The acute stress response of red porgy, Pagrus pagrus, kept on a red or white background

Metabolism, antioxidant and immunity in acute and chronic hypoxic stress and the improving effect of vitamin C in the channel catfish (Ictalurus punctatus)

Hypoxia is the most significant factor that threatens the health and even survival of freshwater and marine fish. Priority should be given to the investigation of hypoxia adaptation mechanisms and their subsequent modulation. Acute and chronic studies were designed for the current study. Acute hypoxia comprised of normoxia dissolved oxygen (DO) 7.0 ± 0.5 mg/mL (N0), low-oxygen 5.0 ± 0.5 mg/mL(L0), and hypoxia 1.0 ± 0.1 mg/mL (H0) and 300 mg/L Vc for hypoxia regulation (N300, L300, H300). Chronic hypoxia comprised of normoxia (DO 7.0 ± 0.5 mg/mL) with 50 mg/kg Vc in the diet (N50) and low oxygen (5.0 ± 0.5 mg/mL) with 50, 250, 500 mg/kg Vc in the diet (L50, L250, L500) to assess the effect of Vc in hypoxia. The growth, behavior, hematological parameters, metabolism, antioxidants, and related inflammatory factors of channel catfish were investigated, and it was found that channel catfish have a variety of adaptive mechanisms in response to acute and chronic hypoxia. Under acute 5 mg/mL DO, the body color lightened (P < 0.05) and reverted to normal with 300 mg/mL Vc. PLT was significantly elevated after 300 mg/L Vc (P < 0.05), indicating that Vc can effectively restore hemostasis following oxygen-induced tissue damage. Under acute hypoxia, the significantly increased of cortisol, blood glucose, the gene of pyruvate kinase (pk), and phosphofructokinase (pfk), together with the decreased expression of fructose1,6-bisphosphatase (fbp) and the reduction in myoglycogen, suggested that Vc might enhance the glycolytic ability of the channel catfish. And the enzyme activities of superoxide dismutase (SOD) and catalase (CAT) and the gene expression of sod rose significantly, showing that Vc might improve the antioxidant capacity of the channel catfish. The significant up-regulation of tumor necrosis factor-alpha (tnf-α), interleukin-1β (il-1β), and cd68 under acute hypoxia implies that hypoxia may generate inflammation in channel catfish, whereas the addition of Vc and down-regulation of these genes suggests that Vc suppresses inflammation under acute hypoxia. We found that the final weight, WGR, FCR, and FI of channel catfish were significantly reduced under chronic hypoxia, and that feeding 250 mg/kg of Vc in the diet was effective in alleviating the growth retardation caused by hypoxia. The significant increase in cortisol, blood glucose, myoglycogen, and the expression of tnf-α, il-1β, and cd68 (P < 0.05) and the significant decrease in lactate (P < 0.05) under chronic hypoxia indicated that the channel catfish had gradually adapted to the survival threat posed by hypoxia and no longer relied on carbohydrates as their primary source of energy. While the addition of Vc did not appear to increase the energy supply of the fish under hypoxia in terms of glucose metabolism, but the significantly decreased expression of tnf-α, il-1β, and cd68 (P < 0.05) also were found, indicating that chronic hypoxia, similar acute hypoxia, may increase inflammation in the channel catfish. This study indicates that under acute stress, channel catfish withstand stress by raising energy supply through glycolysis, and acute hypoxic stress significantly promotes inflammation in channel catfish, but Vc assists the channel catfish resist stress by raising glycolysis, antioxidant capacity, and decreasing the production of inflammatory markers. Under chronic hypoxia, the channel catfish no longer utilize carbohydrates as their primary energy source, and Vc may still effectively reduce inflammation in the channel catfish under hypoxia.

Tank color influences the response of tomato clownfish (Amphiprion frenatus) to an acute stress challenge

The trade of aquarium organisms is growing worldwide. This market depends on a continuous supply of healthy and colorful aquatic animals, but this sector has few initiatives. However, in the last decade, there has been a growing interest in researching captive breeding of these animals, aiming to develop a more sustainable aquarium hobby. Larviculture is an important phase in the cultivation process because the larvae are more sensitive to stress and variations in the bulk of variables, such as temperature, salinity, nutritional management, light intensity and spectrum, and environmental background colors. Because background color could be a promoter variable of proper welfare, we tested whether it affects the endocrine response of tomato clownfish Amphiprion frenatus larvae to an acute stress challenge. We show that background color influences the endocrine stress axis responsiveness in tomato clownfish. When fish were subjected to a standard acute stressor of 61 days after hatching, only fish adapted to white walls increased the whole-body cortisol levels. From the results presented herein, we recommend that white tanks be avoided for A. frenatus larviculture. Both, the less stress level and the good welfare condition of larvae reared in colored tanks may have robust, practical applications since almost all clownfish in the ornamental aquarium trade come from captive breeding.

Intracerebroventricular administration of α-melanocyte-stimulating hormone (α-MSH) enhances thigmotaxis and induces anxiety-like behavior in the goldfish Carassius auratus

α-Melanocyte-stimulating hormone (α-MSH) is a body pigmentation-regulating hormone secreted from the intermediate lobe of the pituitary in vertebrates. It is also produced in the brain, and acts as an anorexigenic neuropeptide involved in feeding regulation. In rodents, intracerebroventricular (ICV) administration of α-MSH has been shown to affect not only feeding behavior, but also psychomotor activity. However, there is still no information regarding the psychophysiological effects of α-MSH on behavior in fish. Therefore, we examined the effect of synthetic α-MSH on psychomotor activity in goldfish. Since this species prefers the edge to the central area of a tank, we used this as a preference test for assessing psychomotor activity. When α-MSH was administered ICV at 1 and 10 pmol g^-1 body weight (BW), the time spent in the edge area of a tank was prolonged at 10 pmol g^-1 BW. However, α-MSH at these doses did not affect locomotor activity. The action of α-MSH mimicked those of FG-7142 (a central-type benzodiazepine receptor (CBR) inverse agonist with an anxiogenic effect) at 10 pmol g^-1 BW and melanotan II (a melanocortin 4 receptor (MC4R) agonist) at 50 pmol g^-1 BW, whereas ICV administration of tofisopam (a CBR agonist with an anxiolytic effect) at 10 pmol g^-1 BW prolonged the time spent in the central area. The anxiogenic-like effect of α-MSH was abolished by treatment with the MC4R antagonist HS024 at 50 pmol g^-1 BW. These data indicate that α-MSH affects psychomotor activity in goldfish, and exerts an anxiogenic-like effect via the MC4R-signaling pathway.

Embryonic development, locomotor behavior, biochemical, and epigenetic effects of the pharmaceutical drugs paracetamol and ciprofloxacin in larvae and embryos of Danio rerio when exposed to environmental realistic levels of both drugs

For several years, the scientific community has been concerned about the presence of pharmaceuticals in the wild, since these compounds may have unpredictable deleterious effects on living organisms. Two examples of widely used pharmaceuticals that are present in the environment are paracetamol and ciprofloxacin. Despite their common presence in the aquatic environment due to their poor removal by sewage treatment plants, knowledge concerning their putative toxic effects is still scarce. This work aimed to characterize the effects of paracetamol (0.005, 0.025, 0.125, 0.625, and 3.125 mg/L) and ciprofloxacin (0.005, 0.013, 0.031, 0.078, 0.195, and 0.488 μg/L) in zebrafish embryos and larvae, exposed to environmentally relevant levels, close to the real concentrations of these pharmaceuticals in surface waters and effluents. The adopted toxic end points were developmental, a behavioral parameter (total swimming time), and a biomarker-based approach (quantification of the activities of catalase, glutathione-S-transferase, cholinesterases, glutathione peroxidase, and lipid peroxidation levels) combined with epigenetic analysis (immunohistochemical detection of 5-methylcytidine). Exposure to paracetamol had effects on all of the adopted toxic end points; however, ciprofloxacin only caused effects on behavioral tests and alterations in biomarkers. It is possible to ascertain the occurrence of oxidative stress following exposure to both drugs, which was more evident regarding paracetamol, an effect that may be related to the observed epigenetic modifications.

QTL Mapping for Red Blotches in Malaysia Red Tilapia (Oreochromis spp.)

Body color is an interesting economic trait in fish. Red tilapia with red blotches may decrease its commercial values. Conventional selection of pure red color lines is a time-consuming and labor-intensive process. To accelerate selection of pure lines through marker-assisted selection, in this study, double-digest restriction site-associated DNA sequencing (ddRAD-seq) technology was applied to genotype a full-sib mapping family of Malaysia red tilapia (Oreochromis spp.) (N = 192). Genome-wide significant quantitative trait locus (QTL)-controlling red blotches were mapped onto two chromosomes (chrLG5 and chrLG15) explaining 9.7% and 8.2% of phenotypic variances by a genome-wide association study (GWAS) and linkage-based QTL mapping. Six SNPs from the chromosome chrLG5 (four), chrLG15 (one), and unplaced supercontig GL831288-1 (one) were significantly associated to the red blotch trait in GWAS analysis. We developed nine microsatellite markers and validated significant correlations between genotypes and blotch data (p < 0.05). Our study laid a foundation for exploring a genetic mechanism of body colors and carrying out genetic improvement for color quality in tilapia.

Cortisol responses of goldfish (Carassius auratus) to air exposure, chasing, and increased water temperature

Fish can respond to stimuli from the internal or external environment with activation of the hypothalamo-pituitary-interrenal (HPI) axis and the secretion of cortisol. Stimuli that activate the HPI axis of fish include short term air exposure and increases in water temperature. The present study was conducted to determine how quickly cortisol concentrations increase in goldfish subjected to an increase in water temperature, and to compare the response to an increase in water temperature with responses to other stimuli. Plasma cortisol concentrations varied widely between individual goldfish, with concentrations ranging from 9.1 to 516.0 ng/mL in goldfish on the day of arrival from the supplier. Mean cortisol concentrations in undisturbed goldfish were low (4.5 ± 1.0 ng/mL). Mean cortisol concentrations in fish exposed to air for 3 min and in fish that experienced chasing for 10 min were markedly elevated 15 min after the beginning of the stimuli (132.6 ± 31.0 and 121.1 ± 23.9 ng/mL respectively). Mean cortisol concentrations in fish that experienced an increase in water temperature rose to 22.2 ± 7.6 ng/mL after 15 min, declined to <10 ng/mL at 30 and 60 min then increased and were elevated (79.0 ± 10.8 ng/mL) at 240 min. Cortisol measurements can be used to indicate the responsiveness of fish to changes in water temperature and goldfish will be a convenient study species for the development of studies of plasticity in responses of fish to increases in water temperature that are happening due to climate change.

Behavior and histopathology as biomarkers for evaluation of the effects of paracetamol and propranolol in the neotropical fish species Phalloceros harpagos

Pharmaceutical drugs in the aquatic environment can induce adverse effects on nontarget organisms. This study aimed to assess the short-term effects of sublethal concentrations of both paracetamol and propranolol on the fish Phalloceros harpagos, specifically light/dark preference, swimming patterns, skin pigmentation, histopathology, and liver glycogen levels. Fish were acutely exposed to sublethal concentrations of both paracetamol (0.008, 0.08, 0.8, 8, 80 mg L^-1) and propranolol (0.0001, 0.001, 0.01, 0.1, 1 mg L^-1) under controlled conditions. For scototaxis, a significant preference for the dark compartment was observed for the group exposed to the highest concentration of paracetamol (80 mg L^-1). Propranolol exposure significantly altered the swimming pattern, especially in fish exposed to the 0.001 mg L^-1 concentration. Pigmentation was reduced in propranolol-exposed fish (0.1, 1 mg L^-1). The lowest concentration of propranolol (0.0001 mg L^-1) induced a decrease of histochemical reaction for hepatic glycogen. These data demonstrate that pharmaceuticals can induce sublethal effects in nontarget organisms, even at low concentrations, compromising specific functions of the individual with ecological relevance, such as energy balance and behavior.

Effect of green light spectra on the reduction of retinal damage and stress in goldfish, Carassius auratus

We investigated the effect of light spectra on retinal damage and stress in goldfish using green (530 nm) and red (620 nm) light emitting diodes (LEDs) at three intensities each (0.5, 1.0, and 1.5 W/m(2)). We measured the change in the levels of plasma cortisol and H2O2 and expression and levels of caspase-3. The apoptotic response of green and red LED spectra was assessed using the terminal transferase dUTP nick end labeling (TUNEL) assay. Stress indicator (cortisol and H2O2) and apoptosis-related genes (caspase-3) decreased in green light, but increased in red light with higher light intensities over time. The TUNEL assay revealed that more apoptotic cells were detected in outer nuclear layers after exposure to red LED over time with the increase in light intensity, than the other spectra. These results indicate that green light efficiently reduces retinal damage and stress, whereas red light induces it. Therefore, red light-induced retina damage may induce apoptosis in goldfish retina.

Eye darkening as a reliable, easy and inexpensive indicator of stress in fish

We expand the use of eye darkening (ED) to indicate non-social stress in the fish Nile tilapia Oreochromis niloticus (L.). ED is easily estimated, not requiring any sophisticated equipment, and is non-invasive, facilitating the collection of several measures of stress over time. In the current study, we showed the following: (i) high- and low-ED occur spontaneously, indicating different fish reactions to adjustments to a novel environment; (ii) fish confinement or air exposure clearly increases ED (air exposure is a stronger stressor than confinement), and the time to restore basal values indicates the severity of the impact of the stressor on the fish (this response is not affected by period of the day, e.g., morning or afternoon); and (iii) in adults, females were more responsive (slower recovery) to 2-min air exposure than to 30-min confinement.

Individual variation in glucocorticoid stress responses in animals

When stimuli from the environment are perceived to be a threat or potential threat then animals initiate stress responses, with activation of the hypothalamo-pituitary-adrenal axis and secretion of glucocorticoid hormones (cortisol and corticosterone). Whilst standard deviation or standard error values are always reported, it is only when graphs of individual responses are shown that the extensive variation between animals is apparent. Some animals have little or no response to a stressor that evokes a relatively large response in others. Glucocorticoid responses of fish, amphibian, reptiles, birds, and mammals are considered in this review. Comparisons of responses between animals and groups of animals focused on responses to restraint or confinement as relatively standard stressors. Individual graphs could not be found in the literature for glucocorticoid responses to capture or restraint in fish or reptiles, with just one graph in mammals with the first sample was collected when animals were initially restrained. Coefficients of variation (CVs) calculated for parameters of glucocorticoid stress responses showed that the relative magnitudes of variation were similar in different vertebrate groups. The overall mean CV for glucocorticoid concentrations in initial (0 min) samples was 74.5%, and CVs for samples collected over various times up to 4 h were consistently between 50% and 60%. The factors that lead to the observed individual variation and the extent to which this variation is adaptive or non-adaptive are little known in most animals, and future studies of glucocorticoid responses in animals can focus on individual responses and their origins and significance.

Environmental light color affects the stress response of Nile tilapia

We investigated the effects of environmental light colors (blue, yellow and white) on the stress responses (measured by changes in ventilatory frequency - VF) of Nile tilapia to confinement. After 7 days of light treatment, the VF was similar for fish in each color. On the 8th day, fish were confined for 15 min. After release, the post-confinement VF was measured six times (first period: 0, 2 and 4 min; second period: 6, 8 and 10 min). Irrespective of the light color treatment, confinement increased the VF to higher levels during the first post-confinement period than during the second one. When color was analyzed, irrespective of time, fish under white light increased their VF post-confinement, and blue light prevented this effect. We conclude that blue light is the preferred color for Nile tilapia in terms of reducing stress. This finding is in contrast to previous choice test studies that indicated that yellow is their preferred color.

Rapid color change in fish and amphibians - function, regulation, and emerging applications

Physiological color change is important for background matching, thermoregulation as well as signaling and is in vertebrates mediated by synchronous intracellular transport of pigmented organelles in chromatophores. We describe functions of and animal situations where color change occurs. A summary of endogenous and external factors that regulate this color change in fish and amphibians is provided, with special emphasis on extracellular stimuli. We describe not only color change in skin, but also highlight studies on color change that occurs using chromatophores in other areas such as iris and on the inside of the body. In addition, we discuss the growing field that applies melanophores and skin color in toxicology and as biosensors, and point out research areas with future potential.

Short fasting and refeeding in red porgy (Pagrus pagrus, Linnaeus 1758): response of some haematological, biochemical and non specific immune parameters

A short fasting-refeeding experience was applied to specimens of red porgy, Pagrus pagrus (Teleostei, Sparidae) to assess its effects on some physiological parameters. Haematological (haematocrit), biochemical (serum cortisol and glucose) and immunological (lysozyme, haemolytic and haemagglutinating activities) parameters were measured. For this study, two fish groups were considered: one was fasted for 14 days and then refed to satiation during further 7 and 15 days (indicated as fasted/refed group), the other was fed throughout the study and was taken as a control group. Significantly lower values were recorded for the condition index, the hepato-somatic index and viscero-somatic index in the fasted/refed group compared to the fed one. Fasting did not affect significantly the examined parameters, except for cortisol; refeeding for 7 days induced a significant increase in the haemoagglutinating titre and the spontaneous haemolytic activity, but when refeeding was extended to 14 days haemagglutinating and haemolytic values remained lower than those measured in fed fish.

Fluorescence detection of the ornamental fish Cardinal Tetra (Paracheirodon axelrodi)

The fluorescence spectra of the tropical fish, Cardinal Tetra (Paracheirodon axelrodi), originating in the Amazon region of Brazil, were determined. These spectra were then treated using factor analysis, generating two contributing spectra and separating out the noise. Time-resolved fluorescence results indicated that the fluorescent system in the epidermis undergoes excited state reaction. Excited state proton transfer is suggested as being present. Both intentionally stressed and nonstressed individuals were used and some small differences were noted in the contributions of the two calculated contributing spectra to the experimental spectra, presumably as a function of stress. The results are compared with those obtained by the standard determination of cortisol level using the whole body extraction method and it is suggested that the method could be tested as an improved, nondestructive way to determine stress in this species, which is a necessary step in the development of "best management practices" of methods for storage and transport of the fish.

Plasma cortisol changes and body composition in Stizostedion lucioperca exposed to handling stress

Stizostedion lucioperca aquaculture/stoking, remains a restrained industry due to several factors such as the paucity of freshwater resources and studies on the physiological responses of this species under environmental changes. The fish were subjected to handling stress by holding them out of the water in a hand-held dip net for 30 sec and netting the fish from the rearing tanks and transferring them to a small confinement tank. Sufficient aeration was supplied to the confinement tank to revert additional stress from oxygen depletion. Then measured changes in plasma cortisol levels and the growth ability (body composition) in Stizostedion lucioperca subjected to handling stress. Blood samples were collected from the fish after exposure to the handling stress. Crude protein (Nx6.25) was determined according to the Kjeldahl method, moisture content was determined by oven drying at 105+/-2 degrees C to constant weight and ash by heating in a muffle furnace at 550 degrees C to constant weight. Total lipids were extracted according to the Bligh and Dyer method. The results indicated that, handling stress significantly increased the plasma levels of cortisol 59.04 ng mL(-1) versus 40.83 ng mL(-1) in control group. Also the decrease of the level of protein and lipid concentrations show a significant difference between treatment and control (p<0.05). As protein and lipid decreased, moisture increased from 78.19% in control to 80.40% in treatment groups. According to the results, there was no significant change in ash content in control and treatment groups which was about 9%. In other words, it could be emphasized that nutrition-related behavior of Stizostedion lucioperca resulting from the activation of the hypothalamic/inter-renal axis in response to stress despite of different reactions bear resemblance to that of other fishes. Present data indicate that cortisol appears to be adequate to assess stress in Stizostedion lucioperca.

Profiles of alpha-melanocyte-stimulating hormone in the Japanese flounder as revealed by a newly developed time-resolved fluoroimmunoassay and immunohistochemistry

Profiles of alpha-melanocyte-stimulating hormone (alpha-MSH) in the Japanese flounder were examined by a newly developed time-resolved fluoroimmunoassay (TR-FIA) and immunohistochemistry. A TR-FIA for alpha-MSH was newly developed, and its levels in the pituitary gland and plasma of Japanese flounder reared in a white or black tank for 5 months were compared. A competitive assay using two antibodies was performed among secondary antibodies in the solid phase, alpha-MSH antibodies, samples, and europium-labeled Des-Ac-alpha-MSH. The sensitivity of the assay, defined as twice the standard deviation at a zero dose, was 0.98 ng/ml (49 pg/well). The intra- and interassay coefficients of variation of the assay were 8.8% (n=8) and 17.3% (n=5), respectively, at about 50% binding. Cross-reactivities of Des-Ac-alpha-MSH and Di-Ac-alpha-MSH were about 100%. Cross-reactivities of adrenocorticotropic hormone, salmon gonadotropin-releasing hormone (sGnRH), and chicken GnRH-II were less than 0.2%, and that of melanin-concentrating hormone was less than 2.0% at 50% binding. Displacement curves of serially twofold-diluted hypothalamus extract, pituitary gland extract, and plasma extract of Japanese flounder with the assay buffer were parallel to the alpha-MSH standard curve. Moreover, displacement curves of serially twofold-diluted hypothalamus and/or pituitary gland extract of masu salmon, goldfish, red seabream, Japanese eel, tiger puffer, and barfin flounder with the assay buffer were also parallel to the alpha-MSH standard. In Japanese flounder, total immunoreactive (ir)-alpha-MSH levels in the pituitary gland were lower in the black tank, whereas those in the plasma tended to be higher in the black tank, suggesting that the synthesis and release of alpha-MSH are higher in the black tank. alpha-MSH-ir cells were detected in the pars intermedia and a small part of the pars distalis of the pituitary gland. alpha-MSH-ir cell bodies were located in the basal hypothalamus and alpha-MSH-ir fibers were distributed not only in the hypothalamus but also in the telencephalon, midbrain, cerebellum, and medulla oblongata, suggesting that alpha-MSH functions as a neuromodulator in the brain.