Acute and subchronic effects of petroleum on the freshwater fish Hoplias aff. malabaricus

Petroleum water soluble fraction (WSF) impairs organisms, but damages may vary among cell and tissue levels. The aim of the present study was to evaluate the acute (24 h, 48 h, 72 h) and subchronic effects (36 days) of WSF (0%, 25% and 100%) in juveniles of the Neotropical top predator fish Hoplias aff. malabaricus. The effects of WSF were evaluated at a molecular level using the comet assay and micronucleus test for genome damage; and at a morphological level through histological identification of liver pathologic lesions. In both acute and subchronic exposure we found low levels of DNA damage (< 10% of comet tail) and non-significant frequency of micronucleus in WSF exposed fish. The most significant liver lesions in WSF exposed fish were fatty vacuolization, hypertrophy and focal necrosis. Since these tissue injuries were progressive and persistent, their irreversibility may negatively affect fish recruitment, even in a such resistant top predator.

Elucidating the acid-base mechanisms underlying otolith overgrowth in fish exposed to ocean acidification

Over a decade ago, ocean acidification (OA) exposure was reported to induce otolith overgrowth in teleost fish. This phenomenon was subsequently confirmed in multiple species; however, the underlying physiological causes remain unknown. Here, we report that splitnose rockfish (Sebastes diploproa) exposed to ~1,600 μatm pCO2 (pH ~7.5) were able to fully regulated the pH of both blood and endolymph (the fluid that surrounds the otolith within the inner ear). However, while blood was regulated around pH 7.80, the endolymph was regulated around pH ~8.30. These different pH setpoints result in increased pCO2 diffusion into the endolymph, which in turn leads to proportional increases in endolymph [HCO3-] and [CO32-]. Endolymph pH regulation despite the increased pCO2 suggests enhanced H+ removal. However, a lack of differences in inner ear bulk and cell-specific Na+/K+-ATPase and vacuolar type H+-ATPase protein abundance localization pointed out to activation of preexisting ATPases, non-bicarbonate pH buffering, or both, as the mechanism for endolymph pH-regulation. These results provide the first direct evidence showcasing the acid-base chemistry of the endolymph of OA-exposed fish favors otolith overgrowth, and suggests that this phenomenon will be more pronounced in species that count with more robust blood and endolymph pH regulatory mechanisms.

Multiple Biomarker Responses in Female Catfish (Clarias Gariepinus) Exposed to Acetaminophen

Acetaminophen is one of the most commonly detected Analgesics and pain killer drug in freshwater environments. This study evaluated the possible multi-toxic effects of environmentally relevant concentrations (15.5, 25.5, 35.5 and 45.5µg/L) of acetaminophen in Clarias gariepinus fish exposed for 28 days using multiple biomarkers. Hepatosomatic index (HIS) and condition factor (K) of acetaminophen–exposed group were not different from the control. The superoxide dismutase (SOD) activity increased significantly at 15.5 and 35.5µg/L and Catalase (CAT) activity in all acetaminophen-exposed groups barely showed an upward trend. The concentration of glutathione S-transferase (GST) activities was not different from the control. Glutathione peroxidase (GPx) activities increased at all concentrations when compared to the control group. There were general inhibitions of Acetylcholinesterase (AChE) activities in all exposed groups including the control. Total antioxidant capacity (TAC) increased significantly at 25.5 and 45.5µg/L and Interluekin-6 (IL-6) showed non-significant increases in all exposed concentrations. Acetaminophen exposure caused non-significant increases in the activities of C reactive protein (CRP). White blood cells (WBC) and lymphocytes (LYM counts) were significant reduced. Acetaminophen induced significant changes in hormones of the hypothalamic-pituitary-gonad (HPG) axis (17β-Estradiol and Testosterone) and vitellogenin (Vtg) synthesis at 45.5µg/L. Histopathological alterations in the liver was evident of apoptotic hyperplasia, sinusoidal congestion and necrosis of the hepatocytes and was concentration dependent. Acetaminophen exposure to the fish gills enhanced the fusion and shortening of some filaments, hyperplasia of the epithelia gills cells, aneurism, congestion and epithelia rupture of the gills. Gonad examination showed acetaminophen exposure triggered the occurrence of intersex in 25.5, 35.5 and 45.5µg/L. The collaborative biomarkers used in this study showed the multiple impacts of acetaminophen on the physiology of C. gariepinus. Multivariate statistical analysis indicated that fish in the control groups exhibited a distinctly response from the acetaminophen-exposed fish and that over 95% of the biomarkers significantly contribute to discriminate between the acetaminophen-exposed fish and the control group. Our research provides evidence supporting the use of multiple-biomarker approach to evaluate the health status of C. gariepinus in future studies.

Assessment of the growth performance and haematological indices of Clarias gariepinus fingerlings exposed to soap effluent

Background Various substances released from modern complex human societies which enter the aquatic ecosystems produce alterations in survivability of aquatic biota. This study assesses the consequence of exposure to industrial effluents containing potentially hazardous constituents, especially soap industrial waste effluent, relative to fish physiology, growth and survival, particularly food fish such as Clarias gariepinus. Five hundred (500) fingerlings of C. gariepinus (15.65 ± 0.02 g) randomly stocked at 50 fish per tank in duplicates were exposed to varying concentration (0, 0.32, 0.66, 1.31 and 2.63%) of homogenous effluent sample and fed Durante® floating feed at 5% of the body weight in two instalments per day for 180 days. The growth performance and feed utilization data were generated to determine the growth performance indices. The haematological parameters of the fish were also determined following routine methods of fish haematology. Result Generally, fish in the control had significantly (p < 0.05) better growth performance indices compared with the exposed fish. It was also observed that most of the significant increase or decrease observed in the growth performance was concentration dependent. Increase in HES concentration which significantly increases (p < 0.05) WBC count of the experimental fish was observed to decrease (p < 0.05) the HGB level of the fish. Significantly higher (p < 0.05) levels of RBC (3.02 ± 0.03 × 106/µL) and HCT (36.70 ± 1.68%) were recorded in the control fish. However, all the exposed fish had significantly higher (p < 0.05) levels of platelet count compared with the control. Conclusion This study concluded that exposure to concentrations of soap effluent induced stress, inhibited growth and altered the haematological indices of the exposed fish. Uncontrolled discharge of soap effluent into receiving water bodies, apart from affecting the wellbeing of an important freshwater food fish, there is every probability of possible accumulation of the chemical/toxic additives of the soap effluent which could have serious implications considering the man as the major and final recipient of these toxic bioaccumulated chemicals via the food chain and the environment.

Cytotoxicity, Redox and Immune Status in African Catfish, Clarias Gariepinus (Burchell, 1822) Exposed to Bisphenol a (BPA) and its Analogues

The objective of the study was to determine the comparative toxicities and immune dysfunction in the African catfish, Clarias gariepinus exposed to bisphenol A (BPA) and its two analogues; bisphenol AP (BPAP) and bisphenol P (BPP). Juveniles of C. gariepinus were exposed to sublethal concentrations (70 and 140 μg/L) of BPA, BPAP and BPP for 7, 14, or 21 days after which various endpoints which are indicative of cytotoxicity, oxidative stress, haematological and innate immune parameters were determined in the liver homogenates or blood plasma. The exposure of C. gariepinus to BPA and its analogues caused significant increased activities of lactate dehydrogenase, catalase and superoxide dismutase. The exposed fish had increased levels of DNA fragmentation, lipid peroxidation, white blood cells, nitric oxide and respiratory burst while the red blood cells counts and the percentage packed cell volume decreased significantly in the exposed fish compared to control. The toxic effects elicited by the bisphenols were both concentration- and duration-dependent. Generally, BPA exerted the most toxic effects on the fish, followed by BPAP while BPP exerted the least toxic effect effects to C. gariepinus. Summarily, the findings indicated that BPA and its two analogues studied in the research are capable of causing cytotoxicity, oxidative stress and immune dysfunction in C. gariepinus.

Haematological and histopathological examinations of African mud catfish (Clarias gariepinus) exposed to petroleum wastewater

Effects of petroleum refinery wastewater on Clarias gariepinus juvenile were investigated. Commercially obtained C. gariepinus fingerlings were acclimatized in a plastic tank (100 L capacity) of de-chlorinated tap water at 25±2°C for 14 days and fed with commercial feed pellet at 2% body weight of the fingerlings. Bioassay tests were carried out in four transparent plastics tank with nominal concentrations of 100 ml, 200 ml, 300 ml of the wastewater added to 40L of de-chlorinated tap water and only de-chlorinated tap water as control. Each tank contains twenty fish samples, while the assay was replicated three times concurrently. Following standard procedures, behavioural response, growth changes, haematological and histopathological tests were carried out on the samples. Significant reduction in the weight was observed in the fingerlings cultured with the wastewaters, while no significant difference occurred in the control fish. Highest values of Packed Cell Volume (PCV) (22), Haemoglobin (HB) (7.0), Red Blood Cell (RBC) (1.62) and endocochlear potential (EP) (5) were recorded for the control fish than exposed fish. On the other hand, Haptoglobin (HP), Mean Corpuscular Volume (MCV) and Mean Corpuscular Haemoglobin (MCH) were higher in the blood of exposed fish than in control. Histopathologically, exposed fishes showed no visible lesion in gills except from the thickening of the lamellae as the concentration of wastewater increases, indicating an increase in tissue disintegration. Similarly, gross tissue disintegration was observed in those fish exposed to 200ml wastewater as evidenced by the presence of large open spaces (hepatocytes) in the liver.

Thermal stability of purified superoxide dismutase from liver of commercially valuable fish, Labeo rohita Exposed to Pb+Cr mixture

In this experiment, effect of lead (Pb) + chromium (Cr) mixture on superoxide dismutase (SOD) in the liver of Labeo rohita at a concentration of 11.1 mgL-1 was observed. The ammonium sulphate precipitation and ion exchange chromatography techniques were successfully used to purify SOD. After purification, SOD activity of control and Pb+Cr treated fish was noted as 581.00 and 645.45 UmL-1, respectively while the specific activity was 1383.33 and 1613.62 Umg-1, respectively. The fold purification value of SOD was 2.75 and 2.45 for control and stressed fish, respectively. The recovery was calculated as 77.06 and 57.43% for control and stressed fish, respectively. The results of kinetic characterization showed that SOD form control and exposed fish had maximum activity at pH 6.5 and 7.0. Temperature also had a significant effect on activity of SOD. The SOD activity was measured maximum at 30°C for both control and Pb+Cr exposed fish. The Km value of liver SOD for control and Pb+Cr treated L. rohita was calculated as 1.48 and 0.62 mM, respectively. The value of Vmax for SOD from liver of control and Pb+Cr exposed fish was 1000 and 570 U mL-1, respectively. The enthalpy of denaturation (∆H*) for liver SOD from control and Pb+Cr exposed L. rohita was computed as 3.492 and 2.802 KJ mol-1 at 40°C, respectively and these values were dropped off with increasing the temperature until it remains 3.251 and 2.561 KJ mol-1 at 70°C, respectively. The free energy of thermal denaturation (ΔGº) of liver SOD was slightly increased with increasing temperature until 75°C which shows its resistance against heat. The values of ΔGº was observed as 58.03 and 57.95 KJ mol-1 for control and exposed fish at 40°C, respectively while the same was increased upto 62.37 and 62.00 KJ mol-1 at 70°C, respectively. It was concluded from negative value of ΔS* (entropy of inactivation) that the SOD is stable thermodynamically.

Acute and Chronic Toxicity of Endocrine Disruptive Heavy Metals and Pesticides Exposed to Freshwater Fish P. reticulata and P. sphenops

Environmental monitoring is a recent world-wide approach to save the future in line. The present study focuses on toxicity of heavy metals and pesticides on the freshwater aquarium fish (Poecilia reticulata and Poecilia sphenops). The study intense on drawing the acute and chronic safe levels of metals and pesticide exposed to 96 h and 28 day respectively. On exposure, the fish were observed to be under stress and showed excitability. It was observed that both species were highly sensitive to arsenic and cypermethrin, meanwhile resistant to cadmium and chlorpyrifos. The acute safe levels for As irrespective of species was comparatively lesser than that of Cd exposed fish and the range of safe values for pesticides exposure were between 0.018 and 0.059 ppb. As the water quality is influencedby many environmental factors, the present study helps the aquarist in monitoring the safe level of toxicants in the medium. This in turn increases the economic growth of the aquarist.

Biomarker approach for assessing chronic toxicity of Captan® herbicide using haematological, growth, endocrine and biochemical endpoints in air breathing catfish, Clarias batrachus

This study was conducted to determine the sub-lethal toxicity of Captan® on selected hematological (Hb, HCT, MCH) growth (K-factor, HSI, SGR), biochemical (serum glucose, protein), and endocrine parameters (growth hormone, T3 and T4) in Clarias batrachus under chronic exposures. Captan® was administered at predetermined exposure concentrations (0.53 and 1.06 mg/L) and monitored at day 15, 30 and 45 of the experimental periods. The experimental groups showed significantly lower values (p < 0.05) of haemoglobin content, haematocrit, MCH in Captan® exposed fish compared to control. Serum glucose was significantly higher (p < 0.05) in treated fish compared to the control group; reverse was the case for serum protein concentrations (p < 0.05). Assessment of growth parameters revealed significantly higher k-factor and SGR in control fish. HSI was however higher in treated fish which highlights the possibility of liver hypertrophy and hyperplasia of liver cells due to higher exposure and uptake of the herbicide. Endocrine responses (T3 and T4) emerged as the most sensitive biomarker category, depicting modulated responses between sub-chronic exposure at day-15 and chronic responses at day-45. In general, the study findings using these biomarkers indicate that Captan® exposures are capable of inducing stress-specific effects at the biochemical and physiological levels negatively impacting the overall health and longevity of such animals. The use of the IBR index provided a visual and easily comprehensible depiction of toxicity effects and biomarker responses in laboratory exposed fish and we anticipate a greater applicability in biomarker data from the wild which are largely heterogenous.