-crowned sparrow fuels by day and expresses peak migratory activity during the first few hours of night. To determine if plasma corticosterone increases in association with the stage of migratory flight also in this short-bout migrant, we induced captive white-crowned sparrows to enter into the migratory condition by placing photosensitive birds on long days (16L:8D) and then evaluated birds for plasma corticosterone and locomotor activity during four time points of the day. Patterns found in long-day birds were compared to those observed in short-day controls (8L:16D). Differences in energy metabolism as determined from plasma metabolites were also evaluated. We found that locomotor activity and corticosterone were significantly elevated at the onset of the dark period, but only in long-day birds. Plasma β-hydroxybutyrate (a ketone body) was also elevated. Thus, findings suggest that plasma corticosterone and ketogenesis increase in association with migratory restlessness in a short-bout migrant. In fact, corticosterone may play a regulatory role, because it shows a trend to increase already before night-time activity. [Copyright &y& Elsevier]

Fecal glucocorticoid metabolite analyses are increasingly being used by a variety of scientists (e.g., conservation biologists, animal scientists) to examine glucocorticoid (i.e., stress hormone) secretion in domestic and wild vertebrates. Adrenocortical activity (i.e., stress response) is of interest to conservation biologists because stress can alter animal behavior, reduce resistance to disease, and affect population performance. The noninvasiveness of fecal-based assessments is attractive, particularly when studying endangered species, because samples can often be obtained without disturbing the animal. Despite such advantages, many confounding factors inhibit the utility of this technique in addressing conservation problems. In particular, interpretation of fecal glucocorticoid metabolite (FGM) measures may be confounded by the length of time animals are held in captivity, normal seasonal and daily rhythms, body condition, sample storage and treatment techniques, diet of the animal, assay selection, animal status (i.e., social ranking, reproductive status), sample age and condition, and sample mass. Further complicating interpretation and utility of these measures is the apparent species-specific response to these factors. The purpose of this paper is to discuss the factors that confound interpretation of FGM measures, summarize research that addresses these issues, and offer an agenda for future research and interpretation. We urge conservation biologists to carefully consider confounding factors and the relationship between FGM secretion and population performance and biological costs when investigating effects of environmental and human-induced disturbances on wildlife. The crisis nature of many decisions in conservation biology often requires decisions from limited data; however, confirmatory results should not be posited when data are incomplete or confounding factors are not understood. Building reliable databases, and research with surrogate species when possible, will aid future efforts and enhance the utility of FGM assays. [Copyright &y& Elsevier]

In many species, seasonal activities such as reproduction or migration need to be fine-tuned with weather conditions. Air pressure and temperature changes are the best parameters for such conditions. Adapting to climatic changes invariably involves physiological and behavioral reactions associated with the adrenals. In the present study, we investigated the effects of ambient temperature and air pressure on excreted immuno-reactive metabolites of corticosterone (BM) and androgens (AM). Focal individuals were 14 paired male greylag geese (Anser anser) from a semi-tame, unrestrained flock. BM and AM were measured in individual fecal samples over 25 days in November and December. Two different ACTH-validated assays were used for the assessment of BM: the first one cross-reacting with 11β,21-diol-20-one structures (“old assay”) and the second one with 5β,3α,11β-diol structures (“new assay”). With the “new assay,” BM correlated negatively with the minimum ambient temperature of the night before, which may reflect corticosterone involvement in thermoregulation. BM also correlated positively with the minimum air pressure of the previous afternoon, which supports the value of air pressure for predicting weather conditions. Together, these reactions suggest a role of the adrenals in responding behaviorally and physiologically to changes in weather. Preliminary analysis indicated a higher sensitivity to the excreted glucocorticosteroid metabolites in the “new assay.” As expected for outside the mating season, no relationships were found between excreted AM and the weather parameters considered. The gradual changes in BM excretion in parallel with weather conditions may be part of the fine-tuning of physiology and behavior by environmental clues. [Copyright &y& Elsevier]