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Sublethal haematological
effects of zinc on the freshwater fish, Heteroclarias
sp. (Osteichthyes: Clariidae)
Kori-Siakpere, Ovie* and
Ubogu, Ewoma Oghoghene
Department
of Animal and Environmental Biology, Delta State University,
P. M. B. 1, Abraka, Nigeria.
*Corresponding author.
E-mail:oviekori@yahoo.com.
Accepted
4 March, 2008 |
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Laboratory study was undertaken to evaluate some
haematological changes resulting from the exposure of a
freshwater fish, Heteroclarias sp. to sublethal
concentrations (5.0 and 10.0 mg L-1) of zinc in
water for a period of fifteen (15) days. Three groups of ten
fish were subjected to serial dilutions of the stock
solution of zinc of 0 (control), 5.0 and 10.0 mg L-1
in three large plastic bowls of 60 litres capacity by the
semistatic (renewal) method. At the end of the 15 days
exposure period, blood samples were taken from the control
and experimental fish. Blood was assayed for selected
haematological parameters (haematocrit, haemoglobin, red
blood cell counts, white blood cell counts, differential
white blood cell counts, erythrocyte sedimentation rate,
total plasma protein and plasma glucose concentration). The
derived haematological indices of mean corpuscular volume (MCV),
mean corpuscular haemoglobin (MCH) and mean corpuscular
haemoglobin concentration (MCHC) were calculated. Sublethal
concentrations (5.0 and 10.0 mg L-1) of zinc
caused a dose dependent decrease in haemoglobin values,
coupled with a decrease in haematocrit values and red blood
cell counts are obvious indication of anemia of the norm
chronic type. The total white blood cell counts and the
differential white blood cell counts were decreased except
for the lymphocytes in which there was a slight increase.
Plasma level of protein and glucose were also lower in the
exposed fish when compared to the control. The
haematological indices MCHC, MCH and MCV were also lowered.
In conclusion, the changes observed indicate that
haematological parameters can be used as an indicator of
zinc related stress in fish on exposed to elevated zinc
levels.
Key words:
Zinc, haematology, anaemia, glucose, protein,
Heteroclarias, Nigeria. |
