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This review analyzes what could be regarded as the “ clandestine organs ” of the endocrine system: the gut microbiome, the immune system, and the stress system. The immune system is very closely related to the endocrine system, with many intertwined processes and signals. Many researchers now consider the microbiome as an ‘organ’ that affects the organism at many different levels. While stress is certainly not an organ, it affects so many processes, including endocrine-related processes, that the stress response system deserved a special section in this review. Understanding the connections, effects, and feedback mechanisms between the different “ clandestine organs ” and the endocrine system will provide us with a better understanding of how an organism functions, as well as reinforce the idea that there are no independent organs or systems, but a complex, interacting network of molecules, cells, tissues, signaling pathways, and mechanisms that constitute an individual. [ABSTRACT FROM AUTHOR]

Optimal feeding strategies improve fish growth and health but may be affected by ammonia stress in closed rearing systems such as tanks or ponds. This study aimed to evaluate the effects of feeding frequency and ammonia levels in rearing water on the enzymes and genes involved in oxidative stress of yellow catfish. Experiment (ammonia exposure) and control groups were randomly assigned to one of three feeding frequencies (1, 2 and 4 times daily) for 8 weeks. Weight gain increased as feeding frequency increased from 1 to 4 times daily, but feed conversion ratio values decreased. The highest survival in ammonia group was found when fish was fed 2 times daily. Glutathione peroxidase activity and total antioxidant capacity in liver and brain of fish exposed to ammonia increased as feeding frequency increased from 1 to 4 times daily. Liver malondialdehyde content in control group decreased as feeding frequency increased from 1 to 4 times daily. The lowest liver malondialdehyde content in ammonia group was observed when fish was fed 2 times daily. Liver mRNA expression of superoxide dismutase and catalase in control group increased as feeding frequency increased from 1 to 4 times daily, but the highest superoxide dismutase and catalase expression in ammonia group were observed when fish were fed 2 times daily. This study indicates that higher feeding frequency of yellow catfish exposed to ammonia could result in oxidative stress and poor survival. The optimal feeding frequency of yellow catfish exposed to ammonia is 2 times daily. [ABSTRACT FROM AUTHOR]

Eutrophication and climate change are increasing the incidence of severe hypoxia in fish nursery habitats, yet the programming effects of hypoxia on stress responsiveness in later life are poorly understood. In this study, to investigate whether early hypoxia alters the developmental trajectory of the stress response, zebrafish embryos were exposed to 4 h of anoxia at 36 h post-fertilization and reared to adults when the responses to secondary stressors were assessed. While embryonic anoxia did not affect basal cortisol levels or the cortisol response to hypoxia in later life, it had a marked effect on the responses to a social stressor. In dyadic social interactions, adults derived from embryonic anoxia initiated more chases, bit more often, entered fewer freezes and had lower cortisol levels. Adults derived from embryonic anoxia also performed more bites towards their mirror image, had lower gonadal aromatase gene expression and had higher testosterone levels. We conclude that acute embryonic anoxia has long-lasting consequences for the hormonal and behavioural responses to social interactions in zebrafish. Specifically, we demonstrate that acute embryonic anoxia favours the development of a dominant and aggressive phenotype, and that a disruption in sex steroid production may contribute to the programming effects of environmental hypoxia. [ABSTRACT FROM AUTHOR]

Hyperosmotic stress has often been investigated from osmoregulation perspectives while the effects of such stress on the immune capacity remain largely unexplored. In this study, striped catfish were submitted to a gradual hyperosmotic stress (up to 20 ppt), followed by an infection with a virulent strain of an intracellular bacteria, Edwardsiella ictaluri . Physiological parameters (plasma osmolarity, gill NaK ATPase) have been investigated. Moreover, a label free quantitative proteomics workflow was used to study how salinity affects the proteome of kidney of no infected and infected fish. The flow consisted in initial global profiling of relative peptide abundances (by LC/MS, peak area quantification based on extracted ion currents) followed by identification (by MS/MS). Differentially expressed proteins were analysed in DAVID interface to isolate functional pathways involved in the response to bacterial infection and which are influenced by environmental salinity changes. In response to hyperosmotic stress, plasma osmolarity increased while gill Na + K + ATPase slightly increased. In kidney proteome, 2024 proteins were identified, among which 496 proteins were differentially expressed. Hierarchical clustering analysis leads to isolation of 4 main clusters. Several pathways and functional categories, mostly related to cell metabolism, response to stress, cell structure, immunity and ion homeostasis were highlighted and discussed. Significance The striped catfish is a highly worldwide commercialized species and is mainly produced in the Mekong Delta (Vietnam), which is currently subjected to sea level rise and increasing salt intrusions in these aquacultures resources. Moreover, salt is commonly used as antiseptic in aquacultures to treat microbial diseases. To date, the effect of prolonged exposure to hyperosmotic condition have been mainly looking at changes regarding the growth and the osmoregulation while the effect of such stress on the immune capacity and susceptibility to pathogen have been poorly investigated. This study aims to highlight molecular changes in kidney occurring during acclimation to hyperosmotic conditions, particularly those involved in fish immune defences. [ABSTRACT FROM AUTHOR]

African sharptooth catfish Clarias gariepinus were housed under continuous dim light (1 lx) or 12L: 12D (350-0 lx) cycles. The number of skin lesions, as indicator of aggressive acts, and plasma cortisol levels, as indicator of stress-axis activity, were measured at baseline as well as following a stressor (given in the light or dark phase). Results showed that (1) baseline plasma cortisol levels were not different between photoperiods, (2) the number of baseline skin lesions was highest for C. gariepinus housed under continuous dim light, (3) stressor-induced peak levels of plasma cortisol were highest in the light phase and (4) the number of skin lesions following a stressor was highest in the dark phase. The higher number of stressor-related skin lesions in the dark (active) phase suggests increased stressor-induced aggression while in the active phase. In addition, the data suggest that housing under continuous dim light does not result in higher stress-axis activity, as measured by baseline levels of cortisol, but does result in more stressor-induced aggression, as measured by the higher number of skin lesions. The latter may be related to the fact that the continuous dim light photoperiod has twice the number of dark-phase (active) hours in which stressor-induced aggression is stronger compared to the 12L: 12D photoperiod, which has a light phase in which stressor-induced aggression is lower. [ABSTRACT FROM AUTHOR]

Jundiá ( Rhamdia quelen ) is a suitable species for aquaculture in regions of temperate or subtropical climate. This species has received great attention regarding several aspects of physiology as well as an organism to study the impact of environmental contaminations. However, experiments using validated and objective tests to evaluate the jundiá behavior are scarce. The effects of acute stress have been studied in other fish species, such as zebrafish ( Danio rerio ), however, the effects in jundiá are lacking. Thus, we evaluated the effects of acute stress (net chasing) on anxiety-like and social behavior in jundiá. For these purpose, all behavioral analyses were carried out using automated tracking software. We showed that the acute stress protocol increased cortisol levels and induced anxiogenic-like behavior in the novel tank test, and decreased social behavior in jundiá. The antidepressant fluoxetine was able to prevent the effects of acute stress on social behavior. Here we show a behavioral evaluation of Rhamdia quelen using consolidated tests and computerized analysis, which allows more measurable, reliable and comparable results. [ABSTRACT FROM AUTHOR]

Structural environmental enrichment, that is, a deliberate addition of physical complexity to the rearing environment, is sometimes utilized to reduce the expression of the undesirable traits that fish develop in captivity. Increasing demands and regulations regarding usage of enrichment to promote fish welfare also make investigations on the effects of enrichment important. Here, we sythesize the current state-of-the-art knowledge about the effects of structural environmental enrichment for fish in captive environments. We find that enrichment can affect several aspects of the biology of captive fish, for example, aggression, stress, energy expenditure, injury and disease susceptibility. Importantly, these effects are often varying in direction and magnitude, and it is clear that just addition of structure is not a solution to all problems in fish rearing. Each species and life stage needs special consideration with respect to its natural history and preferences. A multitude of different enrichment types has been investigated and many studies investigate several enrichment components at the same time, making comparisons among studies difficult. To the present date, the majority of efforts have been directed to investigate salmonid fish in stock-fish hatcheries and cichlids from a basic research perspective. Some contexts are under-studied with respect to environmental enrichment, for instance effects on results in basic research and welfare effects in display aquaria. There are many research opportunities left within this field. However, future studies could utilize experimental designs which make it possible to discriminate between effects of different environmental manipulations to a higher degree than what has been performed to this date. [ABSTRACT FROM AUTHOR]

This two-factor experiment incorporating three photoperiods (12L:12D, 16L:8D and 24L:0D) and two feeding methods (manual and self-feeding) was carried out to determine their effect on the growth performance of striped knifejaw, Oplegnathus fasciatus . Thirty juveniles were stocked into each 300 L tanks in triplicate for each treatment and fed a commercial diet for 10 weeks. Two-way ANOVA revealed that both photoperiod and feeding method have significant effect on the final mean weight, weight gain (%) and feed efficiency (FE) (P < 0.05); however, their interaction did not produce any significant effect (P > 0.05). Although the growth parameters didn't have significant difference between manual and self-feeding in fish exposed to 12L:12D photoperiod (P > 0.05), fish under other two photoperiods showed significant improvement under self-feeding system compared to manual feeding (P < 0.05). Final mean body weights in fish under 16L:8D and 24L:0D were 119.7 and 124.0 g at manual feeding; however, increased to 128.0 and 133.7 g, respectively at self-feeding system. While two daily peaks of feed intake were observed in 12L:12D and 16L:8D photoperiods when self-feeders used, 24L:0D photoperiod showed only one morning peak. At the end, there was no significant difference in different stress indicators such as cortisol, glucose and total protein among the treatments (P > 0.05). Finally, the results suggested that the extended (16L:8D) and continuous (24 L:0D) photoperiods, and the provision of self-feeder could significantly improve the growth performance of striped knifejaw without changing the stress response. Statement of relevance This is the first report on the combined application of photoperiod manipulation and self-feeder on striped knifejaw, which revealed that the combination would help to improve the growth performance significantly. The indoor aquaculture industry, at least, will be benefited from the important insights achieved from this study to stimulate the growth performance of this commercially important species, which has great consumer demand in Japanese market. [ABSTRACT FROM AUTHOR]

Land use changes within watersheds can have large effects on stream ecosystems, but the mechanistic basis of those effects remains poorly understood. While changes to population size presumably reflect underlying variation in organismal health and condition, such individual-level metrics are rarely evaluated in the context of ecosystem disturbance. To address this deficiency, we combined physiological sampling with geographic information systems to quantify the effects of land use on physiological indicators of health in largemouth bass. More specifically, we first quantified blood metrics relating to nutrition, oxidative stress, and the glucocorticoid stress response from largemouth bass residing in eight watersheds. We then used Akaike's information criterion to define relationships between these blood metrics and land cover, including forests, agricultural areas, urban areas, and wetlands. The proportion of forest cover in a watershed was the best predictor of blood metrics representing recent feeding and resistance to oxidative stress, whereas the proportion of wetlands was the best predictor of glucocorticoid function; however, further investigation is needed, as the explanatory power of the models was relatively low. Patterns in energy reserves were not influenced by any land use practices. Interestingly, anthropogenic land use categories, such as urban and agricultural areas, were not the best predictor for any blood metrics. Together, our results indicate that fish health is most related to natural features of a landscape rather than anthropogenic land uses. Furthermore, these findings suggest that physiological methods could supplement traditional population and community assessments to develop a more comprehensive understanding of ecosystem interactions and improve stream management. [ABSTRACT FROM AUTHOR]

Copepods are the optimal live feed for hatcheries and improvement of cultivation techniques, to provide a constant food source, is crucial for the expansion of the industry. However, studies based on experimental work and real observations can be labour intensive and expensive. A simple model was developed based on the well-known life history traits of Acartia tonsa to describe batch cultures and their productivity. Model results were compared to observations from real cultures. For maximizing egg production yields, the optimal stocking density of copepods should be adapted to the design (depth) of the culture tanks. At high densities, stress due to encountering conspecifics, as well as cannibalism of eggs by adults, limits egg production yields. Using this model, the potential selection efficacy of copepod strains was also evaluated in order to increase production yields. Selecting larger copepods increases the egg production per litre of culture, but decreases the optimal stocking density and the range of densities at which egg production yield is high, and vice-versa. Selecting copepods that are less affected by stress due to conspecifics only affect production yields at very high adult densities. However, selecting copepods with a high Specific Growth Rate ( SGR), or improving their SGR, was found to be an alternative which did not affect the optimal cultivation densities but improved egg production yields. [ABSTRACT FROM AUTHOR]

A multi-biomarker approach was developed to evaluate responses of European flounder ( Platichthys flesus ) in three contrasted estuaries over the English Channel: the Canche (pristine site), Tamar (heavy metals and PAHs contamination) and Seine (heavily pollution with a complex cocktail of contaminants). The condition factor and several biomarkers of the immune system, antioxidant enzymes, energetic metabolism and detoxification processes were investigated in young-of-the-year (0+) and one-year-old (1+) flounder. Results underlined the difference between the pristine site and the Seine estuary which showed a lower condition factor, a modulation of the immune system, a higher Cytochrome C oxidase activity, and an up-regulation of BHMT expression. The moderate biomarker responses in the Tamar fish could be linked to the specific contamination context of this estuary. Flounder life history traits were analyzed by otolith microchemistry, in order to depict how the fish use their habitat and thus respond to chemical stress in estuaries. [ABSTRACT FROM AUTHOR]

Fish is highly affected by many environmental stresses such as temperature and invasive infection. The extracellular signal-regulated kinase (ERK) pathway, part of the mitogen-activated protein kinase (MAPK) family, is found to act as crucial mediators for cell differentiation, proliferation and cell response to various stresses. In the present study, ERK2 ( Lc ERK2) and ERK5 ( Lc ERK2) were cloned and characterized from large yellow croaker, Larimichthys crocea . The full length cDNA sequence of Lc ERK2 was of 1910 bp, including an ORF of 1110 bp encoding a polypeptide of 369 amino acids. The full length cDNA sequence of Lc ERK5 was of 3720 bp, including an ORF of 3375 bp encoding a polypeptide of 1124 amino acids. Multiple alignments showed that both Lc ERK2 and Lc ERK5 contained highly conserved TEY motif and S_TKc domain in MAPK family and the unique catalytic and active structures of ERK2 and ERK5. Subcellular localization revealed that both Lc ERK2 and LcERK5 expressed in the cytoplasm and cell nucleus. The expression of Lc ERK2 and Lc ERK5 were detected in most tissues of large yellow croaker, with the most predominant expression of Lc ERK2 in brain and Lc ERK5 in gill, and the weakest expression of Lc ERK2 in liver and Lc ERK5 in intestine, respectively. The expression levels of Lc ERK2 and Lc ERK5 after temperature stress and poly I:C and flagellin challenge were investigated in LCK ( L. crocea kidney) cells. After temperature stress, significant down-regulations of Lc ERK2 transcripts were detected after 10 °C stress ( p < 0.05) whereas Lc ERK2 transcripts increased significantly after 35 °C stress ( p < 0.05). However, significant down-regulations of Lc ERK5 expression were detected at most time points after both cold and heat stress ( p < 0.05). However, significant up-regulations of Lc ERK2 and Lc ERK5 transcripts were found after immune challenge ( p < 0.05). Our results showed that Lc ERK2 transcripts enhanced after heat stress and both Lc ERK2 and Lc ERK5 transcripts could be induced by immune challenge. These findings indicated that Lc ERK2 might be more important in fish response to high temperature stress and both Lc ERK2 and Lc ERK5 might play an important role in fish immune response. [ABSTRACT FROM AUTHOR]

Anthropogenic activities are greatly altering the habitats of animals, whereby fish are already encountering several stressors simultaneously. The purpose of the current study was to investigate the capacity of fish to respond to two different environmental stressors (high temperature and overnight hypoxia) separately and together. We found that acclimation to increased temperature (from 7.7±0.02°C to 14.9±0.05°C) and overnight hypoxia (daily changes from normoxia to 63-67% oxygen saturation), simulating climate change and eutrophication, had both antagonistic and synergistic effects on the capacity of fish to tolerate these stressors. The thermal tolerance of Arctic char (Salvelinus alpinus) and landlocked salmon (Salmo salar m. sebago) increased with warm acclimation by 1.3 and 2.2°C, respectively, but decreased when warm temperature was combined with overnight hypoxia (by 0.2 and 0.4°C, respectively). In contrast, the combination of the stressors more than doubled hypoxia tolerance in salmon and also increased hypoxia tolerance in char by 22%. Salmon had 1.2°C higher thermal tolerance than char, but char tolerated much lower oxygen levels than salmon at a given temperature. The changes in hypoxia tolerance were connected to the responses of the oxygen supply and delivery system. The relative ventricle mass was higher in cold- than in warm-acclimated salmon but the thickness of the compact layer of the ventricle increased with the combination of warm and hypoxia acclimation in both species. Char had also significantly larger hearts and thicker compact layers than salmon. The results illustrate that while fish can have protective responses when encountering a single environmental stressor, the combination of stressors can have unexpected species-specific effects that will influence their survival capacity. [ABSTRACT FROM AUTHOR]

Flora and fauna evolved under natural day and night cycles. However, natural light is now enhanced by artificial light at night, particularly in urban areas. This alteration of natural light environments during the night is hypothesised to alter biological rhythms in fish, by effecting night-time production of the hormone melatonin. Artificial light at night is also expected to increase the stress level of fish, resulting in higher cortisol production. In laboratory experiments, European perch ( Perca fluviatilis ) were exposed to four different light intensities during the night, 0 lx (control), 1 lx (potential light level in urban waters), 10 lx (typical street lighting at night) and 100 lx. Melatonin and cortisol concentrations were measured from water samples every 3 h during a 24 hour period. This study revealed that the nocturnal increase in melatonin production was inhibited even at the lowest light level of 1 lx. However, cortisol levels did not differ between control and treatment illumination levels. We conclude that artificial light at night at very low intensities may disturb biological rhythms in fish since nocturnal light levels around 1 lx are already found in urban waters. However, enhanced stress induction could not be demonstrated. [ABSTRACT FROM AUTHOR]

In the present study, we assessed the responses of the vasotocinergic and isotocinergic systems to chronic stress induced by cortisol administration in the gilthead sea bream (Sparus aurata). Pituitary and plasma arginine vasotocin (AVT) and isotocin (IT) levels, as well as hypothalamic pro-vasotocin (pro-VT) and pro-isotocin (pro-IT) mRNA expression levels, were analysed. In addition, the mRNA levels of three receptors, AVTR type V1a2, AVTR type V2 and ITR, were analysed in several target organs associated with the following physiological processes: (i) integration and control (hypothalamus), (ii) metabolism and its control (liver and hypothalamus), (iii) osmoregulation (gills) and (iv) stress response (head kidney). Specimens were injected intraperitoneally with slow-release implants (5 μL g(-1) body mass) containing coconut oil alone (control group) or with cortisol (50 μg g(-1) body mass; cortisol group). Both AVT and IT synthesis and release were correlated with plasma cortisol values, suggesting a potential interaction between both hormonal systems and cortisol administration. Our results suggest that the activation of hepatic metabolism as well as the hypothalamic control of metabolic processes provide the energy necessary to overcome stress, which could be partly mediated by AVTRs and ITR. Upregulation of branchial AVT and IT receptor expression following cortisol treatment suggests an involvement of the vasotocinergic and isotocinergic systems in the regulation of ion channels/transporters during stressful situations. Finally, changes in AVT and IT receptor mRNA expression in the head kidney suggest these nonapeptides participate in feedback mechanisms that regulate the synthesis/release of cortisol. Our results indicate a relationship between cortisol and both the vasotocinergic and isotocinergic systems during simulated chronic stress in S. aurata. [ABSTRACT FROM AUTHOR]

The present paper deals with the changes in cholesterol level of liver during starvation in Clarias batrachus. In the present investigation, the level of cholesterol content was found relatively higher in females than in males both under normal and starved conditions. The cholesterol content was estimated by the Sackett's method (1925). From the beginning of starvation, the cholesterol concentration of liver showed sharp depletion and after 40 days, it decreased up to 80% in male & 76% in female. This rapid decrease in cholesterol level observed in hepatic tissues may be attributed to the synthesis of stress hormones such as glucocorticoids and adrenocorticoids, which may promote gluconeogenesis and may help the animal to combat the stressful condition of starvation. Clarias adapted well to starvation stress and survived all throughout the experimental period. [ABSTRACT FROM AUTHOR]

Competitive interactions with non-native species can have negative impacts on the conservation of native species, resulting in chronic stress and reduced survival. Here, juvenile Atlantic salmon ( Salmo salar) from two allopatric populations ( Sebago and La Have) that are being used for reintroduction into Lake Ontario were placed into semi-natural stream tanks with four non-native salmonid competitors that are established in Ontario streams: brown trout ( S. trutta), rainbow trout ( Oncorhynchus mykiss), Chinook salmon ( O. tshawytscha) and coho salmon ( O. kisutch). Brown trout and rainbow trout reduced the survival and fitness-related traits of Atlantic salmon, whereas Chinook salmon and coho salmon had no impact on these traits. These data support theories on ecological niche overlap and link differences in observed aggression levels with competitive outcomes. Measurements of circulating hormones indicated that the Atlantic salmon were not chronically stressed nor had a change in social status at the 10-month time point in the semi-natural stream tanks. Additionally, the Sebago population was better able to coexist with the non-native salmonids than the La Have population. Certain populations of Atlantic salmon may thus be more suitable for some environments of the juvenile stream phase for the reintroduction into Lake Ontario. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate immunological, metabolic and osmoregulatory secondary stress responses in Eleginops maclovinus specimens submitted to three different stocking densities: i) low (3.1 kg m −3 ), medium (15 kg m −3 ) and high (60 kg m −3 ) during 10 days, alone or in combination with a previous treatment of a protein extract of the pathogen Piscirickettsia salmonis (0.5 μg g weight body −1 ). Plasma, liver, gill and kidney samples were obtained at the end of both experiments. Plasma cortisol and amino acid levels increased, while plasma glucose, triglyceride and lactate levels decreased at higher stocking densities. However, no effects were observed on serum Immunoglobulin type M (IgM anti P. salmonis level) values. Gill Na + , K + -ATPase activity enhanced under these experimental conditions, suggesting an osmotic imbalance. Energy metabolism changes, assessed by metabolite concentrations and enzyme activities, indicated a reallocation of energetic substrates at higher stocking densities. Specimens inoculated with a protein extract of P. salmonis and maintained at different stocking densities showed primary stress response, as all groups enhanced plasma cortisol concentrations. Serum IgM levels increased after treatment with P. salmonis extract but a negative influence of high stocking density on IgM production was observed when immune system was activated. Furthermore, treatment with P. salmonis protein extract evoked deep changes in the metabolite stores in all tissues tested, indicating a mobilization of energy substrates in response to infection. The results show that stocking density induced immunological, metabolic and osmoregulatory secondary stress responses in E . maclovinus specimens and that previous treatment with P. salmonis compromise these changes. [ABSTRACT FROM AUTHOR]

By interacting with Na+, K+-ATPase (NKA), the FXYD domain-containing ion transport regulator (FXYD) is involved in teleost osmoregulation, but knowledge of FXYD in marine fish is limited. In the present study, fxyd11 and fxyd12 were identified from the spotted scat (Scatophagus argus), and the two members of the FXYD protein family were expressed in a tissue-specific manner. Fxyd11 mRNA was predominantly expressed in gills, whereas fxyd12 mRNA was mainly distributed in kidneys and intestines. Acute hyposaline stress altered the activity of NKA and the expression of fxyd11 and fxyd12 in gills, kidneys, and intestines. Branchial fxyd11 mRNA expression remained at a low level during freshwater acclimation, whereas NKA activity increased, showing a negative correlation that differed from previous reports. Similarly, renal expression of fxyd11 and fxyd12 mRNA was negatively correlated with NKA activity. Unlike in gills and kidneys, intestinal NKA activity and mRNA expression of fxyd11 and fxyd12 were comparably suppressed. Taken together, the salinity-dependent expression of fxyd11 and fxyd12, and correlation with NKA activity suggested that both fxyd11 and fxyd12 were involved in the response to acute hyposaline challenge in the spotted scat. [ABSTRACT FROM AUTHOR]

Abstract: Environmental enrichment may attenuate stress response of several vertebrates. In the case of fish, although their stress response is well investigated, the effect of structural complexity as a means of environmental enrichment on stress response is not widely studied. The present study aims to investigate the possible effect of structural enrichment (blue gravel substrate) on gilthead seabream Sparus aurata primary and secondary stress responses during confinement and after recovery. Fish (initial mass 20.3±0.22g; age 0+) were reared in tanks with blue substrate (BS) or no-substrate (NS) for 75days. Fish (triplicated groups) were subjected to 90min of confinement stress and sampled at 30, 60 and 90min of confinement, as well as at 2, 6 and 24h after stress (recovery). Triplicate groups of BS and NS fish were left undisturbed (unstressed fish). During rearing BS fish had better growth performance and less aggressive behavior than NS fish. Plasma cortisol levels and brain neurotransmitters of BS and NS fish were increased during confinement. Cortisol reduction (after stress-induced increase) occurred earlier in NS fish (60min) than BS fish (90min), while cortisol levels recovered in 2h in both treatments. Serotonin metabolite 5-HIAA levels and serotonergic activity (5-HIAA/5-HT) were recovered in 6h in BS fish, while they remained elevated for NS fish. Dopaminergic system response to confinement showed a transient increase in BS fish (60min), while no effect was observed in NS fish. Concerning secondary stress response, glucose levels of BS fish decreased after 6h of recovery while NS fish were not affected. On the other hand, NS fish presented a reduction of triacylglycerides (60 and 90min) during confinement, while BS fish response was not affected. Osmolality and plasma total protein levels increased at 30min of confinement and returned to unstressed levels in 24h in both treatments. Present results indicate that the presence of blue substrate did modify the time course of gilthead seabream stress response to confinement. The overall performance of fish reared with blue substrate suggests that they are in better fitness than fish reared in plain tanks. The efficacy of the blue substrate as environmental enrichment enhancing gilthead seabream welfare is further reinforced and strongly encourages for additional investigations. [Copyright &y& Elsevier]

Abstract: Bonefish (Albula spp.) are a group of species targeted by recreational anglers in shallow tropical and sub-tropical seas worldwide. Although bonefish angling is almost entirely catch-and-release, mortality can occur because the stress associated with angling and handling causes locomotory impairment that promotes post-release predation. We used tri-axial accelerometer loggers to compare the locomotor activity and behavior of bonefish exposed to angling-related stressors and immediately released (n=10, 39.9±1.1cm FL), to those retained in a recovery bag for 15min prior to release (n=10, 39.6±1.0cm FL) in a tidal creek in Eleuthera, The Bahamas. We also validated the use of reflex action mortality predictors (RAMP) as an impairment index for evaluating bonefish condition upon release. Following release, bonefish were visually tracked for 30min with floats to evaluate short-term survival, after which the accelerometer was retrieved. Bonefish held in recovery bags exhibited significantly less locomotory impairment immediately post-release, and higher maximum tail beat frequencies and amplitudes up to 15min post-release, which was likely due to the time spent in the recovery bag. Bonefish in the recovery bag treatment also spent more time resting in possible refuge areas, which may facilitate further recovery and avoidance from predation. RAMP provided a gradient of impairment scores that were correlated with stressor duration. Retaining bonefish in recovery bags improved swimming abilities during the critical time period where the majority of post-release predation occurs, and one fish that was not placed in the recovery bag was preyed upon during the monitoring period. Further testing is needed to determine if the locomotory and behavioral benefits of retaining bonefish in recovery bags translate into improved survival from predation in more predator rich environments. [Copyright &y& Elsevier]

The purpose of this study was to determine the influence of some phytobiotics on oxidative stress at Oreochromis niloticus reared in a recirculating aquaculture system. The experimental variants were: V1-control, V2-1% rosemary (Rosmarinus officinalis)/kg feed, V3-1% sea buckthorn (Hippophae rhamnoides)/kg feed and V4-1% ginger (Zingiber officinale)/kg feed. Analysis of oxidative stress was performed by measuring the following indicators: reduced glutathione (GSH), lipid peroxidation (malondialdehyde-MDA) and total antioxidant capacity (TAC). The analyses were measured using the spectrophotometer SPECORD 210 Analytikjena, at the beginning and at the end of the experiment from the blood, plasma, muscle tissue, liver and gut. Regarding lipid peroxidation significant differences (p<0.05), in statistical terms, were recorded in plasma and gut level. Concerning the total antioxidant capacity significant differences (p<0.05) were recorded in plasma. Results obtained in determination of reduced glutathione from blood showed between initial and final experimental variants significant differences (p<0.05). At the end of experiment, it was observed a correlation between MDA and TAC in the gut level. In conclusion, based on the results from lipid peroxidation analysis, we can say that oxidative stress was reduced after administration of sea buckthorn in feed of Oreochromis niloticus species. [ABSTRACT FROM AUTHOR]

Abstract: The glucocorticoid receptor (GR) plays an essential role during seawater (SW) acclimation. However, the regulation of GR isoforms 1 and 2 (GR1 and GR2) and the mineralocorticoid receptor (MR) during SW acclimation is poorly understood. To address this, we localized and examined the GR1, GR2 and MR transcripts in the tilapia gill, kidney and intestine. Our results indicated that the GR1, GR2 and MR levels were increased in the kidney and intestine on day 1 in seawater (SW) fish, which is in agreement with the recognized osmoregulatory role of the corticosteroid receptors. The SW transfer increased the GR2 and MR transcripts in the gill on day 1 and 4, respectively. Surprisingly, no significant difference was obtained for the GR1 mRNA level. Analysis of the plasma parameters in freshwater (FW) and SW tilapia showed that the plasma cortisol levels were significantly increased at day 1 in the SW fish compared to the FW fish. This is the first study that focused on the spatial distribution of GR1, GR2 and MR in the osmoregulatory organs of freshwater (FW)- and SW-acclimated tilapia by in situ hybridization. Consistent with the Q-PCR results, the expression levels of the GR1, GR2 and MR transcripts were increased or decreased in the SW-acclimated tilapia’s gill, kidney and intestine compared to the FW fish. We observed that GR1, GR2 and MR were localized in the branchial epithelial cells and chloride cells of the gill, proximal tubules of the kidney and columnar cells of the intestine. Together, these results indicate that the mobilization of corticosteroid receptors is dependent on the target tissue, salinity and exposure time. [Copyright &y& Elsevier]

Cells have evolved different networks of cellular stress responses to adapt during environmental changes and survive combating wide variety of stress. Mitochondrial heat shock protein 70 (mtHSP70) are essential for maintaining cellular homeostasis. c-Jun-N terminal kinase (JNK), a subfamily of MAPK, plays a key role in the transmission of extracellular signal for survival and death. In the present investigation, the differential expression of phosphorylated JNK1/2 with corresponding increases in heat shock transcription factor-1 (HSF-1) under high levels of B-cell lymphoma 2 (Bcl-2), HSP70 transcripts (twofold) and mtHSP70 has been correlated with fish survival in polluted Ennore estuary. This study suggests that in Ennore sample, the amplification in HSP70 transcripts along with corresponding mtHSP70 overexpression might be due to activation of JNK1/2 and HSF-1. This would influence the expression of Bcl-2 protein involved in mitochondrial survival under pollution-stressed condition. [ABSTRACT FROM AUTHOR]

Fluctuating asymmetry (FA), which has been examined in a variety of plants and animals, is widely promoted as a useful bioindicator of exogenous stressors in habitats, whether of natural or anthropogenic origin. Wildlife managers and researchers often use a specific group of organisms as an indicator of the health of a given habitat. The purpose of this review is to demonstrate that FA can be an effective fish biomonitoring tool by presenting a vote counting meta-analysis of 81 fish FA studies published between 1966 and the first half of 2009. The vote counts were analyzed with the G test for independence to determine whether the probability of observing significant morphological asymmetry is determined by character type, exogenous stressor type, or fish order. The information obtained from these papers and their analysis is then used to outline areas in which FA studies can be improved: (1) carefully considering character choice; (2) distinguishing between asymmetry types; (3) determining the level of measurement error in between-sides character variation; (4) determining baseline FA levels in populations; (5) increasing the number of laboratory studies which corroborate field observations of FA; (6) conducting true replications of studies to validate previous findings. Only with more critical experimental design and data analysis can FA be used as a powerful tool for assessing environmental degradation. [ABSTRACT FROM AUTHOR]

The Root effect is a pH-dependent reduction in hemoglobin-O2 carrying capacity. Specific to ray-finned fishes, the Root effect has been ascribed specialized roles in retinal oxygenation and swimbladder inflation. We report that when rainbow trout are exposed to elevated water carbon dioxide (CO2), red muscle partial pressure of oxygen (PO2) increases by 65%--evidence that Root hemoglobins enhance general tissue O2 delivery during acidotic stress. Inhibiting carbonic anhydrase (CA) in the plasma abolished this effect. We argue that CA activity in muscle capillaries short-circuits red blood cell (RBC) pH regulation. This acidifies RBCs, unloads O2 from hemoglobin, and elevates tissue PO2, which could double O2 delivery with no change in perfusion. This previously undescribed mechanism to enhance O2 delivery during stress may represent the incipient function of Root hemoglobins in fishes. [ABSTRACT FROM AUTHOR]