International Journal of Aquaculture, 2013, Vol.3, No.11, 49
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Figure 8 Gonadosomatic index of Oreochromis niloticus
exposed to different concentrations of Atrazine for 14 days
Note: Columns represent means, and means with different
letters are significantly different (p< 0.5)
2
Discussion
Fawole and Arawono (2000) observed
Sarotherodon
galilaeus
gonadosomatic index in Ile-Ife, Nigeria to be
0.33
± 0.21 for males and 1.88±1.01 for females. The
Gonadosomatic index of the parent population of the
fish from The Cross River University of Technology
was 0.086±0.008. This was observed to be reducing
with agro-chemical concentrations. Reduction in liver
size could be due to post stress as Peters et al. (1987)
attributed condensed cells to fat depletion especially
in post spawned females. The shrunken cells often
contain numerous clear vacuoles. Changes which
occurred in the liver are due to the fact that the liver is
a detoxification centre (Cengiz et al. 2001). The liver
has to carry out defensive mechanism to be able to
detoxify the herbicides and since these chemicals are
highly attracted to the organ, the liver is usually highly
affected. There was a reduction in the weight of liver
(
hepatosomatic index). But Couch (1984) reported
enlargement of the pituitary exposed to sub lethal
concentration of trifluralin herbicide. The observed
reduction in hepatosomatic index in this experiment with
increase concentration of Glyphosate may be due to the
degeneration of some liver tissue and cell according to
Jiraungkoorskul et al. (2002), and Olurin et al.
(2006).
The connective tissue may have been degenerated as
well as the fatty tissue. Koumi et al. (2008) pointed to
this fact that high viscerosomatic index found in
Nile Tilapia fed with soybean as substitute for fish
meal was due to high accumulation of fat. But
Gomex-Marquez et al. (2003) noticed an inverse
relationship between gonadosomatic index and
hepatosomatic index in this fish. Such inverse
relationship was not observed here possibly because
the two organs were equally subjected to the same
attacks from the chemicals. The liver, which is the
main site of glucose production, was affected as it was
exposed to Gramoxone, Glyphosate, Butachlor and
Atrizine. Its complete degeneration would have
adversely affected all the normal functions thereby
rendering its detoxification and homeostatic functions
void. This may have resulted from the fact that there
was increased glucose production in the liver, making
the glucose (energy) highly energy demanding. Poison
is capable of marring normal physiological functions
in fish. Vijayan et al. (2001) demonstrated that even
slight change in hyalinity (salinity) was capable of
creating energy deficiency in the tissues of
Oreochromis
niloticus
.
Kamanga et al
.
(2002)
observed that
temperature was positively correlated to the gonadosomatic
index in
Oreochromis karongae
in Malawi. The
exposed fish would have to give off when its total
ability to adapt or adjust is exhausted. This becomes
more realistic when it is known that in nature stressed
fish will more readily reject food. The stored glucose
in form of glycogen could have been rendered
unusable due to the liver’s inability to convert it to
glucose and its subsequent elimination because of the
liver degeneration. The fish metabolism which may
require glucose is diverted to the necessary energy
being supplied by oxidation of fatty acids, which may
caused a rise in cholesterol levels in exposed fish
(
Kori-Siakpere et al., 2007).
Liver and gonads were degenerated at high concentration
of Gramoxone or Paraquat, Glyphosate, Butachlor and
Atrazine in the present study. Paraquat is a contact
poison (Ross and Childs, 1996). Their influence in the
reduction of the hepatosomatic index and gonadosomatic
index is in line with destruction of the liver tissue
since they are the target points as they are used as
organ of poison modification or detoxification as well
as gamete formation (Taylor et al.,
1988).
As the liver
is overwhelmed, it is consequently degenerated so that
the gate way becomes open for the poison to attack
other tissues more freely and intensively.
Ou et al.
(2000)
showed that Butachlor decreased the
doubling time of the liver cells in mouse, which may
be responsible for reduced liver weight. Multiplication
of liver cells must not necessarily mean increase in
size. Rather, some uncontrolled over stimulation of
cell multiplication may result in organ destruction as
earlier pointed out by Ateeq et al.
(2006).
The