Effect of blood glucose level on acute stress response of grass carp Ctenopharyngodon idella

Increased ingestion and toxicity of polyamide microplastics in Nile tilapia with increase of salinity

Microplastics pollution and salinity intrusion in freshwater ecosystem is one of the worldwide climate change consequences those have negative impacts on the physiology of aquatic organisms. Hence, a 15-day experiment was carried out where Nile tilapia (Oreochromis niloticus) was exposed to different salinity gradients i.e. 0 ‰, 3 ‰, 6 ‰, 9 ‰, and 12 ‰ alone and along with 10 mg/L polyamide microplastics (PA-MP) in order to measure its effects on the hematology, gill, and intestinal morphology. The results exhibited that all the fish treated with PA-MP ingested microplastics and the quantity of accumulation was significantly greater in higher salinity gradients (9 ‰ and 12 ‰). In addition, the PA-MP treated fish showed increased glucose level and at the same time reduced hemoglobin concentration with the increase of salinity. The percentages of abnormalities in erythrocytes both cellular (twin, teardrop and spindle shaped) and nuclear (notched nuclei, nuclear bridge and karyopyknosis) significantly enhanced with PA-MP exposure again in higher salinity treatments (9 ‰ and 12 ‰). The principal component analysis (PCA) exhibited that the addition of 10 mg/L PA-MP negatively affected the hematology of Nile tilapia than that of salinity treatments alone. Besides, the exposure of PA-MP in 9 ‰ and 12 ‰ salinity gradients escalated the severity of histological damages in gills and intestine. Overall, this experiment affirms that the increase of salinity enhanced the microplastics ingestion and toxicity in Nile tilapia, therefore, PA-MP possibly is addressed as additional physiological stressors along with increased salinity gradients in environment.

Behavioral and electrophysiological study in Colossoma macropomum treated with different concentrations of Nepeta cataria oil in an immersion bath revealed a therapeutic window for anesthesia

The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 μ L  L-1, 150 μ L  L-1, 175 μ L  L-1, and 200 μ L  L-1 on the behavior of loss of the posture reflex and recovery of the posture reflex and electrocardiographic activity and recording of the opercular beat of Colossoma macropomum during immersion bathing for a period of 5 min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5 g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 μ L  L-1, (b) 150 μ L  L-1, (c) 175 μ L  L-1, and (d) 200 μ L  L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2 ml of alcohol per liter of water), (c) 125 μ L  L-1, (d) 150 μ L  L-1, (e) 175 μ L  L-1, and (f) 200 μ L  L-1 (n = 9), per group. All the concentrations used showed efficacy in inducing loss of the posture reflex and reversibility with recovery of the posture reflex, but the electrocardiographic recordings indicated morphographic changes such as bradycardia during induction and p wave apiculation during recovery at the highest concentrations tested. In this way, we suggest a safe use window for short-term anesthesia with EON in the concentration range of 125 to 150 μ L  L-1 for juvenile Colossoma macropomum.

Efficacy of fennel (Foeniculum vulgare) and anise (Pimpinella anisum) essential oils as anaesthesics in common carp (Cyprinus carpio L. 1758)

In this study, the anaesthetic effects of fennel and anise essential oils were investigated on common carp. Fish (10 ± 0.45 g) were exposed to nine concentrations of essential oils (5, 10, 20, 50, 100, 200, 300, 400 and 500 mg L-1). Additionally, the histopathological effects on the fish tissues including gill, skin and hepatopancreas and physiological effects on some blood parameters (Na+, K+, Ca+2, Cl-, total plasma protein and glucose) of essential oils were investigated in carp. At the end of the experiment, fennel oil showed an anaesthetic effect at a concentration of 500 mg L-1 in carp (anaesthesia induction and recovery times were 308 and 472 s, respectively). Anise essential oil showed deep anaesthesia at a concentration of 100 mg L-1, but anaesthesia induction time was found to be very long (20 min). In addition, anise oil at concentrations above 100 mg L-1 caused 10% mortality in fish. Blood parameters except glucose level in both essential oils were unchanged during deep anaesthesia in carp. However, plasma glucose levels were found lower in fish anaesthetized with anise oil than control and fennel groups (P < 0.05). At the histopathological examination, no pathological findings were observed in any organ of fish in the fennel group. However, severe hyperemia and inflammatory cell infiltrations in gills, erosive lesions in the skin and slight inflammatory reactions in the skin were observed in the anise group. The present study demonstrated that fennel essential oil at 500 mg L-1 concentration can be used as an effective and safe anaesthetic in common carp, but anise essential oil is not suitable.

Integrated mRNA and miRNA analysis reveals the regulatory network of oxidative stress and inflammation in Coilia nasus brains during air exposure and salinity mitigation

BACKGROUND

Air exposure is an inevitable source of stress that leads to significant mortality in Coilia nasus. Our previous research demonstrated that adding 10‰ NaCl to aquatic water could enhance survival rates, albeit the molecular mechanisms involved in air exposure and salinity mitigation remained unclear. Conversely, salinity mitigation resulted in decreased plasma glucose levels and improved antioxidative activity. To shed light on this phenomenon, we characterized the transcriptomic changes in the C. nasus brain upon air exposure and salinity mitigation by integrated miRNA-mRNA analysis.

RESULTS

The plasma glucose level was elevated during air exposure, whereas it decreased during salinity mitigation. Antioxidant activity was suppressed during air exposure, but was enhanced during salinity mitigation. A total of 629 differentially expressed miRNAs (DEMs) and 791 differentially expressed genes (DEGs) were detected during air exposure, while 429 DEMs and 1016 DEGs were identified during salinity mitigation. GO analysis revealed that the target genes of DEMs and DEGs were enriched in biological process and cellular component during air exposure and salinity mitigation. KEGG analysis revealed that the target genes of DEMs and DEGs were enriched in metabolism. Integrated analysis showed that 24 and 36 predicted miRNA-mRNA regulatory pairs participating in regulating glucose metabolism, Ca2+ transport, inflammation, and oxidative stress. Interestingly, most of these miRNAs were novel miRNAs.

CONCLUSION

In this study, substantial miRNA-mRNA regulation pairs were predicted via integrated analysis of small RNA sequencing and RNA-Seq. Based on predicted miRNA-mRNA regulation and potential function of DEGs, miRNA-mRNA regulatory network involved in glucose metabolism and Ca2+ transport, inflammation, and oxidative stress in C. nasus brain during air exposure and salinity mitigation. They regulated the increased/decreased plasma glucose and inhibited/promoted antioxidant activity during air exposure and salinity mitigation. Our findings would propose novel insights to the mechanisms underlying fish responses to air exposure and salinity mitigation.

Responses to graded levels of zinc amino acid complex in Nile tilapia (Oreochromis niloticus)

Zinc (Zn) is an essential micronutrient that plays a crucial role in fish development and physiology. This study aimed to evaluate the effects on growth and health in Nile tilapia (Oreochromis niloticus) supplemented with graded levels of zinc amino acid complex (Zn-AA) and subjected to transport stress. Nile tilapia (21.78 ± 0.17 g; (n = 12 fish per tank; stocking density of 1.045 kg- 3) were fed with 0, 25, 50, 75, or 100 mg Zn-AA kg- 1 (equivalent to 77.49, 102.69, 127.89, 153.09, or 178.29 mg Zn kg- 1) in extruded diets (280 g kg- 1 digestible protein; isoproteic and isocaloric) for 60 days. At the end of the experimental period, after growth performance measurements, the fish were transported by car for 3 h, and blood collection was performed. The linear regression showed that the best growth performance (final weight, final biomass, weight gain, specific growth rate, and feed intake) was found in fish fed with 100 mg Zn-AA kg diet- 1 (p < 0.05). The increased dietary Zn-AA increased linearly plasma triglyceride levels, hemoglobin, mean corpuscular hemoglobin, and leukocyte values and reduced plasma total protein, cholesterol (total and LDL), and aspartate aminotransferase levels (p < 0.05). According to quadratic regression, the highest plasma glucose and alanine aminotransferase values were found in the control group (p < 0.05). In conclusion, under the conditions of this study, 100 mg Zn-AA kg diet- 1 is recommended for Nile tilapia as it can improve their growth, metabolism, physiology, and immunity.

Comparative transcriptome analysis reveals growth and molecular pathway of body color regulation in turbot (Scophthalmus maximus) exposed to different light spectrum

Fish body color changes play vital roles in adapting to ecological light environment and influencing market value. However, the initial mechanisms governing the changes remain unknown. Here, we scrutinized the impact of light spectrum on turbot (Scophthalmus maximus) body coloration, exposing them to red, blue, and full light spectra from embryo to 90 days post hatch. Transcriptome and quantitative real-time PCR (qRT-PCR) analyses were employed to elucidate underlying biological processes. The results showed that red light induced dimorphism in turbot juvenile skin pigmentation: some exhibited black coloration (Red_Black_Surface, R_B_S), while others displayed lighter skin (Red_White_Bottom, R_W_B), with red light leading to reduced skin lightness (L*) and body weight, particularly in R_B_S group. Transcriptomic and qRT-PCR analyses showcased upregulated gene expressions related to melanin synthesis in R_B_S individuals, notably tyrosinase (tyr), tyrosinase-related protein 1 (tyrp1), and dopachrome tautomerase (dct), alongside solute carrier family 24 member 5 (slc24a5) and oculocutaneous albinism type II (oca2) as pivotal regulators. Nervous system emerged as a critical mediator in spectral environment-driven color regulation. N-methyl d-aspartate (NMDA) glutamate receptor, and calcium signaling pathway emerged as pivotal links intertwining spectral conditions, neural signal transduction, and color regulation. The individual differences in NMDA glutamate receptor expression and subsequent neural excitability seemed responsible for dichromatic body coloration in red light-expose juveniles. This study provides new insights into the comprehending of fish adaptation to environment and methods for fish body color regulation and could potentially help enhance the economic benefit of fish farming industry.

An experiment on the glucose metabolite, serum electrolytes, and somatic characteristics of the Levantine Barbel Luciobarbus pectoralis (Heckel, 1843) under the effect of heavy metals

Levantine Barbel (Luciobarbus pectoralis) is a benthopelagic, subtropical native fish living in the inland waters of the Mediterranean region in Türkiye and Syria. Even though it is widely consumed locally, experimental observations on how heavy metals [zinc (Zn), copper (Cu), cadmium (Cd), and lead (Pb)] and their mixtures affect the fish are lacking. Several bioindicators of the fish exposed to heavy metals are the focus of the current investigation. Initially, Fulton condition factor (K) and hepato-somatic index (HSI) were utilized in the somatic characteristics of L. pectoralis. Then, changes in the level of glucose metabolite and electrolytes [sodium (Na+), potassium (K+), and chloride (Cl-)] of blood were determined by Architect C-800 auto-analyzer after exposure durations. The results of the experiments demonstrated that heavy metals can rapidly have a negative impact on the regulation of blood and somatic characteristics of fish. It was observed that the K index decreased in all metal groups at 24 and 96 h, while considerably increased in the 24-h effect of cadmium only (P ≤ 0.05). Along with that, in the 96-h effect of metals, Cu indicated the highest decrease in the HSI value (19.33%, P ≤ 0.05). In general, all heavy metal exposures caused the fish's glucose metabolite level to rise compared to the control (P ≤ 0.05). Furthermore, sublethal effects of metals at both durations caused considerable changes in blood electrolytes of the fish compared to control (P ≤ 0.05). Additionally, putative biomarkers in both durations had the greatest difference in toxic similarity under the Cu impact compared to the control, according to Hierarchical clustering and Euclidean distance metrics. Although the applied concentrations of Zn, Cu, Cd, and Pb and their mixture studied were generally within the limits of the various organizations and the surface water regulations, changes in ecophysiological and somatic indices were nonetheless seen in fish.

Muscle Transcriptome Sequencing Revealed Thermal Stress-Responsive Regulatory Genes in Farmed Rohu, Labeo rohita (Hamilton, 1822)

Rohu, Labeo rohita, is one of the most important aquaculture species in the Indian subcontinent. Understanding the molecular-level physiological responses to thermal stress or climate change is essential. In the present work, transcriptome sequencing was carried out in the muscle tissue of the rohu in response to heat stress (35 °C) in comparison with the control (28 °C). A total of 125 Gb of sequence data was generated, and the raw-reads were filtered and trimmed, which resulted in 484 million quality reads. Reference-based assembly of reads was performed using L. rohita genome, and a total of 90.17% of reads were successfully mapped. A total of 37,462 contigs were assembled with an N50 value of 1854. The differential expression analysis revealed a total of 107 differentially expressed genes (DEGs) (15 up-, 37 down-, and 55 neutrally regulated) as compared to the control group (Log2FC > 2, P < 0.05). Gene enrichment analysis of DEGs indicates that transcripts were associated with molecular, biological, and cellular activities. The randomly selected differentially expressed transcripts were validated by RT-qPCR and found consistent expression patterns in line with the RNA-seq data. Several transcripts such as SERPINE1(HSP47), HSP70, HSP90alpha, Rano class II histocompatibility A beta, PGC-1 and ERR-induced regulator, proto-oncogene c-Fos, myozenin2, alpha-crystallin B chain-like protein, angiopoietin-like protein 8, and acetyl-CoA carboxylases have been identified in muscle tissue of rohu that are associated with stress/immunity. This study identified the key biomarker SERPINE1 (HSP47), which showed significant upregulation (~ 2- to threefold) in muscle tissue of rohu exposed to high temperature. This study can pave a path for the identification of stress-responsive biomarkers linked with thermal adaptations in the farmed carps.

Interaction of low-level dietary supplementation of Chlorella vulgaris Beijerinck, 1890, and feeding duration on growth hormone, growth performance and serum biochemistry of red hybrid tilapia (Oreochromis mossambicus × Oreochromis niloticus)

Chlorella is one of the most widely accepted Chlorophyta used by many as livestock and aquaculture feed. Nonetheless, different studies on the overall performances of fish reported the unfavourable effect of high-level supplementations of Chlorella vulgaris. The current study determined the impact of low-level dietary supplementation of C. vulgaris alongside the different feeding durations and their interactions on the growth hormone (GH), growth performances, serum-biochemical indices, hepatic function and some immunological parameters of red hybrid tilapia. The fingerlings (mean weight: 14.25 ± 0.01 g, length: 13.5 ± 0.49 cm) were fed diets containing 0, 0.99%, 2.91% and 4.76% of C. vulgaris powder per kilogram dry diet for 90 days. GH, growth performance, serum-biochemical indices (total serum protein, albumin, globulin, glucose, aspartate aminotransferase and alanine aminotransferase) and some immunological (respiratory burst and lysozyme activities) parameters of the fish were examined after 30, 60 and 90 days of feeding. The results demonstrated that tilapia fed C. vulgaris-supplemented diets showed increased levels of respiratory burst, lysozyme, albumin and total protein, GH and growth performances (P < 0.05), and the effects were duration dependent. After the 90 days of feeding, there was no adverse effect on the hepatic function of the fish. Besides, low survivability was observed in the control group than in the group fed the experimental diets. The group fed the diet supplemented with 4.76% C. vulgaris had significantly higher (P < 0.05) lysozyme activity throughout the duration of the feeding experiment. These results indicate that C. vulgaris enhanced growth performances, GH concentration, serum-biochemistry and some immunological parameters of red hybrid tilapia.

Effect of static magnetic field on marine mollusc Elysia leucolegnote

Artificial magnetic fields are unavoidable environment for offshore marine organisms. With the substantially increasing submarine cables, the impact of magnetic field generated by cables on marine organisms has gradually attracted people's attention. However, there are few studies on the effect of magnetic field on molluscs. To explore whether magnetic fields could interfere with the physiological functions of offshore molluscs, here we systematically analyzed the change of metabolism and transcriptome of Elysia leucolegnote exposed to either geomagnetic field or 1.1 T static magnetic field. The blood glucose and lipid levels, as well as the activities of antioxidant enzymes in E. leucolegnote were significantly increased upon the exposure to high static magnetic field for 10 days. Meanwhile, the activities of enzymes related to digestive performance and liver functions were decreased. Possible mechanisms were further revealed through comparative transcriptome analysis. A total of 836 differentially expressed genes were identified, 352 of which were up-regulated and 484 of which were down-regulated after exposure to the high static magnetic field. The up-regulated differential genes were mainly concentrated in lysosomal and apoptotic pathways, and down-regulated differential genes were mainly involved in digestive and immune systems including phagocytosis. This pattern was further confirmed by RT-qPCR analysis. In conclusion, prolonged exposure to a 1.1 T static magnetic field increased oxidative stress and blood glucose and lipid levels, and decreased immunity and physiological conditions in E. leucolegnote. The data we presented here provides a comprehensive view of metabolism change and gene expression pattern of E. leucolegnote exposed to static magnetic field. It may expand our knowledge on the magnetic field effects on offshore mollusc at molecular level, and contribute to clarification of the interaction between marine animals and artificial magnetic fields, which is certainly ecologically important.

Blood glucose profile as a rapid method for observing Koi carp (Cyprinus carpio) health status - case study of ectoparasites in Blitar, Indonesia

Assessment of fish health is one of the efforts of farmers in minimizing losses due to disease. Rapid tests on fish health can be done through blood observations. This study aimed to determine the blood glucose profile of koi carp due to ectoparasite infestation from the level of blood glucose. The results showed that reported parasites from Blitar's koi carp were Trichodina, Dactylogyrus, Gyrodactylus, Myxobolus, Thelohanellus, Ichthyophthirius, and Argulus. Trichodina showed the highest prevalence (100%) in this case while Thelohanellus was the highest intensity level (93.8±16.3). The results of blood glucose level measurement based on parasite infestation levels showed no significant difference (p>0.05) though the health problems caused by parasites in light, medium or heavy infestation. This research also indicated that the blood glucose profile could be used as a rapid method to detect fish health caused by parasites. We suggest that other variables such as nutritional status, life stage or feeding must be conducted to ensure the glucose role in parasite identification as a rapid method for the future work.

Protective effects of paeonol against lipopolysaccharide-induced liver oxidative stress and inflammation in gibel carp (Carassius auratus gibelio)

Paeonol (2'-hydroxy-4'-methoxyacetophenone) is a phenol that exhibits antioxidant and anti-inflammatory capabilities. In this study, the underlying mechanism of paeonol against LPS-induced oxidative stress and inflammatory responses in gibel carp was investigated. Three hundred healthy gibel carp were divided into five groups (n = 9), intraperitoneally injected with LPS and thereafter treated with paeonol (16 mg/kg and 64 mg/kg). Fish were anesthetized with MS-222 (100 mg/L), and samples were collected at 72 h to investigate plasma biochemical indexes, liver histopathology, antioxidant enzymatic activity, and TLR receptor-related gene expression. Fish injected with LPS (20 mg/kg) exhibited significantly increased plasma aminotransferase (ALT), aminotransferase (AST), lactate dehydrogenase (LDH), glucose (GLU), diamine oxidase (DAO), and alkaline phosphatase (ALP) levels (P < 0.05). In addition, LPS challenge significantly enhanced myeloperoxidase (MPO) and malondialdehyde (MDA) contents, whereas those of catalase (CAT) and glutathione peroxidase (GSH-Px) decreased (P < 0.05). However, treatment with paeonol attenuated these LPS-induced changes (P < 0.05). The mRNA expression of TLR4, TIRAP, MyD88, TRAF6, NF-κB, TNF-α, IL-1β, and IL-8, which were activated by LPS challenge (P < 0.05), were downregulated by paeonol. Additionally, histopathological examination demonstrated that paeonol alleviates LPS-induced hepatic tissue lesions in fish. Taken together, the results suggest that paeonol mitigates LPS-induced liver oxidative stress and inflammation in gibel carp.

The Effects of Dietary Arthrospira platensis on Oxidative Stress Response and Pigmentation in Yellow Catfish Pelteobagrus fulvidraco

In aquaculture, fish are often exposed to several stress conditions, which will cause oxidative disorder and bring about health and quality problems. Arthrospira platensis contains abundant bioactive ingredients, which are beneficial for animal health. This study was conducted to investigate the effects of A. platensis on pigmentation, antioxidant capacity, and stress response after air exposure of fish. A total of 120 yellow catfish Pelteobagrus fulvidraco (initial weight 70.19 ± 0.13 g) were divided into three tanks per treatment and fed diets supplemented with 0 g kg−1 A. platensis (CON) and 20 g kg −1 A. platensis (AP) for 65 days. The results indicated that dietary A. platensis had no effects on the growth of yellow catfish. The AP diet significantly reduced lactic acid (LD) and cortisol levels stimulated by air exposure stress (p < 0.05). Dietary A. platensis significantly increased plasma superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities and glutathione (GSH) contents, and the relative expression levels of sod and cat, to protect against oxidative stress caused by air exposure (p < 0.05). The AP diet significantly improved the relative expression level of nrf2 (nuclear factor erythroid-2 related factor 2), while the relative expression level of keap1 (kelch-like ECH associated protein 1) was downregulated, and the protein levels of liver Nrf2 were significantly increased after air exposure stimuli (p < 0.05). Dietary A. platensis significantly increased skin lutein contents, increased skin redness, yellowness and chroma (p < 0.05), and improved body color abnormalities after oxidative stress caused by air exposure stimuli. Skin yellowness was associated with lutein contents and the expression levels of some antioxidant genes to varying degrees. Overall, dietary A. platensis could be utilized as a feed additive to activate the antioxidant response, as well as alleviate oxidative stress and pigmentation disorder induced by air exposure.

The Role of Insulin-like Peptide in Maintaining Hemolymph Glucose Homeostasis in the Pacific White Shrimp Litopenaeus vannamei

Insulin-like peptide (ILP) has been identified in various crustaceans, but whether it has a similar function in regulating hemolymph glucose as vertebrate insulin is unclear. We analyzed the components of hemolymph sugar in the Pacific white shrimp, Litopenaeus vannamei, and investigated the changes of hemolymph glucose concentration and the expressions of ILP and glucose metabolism genes under different treatments. We found glucose was a major component of hemolymph sugar in shrimp. Starvation caused hemolymph glucose to rise first and then decline, and the raised hemolymph glucose after exogenous glucose injection returned to basal levels within a short time, indicating that shrimp have a regulatory mechanism to maintain hemolymph glucose homeostasis. In addition, injections of bovine insulin and recombinant LvILP protein both resulted in a fast decline in hemolymph glucose. Notably, RNA interference of LvILP did not significantly affect hemolymph glucose levels, but it inhibited exogenous glucose clearance. Based on the detection of glucose metabolism genes, we found LvILP might maintain hemolymph glucose stability by regulating the expression of these genes. These results suggest that ILP has a conserved function in shrimp similar to insulin in vertebrates and plays an important role in maintaining hemolymph glucose homeostasis.

The Effects of Lemon Balm (Melissa officinalis L.) Essential Oil on the Stress Response, Anti-Oxidative Ability, and Kidney Metabolism of Sea Bass during Live Transport

This study was conducted to enhance the viability and alleviate the oxidative stress response using MO for sea bass during live transport. Six experimental groups were designed, and the effects of the physiological responses of MO were evaluated in comparison with MS-222 and eugenol. The physiological stress levels, proprotein convertase subtilisin/kexin type 9 (PCSK-9), antioxidant enzyme activities, and kidney parameters of blood serum were determined. It was found that cortisol level, glucose (Glu), lactic acid (LD), heat shock proteins (HSPs), catalase (CAT), myeloperoxidase (MPO), glutathione peroxidase (GSH-Px), uric acid (UA), and urea nitrogen (BUN) in the MO-treated samples were lower than that of the control (133.72 ng/L); however, the total antioxidant capacity (T-AOC) was higher after 72 h of the simulated live transport. The ability to resist oxidative stress increased along with the increase in the MO concentration in the water during live transport, which was similar to the results of MS-222 and eugenol treatment. In conclusion, MO, acting as a kind of novel sedative and anesthetic, can be used to improve the oxidative system and survival rate during live transport. The results of this study provide a reference for enhancing animal welfare and anti-oxidative stress ability, reducing mortality and the stress response during live fish transport.

Heavy metal toxicity in Buriganga river alters the immunology of Nile tilapia (Oreochromis niloticus L)

The objective of the current study was to evaluate the biochemical and immunological responses of tilapia, Oreochromis niloticus due to heavy metals pollution. Histomorphological alterations in the liver and kidney suggested tissue damages due to this polluted water exposure. The brain acetylcholinesterase (AChE) as an indicator of neurotoxicity was significantly (P < 0.01) decreased after 10 days exposure of fish to heavy metal contained river water, while plasma glutamate oxalacetate transaminase and plasma glutamate pyruvate transaminase were significantly increased (P < 0.01). Moreover, superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase enzyme activities, as well as reduced glutathione and malondialdehyde levels were significantly increased in heavy metals contained river water treated fish compared to the control. Additionally, glucose level and blood serum Ca2+ concentrations were significantly (P < 0.01) decreased in fish exposed to heavy metal contained river water compared to the control. Hematological indices such as Hemoglobin, RBC, WBC, MCV etc. of polluted river water treated fish were significantly (P < 0.01) different in comparison to that of control fish. The cytokines i.e. IL-1β, IL-6, and TNF-α level were significantly (P < 0.01) increased in the fish exposed to heavy metals contained river water in comparison to that of control fish. The present findings explored the detrimental effects of heavy metal contained river water on fish at biochemical and immunological levels.

Juvenile fish responses to sublethal leachate concentrations: comparison of sensitivity of different behavioral endpoints

The aim of the present study was to investigate changes in the locomotor activity of rainbow trout (Oncorhynchus mykiss) juveniles under the impact (2 h) of landfill leachate (as a multicomponent mixture) based on different endpoints such as average, maximum and angular velocities, movement duration, body mobility, and blood glucose level. Fish were exposed to five different sublethal leachate concentrations (0, 0.0625, 0.125, 0.25, and 0.5%). The locomotor activity of the leachate-exposed fish significantly decreased at 0.25 and 0.5% concentrations. Significant changes in fish behavior in response to sublethal leachate concentrations were determined during the first minutes of exposure. Angular velocity proved to be the most sensitive of all the endpoints tested. A positive correlation was observed among behavioral responses, but no correlation was established between the blood glucose level and behavioral endpoints. The blood glucose endpoint was found to be insensitive, and we suggest that it should be used only in combination with other endpoints to complement toxicity data. To enhance the understanding of rainbow trout behavioral characteristics in relation to time, and relations among behavioral endpoints of the fish under short-term exposure to a multicomponent mixture, in the current study, we investigated dynamics of the selected behavioral endpoints over time, relations among these endpoints and compared behavioral response rapidness and efficacy.

Effect of Dietary Zinc-Nanoparticles on Growth Performance, Anti-Oxidative and Immunological Status of Fish Reared Under Multiple Stressors

Zinc is one of the essential micronutrients that can be obtained via water and diet in aquatic animals to meet their physiological needs. The present study was designed to understand the effect of the supplementation of zinc nanoparticles (Zn-NPs) in mitigating abiotic and biotic stress in Pangasius hypophthalmus. Two zinc nanoparticle-incorporated diets with 10 and 20 mg/kg nanoparticles and a control without zinc nanoparticles were formulated. To study the effect of formulated feeds on stress tolerance, fish were exposed to sublethal dose (4 ppm) of Pb (lead) and temperature at 34 °C. Two hundred and seventy-three fish were randomly distributed into seven treatment groups in triplicates, namely a control group (no Zn-NPs and no Pb and temperature exposure, Ctr/Ctr), control diet fed and exposed to Pb (Ctr/Pb), control diet fed and concurrently exposed to Pb and temperature (Pb-T/Ctr), and Zn-NPs 10 and 20 mg/kg diet with or without stressors (Zn-NPs 10 mg/kg, Zn-NPs 20 mg/kg, Pb-T/Zn-NPs 10 mg/kg, Pb-T/Zn-NPs 20 mg/kg). The effect of Zn-NPs on growth performance, stress biomarkers, biochemical and immunological responses, and survival of P. hypophthalmus following challenge with pathogenic bacteria were evaluated. The growth performance was noticeably (p < 0.01) enhanced, and anti-oxidative stress (catalase, superoxide dismutase, and glutathione-s-transferase) significantly reduced in the Zn-NPs supplemented groups. Similarly, immunological parameters such as total protein, albumin, globulin, and A/G ratio significantly improved, and stress biomarkers such as blood glucose, cortisol, and HSP 70 were reduced in Zn-NPs supplemented groups. Overall, the results suggest that supplementation of dietary Zn-NPs with less concentration in the diet has a definitive role in the mitigation of abiotic and biotic stress in P. hypophthalmus.