Capture Stress Research Articles

Sex, seasonal, and stress-related variations in elasmobranch corticosterone concentrations

Serum corticosterone was previously studied in numerous elasmobranch fishes (sharks, skates and rays), but the role of this steroid, widespread throughout many taxa, has yet to be defined. The goal of this study was to test whether corticosterone varied in response to acute and chronic capture stress, and across the reproductive cycle in the bonnethead shark, Sphyrna tiburo, and Atlantic stingray, Dasyatis sabina. Serum corticosterone in S. tiburo increased following capture and again 24 h post-capture, possibly caused by interference with 1α-hydroxycorticosterone, the primary stress hormone in elasmobranchs. Higher serum concentrations in males compared to females were observed in both species. Variations in corticosterone also occurred during the reproductive cycle in both species. Consistent with other taxa, elevations in male bonnethead sharks and stingrays coincided with peak testicular development and mating. Elevations in female bonnethead sharks occurred from the time of mating through sperm storage into early gestation. In contrast, corticosterone levels in female stingrays were low during their protracted mating season, but elevated through late gestation and parturition. These results indicate that corticosterone has a limited role, if any, in acute and chronic stress associated with capture in S. tiburo, but likely has physiological functions associated with its glucocorticoid properties across the reproductive cycle of both species.

In vivored blood cell sickling and mechanism of recovery in whiting,Merlangius merlangus

Haemoglobin concentrations in vertebrate red blood cells are so high that in human sickle cell disease a single surface amino acid mutation can result in formation of large insoluble haemoglobin aggregates at low oxygen levels, causing peculiar cell deformations or 'sickling'. This may cause vascular occlusion and thereby severe pain, organ failure and death. Here, using light and transmission electron microscopy, we demonstrate extensive in vivo sickling of whiting red blood cells after capture stress without any apparent haemolysis and show its subsequent recovery. We show exceptionally high cooperative proton binding during the sickling process in vitro and identify the reduction of extracellular pH below resting values as the primary cause for in vivo sickling, although the response is modulated to a lesser extent also by oxygen tension. Using isotope tracer fluxes, we further show that beta-adrenergic hormones, which are released under capture stress, activate a powerful endogenous Na/H exchanger in these fish red blood cells, which is known to elevate intracellular pH. beta-adrenergic treatment further leads to a marked reduction of acid-induced in vitro sickling, which is impaired when Na/H exchange is inhibited by amiloride. We propose that this mechanism protects red blood cells of some fishes against the problem of haemoglobin aggregation and red blood cell sickling, except under most severe acidosis. This system offers a unique example of how, over evolutionary time, nature may have overcome what is still a deadly disease in humans.

Immunomodulatory effects of organochlorine mixtures upon in vitro exposure of peripheral blood leukocytes differ between free-ranging and captive southern sea otters ( Enhydra lutris)

Organochlorines (OCs), notably polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD), are ubiquitous environmental contaminants. Contaminant-induced immunosuppression by OCs has been implicated as a co-factor in the deaths of thousands of marine mammals in infectious disease epizootics over the last two decades, and limited studies support the hypothesis that PCBs are immunomodulatory. This study represented a unique opportunity to assess the potential differences in susceptibility to OCs between captive and free-ranging sea otters originating from the same genetic population. In vitro immune assays were utilized to evaluate both innate (phagocytosis and respiratory burst) and acquired (mitogen-induced B and T lymphocyte proliferation) immune functions. Individual PCBs (138, 153, 169 and 180) as well as TCDD and all 26 possible combinations were tested. Mixtures were tested as they represent ‘real life’ exposure. Our results suggest that (1) different immune functions were sensitive to different OC mixtures in both magnitude and direction (enhancement/suppression) and (2) differences in sensitivities upon in vitro exposure to OCs occurred between free-ranging and captive otters. Differences in susceptibility could be explained by the acute stress of capture, the chronic stress of captivity or nutritional differences. Understanding differences in toxicity to different populations of sea otters will have important implications for risk assessment as well as conservation and management strategies.

Effect of acepromazine on the signs of capture stress in captive and free-ranging roe deer (Capreolus capreolus)

The differences between the capture stress responses of captive and free-ranging roe deer (Capreolus capreolus) and their modulation by acepromazine, during a period of three hours' physical restraint after capture...

Searching for the Physiological Mechanism of Density Dependence: Does Corticosterone Regulate Tadpole Responses to Density?

Density-dependent population regulation is important in many natural populations, and in those populations, high population density is a likely stressor. In amphibians, previous laboratory studies with tadpoles suggest that corticosterone, the main glucocorticoid stress hormone, is one of the key regulators of density-dependent growth. To test this relationship in natural settings, we manipulated wood frog (Rana sylvatica) tadpole density at three levels in outdoor mesocosms and used a capture stress protocol to examine the hormonal stress response. In addition, we used the same capture protocol in six natural ponds (three high density and three low density). In the mesocosms, there was an increase in corticosterone levels in tadpoles following 1 h of confinement at weeks 1, 2, and 5. However, while tadpoles maintained at higher densities were smaller after metamorphosis, density did not alter mean levels of corticosterone obtained during confinement, and baseline levels of corticosterone did not differ between the densities. Similarly, in natural ponds, density did not correlate with baseline corticosterone or mean corticosterone levels obtained during confinement. We suggest that the physiological response to density may vary across the range of natural densities and that the role of corticosterone may be limited to periods of extreme high density, such as during pond-drying events.

Effects of capture, loading density and transport stress on the mortality, physiological responses, bacterial density and growth of rohu Labeo rohita fingerlings

This study evaluated the effects of three levels of loading density (200, 300 and 400 g L−1) and four levels of duration (1, 3, 6 and 9 h) on the mortality, plasma cortisol and chloride levels and growth of rohu Labeorohita fingerlings in a transport simulation. While total immediate mortality was low (4–12%), delayed mortality was high (27–49%). Initial capture and handling were found to constitute the most stressful phase as indicated by elevated plasma cortisol. The levels of cortisol continued to rise at 6 and 9 h after transport, with the highest level observed at 9 h after transport. The level of plasma chloride fell after transport across all density levels and treatment durations. Specific growth rate (SGR, %/day) and total bacterial density (cfu/g) were not different between and within treatments, and between treatments and the controls. This study demonstrates that transport has a profound effect on the stress responses of rohu fingerlings. Although the level of immediate mortality was low, the higher level of delayed mortality has serious implications in terms of production inefficiency for grow-out farmers.

Evaluating the physiological and physical consequences of capture on post‐release survivorship in large pelagic fishes

Abstract Sharks, tunas and billfishes are fished extensively throughout the world. Domestic and international management measures (quotas, minimum sizes, bag limits) mandate release of a large, yet poorly quantified, number of these fishes annually. Post‐release survivorship is difficult to evaluate, because standard methods are not applicable to large oceanic fishes. This paper presents information on the current approaches to characterising capture stress and survivorship in sharks, tunas and marlins. To assess mortality associated with capture stress, researchers must examine the cumulative impacts of physical trauma and physiological stress. Physical trauma, manifested as external and internal tissue and organ damage, is caused by fishing gear and handling. Gross examination and histopathological sampling have been used to assess physical trauma and to infer post‐release survivorship. Exhaustive anaerobic muscular activity and time out of water cause physiological stress, which has been quantified in these fishes through the analyses of blood chemistry. Conventional, acoustic and archival tagging have been used to assess post‐release survivorship in these species. Future studies relating capture stress and post‐release survivorship could yield information that helps fishermen increase survivorship when practicing catch and release.

Plasma catecholamine levels as indicators of the post-release survivorship of juvenile pelagic sharks caught on experimental drift longlines in the Southern California Bight

Between 1983 and 2004, nearly 12 000 shortf in mako (Isurus oxyrinchus), common thresher (Alopias vulpinus) and blue (Prionace glauca) sharks were tagged in the Southern California Bight; however, only 1.97% of these have been returned. One possible reason for this low return rate could be post-release mortality caused by capture stress from the experimental longline. Plasma catecholamine levels were analysed to evaluate stress levels in longline-captured, rod-and-reel-captured and unstressed docile sharks. The mean catecholamine values determined for the three tag–release species ranged from 6539 to 22 079 pg mL–1. The level of adrenaline found in moribund I. oxyrinchus (94 807 pg mL–1) was much higher than in either P. glauca (46 845 pg mL–1) or A. vulpinus (36 890 pg mL–1). In contrast, blood obtained from sharks that were landed within minutes had lower catecholamine values (P. glauca, 889 and 1347 pg mL–1; I. oxyrinchus, 2960 and 3946 pg mL–1, adrenaline and noradrenaline respectively). Among the nine I. oxyrinchus specimens that were recaptured long after their longline capture and release, the highest adrenaline level measured just before release was 33 352 pg mL–1. Because these mako sharks survived sufficiently long to be recaptured, their time-of-release catecholamine levels provide a conservative estimate of ~80% viability on the longline-captured and released population.

The estimated short-term discard mortality of a trawled elasmobranch, the spiny dogfish ( Squalus acanthias)

To estimate the short-term bycatch discard mortality of otter trawl captured spiny dogfish ( Squalus acanthias), individuals caught by a Northwest Atlantic commercial bottom-trawl vessel using 45–60 min tows were held in held in pens for 72-h trials in lieu of being released. Mortality rates were compared to those in minimally stressed hook-and-line (control) dogfish subjected to the same protocols. To interpret physiological consequences of trawl capture, blood acid–base parameters were also assessed in dogfish following capture by both trawling and the hook-and-line control. Whole-blood pH (significantly depressed), pCO 2 (significantly elevated) and pO 2 (significantly depressed) were all markedly disturbed in trawled dogfish, indicating that trawl capture elicited a far greater disruption to vascular acid–base balance. However, 72 h mortality was not negligible for control dogfish (24%) but similar to trawling (29%), indicating that pens likely caused the observed (72 h) mortality associated with both capture methods. Still, in evaluating the range of 72 h trawling mortalities found across pen trials, estimated tow-weight was a significant predictor of mortality, explaining 67% of the variation. This suggests that penning stress was merely an additive factor compounding initial capture stress that dictated the 72 h mortality of trawled individuals. When normalized by subtracting out hook-and-line pen mortality, 72 h trawling mortality generally remained well below the 50.0% spiny dogfish discard mortality rate currently estimated for trawling in the Northwest Atlantic and was even superceded by penning stress in lighter tows; a testament to the resiliency of this species. However, catch-weights exceeding 200 kg yielded rapid elevations in 72 h mortality that more closely approached current estimates. This intimates that as tows become more heavily packed, potentially fatal damage inflicted on this species can heighten quickly. Spiny dogfish discard mortality is thus postulated as more commensurate with current estimations for otter trawling when tows are heavily packed.

Corticosterone and the transition from courtship behavior to dispersal in male red-sided garter snakes ( Thamnophis sirtalis parietalis)

Seasonal modulation of baseline glucocorticoid concentrations as well as the sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis plays an important role in supporting critical life-history events such as seasonal reproduction and migration. Despite numerous studies on adrenocortical modulation, little is known about the exact timing of this seasonal modulation with respect to critical life-history stages. We tested the hypothesis that seasonal modulation of the HPA axis during the spring mating season in male red-sided garter snakes ( Thamnophis sirtalis parietalis) is temporally linked to the mechanisms regulating dispersal. We compared hormonal responses to capture stress in courting male red-sided garter snakes collected from the den site and den perimeter to those of dispersing snakes collected 0.6 km from the den. We also investigated possible changes in steroid hormones during the spring mating season. These studies support previous findings that plasma androgen and corticosterone concentrations significantly decline over the mating season. Our results demonstrate that males 0.6 km into a 15–20 km route to the feeding grounds have lower baseline corticosterone concentrations than male snakes actively courting at the den. Dispersing males also exhibit a typical stress response marked by a significant increase in corticosterone while actively courting males do not. Capture stress did not significantly influence androgen concentrations of either courting or dispersing male red-sided garter snakes. There were no significant differences in body composition indices among male snakes collected from the den, den perimeter, or 0.6 km away from the den. However, we did observe a significant negative correlation between baseline corticosterone levels and body composition indices. These data suggest that breeding is a distinct stage accompanied by specific physiological parameters that differ from those during dispersal to the feeding grounds. Our results indicate that declining baseline corticosterone concentrations may play a role in the behavioral switch between actively courting and dispersing (i.e., feeding) in the late spring.

Does adrenal responsiveness vary with sex and reproductive status in Egernia whitii, a viviparous skink?

In mammals, oestrogens generally stimulate adrenal function whilst androgens are inhibitory, and gestating females down-regulate their acute response to stressors in order to protect current reproductive investment. This study aimed to determine if adrenocortical function is similarly modulated by sex and reproductive status in the viviparous lizard, Egernia whitii. We compared the adrenocortical response to acute capture stress in female E. whitii during active (post-ovulatory and gestating) and quiescent (post-partum) phases of their reproductive cycle. We also compared the responses of reproductively quiescent males and females to acute stress and ACTH challenge to determine if there are sex-related differences in HPA axis activity when the influence of reproductive hormones is minimal. The females’ responses to acute capture stress varied significantly with reproductive stage, and quiescent females displayed the strongest immediate response, with a rapid and sustained increase in plasma corticosterone (CORT) concentrations. Post-ovulatory females showed the most conservative adrenocortical response and while gestating females showed a large immediate response, this was not as prolonged as in quiescent females. Reproductively quiescent males and females exhibited similar responses to acute stress, and also responded similarly to ACTH injection, with plasma CORT reaching maximal concentrations of 52.1 and 59.4 ng/mL, respectively. Reproductively quiescent females treated with oestrogen exhibited greater responsiveness to ACTH than control females, although basal plasma CORT concentrations were unaltered: these results suggest that the attenuation of the acute stress response observed in reproductively active females of E. whitii may be regulated upstream of ACTH secretion. Our results demonstrate that the activity of the HPA axis is modulated by reproductive status in this viviparous reptile, and that gestating females are able to buffer their embryos from the potentially adverse effects of elevated plasma corticosteroids.

Sources of stress in captivity

Animals housed in artificial habitats are confronted by a wide range of potentially provocative environmental challenges. In this article, we review many of the potential stressors that may adversely affect animals living in captivity. These include abiotic, environmental sources of stress such as artificial lighting, exposure to loud or aversive sound, arousing odors, and uncomfortable temperatures or substrates. In addition, confinement-specific stressors such as restricted movement, reduced retreat space, forced proximity to humans, reduced feeding opportunities, maintenance in abnormal social groups, and other restrictions of behavioral opportunity are considered. Research in support of the claims for these environmental elements as stressors for captive animals reveals no unique suite of behavioral or physiological responses that will clearly indicate the cause of those responses; rather, it is up to us as managers and caretakers of animals in captivity to evaluate enclosures and husbandry practices to ensure the optimal well-being of animals in our care.

Uterine evaluation and gestation diagnosis in owl monkey (Aotus azarai infulatus) using the B mode ultrasound

Gynecological and obstetrical ultrasonography has become an indispensable tool in the routine management, health evaluation and research on captive non-human primates. Ultrasound was used to evaluate the uterus and estimate the gestation of owl monkeys. Twelve couples were selected, where five were primiparous and seven multiparous females from the National Primate Center reproductive colony, Ananindeua-PA, Brazil. The procedures were carried out using the GE Logiq 100 MP, equipped with a 7.5 MHz linear probe. The females showed a simple uterus, of elongated shape, regular outline and homogeneous echogenic texture. In the uterine measurements craniocaudal diameter, dorsoventral diameter and uterine volume (UV), significant differences were identified (P < 0.05) between ultrasound examinations of primiparous and multiparous females. The UV showed a positive correlation with the number of births. The gestational sac and the embryonic echo were visible between 28 and 38 days after mating. Between 48 and 68 days after mating, embryonic death was identified in all the gestations. The chemical (use of tranquilizers) and husbandry factors (capture stress) may be related to the prenatal death. The establishing methods of conditioning the female to the ultrasonographic exam may offer a solution to this problem.

Up-regulation of the alligator CYP3A77 gene by toxaphene and dexamethasone and its short term effect on plasma testosterone concentrations

In this study we describe an alligator hepatic CYP3A gene, CYP3A77, which is inducible by dexamethasone and toxaphene. CYP3A plays a broad role in biotransforming both exogenous compounds and endogenous hormones such as testosterone and estradiol. Alligators collected from sites in Florida that are contaminated with organochlorine compounds exhibit differences in sex steroid concentrations. Many organochlorine compounds induce CYP3A expression in other vertebrates; hence, CYP3A induction by organochlorine contaminants could increase biotransformation and clearance of sex steroids by CYP3A and provide a plausible mechanism for the lowering of endogenous sex steroid concentrations in alligator plasma. We used real time PCR to examine whether known and suspected CYP3A inducers (dexamethasone, metyrapone, rifampicin, and toxaphene) up-regulate steady state levels of hepatic CYP3A77 transcript to determine if induction patterns in female juvenile alligators are similar to those reported in other vertebrates and whether toxaphene, an organochlorine compound found in high concentrations in Lake Apopka alligators, induces this gene. Estrogen receptor α (ERα), estrogen receptor β (ERβ), androgen receptor (AR), glucocorticoid receptor (GR), progesterone receptor (PR), and steroid-xenobiotic receptor (SXR) transcripts were also measured to determine whether any of these nuclear receptors are also regulated by these compounds in alligators. Dexamethasone (4.2-fold) and toxaphene (3.5-fold) significantly induced CYP3A77 gene transcript, whereas rifampicin (2.8-fold) and metyrapone (2.1-fold) up-regulated ERβ after 24 h. None of the compounds significantly up-regulated AR, ERα, GR, PR, or SXR over this time period. Plasma testosterone (T) did not change significantly after 24 h in alligators from any of the treatment groups. Dexamethasone treated animals exhibited a strong relationship between the 24 h plasma T concentrations and CYP3A77 ( R 2 = 0.9, positive) and SXR ( R 2 = 0.77, negative) transcripts, which suggests that the expression of these genes is related to plasma T in alligators. In light of our findings, we hypothesized that higher steady state CYP3A77 (and possibly SXR) gene expression would be observed in alligators collected from Lake Apopka, a polluted lake containing organochlorine compounds known to induce CYP3A isoforms in other taxa. Therefore, we measured basal levels of CYP3A77 and SXR gene transcripts in wild juvenile alligators collected from Orange Lake (reference lake), Lake Woodruff (reference lake), and Lake Apopka (contaminated lake). We found that no differences existed in CYP3A77 or SXR gene expression among animals from the lakes sampled suggesting that exposure to organochlorine compounds at concentrations present in Lake Apopka does not lead to variation in the expression of these genes, although capture stress could be interfering with these results since the glucocorticoid dexamethasone induces CYP3A77 transcript in alligators.

Capture Stress and the Bactericidal Competence of Blood and Plasma in Five Species of Tropical Birds

In wild birds, relatively little is known about intra- or interspecific variation in immunological capabilities, and even less is known about the effects of stress on immune function. Immunological assays adaptable to field settings and suitable for a wide variety of taxa will prove most useful for addressing these issues. We describe a novel application of an in vitro technique that measures the intrinsic bacteria-killing abilities of blood. We assessed the capacities of whole blood and plasma from free-living individuals of five tropical bird species to kill a nonpathogenic strain of E. coli before and after the birds experienced an acute stress. Killing invasive bacteria is a fundamental immune function, and the bacteria-killing assay measures constitutive, innate immunity integrated across circulating cell and protein components. Killing ability varied significantly across species, with common ground doves exhibiting the lowest levels and blue-crowned motmots exhibiting the highest levels. Across species, plasma killed bacteria as effectively as whole blood, and higher concentrations of plasma killed significantly better. One hour of acute stress reduced killing ability by up to 40%. This assay is expected to be useful in evolutionary and ecological studies dealing with physiological and immunological differences in birds.

Capture, care, and captive breeding of 13-lined ground squirrels, Spermophilus tridecemlineatus

Researchers use the 13-lined ground squirrel for studies of hibernation biochemistry and physiology, as well as for modeling a variety of potential biomedical applications of hibernation physiology. It is currently necessary to capture research specimens from the wild; this presents a host of unknown variables, not least of which is the stress of captivity. Moreover, many investigators are unfamiliar with the husbandry of this species. The authors describe practical methods for their capture, year-round care (including hibernation), captive mating, and rearing of the young. These practices will allow the researcher to better standardize his or her population of research animals, optimizing the use of this interesting model organism.

Assessing Mortality of Released or Discarded Fish Using a Logistic Model of Relative Survival Derived from Tagging Data

AbstractThe mortality of released or discarded fish in commercial and recreational fisheries and in fisheries‐independent research is a critical area of study for contemporary fisheries science. Key questions involving postrelease survival include the following: What fraction of the bycatch discarded in a commercial fishery survives? What is the hooking mortality of fish released by recreational anglers, and how does this vary with the treatment and condition of the fish? What fraction of tagged fish do not survive the stress of capture and tagging? What percentage of hatchery‐raised fish survive after stocking? To address these and related questions, we develop a two‐step approach to estimating absolute postrelease survival rates. First, fish are tagged and assigned to discrete classes based on their condition (from best to worst) at release. The relative survival of fish released in different conditions is estimated from tag returns by fitting a logistic model. Then, assuming that fish in the best condition survive to the same degree as fish that were not captured, absolute survival rates in the other categories are determined. Applying this method to one example from field research, we estimate that 69% of blacktip sharks Carcharhinus limbatus and 60% of bonnetheads Sphyrna tiburo survived the stress of gill‐net capture, tagging, and release in a 1992–2004 study in Florida. Our method has broad application to determining the condition‐ or treatment‐specific survival rates of released fish of many types in fisheries and research projects in which tag‐and‐recapture methods can be used.

Effect of holding duration on the immune system of western rock lobster, Panulirus cygnus

Live holding of lobsters is a major part of the post-harvest process in lobster fisheries. Following capture, animals are placed in factory tanks and held for varying lengths of time for recovery from stress due to handling, air exposure, disturbance and environmental variations. The aim of the present study was to determine the pattern of response of a range of immune and physiological parameters over varying holding periods and assess their possible application as a measure of recovery from stress of post-harvest procedures and in the determination of an appropriate duration of acclimation prior to live transport. The effect of holding duration on the following immune parameters: total haemocyte counts (THC), haemolymph clotting times, haemolymph pH, haemolymph protein concentration and the differential proportion of haemocytes, was assessed. Lobsters brought to the factory were placed in holding tanks and sampled over a period of up to 10 days. Two studies were conducted, the first on lobsters from different catch groups and the second on lobsters from the same day's catch from the same area. Experiments were conducted on adult animals (10–12 animals/treatment group) with a different group of lobsters being sampled at each time point. Various immune parameters showed alterations with time during holding. A consistent observation was significantly prolonged clotting times following four days of holding. The haemolymph pH showed a strong positive correlation to clotting time and the hyaline cell proportion showed a strong negative correlation with semi-granular cells. Although the levels of THC, clotting time and differential cell counts after one day of holding were similar to those observed in other studies on rested post-harvest lobsters, suggesting that the lobsters had recovered from the acute stress of capture and transport, subsequent alterations in pH, clotting time and differential cell counts indicated other physiological adjustments were still occurring for up to 4 days post capture. Overall the results suggest that though the effects of post-harvest procedures on the immune parameters appear to be resolved after a short duration of holding at low temperatures, no single immune parameter can provide predictable indication of the acclimation process.

Neuroendocrine modulation of stress response in the anuran, Rana esculenta

AbstractIn amphibians, as in other vertebrates, stress stimuli have been found to affect different functions, including development, growth, and reproduction. A wide range of responsiveness to stressors has been reported for amphibians; for instance, capture and/or captivity stress induced changes both in the hypothalamus-pituitary-interrenal and hypothalamus-pituitary-gonadal axes. However, few studies have examined the response to stress in terms of recovery and/or adaptation by applying stress paradigms for a short and long-term duration. In the present paper, the short-term captivity stress responses were evaluated in the anuran Rana esculenta by measuring peripheral corticosterone, androgens, prolactin (PRL), and growth hormone (GH) changes. Moreover, in long-term captivity and salinity stress, effects were evaluated by measuring peripheral PRL changes and those of PRL mRNA in the pituitary together with plasma corticosterone and androgens. Short-term (24 h) captivity stress induced an increase of peripheral corticosterone together with that of GH and PRL since these hormones are involved in the "alarm phase" and in energy demand of stressed animals. The opposite trend was found for peripheral androgens, in view of the negative effects exerted by stress in the reproductive axis. In long-term (1 month) captivity and salinity stress, responses were consistent with the increasing of PRL mRNA at pituitary level, through a long-loop feedback mechanism depending on the decreasing levels of peripheral PRL, whereas no changes were found in the levels of plasma corticosterone and androgens. Therefore, it seems that Rana esculenta activates different neuroendocrine mechanisms depending on the duration of stress and on the types of stressors.

Bisphenol A in Artificial Indoor Streams: II. Stress Response and Gonad Histology in Gammarus fossarum (Amphipoda)

The effects of the world wide-distributed chemical bisphenol A (BPA) on the endocrine system of vertebrates have been demonstrated in several studies. Here, we report on the impact of BPA (0, 5, 50 and 500 microg/l nominally, deduced effective concentrations 0, 0.24, 2.4, and 24.1 microg/l, respectively, all at 15 degrees C) on the 70 kD stress protein family (hsp70), the 90 kD stress protein family (hsp90), and gonad histology of the crustacean Gammarus fossarum exposed in artificial indoor streams. The animals were exposed for a maximum of 103 days and samples were taken at the beginning and at days 34, 69 and 103 of the experiment. Exposure to BPA resulted in accelerated maturation of oocytes in females and in a decline in the number and size of early vitellogenic oocytes. The level of hsp90, which plays a pivotal role in vertebrate sex steroid signal transduction, was significantly reduced by BPA. In all five streams, measured parameters did not indicate any captivity stress for a period of 69 days. Beyond this time, the mortality rate and proteotoxic effects, the latter measured by hsp70 expression, were found to be elevated.