International Journal of Aquaculture, 2017, Vol.7, No.9, 64-70
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haematological picture are frequently utilised for the detection of pathological changes in different stress
conditions such as exposure to heavy metals (Nussey et al., 1995). Jayapakash and Shettu (2013) reported after the
exposure of
Channa punctatus
to deltamethrin that anaemia might have led to a fall in the red blood cell count,
haemoglobin and pack cell volume. In the present study, PCV% value, Hb%, and RBC count of
C. gariepinus
exposed to selenium decreased significantly P < 0.05 when compared to the control group. This reduction could
be an indication of anaemia condition caused by the exposure of experimental fish to selenium in water. The
observed decrease in the haemoglobin and pack cell volume value in the fish could also be as a result of
erythrocyte lysing. The decreased haemoglobin concentration also signifies that the fish ability to provide
sufficient oxygen to the tissue is restricted considerably and this will result in decreased physical activity (Nussey
et al., 1995). Several studies have been reported on the reduction of haematological parameters of fish exposed to
heavy metals (Dhiaram et al., 2008; Ololade and Oginni, 2010; Khalid, 2011). A decrease in the haematological
values of common carp fish when exposed to nickel, Khalid (2011). Ololade and Oginni (2010) also had similar
report when African cat fish was exposed to nickel. Pamile et al. (1991) explained that reduction in haemoglobin
content in fish exposed to toxicant could be due to the inhibiting effect of the toxic substance in the enzyme
system responsible for synthesis of haemoglobin.
The reduction in WBC count of the treatment groups that was observed in this study agreed with the finding of
Adeyemo et al. (2007) following the exposure of
C. gariepinus
to lead nitrate. This result is also similar to the
findings of Olanike (2007) and Witeska (2003) that attributed this to the release of epinephrine during stress
which causes a decrease in leucocyte count, and also shows the weakening of the immune system.
There were variations in the values of blood indices MCV, MCH and MCHC. Mean corpuscular volume (MCV)
of treatment 4 and 5 were significantly higher (p ˃ 0.05) compared to control group while mean corpuscular
haemoglobin (MCH) also increased significantly in fish exposed to highest concentration of selenium. This result
is similar to the finding of Adeyemo et al. (2007) that exposed
C. gariepinus
to lead nitrare. It also agreed with the
work of Shah, (2006) following a short term exposure of tench (Tinca tinca) to lead. Mean corpuscular
haemoglobin concentration (MCHC) was significantly higher in the control than treatment group. MCHC is a red
blood cell morphological index reflecting the haemoglobin concentration, the observed decrease in this parameter
may indicate that the haemoglobin concentration in the unexposed fish was higher than in the selenium exposed
fish and this may further suggest impaired haemoglobin synthesis in the treated fish. These alterations were
attributed to direct or feedback responses of structural damage to RBC membranes resulting in haemolysis and
impairment in haemoglobin synthesis, stress-related release of RBCs from the spleen and hypoxia, induced by
exposure to lead (Shah, 2006).
Water parameters such as pH, turbidity, alkalinity, dissolved oxygen, temperature, and conductivity were
influenced by the rate of pollutant entering aquatic environment (Fagbenro, 2002; Olufayo, 2009). The dissolved
oxygen is significantly lower (P < 0.05) in the test medium of the treatment groups. This could be that the oxygen
molecules is been degraded by selenium. This study agreed with the study carried out by Ololade and Oginni
(2010) when
C. gariepinus
was exposed to nickel. No significant difference was recorded in pH.
Selenium has been examined to have toxic effect on
C. gariepinus
juveniles. It is therefore recommended that
industries should install waste treatment plant, with a view to properly treat waste water before discharging them
into aquatic environment.
References
Abba H.H.H., and Authman M.M.N., 2009, Effects of accumulated selenium on Some physiological parameters and oxidative stress indicators in Tilapia fish
(Oreochromis spp.). Eurasian Journal of Agriculture and Environmental Science, 5: 219-225
Adeyemo O., Ajani F., and Ajiboye O., 2007, Acute toxicity and blood profile of adult Clarias gariepinus exposed to lead nitrate. The Internet Journal of
Hematology, 4 (2)
Aguigwo J.N, 1998, Studies on acute toxicity of Cassava leaf extracts on African catfish Clarias angullaris, Journal of Aquatic Science, 13: 29-32
