International Journal of Aquaculture, 2017, Vol.7, No.9, 64-70
65
gariepinus
) is appreciated by large population (Prusynski, 2003). It is an excellent species for aquaculture as it is
omnivorous, grows fast, and tolerates relatively poor water quality (Rad et al., 2003). Several investigations have
been carried out on various toxicants with
Clarias sp
. (Aguigwo, 1998; Maheswaran et al., 2008). Changes in
several haematological variables are recognized as indicators of metal exposure (Cyriac et al., 1989). Blood
parameters has been used as an indicator of stress in fish exposed to different toxicants such as heavy metals and
industrial effluents. In fish, exposure to chemical pollutants can induce either increase or decrease in
haematological levels (Mehjbeen and Nazura, 2012). The haematological effects of various metals such as Hg, Cu,
Cd and Pb on
Clarias sp
have been reported in various studies. Oshode et al., (2008) reported that observation of
haematological parameters allows the most rapid detection of changes in fish. Disrupted haematological patterns
appear very quickly and precede changes in fish behaviour and visible lesions. The rapidity of toxic effects,
exerted by heavy metals, is related to the blood’s transport function, with the blood distributing the metals to all
the body parts. Literatures has reviewed that there are no much work on the haematological effects of selenium on
C. gariepinus
. Therefore this present study was to investigate the acute toxicity of selenium and its effect on blood
parameters of
C. gariepinus
juvenile.
2 Materials and Methods
Juveniles of African catfish (
C. gariepinus
) with average weight of 7.4 ± 0.64 g were used for the study. 180
healthy fish which were purchased from a reputable fish farm were acclimatized (10 each) in eighty litres plastic
container filled with forty litres of tap water each for a period of 4 weeks to the laboratory condition. During this
period of acclimatization, the fish were fed with commercial pellets 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 waste from fish.
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 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 multiparameter test kit.
Blood samples were collected from both the control and experimental fishes that survived the 96 h toxicant
exposure period. The blood samples were taken by puncturing posterior caudal vein and collected into
ethylenediaminetetraacetate (EDTA) bottle (Schmitt et al., 1999). Automated haematology analyser mindray Bc
300 plus was used to determine haematological parameter. The derived haematological indices of mean
corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin
concentration (MCHC) were calculated using standard formulae as described by Jain (1986): MCV was calculated
in fentoliters = PCV/RBC x 10; MCH was calculated in picograms = Hb/RBC x 10; and MCHC = (Hb in 100 mg
blood / Hct) x 100.
Data obtained were subjected to one-way analysis of variance (ANOVA) test and the means from the various
treatments were compared for significant differences (P>0.05) using Duncan’s multiple range tests. Values were
expressed as mean ± S.E. 96 hours LC
50
was determined using probit analysis (Finney, 1971) and simple
graphical method.
