Immune response in the tilapia, Oreochromis mossambicus on exposure to tannery effluent

Ecotoxicology of hexavalent chromium in fish: An updated review

Chromium (Cr) is prevalently found in trivalent and hexavalent forms. Though the former is toxicologically benign due to its poor cellular permeability, hexavalent chromium i.e. Cr [VI] crosses the biological membrane and induces toxic effects in organisms. While Cr [VI] toxicity in humans is a subject of occupational exposure at industries involved in ferrochrome production, leather tanning, textile dyeing etc., aquatic abundance of Cr [VI] due to discharge of Cr-laden effluents by these industries lead to extensive toxicity in piscine species. The present review aims to discuss the mode of Cr [VI] entry in fish and the several inimical effects that it imparts on fish health. Such effects have been reported in various studies through behavioral, hormonal and hematological alterations. Bio-accumulation of Cr [VI] in vital organs and subsequent perturbation of the oxidative homeostasis leads to organotoxic effects like changes in organo-somatic indices and histo-architecture. At cellular level, Cr [VI] induced genotoxicity is often found to trigger cellular demise including apoptosis. This review also highlights the stress response in fish against Cr [VI] induced toxicity that is mediated through the expressional alteration of a myriad of anti-oxidant and xenobiotic-metabolizing proteins which is, in turn, a function of activated transcription programs including the Nrf2-ARE pathway.

Spatial-temporal dynamics of Cr in fish from Puruzinho Lake (Western Amazon) and dietary risk assessment

Cr contamination is a growing concern in the Amazon. Along with the rise of cattle farming in the region, tanneries are becoming more common and threatening environmental quality, since the effluents from this activity are rich in Cr. The objective of this study was to evaluate the seasonal and spatial dynamics of Cr in fish with different feeding habits from Puruzinho Lake, located in the Madeira River basin, also determining the daily intake of Cr associated with the consumption of these fish by the population that lives around the lake. Seasonality and feeding habits directly affected Cr dynamics in fish (p < 0.0001), with medians of Cr concentration ranging between 0.07 mg kg^-1 in the species Cichla pleiozona, a carnivorous fish, and 0.62 mg kg^-1 in Mylossoma duriventre, a herbivorous fish. The high Cr concentrations in M. duriventre were related to the biodilution effect of Cr in the trophic chain (R² = 0.14, p < 0.0001). The consumption of M. duriventre by the population was associated with the highest daily intake of Cr (55.5 μg∙day^-1), exceeding the recommended limits of Cr intake (35 μg∙day^-1). However, no harmful effects on health are expected due to the ingestion of Cr through the consumption of fish from Puruzinho Lake. Spatial analysis showed an increasing trend in Cr concentrations along the Madeira River, suggesting that contaminants present in the river are being carried over long distances and are reaching preserved areas of the Amazon.

Toxic Effects on Oxidative Stress, Neurotoxicity, Stress, and Immune Responses in Juvenile Olive Flounder, Paralichthys olivaceus, Exposed to Waterborne Hexavalent Chromium

Simple Summary

Metals such as chromium can be exposed at high levels in the marine environment, and exposure to these heavy metals can have a direct effect on marine organisms. High levels of chromium exposure can have a direct impact on organisms in a coastal cage and terrestrial aquaculture. Hexavalent chromium exposure of more than 1.0 and 2.0 mg Cr⁶⁺/L induced physiological responses such as antioxidant, neurotransmitter, immune, and stress indicators in Paralichthys olivaceus. Therefore, this study will provide a reference indicator for stable aquaculture production through reference indicators for toxicity due to chromium exposure that may exist in the marine environment.

Abstract

Juvenile Paralichthys olivaceus were exposed to waterborne hexavalent chromium at various concentrations (0, 0.5, 1.0, and 2.0 mg/L) for 10 days. After chromium exposure, the activities of superoxide dismutase and glutathione S-transferase, which are oxidative stress indicators, were significantly increased; however, the glutathione level was significantly reduced. Acetylcholinesterase activity as a neurotoxicity marker was significantly inhibited upon chromium exposure. Other stress indicators, including plasma cortisol and heat shock protein 70, were significantly increased. The immune response markers (lysozyme and immunoglobulin M) were significantly decreased after chromium exposure. These results suggest that exposure to environmental toxicity in the form of waterborne chromium at concentrations higher than 1.0 mg/L causes significant alterations in antioxidant responses, neurotransmitters, stress, and immune responses in juvenile olive flounders. This study will provide a basis for an accurate assessment of the toxic effects of hexavalent chromium on aquatic organisms.

Serum Immunoglobulin Levels and Complement Function of Tannery Workers in Bangladesh

BACKGROUND

Occupational exposures to chromium (Cr), which can have adverse effects on immune function, have not yet been extensively investigated. Hexavalent chromium (Cr (VI)), used in mineral tanning processes, poses a threat to the health of workers in the leather tanning industry.

OBJECTIVES

The aim of the present study was to evaluate the effects of long-term Cr exposure on the physical health and immunological parameters of male tannery workers in Bangladesh compared with a control group.

METHODS

A health examination was performed with tannery workers (N=195) and control subjects (N=125) by physicians, demographic data were recorded in questionnaires and peripheral blood samples were collected. Serum Cr levels were analyzed by an atomic absorption spectrophotometer (AAS), immunoglobulin (Ig)G, IgA, and complement components C3 and C4 were determined by nephelometry, IgE was measured by sandwich enzyme-linked immunosorbent assay and complement function was assayed by bactericidal activity.

RESULTS

The mean duration of work exposure for the tanners was 9.4±7.1 years. Their body mass index (21.8±3.0 kg/m²), was not significantly different from the controls (22.7±3.2 kg/m²). The mean serum level of Cr in 30 long-term exposed tannery workers (26.97±21.11 μg/dL) was significantly higher than that of 30 randomly selected control subjects (7.38±6.81 μg/dL). The tannery workers had rough skin, rashes, itchy and decolorized skin, allergic diseases and respiratory illness, and had significantly lower levels of serum IgG, IgA, C3 and C4, but significantly higher levels of IgE than the controls. IgG, IgA and C3 levels were all inversely associated with Cr, while IgG, IgE and bactericidal activity showed an inverse correlation with duration of exposure.

CONCLUSIONS

The results of the present study suggest that chronic exposure to Cr is associated with impaired immune function in male tannery workers.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

The present study was approved by the Ethical Review Committee of the faculty of Biological Sciences, University of Dhaka, Bangladesh.

COMPETING INTERESTS

The authors declare no competing financial interests.

Effects of effluent from electoplating industry on the immune response in the freshwater fish, Cyprinus carpio

The present study was designed to assess the effect of sublethal concentrations of electoplating industry effluent (EIE) on the non-specific and specific immune responses in the freshwater fish, Cyprinus carpio. Sublethal concentrations of electroplating industry effluent such as 0.004, 0.007, 0.010 and 0.013% were chosen based on the LC₅₀ values. Experimental fish were exposed to these sublethal concentrations of EIE for 28 days. After 7, 14, 21 and 28 days of treatment, non-specific immune response by serum lysozyme activity, myeloperoxidase activity and antiprotease activity and specific immune response by antibody response to Aeromonas hydrophila using bacterial agglutination assay and ELISA were assessed. The results showed that chronic exposure of fish to 0.004, 0.007, 0.010 and 0.013% EIE, dose-dependently decreased the non-specific and specific immune responses on all the days tested compared to control fish whereas statistically significant suppressive effects were observed in fish exposed to 0.013% of EIE on all activities tested.

A comprehensive review on chromium induced alterations in fresh water fishes

Chromium is considered as one of the most common ubiquitous pollutants in the aquatic environment, but the pure metallic form is absent naturally. There are three oxidation states in case of Chromium viz., Cr (II), Cr (III), Cr (VI). Among which Cr (II) is most unstable. Cr (III) and Cr (VI) are the stable oxidation state of Chromium in the environment. Being one of the commonly used metals Chromium and its particulates enter the aquatic medium through effluents discharged from different industries like textiles, tanneries, electroplating workshops, ore mining, dyeing, printing-photographic and medical industries. Among these, hexavalent chromium is considered as the most toxic form because it readily passes cellular membranes and then reduced to trivalent form. This trivalent chromium combines with several macromolecules including genetic material inside the cytosol, and is ultimately exposes the toxic and mutagenic alterations due of chromium toxicity. Chromium is taken up either through gastrointestinal tract or respiratory tract. The amount varies depending upon the medium and the form of chromium. In this review, an attempt has been made to accumulate the mammoth available data regarding impact of chromium on fresh water fishes into a systematic representation. The main objective of the review is to provide a future guideline for the scientific community and public officials involved in health risk assessment and management ensuring a better environmental condition for human health.

Histological liver chances in Swiss mice caused by tannery effluent

Although tannery effluents are known for being highly toxic to organisms, reports about the effects of the intake of these xenobiotics on experimental mammal models are recent. Studies about the damages the chronic intake of these effluents can cause in the liver of outbred mice remain an unexplored field. Thus, the aim of the present study is to assess (histological) the hepatic condition of Swiss mice (outbred strain) chronically exposed to the intake of different raw tannery effluent concentrations diluted in water for 150 days. Accordingly, the mice (males and females) were divided in the following groups: control group-animals treated with drinking water, only; and groups 5 and 10%-treated with raw tannery effluent diluted in water. After exposure, the animals were subjected to euthanasia for liver fragment sample collection and histological analysis, respectively. Moderate hydropic degeneration was observed in the centrilobular regions of the liver of mice exposed to 5 and 10% tannery effluent, as well as greater amounts of hepatocytes presenting karyomegaly and necrotic hepatocytes, and a smaller amount of Kuffer cells in the liver of mice exposed to the xenobiotic. Finally, animals exposed to 10% tannery effluent showed mild hyperplasia of the bile ducts in the portal areas and fibroblast proliferation around the bile ducts, thus suggesting a fibrous process. Except for the frequency of hepatocytes presenting karyomegaly (lower in females), the herein observed hepatic changes were similar in male and female Swiss mice. Accordingly, the present data support the hypothesis that the chronic intake of tannery effluent by outbred mice (Swiss) causes damages in the liver, a fact that broadens the knowledge about the toxic potential of this pollutant, which goes beyond that of C57Bl/6J male mice (inbred strain).

Effects of tannery wastewater exposure on adult Drosophila melanogaster

Our aim was to evaluate the effects of exposure to tannery wastewater on mortality and/or antioxidant enzyme system in adult wild-type Canton-S Drosophila melanogaster. Exposure to tannery wastewater induced a concentration-dependent lethality in adult Canton-S flies. Tannery wastewater was able to alter antioxidant enzyme activities, specifically glutathione peroxidase-like and glutathione S-transferase, in adult Canton-S D. melanogaster. We conclude that D. melanogaster is a reliable model to evaluate the toxicity induced by tannery wastewater.

Application of fish cell lines for evaluating the chromium induced cytotoxicity, genotoxicity and oxidative stress

In the present study, we hypothesize that cytotoxicity, genotoxicity and oxidative stress play a key role in chromium induced toxicity in SISS, SISK, IEE, IEK, IEG, SICH and ICG cell lines after 24 h exposure. Three fish species namely Lates calcarifer, Etroplus suratensis and Catla catla were exposed to the concentrations of 0, 10, 20, 30, 40 and 50 mg/L of chromium for 96 h under static conditions for conducting acute toxicity tests. LC₅₀ was then calculated. The percentage cell survival was assessed by multiple endpoints such as MTT, NR, AB and CB assays in the seven fish cell lines exposed to different concentrations of chromium and EC₅₀ values of all the four endpoints were calculated. High significances were noted in the correlations between each in vitro cytotoxicity assays and in vivo mortality data. Cell shrinkage, cell detachment, vacuolations and cell swelling at the highest concentration of chromium (50 mg/L) were seen on microscopic examination of cell morphology. Comet assay and Hoechst staining were carried out to assess DNA damage and nuclear fragmentation in the seven fish lines exposed to chromium. The results of antioxidant parameters obtained indicate a significant reduction in the level of catalase, superoxide dismutase, glutathione S-transferase and Glutathione peroxidase, and increased level of lipid peroxidation in all the cell lines exposed to chromium. These results confirm that fish cell lines could be used as an alternative to whole fish for cytotoxicity, genotoxicity and oxidative stress assessment in chromium toxicity studies.

The genotoxicity and cytotoxicity of tannery effluent in bullfrog (Lithobates catesbeianus)

Some of the most polluting activities occur in bovine skin processing. Tannery generates effluents containing high concentrations of heavy metals and organic compounds. The phases composing the leather production process generate a large volume of tannery effluents that are often discarded in aquatic environments without any previous treatment. However, the effect these xenobiotics have on adult representatives belonging to the class Amphibia remains unknown. Thus, the aim of the present study is to assess the geno- and cytotoxic effects of tannery effluent on adult male bullfrogs (Lithobates castesbeianus) exposed to it. Accordingly, the animals were divided into the following groups: negative control (tannery effluent-free water), positive control (cyclophosphamide), and effluent (water added with 5% tannery effluent). The animals were euthanized for blood collection, and erythrocyte analyses were conducted after 35 and 90 days of exposure. The micronuclei (MN) frequency and the frequency of other nuclear abnormalities in each of the animals in the experimental groups were assessed in 2000 erythrocytes. According to the present results, the exposure to tannery effluents increased MN frequency as well as other nuclear abnormalities (i.e., lobed nuclei, binucleated cell, kidney-shaped nuclei, notched nuclei, and apoptotic cell) in the erythrocytes of animals in the effluent group and in the positive control group after 35 and 90 exposure days. Thus, the current study corroborated the hypothesis that the tannery effluent has aneugenic and clastogenic potential in adult male bullfrogs (L. castesbeianus). The present study is the first to report such effect.

Effect of tannery effluent on oxidative status of brain structures and liver of rodents

Oxidative stress has been considered as a central mechanism of toxicity induced by xenobiotics. Previously, it was demonstrated that mice exposed to tannery effluent showed an anxiety-like behavior, without any comparable behavioral effects in rats. The aim of the present study was to investigate the impact of tannery wastewater on oxidative status in in vitro and in vivo assays with two mammal species, mice and rats. Specifically, homogenates of two brain areas and the liver were incubated with tannery wastewater; reactive species and lipid peroxidation levels and antioxidant enzyme activities were detected. In addition, the effects of in vivo exposure of mice to tannery effluents on and lipid peroxidation levels and the total reactive antioxidant capacity in brain areas and liver. Brain areas, the hippocampus and frontal cortex, and the liver of mice exposed to tannery wastewater showed oxidative stress. Our data suggest that divergent species-dependent hepatic enzymes adaptations, such as glutathione peroxidase and glutathione S-transferase activities, induced by tannery effluent could explain previous behavioral findings.

The C57BL/6J mice offspring originated from a parental generation exposed to tannery effluents shows object recognition deficits

The main aim of the present paper is to assess whether the parental generation exposure to such discharges could cause object recognition deficits in their offspring. Male and female C57Bl/6J mice were put to mate after they were exposed to 7.5% and 15% tannery effluents or water (control group), for 60 days. The male mice were withdrawn from the boxes after 15 days and the female mice remained exposed to the treatment during the gestation and lactation periods. The offspring were subjected to the object recognition test after weaning in order to assess possible cognition losses. The results of the analysis of the novel object recognition index found in the testing session (performed 1 h after the training session) applied to offspring from different experimental groups appeared to be statistically different. The novel object recognition index of the offspring from female mice exposed to tannery effluents (7.5% and 15% groups) was lower than that of the control group, and it demonstrated object recognition deficit in the studied offspring. The present study is the first to report evidences that parental exposure to effluent of tannery (father and mother) can cause object recognition deficit in the offspring, which is related to problems in the central nervous system.

Immunological and health-state parameters in the Patagonian rockfish Sebastes oculatus. Their relation to chemical stressors and seasonal changes

We present the results of a field study that evaluates whether exposure to anthropogenic pollution impacts immunological and health-state parameters of wild marine fish during the breeding and non-breeding periods. We assessed aspects of innate immunity (bactericidal capacity, bacterial agglutination, and leukocyte profile) and general health-related parameters (neutrophil to lymphocyte ratio, hematocrit, and condition factor) in the Patagonian rockfish (Sebastes oculatus) sampled from polluted (exposed) and reference (control) sites during winter (i.e., coolest temperatures and active reproductive period) and in summer (i.e., warmest temperatures and non-reproductive period). Results showed lower bactericidal competence, hematocrit, and condition factor in fish from exposed sites independently of season, whereas lymphocytes were higher and monocytes lower at the exposed site only during summer. Moreover, fish sampled during winter displayed lower bactericidal competence, hematocrit, and condition factor than those sampled in summer independently of site, whereas the opposite pattern was found for bacterial agglutination. These results could be explained by life-history theory, which predicts a re-allocation of resources between reproduction and other physiological functions (including immunity) during the most energetically demanding season. The present results show an alteration in immunological and health-state parameters of wild marine fish exposed to anthropogenic pollution independently of season, which could potentially result in higher susceptibility to disease and in turn population decline.

Generation of reactive oxygen species by leukocytes of Prochilodus lineatus

Prochilodus lineatus (curimbatá), from the Procholodontidae family, is a Brazilian freshwater fish, which is important commercially, nutritionally and ecologically. It is encountered in the Rio da Prata Bay in Southern South America. Studies on the immune system of this fish are scarce, but the physiological mechanisms of the species are analogous to those of other vertebrates. Thus, this work discusses the present study, which correlates P. lineatus leukocytes and the generation of reactive oxygen species after modulatory stimuli. Leukocytes were characterized by light and electron transmission microscopy and investigated by the generation of H2O2 and O2 (-), using phenol red, flow-cytometry and electron transmission histochemistry. The study determined that monocytes and neutrophils are the main cells responsible for generating O2 after stimulation with phorbol myristate acetate. Superoxide dismutase successfully inhibited the generation of reactive oxygen species in neutrophils and monocytes, but stimulated generation when in association with phorbol myristate acetate. Fish leukocyte samples from P. lineatus showed cross-reactivity with antibodies directed against human NADPH-oxidase antibody subunits (p47(phox) and p67(phox)). Thus, catalase enhanced the presence of p47(phox). Neutrophil mitochondria were shown to be generators of H2O2 (charged by cerium precipitate), being enlarged and changing their format. The present study contributes to a better understanding of the respiratory burst pathways in this species and suggests mitochondria as the organelle responsible for generation of reactive oxygen species.

Immunotoxicity of tannery effluent to the freshwater fish Cyprinous carpio

This study was undertaken to determine the effect of chronic exposure to sub-lethal concentrations of tannery effluent (TE) on the humoral antibody response and the cell-mediated immune response of the fish Cyprinous carpio. The LC(50) value of the TE for C. carpio was determined by bioassay to be 3.8%. Sub-lethal concentrations of TE (0.6% and 0.3%) significantly suppressed the humoral and cell-mediated immune responses. Exposure of C. carpio to the TE had a significant effect on mean acceptance time (MAT) for transplanted scales. MAT was found to be 5-8 days for autografts and 4-7 days for allografts. The somatic indices of the kidney and spleen were reduced compared with controls.

Immunotoxicity of 1-methyl-3-octylimidazolium bromide on brocarded carp (Cyprinus carpio L.)

In the present study, the immunotoxicity of 1-methyl-3-octylimidazolium bromide ([C(8)mim]Br) on brocarded carp was evaluated by an acute exposure of 100-300mgL(-1) of [C(8)mim]Br for 7 days. The results showed 300mgL(-1) of [C(8)mim]Br exposure caused activity inhibition of specific and non-specific immune systems, mainly including IgM level, lysozyme activity, and complement C3 content, while 100mgL(-1) of [C(8)mim]Br activated fish immune system during the early periods of exposure (2-5 days). This result indicates that [C(8)mim]Br has immunotoxicity on brocarded carp. Additionally, histological observation revealed that 300mgL(-1) of [C(8)mim]Br-exposure led to remarkable damages to the hepatopancreas, kidney, and spleen of brocarded carp after 7 days of [C(8)mim]Br treatment, although not only change in kidney and spleen somatic indexes was found, but also no swelling or hemorrhage of carp viscera occurred.

Chromium-induced biochemical, genotoxic and histopathologic effects in liver and kidney of goldfish, carassius auratus

Fish constitute an excellent model to understand the mechanistic aspects of metal toxicity vis-à-vis oxidative stress in aquatic ecosystems. Hexavalent chromium (Cr (VI)), due to its redox potential can induce oxidative stress (OS) in fish and impair their health. In the present investigation, we hypothesize that OS plays a key role in chromium induced toxicity in goldfish; leading to the production of reactive oxygen species (ROS) such as O(.)(2), H(2)O(2), OH(.), and subsequent modulation of the activities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), metallothioneins (MT), glutathione proxidase (GPx), genotoxicity and histopathology. To test this hypothesis, antioxidant enzymes, DNA damage and histopathology assays were performed in liver and kidney tissues of goldfish exposed to different concentrations of Cr (VI) (LC(12.5), LC(25) and LC(50)) following 96h static renewal bioassay. The results of this study clearly show that the fish experienced OS as characterized by significant modulation of enzyme activities, induction of DNA damage and microscopic morphological changes in the liver and kidney. In both tissues, CAT activity was decreased whereas SOD activity and hydroperoxide levels were increased. In addition, GPx activity also increased significantly in higher test concentrations, especially in the kidney. MT induction and DNA damage were observed in both tissues in a concentration dependent manner. Microscopic examination of organ morphology indicated degeneration of liver tissue and necrosis of central vein. Necrosis of kidney tubular epithelial cells and tubules was observed at higher Cr (VI) concentrations. Taking together the findings of this study are helpful in organ-specific risk assessment of Cr (VI)-induced oxidative stress, genotoxicity and histopathology in fish.

Effect of hexavalent chromium exposure on the pituitary-interrenal axis of a teleost, Channa punctatus (Bloch)

The immunocytochemistry of pituitary corticotrophs, interrenal histopathology and serum cortisol assay revealed adverse effects of hexavalent chromium [Cr(VI)] exposure (as potassium dichromate; K(2)Cr(2)O(7)) on the pituitary-interrenal axis of a freshwater fish, Channa punctatus. On acute exposure (10, 20 and 40 mg L(-1) for 96 h), corticotrophs showed hypertrophy and intense immunoreactivity to anti-human (h) ACTH(1-29). Cytoplasmic degranulations in some of the cells were also noticed. On the contrary, atrophy and weak anti-h ACTH(1-29) immunoreactivity of corticotrophs was observed with the chronic exposure (2 and 4 mg L(-1) for one month). Exposure-dependent varied effects also reflected in the histopathology of head kidney interrenal tissue and serum cortisol levels. Acute exposure induced hypertrophy and degranulation of interrenal cells along with significant elevation of serum cortisol levels in a concentration-dependent manner (42+/-0.72, 44.6+/-1.34 and 52+/-3.06 ng mL(-1), respectively in 10, 20 and 40 mg L(-1) group, compared to 36.65+/-0.83 of control). Atrophy of interrenal cells and low serum cortisol levels as compared to that of control (34.1+/-0.78 and 29.3+/-0.92 ng mL(-1), respectively in 2 and 4 mg L(-1) groups) in chronic-exposed fish indicates attenuated functioning of the hypothalamic-pituitary-interrenal (HPI) axis. The stress response of the fish (under confinement) further confirmed the impairment of the HPI axis, as the elevation in serum cortisol levels were significantly less (258% and 166% of basal level, respectively in 2 and 4 mg L(-1) group, compared to 374% of control). The long-term interference of this axis by metal exposure therefore, may pose serious threat to fish making them unable to adapt to stress.

Ecotoxicology of hexavalent chromium in freshwater fish: a critical review

Chromium (Cr) is a naturally occurring element found in rocks, animals, plants, and soil, predominantly in its insoluble trivalent form [Cr(III)]. Intense industrialization and other anthropogenic activities have led to the global occurrence of soluble hexavalent chromium Cr(VI), which is readily leached from soil to groundwater or surface water, in concentrations above permissible levels. The ecotoxicology of Cr(VI) is linked to its environmental persistence and the ability to induce a variety of adverse effects in biologic systems, including fish. In aquatic ecosystems, Cr(VI) exposure poses a significant threat to aquatic life. This paper reviews the fate and transport of Cr(VI) in the environment and its acute and chronic effects on fish. We also discuss Cr(VI) toxicity at the cellular, biochemical, and genetic levels. An attempt is made in this review to comprehend the staggered data on the toxic effects of Cr(VI) to various species of fish. Such data are extremely useful to the scientific community and public officials involved in health risk assessment and management of environmental contaminants as a guide to the best course of action to restore ecosystems and, in turn, to preserve human health.

Acute osmotic stress affects Tilapia (Oreochromis mossambicus) innate immune responses

Most of the tilapia studies are focused on its osmoregulatory mechanism. Meanwhile, less information is available about its innate immune response on fish faced with hyperosmolality. In the present study, in vivo analyses were carried out to investigate the innate immune response of Oreochromis mossambicus, transferred from freshwater to 25 ppt seawater (SW). In vivo, lysozyme activities of plasma and head kidney (HK) were increased at 1h and at 24h after transfer to SW but decreased at 8h after SW transfer. Surprisingly, the alternative complement pathway in plasma increased 8h after SW transfer. The phagocytic capacity of spleen and HK immune cells increased modestly at 1h and at 4h, after SW transfer, but the respiratory burst activity of immune cells in both HK and spleen shows an increase in superoxide release at 8h after SW transfer. Our results reveal that the transfer of fish from conditions of hypoosmolarity to hyperosmolality significantly enhances plasma lysozyme, ACP activity, and both phagocytic and respiratory burst activity. Taken together, the results indicate that exposure of tilapia to hyperosmotic conditions has immunostimulatory effects on its cellular immune reactions (phagocytosis and respiratory burst activity) and humoral reactions (lysozyme activity and complement activity).