Research Article

Responses and Histopathological Studies of Clarias gariepinus Exposed to Selenium Toxicity  

Kehinde Esther Odo , Dominic Olabode Odedeyi
Department of Animal and Environmental Biology, Faculty of Science, Adekunle Ajasin University, Akungba-Akoko, Ondo State, Nigeria
Author    Correspondence author
International Journal of Marine Science, 2017, Vol. 7, No. 29   doi: 10.5376/ijms.2017.07.0029
Received: 04 Jul., 2017    Accepted: 01 Aug., 2017    Published: 03 Aug., 2017
© 2017 BioPublisher Publishing Platform
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:

Odo K.E., and Odedeyi D.O., 2017, Responses and histopathological studies of Clarias gariepinus exposed to selenium toxicity, International Journal of Marine Science, 7(29): 284-291 (doi: 10.5376/ijms.2017.07.0029)

Abstract

Various toxicants have been deposited into aquatic environment due to human activities, in light with this, 180 healthy Clarias gariepinus juveniles with mean weight of 7.4±0.64 g and length of 11.2±0.88 cm were exposed to different concentrations of selenium (a typical toxicant) to evaluate its behaviour and histopathological response. The fish were exposed to different concentrations (2, 3, 4, 5 and 6 mg/L) of selenium under a static bioassay for 96 hours after a range finding test and 96 hours LC50 was determined using probit method. 10 fish per concentration was used for the bioassay in triplicates. The 96 hours lethal concentration (LC50) was estimated to be 3.39 mg/L. The histological examination of the gill revealed hyperplasia and haemorrhage of the gill lamellar. The kidney showed vacuolation and blood stains while the skin demonstrated mucosal eruption. These alterations increase with increase in selenium concentration. Selenium at high concentration has shown to induce behavioural changes on fish and also alterations to organs of Cgariepinus juvenile. It is therefore recommended that industries ensure the incorporation of effluents treatment plants to treat wastes before discharging into the environment.

Keywords
Selenium toxicity; Histopathology; Behavioural changes; Clarias gariepinus

Introduction

Human activities have been identified as the major cause of aquatic pollutant over decades and industries discharge their effluents indiscriminately into water body without proper treatment (Mehjbeen and Nazura, 2013). Heavy metals have been found to be the major chemicals present in these industrial effluents which are harmful to aquatic life. Freshwater are highly vulnerable to pollutants since they act as immediate sink for the consequences of human activity and always associated with danger of accidental discharges or criminal negligence (Vutukuru, 2003). Fish mostly have the tendency to bioaccumulate heavy metals and human might be at great risk some time even lethal, through contamination of food chain (Ui, 1972). Heavy metals have devastating effects on ecological balance of the recipient environment and a diversity of aquatic organisms. Selenium is a metalloid that is commonly used in industrial and manufacturing processes like photoelectric cells, steel manufacture, anti-dandruff shampoos, fungicide, and glass manufacturing (Nagpal, 2001). Major anthropogenic sources of selenium include fossil fuel combustion, mining, and agricultural drain water (Haygarth, 1994; Lemly, 1999). Sources that may increase selenium contamination are open pit phosphate mining, wetlands constructed to treat Se-laden wastewater, and feedlot waste (Lemly, 1999). When selenium entered aquatic ecosystem, it may be absorbed or ingested by aquatic organisms, bind to particulate matter, or stay free in solution (Lemly and Smith, 1988). Selenium accumulates primarily in the gonad and muscle tissue (Kennedy et al., 2000). Thus, even small inputs of selenium into a water body may quickly accumulate up the food chain poisoning higher trophic levels (Farombi et al., 2007). Behavioural measurement has been used as indicator of toxic stress in fish. Fishes in a contaminated environment show some altered behavioural patterns which may include avoidance, locomotive activity and aggression and these may cause fish attempt to escape or adjust to the stress condition (Morgan et al., 1991; Gormley and Teather, 2003). Behavioural functions are generally quite vulnerable to contaminant exposures, and fish often exhibit these responses first when exposed to pollutants (Little et al., 1993; Ololade and Oginni, 2010). Histological biomarkers of toxicity in fish organ are a useful indicator of environmental pollutant (Peebua et al., 2008). Several histological changes have been reported in the gills, liver, kidney and gonads of fish in response to agricultural, sewage and industrial pollutants (Mohamed, 2003). There have been numerous reports on histopathological changes in gill, kidney, and flesh of fish exposed to different toxicant (Olufayo and Alade, 2012; Vinodhini and Narayanan, 2008). Histopathological alterations have been used as indicators of the effects of various pollutants on the organism including fish, and reflection of the overall health of the entire pollution. Mohamed (2009) reported several pathological changes in different tissues of fish exposed to chemicals. The exposure of fish to pollutants that is agricultural and industrial chemicals, were resulted in several pathological changes in different tissues of fish. Alterations in histopathology were also reported in Heterobranchus Bidorsalis exposed to cypermethrin (Olufayo and Alade, 2012). Information on lethal exposure of selenium and its compounds on the physiology of fish are limited and its effects on organs of Clariasgariepinus juveniles are scarce. This paper therefore presented to the effects of selenium on the behaviour and some organs of C. gariepinus juveniles.

 

1 Materials and Methods

Juveniles of African catfish (Clarias gariepinus) with average weight of 7.4±0.64 g were used for the study. 180 fish were purchased from a reputable fish hatchery 10 fish were acclimatized in 80L plastic container filled with 60 L of water each for a period of 4 weeks to the laboratory condition. During this period of acclimatization, the fish were fed with artificial feed twice daily at 3% body weight and water was changed every other day. The fish were not fed 48 hours prior to experiment in order to minimise ammonia production as a result of fish waste. The selenium was in the form of sodium biselenite (NaHSeO3) which was purchased from a reputable scientific store. Toxicant stock solution of the tested metal, a pure chemical: sodium bi- selenite was prepared by dissolving 5 g of reagent equivalent to 1 g of selenium in 1000 mL tap water at concentration of 1000 mg/L. From the stock solutions, different concentrations required were prepared after a range – finding test using a screening procedure. The concentrations prepared for the experiment were: 2, 3, 4, 5 and 6 mg/L based on literature guidance (Burba, 1999; Vinodhini and Narayanan, 2008). This was prepared 24 hours before the experiment in other for the chemical to properly dissolve. Water quality monitoring was done every 24 hours throughout the period of the experiment. The pH, conductivity, dissolved oxygen, and temperature was done with the use of HI-769828 multi-parameter water analysis probe. Ammonia, nitrate and nitrite test was done with the use of NT LABS pond water multipara meter test kit. The histological examination of Clarias gariepinus juvenile exposed to sodium bi-selenite was done on the survived fish after 96 hours by the removal of the desired organ (gill, kidney, and flesh). Three fish were randomly selected from each group after 96 hours for the histological extermination. The tissues were fixed in 10% formalin and were processed (dehydrated in ascending grades of alcohol, clear in xylene, and impregnated in molten paraffin wax) in Automatic tissue processor. These were then observed under microscope.

 

2 Results

Behavioural response observed during the 96 hours experiment include: attempt escapement especially at the point of death, erratic swimming, and irregular movement of the opercula. These behavioural changes were observed more in group exposed to higher concentrations (5 and 6 mg/L). These responses indicated that the culture environment containing selenium was unsuitable for the fish. No visible lesion was seen in the gill section of the control group (Figure 1) which remained an ordinary structure and non-differentiated cell were found in the lamellae. Damage to organs was more pronounced in the fish exposed to higher concentrations. The gill section of C. gariepinus exposed to 2 and 3 mg/L of selenium showed stunted secondary gill lamellae (Figure 2; Figure 3; Figure 4). Degenerative changes were seen in the groups exposed to higher concentrations (5 mg/L and 6 mg/L) of selenium (Figure 5; Figure 6). These showed many areas of mucosal erosion, lamellar necrosis and hyperplasia which change the normal structure of the gill section. Sections of unexposed kidney of C. gariepinus showed no visible lesion (Figure 7). Pathological changes were seen in the kidney sections of the exposed group. The kidney section of C. gariepinus exposed to lower concentration (2 mg/L and 3 mg/L) of selenium shows few foci tubular necrosis within the parenchyma cell (Figure 8; Figure 9). Kidney of C. gariepinus exposed to 4 mg/L selenium revealed some blood stains in the glomerulus (Figure 10). The kidney sections of C. gariepinus exposed to the highest concentration 5 mg/L and 6 mg/L of sodium selenium showed a severe interstitial congestion and blood stains in the glomerulus. The medullary area also appears highly congested and haemorrhagic (Figure 11; Figure 12). The skin section of the control group showed a normal architecture of a skin structure with no visible lesion. Also, the melanin is well expressed with no abnormalities (Figure 13). Visible lesion were not found in the skin section of C. gariepinus exposed to 2, 3 and 4 mg/L selenium (Figure 14; Figure 15; Figure 16) but little histological damage were seen in groups exposed to higher concentrations 5 and 6 mg/L of selenium (Figure 17; Figure 18). This damage was majorly skin lesion and eroded epithelia surface which changes the normal architecture of the skin structure. Table 1 shows the water quality parameters, dissolved oxygen decreases with increase in concentration of selenium. However, all other parameters shows no significant difference.

 

 

Figure 1 Gill structure of the control group shows no fisible lesion ×400

 

 

Figure 2 Gill section of C. gariepinus exposed to 2 mg/L of NaHSeO3 shows stunted secondary gill lamellae ×400

 

 

Figure 3 Gill of C. gariepinus esposed 3 mg/L of selenium shows lamellar necrosis and lamellar hyperplasia ×400

 

 

Figure 4 Gill of C. gariepinus esposed to 4 mg/L of selenium shows hyperplasia and haemorrragic of the secondary gill lamellar ×400

 

 

Figure 5 Gill of C. gariepinus esposed to 5 mg/L of selenium shows lamellar necrosis and lamellar hyperlasia ×400

 

 

Figure 6 Gill of C. gariepinus esposed to 6 mg/L of selenium shows lamellar necrosis and lamellar hyperplasia ×400

 

 

Figure 7 Kidney section of control group shows no pathological change ×400

 

 

Figure 8 Kidney of C. gariepinus esposed to 2 mg/L of selenium shows few foci of tubular necrosis within the parencyma ×400

 

 

Figure 9 Kidney of C. gariepinus esposed to 3 mg/L of seleniun shows blood stains on the glomerulus ×400

 

 

Figure 10 Kidney of C. gariepinus esposed to 4 mg/L of selenium shows cytoplamic vacuolarization and blood stains on the glomerulus ×400

 

 

Figure 11 Kidney of C. gariepinus esposed to 5 mg/L selenium shows interstial congestion and blood stains in the glomerulus ×400

 

 

Figure 12 Kidney of C. gariepinus esposed to 6 mg/L of selenium shows severe interstitial congestion with blood stains ×400

 

 

Figure 13 Flesh structure unesposed group of C. gariepinus shows no visible lesion. melanin is well expressed ×400

 

 

Figure 14 Flesh structure of C. gariepinus esposed to 2 mg/L of selenium shows no visible lesion ×400

 

 

Figure 15 Flesh section of C. gariepinus esposed to 3 mg/L of selenium shows no visble lesion ×400

 

 

Figure 16 Flesh of C. gariepinus esposed to 4 mg/L of selenium shows no pathological change ×400

 

 

Figure 17 Flesh of C. gariepinus esposed to 5 mg/L of selenium shows skin lesion ×400

 

 

Figure 18 Flesh of C. gariepinus esposed to 6 mg/L of selenium shows skin lesion and eroded epithelia surface ×400

 

 

Table 1 Water quality parameters of culture system of Clariasgariepinus observed over period of 96 hours

Note: Mean with different superscripts are significantly different

 

3 Discussion

Behavioural responses has been used as indicator of toxic stress in fish (Little et al., 1993); Ololade and Oginni (2010) reported that behavioural responses may be useful indicators of sub-lethal contamination even at concentrations being lower than those that affect growth. Fishes in a contaminated environment show some altered behavioural patterns which may include avoidance, locomotive activity and aggression and these may cause fish attempt to escape or adjust to the stress condition (Morgan et al., 1991; Gormley and Teather, 2003). Behavioural functions are generally quite vulnerable to contaminant exposures, and fish often exhibit these responses first when exposed to pollutants (Little et al., 1993; Ololade and Oginni, 2010). The behavioural activities of Clarias gariepinus juveniles on introduction of selenium at different concentrations were observed. The noticeable behaviours include aggressiveness, loss of equilibrium, slow motion, erratic swimming and sound making which is not uncommon because it has been reported by Gormley and Teather (2003) who worked on Japanese medaka (Oryziaslatipes) exposed to endosulfan. Erratic swimming exhibited by the fish could be as a result of loss of equilibrium caused by the intoxication of the selenium. Opercular movement and loss of equilibrium observed in this study is similar to the report of Ghatak and Konar (1990) on Tilapia mossambica exposed to cadmium. Attempt to escape by the experimental fish especially at higher concentration (5 and 6 mg/L) is no doubt caused by the toxic substance. This particular behaviour indicates that the environment has become unsuitable for the fish to survive. Fish may take up selenium through their gills, as selenium accumulation in rainbow trout is greater after gill development (Hodson et al., 1986). Gill lamellae which are normally thin and delicate are necessary for gas exchange in respiration. As a result of lamellar necrosis in this study, the function of the lamellar to increase the surface area for oxygen exchange could not be achieved. Similar results were reported by Cavan and Muley (2004) when Cirrhinu smrigala was exposed to mercury and lead. There were necrotic change in intercellular epithelial cells, lamellar degeneration and epithelia lifting. Lamellar hyperplasia that was revealed in this study is also similar to the findings of Olufayo and Alade (2012) that reported hyperplasia at the secondary gill lamellar after the exposure of Heterobranchus Bidorsolis to Cypermethrin concentration. It also agreed with the finding of Vinodhini and Narayanan (2008) who that expose the organs of Cyrinus carpio to heavy metals. Fish kidney is made up of glomeruli, mesangial cells, podocytes, endothelial and tubular cells, and both capillary and central veins (which collect and transport urine). In fish, kidney performs an important function to maintain the homeostasis. The kidney is one of the first organs to be effected by contaminants in water (Thophon et al., 2003; Mela et al., 2007). Glomerular disease which is associated with toxic substance in the kidney was revealed in this study and this could be the cause of blood stain on the glomerulus. A clear vacuole (cytoplasmic vacuolization) was also observed in the renal tubule. Similar report was made by Olufayo and Alade (2012). Tubular necrosis which is also associated with kidney poison was revealed in the study. This condition involves the death of tubular epithelia cells that form the renal tubules of the kidney and it could result in the failure of the kidney to remove waste product and excess fluids. Similar finding was revealed in common carp when exposed to mixture of heavy metal (Cd+pb+Cr+Ni) (Vinodhiniand Narayanan, 2008). The invisible effect on the skin structure of fish that were exposed to lower concentration could be as a result of the hardy nature of Clarias gariepinus. Lesions and eroded epithelia surface that was revealed on the skin of groups exposed to higher concentration (5 and 6 mg/L) do not allow for expression of melanin and it also changes the architecture of the skin structure. High level of selenium could cause the exhaustion of mucous cell which might have led to the erosion of the epithelia surface. This report is similar to the finding of Samson et al. (2015) following the exposure of Clarias gariepinus to ethanol extract of Adenium obesum stem bark. Behavioural changes histological alterations and have been observed in Clarias gariepinus juvenile exposed to selenium toxicity, these parameters can be used as toxicological biomarker in a polluted environment. It is recommended that industries should treat effluents before discharging it into the environment. Government institution concerned about environmental protection should put necessary machinery in place to ensure compliance of industries to environmental laws and regulations.

 

Acknowledgments

I would like to thank Ex-Director, Dr. Mane U.H., Center for Coastal and Marine Biodiversity of Dr. Babasaheb Ambedkar Marathwada University, Ratnagiri for his invariable encouragement and scientific support in the analysis throughout the study period. Thanks for that The Indian National Center for Ocean Information Services (INCOIS), Ministry of Earth Sciences, and Government of India offerred the valuable pecuniary support for this study through PFZ-Mission project to the first author as JRF-SRF.

 

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