2 Chemical Properties of the Blood

Growth performance, health status, gut microbiome, and expression of immune and growth-related genes of rainbow trout (Oncorhynchus mykiss) fed diets with pea protein replacement of fish meal

The need for fish meal constrains fish farming and significantly impacts sustainability of the aquaculture industry. Hence, it is important to investigate the use of plant-based protein sources in fish diets. The present study was conducted to determine the effects of different levels of fish meal (FM) replacement by pea protein (PP) in a 60-day feeding experiment in rainbow trout, Oncorhynchus mykiss. Effects on growth performance, body composition, hematology, serum biochemistry and immunology, and immune (TNF-α, IL1-ß and Il-8) and growth-related (GH and IGFI) gene expression were investigated. Five experimental diets (45% protein and 20% lipid) differed in replacement level of FM by PP at rates of 0% (control (PP0)), 25% (PP25), 50%(PP50), 75%(PP75) and 100%(PP100). Fish were fed with experimental diets in triplicate twice daily. The best growth performance was obtained in PP0 and PP25 groups. While fat ratios of fish fillets significantly differed (p < 0.05), there was no significant effects on protein ratios (p < 0.05). There was no significant change in the hematological values of fish, except those fed the PP100 diets, which displayed a reduction in eyrthocyte counts, hemoglobin content and hematocrit. As PP supplementation increased fish showed elevated serum glucose, total protein, cholesterol and myeloperoxidase activity and decreased glutamic pyruvic transaminase and alkaline phosphatase activity. Fish fed diets with between 25 and 75% replacement showed a decline in lactic acid bacteria in the gut. Significant increases in expression were observed in the liver of the PP25 fish relative to the 0% control for all immune and growth-related genes except for IL1-ß. These data suggest that up to 25% of FM can be replaced by PP without any adverse effects on rainbow trout.

Comparative analysis of blood protein fractions in two mediterranean farmed fish: Dicentrarchus labrax and Sparus aurata

Total protein levels in fish are widely used in health and welfare studies, providing a simple and accessible measure. However, the multifaceted role of blood proteins makes it sometimes challenging to link total protein content to specific health issues, while specific protein fractions may offer more precise insights into fish biology and health, particularly in farmed fish species where such data is often lacking. Data were gathered from two experiments involving Dicentrarchus labrax and Sparus aurata, key species in European marine aquaculture. The aim was (1) to assess how different globulin fractions contribute to total protein content in blood and (2) how these contributions vary across different sampling times in healthy animals. In D. labrax, the beta1 globulin fraction emerged as the major contributor (34.16%), followed by albumin and alpha2 globulins (18.24% and 16.41%, respectively). In contrast, pre-albumins and alpha1 fractions had the least contribution (5.49% and 7.71%). S. aurata exhibited albumin as the primary contributor (23.39%), followed by beta1 and alpha2 globulins (19.71% and 19.15%, respectively), with gamma and alpha1 fractions contributing the least (5.34% and 8.63%). Notably, the study revealed relatively stable contributions of globulin fractions to total proteins within both species, albeit with minor variations over time, potentially linked to environmental and individual factors. Furthermore, larger fish displayed higher total protein levels. This research underscores the need for further investigation into the diverse factors influencing globulin contributions to total proteins, ultimately enhancing health and welfare monitoring for farmed fish species.

Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

Exposing Atlantic Salmon Post-Smolts to Fluctuating Sublethal Nitrite Concentrations in a Commercial Recirculating Aquaculture System (RAS) May Have Negative Consequences

Salmon farmers are interested in extending the time post-smolts are reared in recirculating aquaculture systems (RAS). However, there is a lack of knowledge regarding optimal water quality for post-smolts in RAS, and regarding potential consequences of long term exposure to different toxic compounds, such as nitrite, in the RAS water. To address this issue, we conducted a case study at a Faroese Atlantic salmon farm, that rears large post-smolts in fresh water RAS for 22 months before sea transfer, with no additional chloride salt, a known treatment for nitrite toxicity. The aim was to document the potential effects of long-term exposure of fluctuating sub-lethal nitrite concentrations in fresh water RAS on blood physiology of large post-smolts. The study was conducted over six weeks, at the end of the RAS production cycle. Our case study shows that after ~22 months in RAS with no additional chloride, the fish had accumulated a plasma nitrite concentration 8 to 16 times higher than the ambient water. Our results indicate that the accumulation may have resulted in extracellular hyperkaliemia, since there was a positive correlation between plasma nitrite and potassium levels (p=0.00095), with potassium levels almost twice as high than previously reported for Atlantic salmon. This could indicate that Atlantic salmon health is challenged due to prolonged sub-lethal nitrite exposure in fresh water RAS. Further research related to long-term nitrite exposure in RAS is needed to asses the potential negative impact, in order to optimize welfare and growth performance during production of Atlantic salmon post-smolts.

Effect of potassium supplementation on osmoregulatory and stress response of Pangasianodon hypophthalmus (Sauvage, 1878) with Spinacia oleracea L. in aquaponics

This study evaluated the effect of different potassium supplementation dosages on the physiological responses of Pangasianodon hypophthalmus reared in an aquaponic system with Spinacia oleracea L. for 60 days. The system comprised of a rectangular fish tank of 168 l capacity (water volume = 100 l) with nutrient film technique (NFT)-based hydroponic component with fish to plant ratio of 2.8 kg m^-3 : 28 plants m^-2 in all the treatments. The osmoregulatory and stress parameters of P. hypophthalmus at four different potassium dosages of T1 (90 mg l^-1 ), T2 (120 mg l^-1 ), T3 (150 mg l^-1 ) and T4 (180 mg l^-1 ) were compared with C (control, 0 mg l^-1 ) to examine the potassium level to be applied to aquaponics. The water quality parameters and fish production were found to have no adverse impact due to potassium supplementation. The spinach yield during two harvests, i.e., before and after potassium supplementation, revealed that the yield was significantly higher (P < 0.05) after supplementation with the highest yield in T3 and T4. The osmoregulatory parameters such as plasma osmolality, Na⁺ , K⁺ ATPase activity in gill and plasma ionic profile (Cl^- , Ca²⁺ and Na⁺ ) showed an insignificant variation (P > 0.05) between control and treatments except for higher plasma potassium concentration (1.98 ± 0.19 mmol l^-1 ) in T4. The stress and antioxidant enzyme analysis exhibited significantly higher plasma glucose and superoxide dismutase (SOD) activity in gill and liver in T4, whereas cortisol and catalase showed an insignificant difference (P > 0.05). The experimental findings demonstrated that the potassium dosage up to 150 mg l^-1 could be suggested as optimum for P. hypophthalmus and spinach aquaponics without impairing the health and oxidative status of P. hypophthalmus.

Effects of hydroxy-selenomethionine on performance, innate immune system and antioxidant defense of tambaqui (Colossoma macropomum) exposed to a physical stressor

Selenium (Se) is a mineral with natural antioxidant properties that constitutes a number of enzymes with a fundamental role in the immunity and antioxidant systems and may confer a protective role against oxidative stress in fish following exposure to physical stressors. Adopting an integrated approach, this study investigated simultaneously the role of hydroxy-selenomethionine (OH-SeMet) supplementation in performance, hematological parameters, innate immune, antioxidant capacity and tissue Se retention of tambaqui (Colossoma macropomum) and the possible protective role of dietary selenium when fish are exposed to a physical stressor (transport). Juvenile specimens (15.71 ± 1.90 g) were fed one of five diets: a basal unsupplemented diet (0.0 mg kg^-1 Se) or diets supplemented with OH-SeMet to provide 0.3, 0.6, 0.9 and 1.2 mg kg^-1 Se of diet for 75 days prior to subjection of fish to transport stress. Dietary supplementation with Se in the form of OH-SeMet for 75 days did not affect the production performance of juvenile tambaqui, but increased innate immunity parameters (oxidative burst) from the Se inclusion level of 0.6 mg kg^-1 and induced the activation of the antioxidant defense system (GPX, GSH and GST) especially at the Se inclusion level of 0.9 mg kg^-1. In addition, the Se content in the fillet rose significantly, as the OH-SeMet contents in the diet were increased. The stress caused by transport resulted in alterations in hematological parameters, blood protein profile and immune and enzymatic responses in the species. However, Se supplementation at 0.9 mg kg^-1 had a positive effect, increasing innate immunity and activating antioxidant defenses (CAT and GPx, especially) after this physical stressor was applied. These results demonstrate that, when submitted to transport stress, juvenile tambaqui use Se stored in the muscle and dietary supplementation with OH-SeMet at 0.9 mg kg^-1 improves the innate immunity and antioxidant system parameters of fish after transport. These findings reinforce the need for supplementing hydroxy-selenomethionine in commercial diets for tambaqui to ensure tissue Se reserves as a contingency in cases of stress.

Hematological and serum biochemical reference intervals of rainbow trout, Oncorhynchus mykiss cultured in Himalayan aquaculture: Morphology, morphometrics and quantification of peripheral blood cells

De novo reference intervals (RIs) for a total of thirty two hematological and serum biochemical attributes were established for rainbow trout (Oncorhynchus mykiss) cultured in Himalayan aquaculture system. For this purpose, long term assessment of hemato-biochemical parameters was carried over a period of one year from March 2019 to February 2020 and a total of 444 blood samples were analysed. Blood examination results were recorded systematically and reference intervals were established, notably for erythrocyte parameters: hematocrit (Hct) 29–40%, hemoglobin 8.32–12.28 g/dL, red blood cell (RBC) count 1.01–2.04 (×10⁶/mm3); leukocyte parameters (x 10³/mm3): total leukocytes 31.32–90.60, neutrophils 4.21–18.85, total lymphocytes 20.55–63.63, small lymphocytes 14.86–46.50, large lymphocytes 6.35–22.34 and monocytes 1.22–7.56; thrombocyte count 23.00–68.00 (×10⁶/mm3). RIs were also established for red blood cell indices, vital serum constituents involved in carbohydrate, protein, lipid and nitrogen metabolism including the less known, diagnostically important, serum enzymes and electrolyte concentrations. Principal component analysis revealed that certain serum components were more efficient at distinguishing between the life stages (juvenile, adult) of fish by explaining about 92.7% of variation in the whole dataset compared to the principal hematological components which explained only about 80% of the variation. Significant (P < 0.05) differences were noted for RBC count, total leukocyte count (TLC), total protein, total cholesterol and uric acid with respect to the sex of fish. Moreover, clearly differentiable morphometric and morphological attributes were also noticed among erythrocytes, leukocytes (lymphocytes, neutrophils and monocytes) and thrombocytes. To our knowledge, the present study is the first of its kind that elucidates blood chemistry of cultured rainbow trout, O. mykiss in accordance to the guidelines framed by the American society of veterinary clinical pathologists (ASVCP). RIs reported here can help monitor the fish health status by improving the use of non-lethal diagnostics in piscine medicine.

Growth, serum biochemical parameters, salinity tolerance and antioxidant enzyme activity of rainbow trout (Oncorhynchus mykiss) in response to dietary taurine levels

This study evaluated the effect of dietary taurine levels on growth, serum biochemical parameters, salinity adaptability, and antioxidant activity of rainbow trout (Oncorhynchus mykiss). Four diets were formulated with taurine supplements at 0, 0.5, 1, and 2% w/v (abbreviated as T₀, T_0.5, T₁, and T₂, respectively). Rainbow trouts (initial weight of 80.09 ± 4.72 g) were stocked in tanks (180 L capacity), and were fed these diets for six weeks and subsequently underwent salinity acclimation. Physiological indicators were determined before salinity acclimation at 1, 4, 7, and 14 days afterwards. Results showed that there were no significant differences in growth performance (final mean weight ranged from 182.35 g to 198.48 g; percent weight gain was between 127.68% and 147.92%) of rainbow trout in freshwater stage, but dietary taurine supplement significantly increased serum-free taurine content. After entering seawater, the Na⁺-K⁺-ATPase activity of T₂ group returned to its freshwater levels, and the serum cortisol content was significantly higher than T₀ and T_0.5 groups. At the end of this experiment, the liver superoxide dismutase activity in the T₀ and T_0.5 groups was significantly lower than in the T₁ and T₂ groups, and the liver catalase in the T₀ group was the lowest whereas that in the T₂ group was the highest. Muscle malondialdehyde content was the highest in the T₀ group, and the lowest in the T₂ group. Based on the results of this study, supplement of dietary taurine (0.5-2%) enhanced the salinity tolerance in rainbow trout, which increased with the higher taurine concentration.

Haematological and serum biochemical reference values of snow trout, Schizothorax labiatus habiting in river Sindh of Indian Himalayan region

Haematological and serum biochemical parameters are a valuable tool in determining the wellbeing status of different fish species and response in close association to various biological and environmental factors, therefore the aim of the present study was to establish sex-wise reference values of haemato-biochemical parameters of S. labiatus. The haematological parameters such as haemoglobin (Hb) concentration, total erythrocyte count (RBC), total leucocyte count (WBC), packed cell volume (PCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), mean corpuscular volume (MCV) and serum biochemical parameters such as glucose, cholesterol, urea, total protein, albumin and globulin were analysed. The results revealed that the haematological parameters, i.e., Hb, RBC, WBC and PCV showed significant (P < 0.05) differences with respect to sex. Significantly (P < 0.05) higher values of Hb content (11.18 g dl-1 ), RBC count (1.88 × 106  mm-3 ) and PCV (36.15%) were noted in male fish than females throughout the study period, while significantly (P < 0.05) higher WBC count was noted in females (20.38 × 103  mm-3 ) compared to males. However, no significant (P > 0.05) difference was observed in erythrocyte indices like MCH, MCHC and MCV between sexes. The serum biochemical parameters, i.e., glucose, cholesterol and urea, also showed significant (P < 0.05) difference between the sexes, but no significant (P > 0.05) difference was noticed in total protein, albumin and globulin. Significantly (P < 0.05) highest values of glucose (116.76 mg dl-1 ) and urea (9.01 mg dl-1 ) were recorded in male S. labiatus, while highest value of cholesterol (223.53 mg dl-1 ) was noted in females. The information generated in the present study gives the basic reference values of haematological and serum biochemical parameters of S. labiatus which will be useful in monitoring the wellbeing status of fish populations. Moreover, the data will also be helpful to ascertain the occurrence of different clinical and subclinical diseases, which may in turn help to boost the overall production of this species.

Ammonia excretion and blood gas variation in naked carp (Gymnocypris przewalskii) exposed to acute hypoxia and high alkalinity

Naked carp (Gymnocypris przewalskii), endemic to the saline-alkaline Lake Qinghai, have the capacity to tolerate combined hypoxia and high alkalinity. This study evaluated the effect of the interaction between carbonate alkalinity and hypoxia on ammonia excretion and blood gas variation in naked carp. Naked carp were subjected to normoxic, hypoxic and reoxygenation phases at two different carbonate alkalinity levels (CA0 = 0 mmol/L; CA32 = 32 mmol/L) for 4 days. The ammonia excretion rate (J_Amm) of the CA0 group rapidly decreased under hypoxia and recovered under normoxia for four consecutive days. The J_Amm under CA32 also decreased under hypoxia and recovered to its previous level in the first 2 days. However, the J_Amm under CA32 was lower than that under CA0. The blood pO₂, sO₂ of CA0 and CA32 group was significantly reduced under hypoxia, after which both groups recovered. Blood pCO₂ of the CA32 group was lower than CA0 throughout the experiment. There were no changes in haematocrit of the naked carp exposed to carbonate alkalinity and hypoxia. The alkaline water increased the pH of the blood and contributed to increased haemoglobin O₂ affinity. Overall, the present findings reveal that naked carp is a tolerant species that can maintain main ionic homeostasis under severe alkalinity and hypoxia. The high alkaline water is beneficial for naked carp to adapt to hypoxic environment.

Understanding the cardiac toxicity of the anthropogenic pollutant phenanthrene on the freshwater indicator species, the brown trout (Salmo trutta): From whole heart to cardiomyocytes

Freshwater systems are faced with a myriad of stressors including geomorphological alterations, nutrient overloading and pollution. Previous studies in marine fish showed polyaromatic hydrocarbons (PAHs) to be cardiotoxic. However, the cardiotoxicity of anthropogenic pollutants in freshwater fishes is unclear and has not been examined across multiple levels of cardiac organization. Here we investigated the effect of phenanthrene (Phe), a pervasive anthropogenic pollutant on a sentinel freshwater species, the brown trout (Salmo trutta). We first examined the electrical activity of the whole heart and found prolongation (∼8.6%) of the QT interval (time between ventricular depolarization and repolarization) of the electrocardiogram (ECG) and prolongation (∼13.2%) of the monophasic action potential duration (MAPD) following ascending doses of Phe. At the tissue level, Phe significantly reduced trabecular force generation by ∼24% at concentration 15 μM and above, suggesting Phe reduces cellular calcium cycling. This finding was supported by florescent microscopy showing a reduction (∼39%) in the intracellular calcium transient amplitude following Phe exposure in isolated brown trout ventricular myocytes. Single-cell electrophysiology was used to reveal the mechanism underlying contractile and electrical dysfunction following Phe exposure. A Phe-dependent reduction (∼38%) in the L-type Ca²⁺ current accounts, at least in part, for the lowered Ca²⁺ transient and force production. Prolongation of the MAPD and QT interval was explained by a reduction (∼70%) in the repolarising delayed rectifier K⁺ current following Phe exposure. Taken together, our study shows a direct impact of Phe across multiple levels of cardiac organization in a key freshwater salmonid.

Exploring relationships between cardiovascular activity and parental care behavior in nesting smallmouth bass: A field study using heart rate biologgers

Research in a variety of vertebrate taxa has found that cardiac function is a major limiting factor in the ability of animals to cope with physiological challenges, and thus is suggested to play an important role in mediating fitness-related behaviors in the wild. Yet, there remains a paucity of empirical assessments of the relationships between physiological performance and biological fitness in wild animals, partially due to challenges in measuring these metrics remotely. Using male smallmouth bass (Micropterus dolomieu) as a model, we tested for relationships between cardiac performance (measured using heart rate biologgers) and fitness-related behaviors (assessed using videography and snorkeler observations) in the wild during the parental care period. Our results showed that heart rates were not significantly related to any measured parental care behaviors (e.g., nest tending) except for individual aggression level. After accounting for the effect of water temperature on heart rate, we found within-individual heart rate differed between days and also differed between nights. There was, however, evidence of diel variation in heart rate, where heart rate was higher during the day than at night. Although fitness is thought to be dependent on physiological capacity for exercise in wild animals, inter-individual variation in heart rate alone does not appear to relate to parental care behavior in smallmouth bass at the temporal scales examined here (i.e., hours to days). Further studies are required to confirm relationships between physiological performance and parental care behavior to elucidate the apparently complex relationships between physiology, behavior, and fitness in wild animals.

Differential Effects of Adult Salmon Lice Lepeophtheirus salmonis on Physiological Responses of Sockeye Salmon and Atlantic Salmon

The salmon louse Lepeophtheirus salmonis, a type of sea lice (family Caligidae), is enzootic in marine waters of British Columbia and poses a health risk to both farmed Atlantic Salmon Salmo salar and wild Pacific salmon Oncorhynchus spp. At the adult stage, sea lice infections can often result in severe cutaneous lesions in their salmonid hosts. To evaluate and compare the physiological consequences of adult L. salmonis infections, smolts of Atlantic Salmon and Sockeye Salmon O. nerka were exposed to 2 (low), 6 (medium), or 10 (high) adult female lice/fish. Mean lice abundance decreased over time in all groups. Skin disruption due to parasite infection was observed in both species. Plasma samples were collected from infected fish and uninfected controls at 1, 3, 5, and 7 d postinfection and measured for indicators of osmoregulatory function and stress. Sockeye Salmon, regardless of L. salmonis exposure level, showed a rapid onset of elevated osmolality and sodium and chloride ion concentrations which were sustained until 7 d postinfection when values returned to levels comparable with the unexposed controls. Conversely, these effects were not measured in Atlantic Salmon. Additionally, differential host effects in blood glucose levels were observed, with Sockeye Salmon displaying immediate elevation in glucose. Relative to Atlantic Salmon, infection with L. salmonis caused a profound physiological impact to Sockeye Salmon characterized by loss of osmoregulatory integrity and a stress response. This work provides the first comprehensive report of the physiological consequences of infections with adult L. salmonis in Sockeye Salmon smolts and helps to further define the mechanisms of susceptibility in this species.

SDS-PAGE technique as biomarker for fish toxicological studies

Although many studies on the hematological and biochemical parameters in fishes have been done, still there are some shortage in the estimation and evaluation of the baseline's values of marine and freshwater fishes. Recently, the use of hematology and biochemistry of fishes in toxicology, aquaculture, environmental pollution, feeding, and antioxidants studies has been increased. In this study we introduced the importance of those parameters and their importance as biomarkers in fish toxicology from previous literature and as new findings. Hemato-biochemical parameters were widely used in fish toxicological studies. Many researches have used the protein electrophoresis as a valid tool to determining intra and inter-specific variation among species. Protein profile was extensively used in determining the health of fish, as indicators of anemia or other diseases provide information about the existence of the disease, and in the diagnosis of disease. So, to carry out the aim of this study, we reported one of the more advanced techniques used SDS-PAGE as molecular biomarker for protein profile analysis in fish with shedding the light on the importance of hematological and biochemical parameters in fish toxicological studies.

Effect of excessive doses of oxytetracycline on stress-related biomarker expression in coho salmon

Fish are exposed to a wide variety of environmental stressors, such as chemicals and acute changes in temperature. Oxytetracycline (OTC) has been used as an antibiotic for many kinds of bacterial diseases in cultured fish, but excessive doses of OTC are known to cause side effects in fish and can have negative effects on their environment. In the present study, we examined stress-related biomarker expression in response to excessive doses of dietary OTC in coho salmon (Oncorhynchus kisutch). Fish received OTC (100 mg/kg body weight/day) orally for 2 weeks. The percentage of liver to body weight (hepatosomatic index; HSI) and plasma biochemical parameter, alanine aminotransferase (ALT) activity, of the group fed a diet containing OTC were observed to be significantly higher than those of the control group. The total glutathione (tGSH) levels in the liver of OTC-fed fish were four fold higher than those in control fish and double the control levels in muscle and stomach. Plasma tGSH levels in OTC-fed fish were also higher than those in control fish. Expression levels of heat shock protein 70 in the liver, muscle, and stomach decreased by OTC administration. Accordingly, OTC-induced stress might increase the metabolic turnover of GSH due to consumption by scavenging oxidants generated by stress. These results concerning the changing patterns of stress-related biomarkers indicate that excessive doses of OTC fed to coho salmon induce oxidative stress, which might enhance oxidation in the body and result in damage to tissues, especially in the liver. The present results also suggest that tissue-specific damage caused by OTC might already exist in fish.

Virgin microplastics cause toxicity and modulate the impacts of phenanthrene on biomarker responses in African catfish (Clarias gariepinus)

Despite the ubiquity of microplastics (MPs) in aquatic environments and their proven ability to carry a wide variety of chemicals, very little is known about the impacts of virgin or contaminant-loaded MPs on organisms. The primary aim of this study was to investigate the impacts of virgin or phenanthrene (Phe)-loaded low-density polyethylene (LDPE) fragments on a suite of biomarker responses in juvenile African catfish (Clarias gariepinus). Virgin LDPE (50 or 500µg/L) were preloaded with one of two nominal Phe concentrations (10 or 100µg/L) and were exposed to the fish for 96h. Our findings showed one or both Phe treatments significantly increased the degree of tissue change (DTC) in the liver while decreased the transcription levels of forkhead box L2 (foxl2) and tryptophan hydroxylase2 (tph2) in the brain of C. gariepinus. Exposure to either levels of virgin MPs increased the DTC in the liver and plasma albumin: globulin ratio while decreased the transcription levels of tph2. Moreover, MPs modulated (interacted with) the impact of Phe on the DTC in the gill, plasma concentrations of cholesterol, high-density lipoprotein (HDL), total protein (TP), albumin, and globulin, and the transcription levels of fushi tarazu-factor 1 (ftz-f1), gonadotropin-releasing hormone (GnRH), 11 β-hydroxysteroid dehydrogenase type 2 (11β-hsd2), and liver glycogen stores. Results of this study highlight the ability of virgin LDPE fragments to cause toxicity and to modulate the adverse impacts of Phe in C. gariepinus. Due to the wide distribution of MPs and other classes of contaminants in aquatic environments, further studies are urgently needed to elucidate the toxicity of virgin or contaminant-loaded MPs on organisms.

Salinity effects on plasma ion levels, cortisol, and osmolality in Chinook salmon following lethal sampling

Studies on hydromineral balance in fishes frequently employ measurements of electrolytes following euthanasia. We tested the effects of fresh- or salt-water euthanasia baths of tricaine mesylate (MS-222) on plasma magnesium (Mg(2+)) and sodium (Na(+)) ions, cortisol and osmolality in fish exposed to saltwater challenges, and the ion and steroid hormone fluctuations over time following euthanasia in juvenile spring Chinook salmon (Oncorhynchus tshawytscha). Salinity of the euthanasia bath affected plasma Mg(2+) and Na(+) concentrations as well as osmolality, with higher concentrations in fish euthanized in saltwater. Time spent in the bath positively affected plasma Mg(2+) and osmolality, negatively affected cortisol, and had no effect on Na(+) concentrations. The difference of temporal trends in plasma Mg(2+) and Na(+) suggests that Mg(2+) may be more sensitive to physiological changes and responds more rapidly than Na(+). When electrolytes and cortisol are measured as endpoints after euthanasia, care needs to be taken relative to time after death and the salinity of the euthanasia bath.

Effects of garlic and ginger oils on hematological and biochemical variables of sea bass Dicentrarchus labrax

This study was conducted to investigate the effects of garlic and ginger oils on hematological and biochemical health characteristics of sea bass Dicentrarchus labrax. Fish were exposed to garlic oil (0.01 or 0.02 mL/L), ginger oil (0.01 or 0.02 mL/L), or a combination of the two oils (each oil at a concentration of 0.005 or 0.01 mL/L) for 96 h via bath immersion. Results showed that the red blood cell count, hematocrit (%), hemoglobin (Hb) concentration (g/dL), mean corpuscular volume (μm(3)), mean corpuscular Hb (pg), and mean corpuscular Hb concentration (%) were not significantly affected by herb oil exposure. However, some changes in biochemical variables were observed. Sea bass exposed to the 0.005-mL/L garlic oil-ginger oil mixture exhibited a significant increase in serum glucose. Serum total protein and albumin levels decreased in sea bass that were exposed to a garlic oil-ginger oil mixture (0.005 or 0.01 mL/L) or to garlic oil at 0.02 mL/L. Serum globulin levels decreased and triglyceride levels increased in sea bass exposed to 0.02-mL/L garlic oil or to the 0.01-mL/L mixture. The serum lipase level decreased and the cholesterol level increased in fish that were exposed to 0.02-mL/L garlic oil. In summary, ginger oil at 0.01-0.02 mL/L can be used without negative effects, while the garlic oil or garlic oil-ginger oil mixture should be applied at a concentration below 0.005 mL/L for bath immersion of sea bass. This is the first study to examine how garlic oil and ginger oil exposure via bath immersion affects the hematological and biochemical status of sea bass.

Dietary administration of Zooshikella sp. enhance the innate immune response and disease resistance of Paralichthys olivaceus against Sreptococcus iniae

We report the growth, innate immune response, and disease resistance in olive flounder (Paralichthys olivaceus) challenged with Streptococcus iniae after feeding with diet enriched with Zooshikella sp. strain JE-34 three different concentration i.e. Low (3.4 x 10(4), n = 50), medium (3.5 x 10(6), n = 50), and high (3.4 x 10(8), n = 50) cfu ml(-1) supplemented diets, the changes were monitored on weeks 1, 2, 4, 8, 12, and 16. With all diets the innate immune parameters, such as superoxide anion production, phagocytic and lysozyme activity were not enhanced on week 1 and 4. On the other hand, all tested immune parameters in the treated groups significantly enhanced after 8th week; the weight gain significantly increased after 4th week in fish fed with enriched diets. The mortality in olive flounder after administration with high concentration diet showed 25%. With low and medium enriched diets the mortality was 40% and 35%, respectively. In the infected untreated group mortality was 85% while there was no mortality in the control group. The results suggested that Zooshikella sp. strain JE-34 enriched diets could be used to enhance the innate immune response and disease resistance of P. olivaceus against S. iniae.

HCO (3)(-) secretion and CaCO3 precipitation play major roles in intestinal water absorption in marine teleost fish in vivo

The intestine of marine teleosts must effectively absorb fluid from ingested seawater to avoid dehydration. This fluid transport has been almost exclusively characterized as driven by NaCl absorption. However, an additional feature of the osmoregulatory role of the intestine is substantial net HCO(3)(-) secretion. This is suggested to drive additional fluid absorption directly (via Cl(-)/HCO(3)(-) exchange) and indirectly by precipitating ingested Ca(2+) as CaCO(3), thus creating the osmotic gradient for additional fluid absorption. The present study tested this hypothesis by perfusing the intestine of the European flounder in vivo with varying [Ca(2+)]: 10 (control), 40, and 90 mM. Fractional fluid absorption increased from 47% (control) to 73% (90 mM Ca(2+)), where almost all secreted HCO(3)(-) was excreted as CaCO(3). This additional fluid absorption could not be explained by NaCl cotransport. Instead, a significant positive relationship between Na(+)-independent fluid absorption and total HCO(3)(-) secretion was consistent with the predicted roles for anion exchange and CaCO(3) precipitation. Further analysis suggested that Na(+)-independent fluid absorption could be accounted for by net Cl(-) and H(+) absorption (from Cl(-)/HCO(3)(-) exchange and CO(2) hydration, respectively). There was no evidence to suggest that CaCO(3) alone was responsible for driving fluid absorption. However, by preventing the accumulation of luminal Ca(2+) it played a vital role by dynamically maintaining a favorable osmotic gradient all along the intestine, which permits substantially higher rates of solute-linked fluid absorption. To overcome the resulting hyperosmotic and highly acidic absorbate, it is proposed that plasma HCO(3)(-) buffers the absorbed H(+) (from HCO(3)(-) production), and consequently reduces the osmolarity of the absorbed fluid entering the body.

Perfil proteico de tilápia nilótica chitralada (Oreochromis niloticus), submetida ao estresse crônico por hipóxia

Avaliou-se a variação da resposta secundária ao estresse causado por hipóxia durante 18 dias, em sistema de recirculação, em uma linhagem de tilápia nilótica (Oreochromis niloticus), chitralada, refletida no perfil proteico eletroforético do peixe e avaliou-se a diferença entre sexos para essa resposta. Foram utilizados 126 peixes, sendo 60 machos e 66 fêmeas, ambos com média de peso de 800g. O estresse crônico por hipóxia alterou (P<0,05) os valores médios relativos de albumina, α+β-globulinas e de γ-globulina, provocou alteração (P<0,05) nos níveis de proteína total relativo ao aumento no grupo dos machos, diminuição significativa dos valores médios absolutos de albumina devido à diminuição nas fêmeas e à diminuição de γ-globulina nos machos. As variantes proteicas, albumina e γ-globulina tiveram influência do sexo.

Molecular cloning of PEPCK and stress response of black porgy (Acanthopagrus schlegeli) to increased temperature in freshwater and seawater

Stress responses to increased temperature in black porgy reared in freshwater (FBP) and seawater (SBP) were examined via endocrinological and blood physiological methods. A rise in temperature increased plasma cortisol levels, which were significantly higher in FBP compared to SBP. The stimulated expression of phosphoenolpyruvate carboxykinase (PEPCK) mRNA in liver might result from the high cortisol level, and this explains the observed higher plasma glucose levels in FBP versus SBP. Full-length cDNA sequence for PEPCK was determined by 3' and 5' RACE procedures. PEPCK cDNA clone was found to contain 2563 nucleotides including an open reading frame that encodes 624 amino acids. While aspartate aminotransferase (AST) and alanine aminotransferase (ALT) of FBP increased with temperature, there was no change in SBP. In FBP, T(3) were 2.3+/-0.3 ng/ml at 20 degrees C and significantly decreased to 1.0+/-0.3 ng/ml at 30 degrees C. On the other hand, in SBP, it were 3.1+/-0.5 ng/ml at 20 degrees C but significantly increased to 5.2+/-0.4 ng/ml at 30 degrees C. When comparing osmolality at the temperature of 30 degrees C and of 20 degrees C, the difference was found to be greater for FBP than SBP. Accordingly, the results suggest that FBP suffers greater stress than SBP with increased temperature, and provide stress responses and osmoregulatory abilities against stressors in black porgy that could differ depending on salinities.

Effect of the establishment of dominance relationships on cortisol and other metabolic parameters in Nile tilapia (Oreochromis niloticus)

The objective of the present study was to investigate the influence of the establishment of dominance relationships and social stress on plasma cortisol and metabolite levels in Nile tilapia (Oreochromis niloticus). During the 30-day experiment, the fish weighing 236 29 g were kept in individual aquaria, except for two pairings lasting 6 h each. Blood samples were taken from the animals before and after pairing. Display, approach, attack, rebuff, chase flight, and coloration were carried out on days 16 and 30. Activities and behaviors characteristic of the establishment of dominance relationships were described. It was possible to classify all experimental fish (N = 30) as dominant or subordinate. No differences were detected between dominant (N = 15) and subordinate (N = 15) fish during isolation or after pairing in cortisol (isolated: 5.76 0.98 vs 5.42 0.63; paired: 10.94 1.62 vs 11.21 2.45 g/dl), glucose (isolated: 60.02 4.9 vs 67.85 16.16; paired: 110.44 15.72 vs 136.26 22.46 mg/dl), triglyceride (isolated: 167.87 5.06 vs 185.68 7.24; paired: 210.85 13.40 vs 221.82 12.70 mg/dl) or total protein levels (isolated: 7.01 0.42 vs 6.69 0.59; paired: 9.21 0.62 vs 9.51 0.66 g/dl). However, when isolated (N = 30) and paired (N = 30) tilapia were compared, there were significant differences in cortisol and metabolite levels. The similar response presented by dominant and subordinate tilapia indicates that establishment of dominance relationships was a stressor for both groups.

Unusual physiology of scale-less carp, Gymnocypris przewalskii, in Lake Qinghai: a high altitude alkaline saline lake

The scale-less carp (Gymnocypris przewalskii) inhabits Lake Qinghai located on the Qinghai-Tibet plateau (elevation, 3200 m) in western China. The lake waters are alkaline (pH 9.4, titratable alkalinity=30 mmol l(-1)), Mg(2+)-rich (18.7 mmol l(-1)), Ca(2+)-poor (0.30 mmol l(-1)) and saline (9 per thousand ). These fish make annual spawning migrations into freshwater rivers. We investigated the physiology of nitrogen excretion and ionoregulation of fish from the lake and river. Fish from both waters were ammonotelic, although ammonia-N excretion rates were lower in lake fish (175 vs. 344 micromol kg(-1) h(-1), P<0.05) resulting in unusually high levels of ammonia in blood plasma (2.23 vs. 0.32 mmol l(-1)), bile, liver, muscle and brain. Exposure to 0.4 mmol l(-1) total ammonia in lake water ([NH(3)]=0.16 mmol l(-1)) killed fish within 8 h. River fish survived exposure to 1.0 mmol l(-1) total ammonia in river water at pH 8.0 ([NH(3)]=0.023 mmol l(-1)) for 24 h suggesting high ammonia tolerance in lake fish. High glutamate dehydrogenase and glutamine synthetase activities in tissues probably allow the fish to alleviate ammonia toxicity by amino acid accumulation. Neither lake nor river fish relied on urea excretion to remove excess N. Urea-N excretion rates were below 20 micromol kg(-1) h(-1) for both groups, and levels of urea in plasma and tissues were moderate. When exposed to elevated ammonia, urea-N excretion increased slightly (approximately 50 micromol kg(-1) h(-1)) and liver and muscle urea levels increased in the river fish. Plasma ion levels were within the range typical of cyprinids, but river fish had significantly higher plasma [Na(+)] and [Cl(-)] and lower [K(+)] than fish from the lake. During 48-h lake-to-river water transfer, plasma Na(+) and Cl(-) levels rose significantly. Significantly higher Na(+)/K(+)-ATPase activity in the gills of river fish may be related to the higher plasma ion levels. Plasma [Mg(2+)] and [Ca(2+)] were tightly regulated despite the great differences in the lake and river water levels.

Synaptic drive to motoneurons during fictive swimming in the developing zebrafish

The development of swimming behavior and the correlated activity patterns recorded in motoneurons during fictive swimming in paralyzed zebrafish larvae were examined and compared. Larvae were studied from when they hatch (after 2 days) and are first capable of locomotion to when they are active swimmers capable of capturing prey (after 4 days). High-speed (500 Hz) video imaging was used to make a basic behavioral characterization of swimming. At hatching and up to day 3, the larvae swam infrequently and in an undirected fashion. They displayed sustained bursts of contractions ('burst swimming') at an average frequency of 60-70 Hz that lasted from several seconds to a minute in duration. By day 4 the swimming had matured to a more frequent and less erratic "beat-and-glide" mode, with slower (approximately 35 Hz) beats of contractions for approximately 200 ms alternating with glides that were twice as long, lasting from just a few cycles to several minutes overall. In whole cell current-clamp recordings, motoneurons displayed similar excitatory synaptic activity and firing patterns, corresponding to either fictive burst swimming (day 2-3) or beat-and-glide swimming (day 4). The resting potentials were similar at all stages (about -70 mV) and the motoneurons were depolarized (to about -40 mV) with generally non-overshooting action potentials during fictive swimming. The frequency of sustained inputs during fictive burst swimming and of repetitive inputs during fictive beat-and glide swimming corresponded to the behavioral contraction patterns. Fictive swimming activity patterns were eliminated by application of glutamate antagonists (kynurenic acid or 6-cyano-7-nitroquinoxalene-2,3-dione and DL-2-amino-5-phosphonovaleric acid) and were modified but maintained in the presence of the glycinergic antagonist strychnine. The corresponding synaptic currents underlying the synaptic drive to motoneurons during fictive swimming could be isolated under voltage clamp and consisted of cationic [glutamatergic postsynaptic currents (PSCs)] and anionic inputs (glycinergic PSCs). Either sustained or interrupted patterns of PSCs were observed during fictive burst or beat-and-glide swimming, respectively. During beat-and-glide swimming, a tonic inward current and rhythmic glutamatergic PSCs (approximately 35 Hz) were observed. In contrast, bursts of glycinergic PSCs occurred at a higher frequency, resulting in a more tonic pattern with little evidence for synchronized activity. We conclude that a rhythmic glutamatergic synaptic drive underlies swimming and that a tonic, shunting glycinergic input acts to more closely match the membrane time constant to the fast synaptic drive.

Skin ulcers in fish: Pfiesteria and other etiologies

Skin ulcers on fish are one of the most well-recognized indicators of polluted or otherwise stressed aquatic environments. In recent years, skin ulcer epidemics have been either experimentally or epidemiologically linked to exposure to a number of xenobiotic chemicals as well as to biotoxins. Some of these agents, such as toxins produced by the dinoflagellate alga Pfiesteria, have led to serious concerns about the health of aquatic ecosystems, such as estuaries along the east coast of the United States. However, a number of other risk factors besides Pfiesteria have been shown to damage epithelium and may also play important roles in skin ulcer pathogenesis. In addition, increasing evidence indicates that not only may skin damage occur via direct contact with toxins, but it may also be induced indirectly from physiological changes that result from exposure not only to toxins but also to other environmental stressors, such as pH and temperature extremes. The multifactorial pathways that operate at both the ecological and the organismal levels as well as the nonspecific response of the skin to insults make it very challenging to link epidemic skin ulcers to any single cause in natural aquatic populations. Consequently, using pathology to unequivocally identify the specific cause of a lesion (eg. Pfiesteria exposure) is not a valid approach. Only with an increased understanding of the basic mechanisms leading to skin damage (including development of specific biomarkers for specific toxins), along with a better understanding of ecological processes operating in these environments, will we be able to discern the relative importance of various risk factors in skin ulcer development.

Comparative effects of UVA and UVB irradiation on the immune system of fish

Aquatic organisms can be harmed by the current levels of solar ultraviolet radiation. We have recently shown that exposure of fish to UVB irradiation alters the functioning of the fish immune system, but the effects of UVA radiation are unknown. The present study continues this work by characterizing UVA irradiation-induced immunological changes in fish. Roach, a cyprinid fish, were exposed to a single dose of either UVA (3.6 J/cm2) or UVB (0.5 J/cm2) irradiation. Both irradiations suppressed transiently mitogen-stimulated proliferation of blood lymphocytes. UVA, but not UVB, decreased hematocrit, plasma protein, and plasma immunoglobulin levels and increased the proportions of blood cells classified as unidentified leukocytes, possibly consisting of UVA-damaged lymphocytes. UVB, but not UVA, altered the functioning of head kidney and blood phagocytes, induced granulocytosis and lymphocytopenia in the blood and increased plasma cortisol concentration. These results imply that both UVA and UVB are potent modulators of the immune defence of fish.

Ca2+-dependent antifreeze proteins. Modulation of conformation and activity by divalent metal ions

The antifreeze proteins (AFPs) are structurally diverse molecules that share an ability to bind to ice crystals and inhibit their growth. The type II fish AFPs of Atlantic herring and smelt are unique among known AFPs in their requirement of a cofactor for antifreeze activity. These AFPs are homologous with the carbohydrate-recognition domains of Ca2+-dependent (C-type) lectins and require Ca2+ for their activity. To investigate the role of metal ions in the structure and function of type II AFPs, the binding of Ca2+ and other divalent cations to herring AFP was investigated. Binding studies using 45Ca2+ demonstrated that the AFP has a single Ca2+-binding site with a Kd of 9 microM. Proteolysis protection studies and measurement of antifreeze activity revealed a conformational change from a protease-sensitive and inactive apoAFP to a protease-resistant active AFP upon Ca2+ binding. Other divalent metal ions including Mn2+, Ba2+, and Zn2+ bind at the Ca2+-binding site and induce a similar change. A saturatable increase in tryptophan emission intensity at 340 nm also occurred upon Ca2+ addition. Whereas antifreeze activity appeared normal when Ca2+ or Mn2+ were bound, it was much lower in the presence of other metal ions. When Ba2+ was bound to the AFP, ice crystals showed a distinct difference in morphology. These studies demonstrate that herring AFP specifically binds Ca2+ and, consequently, adopts a conformation that is essential for its ice-binding activity.

Metabolic organization of liver and somatic muscle of landlocked sea lamprey,Petromyzon marinus, during the spawning migration

The metabolic organization of liver and muscle of the landlocked sea lamprey, Petromyzon marinus, during the spring spawning migration was assessed by measuring activities of key enzymes for several metabolic pathways, the oxidative properties of mitochondria, and plasma concentrations of nonesterified fatty acids (NEFAs) and free amino acids. These determinations indicate that several metabolic sources are used to fuel the energy requirements of muscle. Lamprey muscle has a high capacity to oxidize lipids but the plasma NEFAs are lower than those reported for other species. Of the NEFAs measured in plasma, 18:0 was prominent, accounting for 23% of the total NEFA content of the plasma. High plasma concentrations of ketogenic amino acids and high levels of tissue ketogenic/ketolytic enzyme activities indicate that ketone bodies may also be a major fuel source for migrating sea lampreys. Based on mitochondrial oxidation and enzyme measurements, glutamine catabolism in somatic muscle of lampreys is less important than in other fish red muscle.