Plasma Cortisol Levels In Fish Research Articles

Effects of tank color on the growth, survival rate, stress response, and skin color of juvenile hybrid catfish (Clarias macrocephalus × Clarias gariepinus)

This study focused on the effects of tank color on the growth, survival rate, stress response, and skin color of juvenile hybrid catfish (Clarias macrocephalus × Clarias gariepinus) reared in tanks of 5 different colors (white, red, green, blue, and black). Experiments were performed in triplicate with a duration of 8 weeks. Growth performance, feed utilization efficiency, survival rates, stress levels (as indicated by hematocrit, blood glucose, and plasma cortisol levels), and skin color parameters were evaluated in this study. Fish reared in red tanks exhibited a significantly higher mean final body weight (FBW) (27.50 ± 0.26 g), greater weight gain (WG) (18.57 ± 0.30 g), and a higher specific growth rate (SGR) (2.08 ± 0.03% per day) than those reared in tanks of other colors (P < 0.05). In addition, fish reared in red tanks had the lowest mean feed conversion ratio (FCR) (1.23 ± 0.05), which was significantly different from those reared in green (1.86 ± 0.10), blue (1.88 ± 0.04), and black (1.88 ± 0.16) tanks (P < 0.05). Fish reared in red (95.55 ± 2.22%) and blue tanks (95.56 ± 4.44%) had higher survival rates (SR) than fish reared in white (93.33 ± 3.85%), green (84.44 ± 5.88%), and black (80.00 ± 3.85%) tanks. The survival rates of fish reared in red and blue tanks were significantly higher than those reared in black tanks (P < 0.05). The stress indicators revealed the highest levels of hematocrit for fish reared in green tanks (41.80 ± 2.26%), followed by those reared in black (37.86 ± 2.19%), blue (37.76 ± 4.24%), red (36.38 ± 2.39%), and white (31.06 ± 4.45%) tanks. Of these, the fish reared in green tanks had a significantly higher mean hematocrit level than those reared in white tanks (P < 0.05). The plasma cortisol levels of fish reared in red tanks (18.73 ± 4.48 nmol/L) were lower than those reared in tanks of other colors. The skin color of fish reared in white tanks was the lightest (grayish–brown and yellowish–white), followed by fish reared in red, green, blue, and black tanks, which had the darkest skin color (black). This study demonstrated that the lightness (L*) of the tank color had an effect on fish skin color (74%). The assessment of growth performance, feed utilization efficiency, survival rate, stress responses, and skin color indicated that red is the most appropriate tank color for rearing hybrid catfish.

Spurge ( Euphorbia rigida ) exhibits anaesthetic effect in rainbow trout ( Oncorhynchus mykiss ) without altering plasma cortisol levels

This study was conducted to investigate a potential new organic anaesthetic for aquaculture practices. Aqueous macerate of spurge stem (Euphorbia rigida) was obtained by adding 200 g of plant powder to 1.5 L of distilled water and applied to rainbow trout (Oncorhynchus mykiss) at 5 different concentrations (30000, 40000, 50000, 60000 and 70000 µL L−1) to determine induction (loss of equilibrium and deep anaesthesia) and recovery (recovery of equilibrium and full recovery) durations. In addition, plasma cortisol levels of fish within 0 hours were determined to evaluate stress response. It was determined that there were 4 concentrations that can be used as suitable anaesthetics for rainbow trout: 40000, 50000, 60000 and 70000 µL L−1. These concentrations provided deep anaesthesia in 196.67±1.45, 173.00±11.24, 138.33±8.29 and 136.33±5.23 seconds, respectively. Plasma cortisol levels of the mentioned groups were measured as 4.49±1.04, 8.64±0.73, 8.18±0.64 and 9.64±0.78 ng mL−1, respectively. On the other hand, the plasma cortisol level of the control group (anaesthetized with 2-phenoxyethanol) was 10.95±0.89 ng mL−1. These findings suggest that 40000–70000 µl L−1 of E. rigida can be used as an alternative anaesthetic in rainbow trout. However, further studies need to be conducted to evaluate the long term effects of the plant, especially in consecutive use.

Dietary l-tryptophan leaves a lasting impression on the brain and the stress response.

Comparative models suggest that effects of dietary tryptophan (Trp) on brain serotonin (5-hydroxytryptamine; 5-HT) neurochemistry and stress responsiveness are present throughout the vertebrate lineage. Moreover, hypothalamic 5-HT seems to play a central role in control of the neuroendocrine stress axis in all vertebrates. Still, recent fish studies suggest long-term effects of dietary Trp on stress responsiveness, which are independent of hypothalamic 5-HT. Here, we investigated if dietary Trp treatment may result in long-lasting effects on stress responsiveness, including changes in plasma cortisol levels and 5-HT neurochemistry in the telencephalon and hypothalamus of Atlantic salmon. Fish were fed diets containing one, two or three times the Trp content in normal feed for 1 week. Subsequently, fish were reintroduced to control feed and were exposed to acute crowding stress for 1 h, 8 and 21 d post Trp treatment. Generally, acute crowding resulted in lower plasma cortisol levels in fish treated with 3×Trp compared with 1×Trp- and 2×Trp-treated fish. The same general pattern was reflected in telencephalic 5-HTergic turnover, for which 3×Trp-treated fish showed decreased values compared with 2×Trp-treated fish. These long-term effects on post-stress plasma cortisol levels and concomitant 5-HT turnover in the telencephalon lends further support to the fact that the extrahypothalamic control of the neuroendocrine stress response is conserved within the vertebrate lineage. Moreover, they indicate that trophic/structural effects in the brain underlie the effects of dietary Trp treatment on stress reactivity.

Effects of amino acid supplementations on metabolic and physiological parameters in Atlantic cod (Gadus morhua) under stress.

The effects of tryptophan (Trp) and phenylalanine (Phe) diet supplementation on the stress and metabolism of the Atlantic cod have been studied. Fish were fed diet supplemented with Trp or Phe or control diet for 1week. At the end of the feeding trial, fish were subjected to air exposure or heat shock. Following samples of blood, liver and muscle were taken from the fish and were analyzed for stress and metabolic indicators. After an air exposure, plasma cortisol levels in fish fed with Trp and Phe diets were lower compared to the fish fed the control diet. Diets containing both amino acids increased significantly the liver transaminase activities in juvenile cod. During thermal stress, high Trp contents had significant effects on fructose biphosphatase activity though Phe did not. Overall, activities of glucose 6-phosphate dehydrogenase, pyruvate kinase, and phosphofructokinase increased significantly for both amino acid diets. For the thermal stress, fish had the highest values of those activities for the 3Trp diet. Trp content in the diet had significant effects on the transaminase activity in muscle during air stress compared to fish fed control and Phe diets. Muscle alanine transaminase activity for thermal stress in fish fed any diet was not significantly different from the control. Both Trp and Phe supplementations reduced the stress markers in the cod; hence, they could be used as additives for the stress attenuation. However, they also raised the activity of key enzymes in glycolysis and gluconeogenesis, mainly the Trp diets.

Effect of (+)-dehydrofukinone on GABAA receptors and stress response in fish model.

(+)-Dehydrofukinone (DHF) is a major component of the essential oil of Nectandra grandiflora (Lauraceae), and exerts a depressant effect on the central nervous system of fish. However, the neuronal mechanism underlying DHF action remains unknown. This study aimed to investigate the action of DHF on GABAA receptors using a silver catfish (Rhamdia quelen) model. Additionally, we investigated the effect of DHF exposure on stress-induced cortisol modulation. Chemical identification was performed using gas chromatography-mass spectrometry and purity was evaluated using gas chromatography with a flame ionization detector. To an aquarium, we applied between 2.5 and 50 mg/L DHF diluted in ethanol, in combination with 42.7 mg/L diazepam. DHF within the range of 10-20 mg/L acted collaboratively in combination with diazepam, but the sedative action of DHF was reversed by 3 mg/L flumazenil. Additionally, fish exposed for 24 h to 2.5-20 mg/L DHF showed no side effects and there was sustained sedation during the first 12 h of drug exposure with 10-20 mg/L DHF. DHF pretreatment did not increase plasma cortisol levels in fish subjected to a stress protocol. Moreover, the stress-induced cortisol peak was absent following pretreatment with 20 mg/L DHF. DHF proved to be a relatively safe sedative or anesthetic, which interacts with GABAergic and cortisol pathways in fish.

Development of a label-free immunosensor system for detecting plasma cortisol levels in fish.

Fishes display a wide variation in their physiological responses to stress, which is clearly evident in the plasma corticosteroid changes, chiefly cortisol levels in fish. In the present study, we describe a novel label-free immunosensor for detecting plasma cortisol levels. The method is based on immunologic reactions and amperometric measurement using cyclic voltammetry. For the immobilization of the antibody on the surface of sensing electrode, we used a self-assembled monolayer of thiol-containing compounds. Using this electrode, we detect the CV signal change caused by the generation of antigen-antibody complex. The immunosensor showed a response to cortisol levels, and the anodic peak value linearly decreased with a correlation coefficient of 0.990 in diluted plasma. The specificity of the label-free immunosensor system was investigated using other steroid hormones, such as 17α, 20β-dihydroxy-4-pregnen-3-one, progesterone, estriol, estradiol, and testosterone. The specific detection of cortisol was suggested by a minimal change from -0.32 to 0.51 μA in the anodic peak value of the other steroid hormones. The sensor system was used to determine the plasma cortisol levels in Nile tilapia (Oreochromis niloticus), and the results were compared with those of the same samples determined using the conventional method (ELISA). A good correlation was obtained between values determined using both methods (correlation coefficient 0.993). These findings suggest that the proposed label-free immunosensor could be useful for rapid and convenient analysis of cortisol levels in fish plasma samples.

The effects of ammonia and water hardness on the hormonal, osmoregulatory and metabolic responses of the freshwater silver catfish Rhamdia quelen

The aim of the present study was to assess the effects of ammonia and water hardness on endocrine, osmoregulatory and metabolic parameters in silver catfish (Rhamdia quelen). The specimens (60–120g) were subjected to six treatments in triplicate, combining three levels of un-ionized ammonia (NH3) (0.020±0.008mg/L [1.17±0.47μM], 0.180±0.020mg/L [10.57±1.17μM] and 0.500±0.007mg/L [29.36±0.41μM]) and two levels of water hardness (normal: 25mgCaCO3/L and high: 120mgCaCO3/L), and sampled after two exposure times (1 and 5 days post-transfer). Plasma cortisol, metabolites, osmolality and ionic values were determined concomitantly with the mRNA expression levels of different adenohypophyseal hormones (growth hormone, GH; prolactin, PRL; and somatolactin, SL). Previously, full-length PRL and SL as well as β-actin cDNAs from R. quelen were cloned. Exposure to high NH3 levels enhanced plasma cortisol levels in fish held under normal water hardness conditions but not in those kept at the high hardness value. The increase in water hardness did not alter plasma metabolites, whereas it modulated the osmolality and ion changes induced by high NH3 levels. However, this hardness increase did not lead to the decreased GH expression that was observed 5 days after exposure to 0.18mg/L NH3 in fish held at the normal water hardness level, whereas PRL expression was enhanced after one day of exposure under the increased hardness conditions. Additionally, SL expression decreased in specimens exposed for 5 days to 0.18mg/L NH3 and maintained at the high water hardness level. The results showed that increasing water hardness attenuated the hormonal parameters evaluated in R. quelen specimens exposed to high NH3 levels, although plasma metabolism do not appear to suffer major changes.

Effects of dietary nucleotides supplementation on rainbow trout (Oncorhynchus mykiss) performance and acute stress response

This experiment was conducted to examine the effect of dietary nucleotides (NT) on fish performance and acute stress response on fingerling rainbow trout (23 g ± 0.01, mean weight ± SEM). Five experimental diets according to different levels of supplemented nucleotides (0, 0.05, 0.1, 0.15, and 0.2%) were assayed on experimental fish for 8 weeks. Growth, hematological parameters (hematocrit, hemoglobin, erythrocyte, lymphocyte, and neutrophil count), serum proteins (globulin, albumin), and plasma enzymatic activity (alkaline phosphatase, ALP; aspartate transaminase, AST; lactate dehydrogenase, LDH; alanine transaminase, ALT) were assayed. At the end of feeding trial, fish fed the control and 0.2% diets were subjected to handling and crowding stress. Modulatory effects of nucleotides on acute stress response (cortisol and glucose) and plasma electrolytes (Na(+), Cl(-), K(+), and Ca(2+)) were studied. The percentage of body weight gain (WG) and feed efficiency (FE) of fish were better when the fish were fed 0.15-0.2% diets. Fish fed the nucleotide-supplemented diets tended to have lower levels of serum enzymes including ALP, AST, LDH, and ALT. Plasma cortisol levels of fish fed on 0.2% diet under handling and crowding stress were significantly lower than fish fed the control diet at all post-stress time intervals. In our study, fish fed nucleotide-supplemented diet had significantly lower concentrations of glucose compared to those fed the basal diet. The concentrations of sodium, chloride, calcium, and potassium of fish fed the control diet were significantly lower than in fish fed nucleotide-supplemented diet. Dietary nucleotides administration seems to promote growth and to enhance resistance against handling and crowding stress in fingerling rainbow trout.

The Effect of Food Deprivation on the Cortisol Response to Crowding in Juvenile Steelhead

AbstractRoutine salmonid hatchery procedures include food deprivation, handling, and crowding of fish before sorting, transporting, or stocking. Although several studies have examined the effects of food deprivation or husbandry stressors on salmonid physiology, few have examined the effects of food deprivation and standard hatchery procedures, such as handling and crowding. The objective of this study was to determine whether food deprivation of juvenile steelhead (anadromous rainbow trout Oncorhynchus mykiss) affects the cortisol response to stress from low‐water crowding. Plasma cortisol levels of fish held in circular fiberglass tanks at 8°C under normal daily feeding conditions were compared with levels in fish subjected to 3 d of food deprivation; both groups were held at 3.8 kg/m3 (control density). Additionally, these groups were compared with fed and food‐deprived fish held at a density of 12.8 kg/m3 for 3 h (low‐water crowding stressor). There was a significant increase in plasma cortisol levels of fish subjected to low‐water crowding (129.9 ng/mL) relative to fish held at the control density (14.7 ng/mL), regardless of previous feeding treatment. However, for fish at a given density (control or crowded), there was no difference in cortisol levels between fed and food‐deprived groups. We conclude that depriving juvenile steelhead of food does not significantly alter their cortisol response to low‐water crowding. Consequently, the standard hatchery practice of withholding food before performing stressful husbandry procedures does not appear to cause additional stress or exacerbate physiological responses typically observed in steelhead after they are subjected to physical stressors.

Assessment of Water Pollution in the Tronto River (Italy) by Applying Useful Biomarkers in the Fish Model Carassius auratus

The Tronto River (southern Marche region of central Italy) is located in an area with neighboring industrial activities and is contaminated with domestic and industrial wastewater. Water quality data analyses revealed the presence of a mixture of low levels of heavy metals and organic compounds. The effects of long-term exposure to Tronto River water on juvenile Carassius auratus were evaluated with an integrated approach using xenoestrogens biomarkers, such as vitellogenin (VTG) and ER beta-1 mRNA expression, and stress parameters (i.e., cortisol and glucose in the blood and glycogen in the liver). Treatment with Tronto River water did not induce VTG synthesis in fish and did not affect ER beta-1 mRNA expression. Moreover, cortisol titers found in the plasma of fish exposed to Tronto River water were lower than those found in the control group. Regarding energy parameters, treatment with Tronto River water induced an increase in plasma glucose and a depletion of liver glycogen reserves.The effects of Tronto River water were studied in parallel with those of 4-NP and CdCl(2). The 4-NP at the dose of 22 microg/L induced the synthesis of peripheral vitellogenin and increase of ER beta-1 titers; on the contrary, CdCl2 exposure at the concentration of 22 microg/L did not induce significant changes on plasma VTG and/or hepatic ER beta-1 levels. In addition, no significant changes in plasma cortisol levels in fish exposed to 4-NP or CdCl(2) were found. Fish exposed to CdCl(2) displayed liver glycogen depletion, but no significant increase in plasma glucose was observed. On the contrary, a 30-day exposure to 4-NP induced only a slight decrease of glycogen reserves without any changes in plasma glucose levels. In conclusion, our study demonstrated that long-term exposure of juvenile goldfish to the water of the Tronto River significantly affects both stress and energy parameters. There is evidence that pollutants, present in Tronto River water, were not able to induce xenoestrogenic effects but caused a functional impairment of the hypothalamum-pituitary-interrenal axis.

Osmoregulatory and metabolic changes in the gilthead sea bream Sparus auratus after arginine vasotocin (AVT) treatment

The influence of arginine vasotocin (AVT) on osmoregulation and metabolism in gilthead sea bream Sparus auratus was evaluated by two experimental approaches. In the first, seawater (SW, 36 ppt)-acclimatized fish were injected intraperitoneally with vehicle (vegetable oil) or two doses of AVT (0.5 and 1 μg/g body weight). Twenty-four hours later, eight fish from each group were sampled; the remaining fish were transferred to low saline water (LSW, 6 ppt, hypoosmotic test), SW (transfer control), and hypersaline water (HSW, 55 ppt, hyperosmotic test). After another 24 h (48-h post-injection), fish were sampled. The only significant effect observed was the increase of sodium levels in AVT-treated fish transferred to HSW. In the second experiment, fish were injected intraperitoneally with slow-release vegetable oil implants (mixture 1:1 of coconut oil and seeds oil) alone or containing AVT (1 μg/g body weight). After 3 days, eight fish from each group were sampled; the remaining fish were transferred to LSW, SW, and HSW as above, and sampled 3 days later (i.e. 6 days post-injection). In the AVT-treated group transferred from SW to SW, a significant increase vs. control was observed in gill Na +,K +-ATPase activity. Kidney Na +,K +-ATPase activity decreased in the AVT-treated group transferred to LSW and no changes were observed in the other groups. These osmoregulatory changes suggest a role for AVT during hyperosmotic acclimation based on changes displayed by gill Na +,K +-ATPase activity. AVT treatment increased plasma cortisol levels in fish transferred to LSW and HSW. In addition, AVT treatment affected parameters of carbohydrate, lipid, amino acid, and lactate metabolism in plasma and tissues (gills, kidney, liver, and brain). The most relevant effects were the increased potential of liver for glycogen mobilization and glucose release resulting in increased plasma levels of glucose in AVT-treated fish transferred to LSW and HSW. These changes may be related to the energy repartitioning process occurring during osmotic adaptation of S. auratus to extreme environmental salinities and could be mediated by increased levels of cortisol in plasma.

Efficacy of Electrofishing to Assess Plasma Cortisol Concentration in Juvenile Chinook Salmon Passing Hydroelectric Dams on the Columbia River

Abstract We tested the efficacy of using electrofishing to collect juvenile fall chinook salmon Oncorhynchus tshawytscha to assess their plasma cortisol concentrations. In laboratory experiments, plasma cortisol titers offish sampled immediately (<4 s) after a 1.5-s, 500-V DC electroshock were not different from controls (mean ± SE, 28.8 ± 5.2 ng/mL), but within 15 min they were significantly higher (148.2 ± 19.0 ng/mL) than controls. Plasma cortisol levels of fish released through turbines and of those released through the juvenile-bypass system at Bonneville Dam, Oregon-Washington, and collected by electrofishing did not differ from each other or from prerelease samples (about 70 ± 7 ng/mL). Our results indicate that electrofishing can be used to collect fish for stress assessment in the wild, provided fish are sacrificed immediately after capture, We are concerned, however, that the small number of fish we captured by electrofishing may not be representative of the majority of fish that pass through tu...