International Journal of Aquaculture, 2018, Vol.8, No.11, 77-89
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3 Discussion
NPIC (2011) noted that the salt of this herbicide (2, 4-Dimethyl Amine) dissociates in water to form acid. It is
noted that pH range outside optimal (6.5-9.0) does not favour normal metabolism in fish and so growth,
reproduction and other life processes are hampered. U.S. EPA (2005) observed that the herbicide has low toxicity;
this was reflected in the pH here being optimal (7.6 to 8.76) as shown in Table 1. Its low toxicity value is
explicable from the fact that that herbicide is highly water soluble in the bodies of organisms and so it is excreted
in urine. Observations shown in Table 3 revealed that at low concentration of the herbicide, there were no visible
abnormal biological and behavioural changes in the fish. It is also recorded that some fish died at these low
concentrations. The causes of death here, if attributable to the herbicide could said to be physiological. It is
worthy of note that mortality at these concentrations where there were no visible biological abnormality may have
affected those specimens that had extreme inability to adapt to changes in environmental situations such as
exposure to 2, 4-Dimethyl Amine. This phenomenon is explained in statistical books for individuals falling out at
the extremes of population distribution (Frank and Althoen, 1995). As was observed, some red blood cells
parameters were lowered, which could result in reduction in oxygen carrying capacity. It is less toxic to aquatic
organisms also because bodies of organisms do not make attempt to metabolise it as it is reported that the kidney
is constantly excreting it from the body. In spite of the low toxicity of 2, 4-D, it was observed to be highly toxic in
a synergistic manner in combination with Carbaryl (Jervais et al., 2008).
Figure 1 The LC
50
24 hours (22.5 mg/L), 48 hours (18.0 mg/L), 72 hours (16.5 mg/L) and 96 hours (15.0 mg/L) of
Clarias
gariepinus
sub-adults exposed to 2, 4-Dimethyl Amine
Figure 2 Changes in total white blood cells counts in
Clarias gariepinus
sub-adults exposed to 2, 4-Dimethyl Amine (mg/L)
Note: The means were observed not to be statistically different among each other (α = 0.05)
0
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
WBC X10
3
/L
Conc. of 2, 4-Dimethyl Amine (mg/L)
0
2
4
6
8
10
12
0
10
20
30
40
Murtality x10 (%)
Concentration of 2, 4-Dimethyl Amine (mg/L)
24 hours
48 hours
72 hours
96 hours
0 5 10 15 20 25 30
