Haemato-biochemical and ionic regulatory responses of the hybrid catfish, Heteroclarias, to sublethal concentrations of palm oil mill effluents
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Date
2021
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Abstract
Background: Pollution arising from the noxiousness of palm oil mill effluent (POME) has become a serious threat to
aquatic biotas. However, a paucity of information exists on fish response to POME-mediated oxidative stress, lipid per-
oxidation, haemato-biochemical, enzymatic and ionic changes. This study, therefore, evaluates the effects of 28-day
exposure of Heteroclarias, a hybrid catfish, to POME. Juvenile Heteroclarias (n = 350, average weight: 11.90 ± 0.70 g
and average length: 9.04 ± 0.71 cm) were exposed to sublethal concentrations (0-control, 4.00, 8.00 and 12.00 mg/l)
of POME to determine its effects on red blood cells (RBC), haemoglobin (HB), packed cell volume (PCV), white blood
cells (WBC), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC) and mean cell volume
(MCV). The activities of alanine aminotransaminase (ALT), aspartate aminotransaminase (AST), lactate dehydrogenase
(LDH), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and the levels of malondialdehyde
(MDA), calcium (Ca+), potassium (K+), magnesium (Mg2+) and sodium (Na+) ions were also assayed in the gill and
liver.
Results: Exposure to POME caused significant (p < 0.05) concentration-dependent decrease in RBC, HB, PCV, MCV,
MCH and MCHC values, whereas a significant (p < 0.05) concentration-dependent increase in WBC was observed in
POME-exposed fish compared to the control. ALT, AST, LDH, GPx, SOD and CAT activities in the gill and liver signifi-
cantly (p < 0.05) increased in a concentration-dependent manner. MDA level significantly (p < 0.05) increased in the gill
relative to control, while in the liver it was insignificantly different. Both tissues exhibited an increase in Ca+, K+, Mg2+
and Na+ levels at the highest toxicant concentration with a rise of 77.93, 38.46, 109.54 and 41.99% recorded for the
electrolytes in the gill and 79.17, 26.92, 55.48 and 38.78% in the liver above the control value, respectively. The levels
of all the electrolytes except K+ were higher in the gill than the liver and were in the order: Na+ > K+ > Mg+ > Ca2+ in
both tissues.
Conclusions: These results may be used as a suitable tool for pollution assessment and policy formulation to miti-
gate the discharge of untreated POME into aquatic ecosystems and their impacts on resident organisms.
Keywords: Chronic toxicity, Haematology, Enzymatic changes, Malondialdehyde, Ionic changes, Untreated palm oil
mill effluent.