Chapter-III
WHOLE ANIMAL OXYGEN
CONSUMPTION
127
EFFECT OF QUINALPHOS TECHNICAL GRADE AND 25% EC ON
OXYGEN CONSUMPTION IN THE FISH CHANNA PUNCTATUS
Fish are adapted for aquatic respiration, during which they take water in, through the
mouth and passed through gill chambers covered by the operculum. The flow of water is
continuous for almost the whole of the respiratory cycle. In its passage, the water gives up
oxygen to the blood and takes away the carbondioxide through diffusion. The process of oxygen
is transported in the circulating fluid by haemoglobin present in the blood corpuscles. Oxygen
uptake is widely used in physiology as a biological indicator that integrates the overall metabolic
activity of an animal in response to specific environmental factors (Mehrle and Mayer, 1984)
because it reflects energy expenditure and, ultimately, the food requirements. The metabolic rate
of fish is usually measured by their rate of oxygen uptake from water (Mo2); Mo2 is a criterion
that has been suggested as an index of sublethal for fish and one that, if altered, may directly
limit a fish’s aerobic performance (MacKinnon and Farrell, 1992).
Environmental pollution in freshwater ecosystems is caused by a variety of pollutants. In
an agricultural country like India, insecticides constitute the major components of aquatic
chemicals as pollutants. Generally pesticide concentrations are toxic which may be lethal or
sublethal concentrations in aquatic environment. Lethal concentrations cause the death of the
organisms directly. But the sub-lethal concentrations effect and disturb the metabolic activities.
The early symptoms of acute pesticide poisoning are the alteration/failure of respiratory
metabolism (Holden, 1973).
The changes in the respiratory activity of fish have been used by several investigators as
indicators of response to pesticides (Tilak and Japamalai, 2009; Chebbi and David, 2009a; Patil
and David 2008; Veeraiah and Durga Prasad, 2001; Luther Das et al., 2000). Although these
investigations have proved to be very useful in describing responses to sublethal exposures and
have direct implications for mode of action, the interpretation of the ecological significance of
these numerous respiratory responses remain difficult. The oxygen consumption is a useful
measure of sublethal effects because energy processes being disturbed are indicators of overall
physiological state and of pesticide poisoning leading to respiratory distress (Janardana Reddy,
1988) which is used to assess the toxic stress.
It is well known that pollutant bioaccumulation as it is bioconcentrated and the resulting
physiological changes is reflected in the oxygen uptake rate, either through disrupted metabolism
128
or in the mobilization of a compensatory homeostatic mechanism. Thus respiratory rate provides
a critical index of environmental suitability for survival (Correa and Coler, 1983). The change in
oxygen consumption rate is useful to measure sublethal effects of pollutants on fishes because
energy processes serves as an indicator of over all physiological state (Chitra and Ramana Rao,
1984). Unlike the terrestrial environment, in the aquatic environment the body of the organism is
bathed by the medium containing the toxicant and hence, the effect of toxicants on the
respirations is more pronounced. Pesticides enter into the body of fish mainly through gills and
with the onset of symptoms of poisoning, the rate of oxygen consumption increases (Anderson
and Premdas, 1982). The severity of distress may lead to respiratory failure by affecting the
respiratory centers of the brain or the tissue involved in breathing (‘O’ Brien, 1967). This serves
not only as a tool in the evaluation of the susceptibility or resistance potentiality of the animal,
but also useful to correlate the behaviour of the animal. Hence, the differential oxygen
consumption can be used as bio-indicator to evaluate basic damage inflicted on the animal which
could either increase or decrease the oxygen uptake.
The pesticides and the resultant metabolites are reported to cause respiratory distress or
even failure of activity by affecting the other related tissues, gill and brain (O’Brien, 1967). In
the gill epithelium, the tissue which will have intracellular and extracellular exchange of ions
related to oxygen and chloride shift (Prosser and Brown, 1973) are affected causing changes in
the oxygen carrying capacity for the uptake by haemoglobin. In the earlier reports, it was
mentioned that the damage observed in fish gill exposed to toxicant was due to impairment in the
respiratory metabolism (Rama Murthy, 1988; and Jayantha Rao, 1982). This is also due to the
fact that any pollutant including pesticide should enter into the fish, mainly through the gills only
(Vijayalakshmi and Tilak, 1996; Tilak and Yacob, 2002; Tilak and Marina Samuel, 2001; Tilak
et al., 2005 a & b).
Exposure to sublethal concentrations is reported to increase respiratory activity, resulting in
increased ventilation and hence increased uptake of the toxicant. OCs have been reported to
stimulate oxygen consumption at sublethal concentrations and inhibit the oxygen uptake at lethal
concentrations.
In the case of synthetic pyrethroids a steady and progressive decline in
ventilatory pattern and thereby decline in oxygen consumption is noticed (Veeraiah and Durga
Prasad, 2001). However, there have been exceptions to this statement and it is difficult to
129
generalize (Murty, 1986). The severity of distress may lead to respiratory failure by affecting the
respiratory centres of the brain or the tissue involved in breathing (‘O’ Brien, 1967).
The metallic pollution and pesticides of different classes like organochlorines
organophosphates carbamates and other new generation ones affect the fish in oxygen
consumption in sublethal concentrations.
By cannulating the blood system of fishes, it is
possible to measure the concentrations of oxygen, metabolites and pollutants and hence the mode
of action of toxic pollutants can be understood more fully. Skidmore (1970) reported that zinc
reduced the efficiency of oxygen transport across the gill membrane, so that the fish dies of
hypoxia. This evaluation was done by using cannulation technique. Respiratory responses to
lethal concentrations increase the ventilation volume and symptoms of organophosphate
intoxication suggesting that the effect on respiratory surface is lethal in fish (Veeraiah and Durga
Prasad, 2001). Murty (1986) reported that organophosphate pesticides are the second generation
pesticides and are less persistent and are effective substitutes for organochlorine pesticides. The
mechanism of action of organophosphate pesticide interference is with nerve membrane function
through the inhibition of Acetylcholinesterase AChE activity (‘O’ Brien, 1967). Hence an
attempt has been made to study the effect of sublethal and lethal concentrations of quinalphos
technical grade and 25% EC on oxygen consumption for 24 hours at alternate hours of intervals
to the fish Channa punctatus.
MATERIALS AND METHODS
The experiments on the oxygen consumption of the fish Channa punctatus was carried
out in a respiratory apparatus developed by Job (1955). The fish were brought from a local fish
farm and acclimatized to the laboratory conditions in well aerated water for one week. The water
used for acclimatization and experimentation was the same as used in the toxicity experiments
(Table: II.A.1). During this period, the fish were regularly fed, but the feeding was stopped for
two days prior to the experiment. The fish measuring 6 to 8 cm in length and 6.5 to 7.5 gm in
weight were used in the experiment. All the precautions laid down by APHA et al., (1998) are
followed, for maintaining the fish. The fish were exposed to organophosphorus pesticide
quinalphos technical and 25% EC (Ekalux) to 48 hours LC50 Technical lethal (3.9362 mg L-1),
Technical sublethal (1/10th of 48 hr LC50 i.e., 0.3936 mg L-1), 25% EC Lethal (3.5509 mg L-1)
and 25% EC sublethal (1/10th of 48 hr LC50 i.e., 0.3550 mg L-1) concentrations. The samples
130
for estimation were taken from the respiratory chamber, at alternate hours of intervals for 24
hours.
Description of respiratory chamber
The apparatus used for the measurement of whole animal oxygen consumption is a wide
mouthed bottle which is called a respiratory chamber. Its mouth was fitted with a four holed
rubber stopper and through one of the holes a thermometer was passed to know the temperature
of the medium in the respiratory chamber. From the remaining three holes three glass tubes were
passed whose outer ends were fitted with rubber tubes. These three tubes served as delivery
tubes are designated as T1, T2 and T3 respectively. They were fitted with pinch locks P1, P2
and P3. T1 was connected with the reservoir and through this water could be drawn (inlet) into
the respiratory chamber. T2 was atmospheric tube; useful for testing the air tightness of the
respiratory chamber. Through the T3 tube (outlet) water samples from the respiratory chamber
were collected for estimation of dissolved oxygen. The respiratory chamber was coated black to
avoid photochemical reactions and to keep the animal activity at normal during the experiment.
Setting up of the Apparatus
Only one fish was introduced into each respiratory chamber and was filled with water
drawn through T1 from the reservoir. After checking the air tightness pinch lock P2 was closed
and pinch lock P3 was opened slightly so that a very gentle and even flow of water was
maintained through the respiratory chamber. This was continued for 15 minutes to facilitate the
animal in returning to a state of normality from the state of excitement, if any, due to the
handling and also to allow the animal to adjust to the darkness in the chamber (acclimatization).
C) Collection of the initial and final samples
After allowing the animal to settle in the chamber, the initial sample was collected from
the respiratory chamber through T3.
After the collection of initial sample, the respiratory
chamber was closed by closing P3 first and then P1 after one hour. The next sample was
collected from the respiratory chamber. Likewise, other samples also were collected at the end
of each alternate hour for total 24 hours period of the experiment.
Along with four experimental fish chambers and control, one respiratory chamber
without fish was maintained to estimate the initial amount of oxygen.
The experiments were conducted with sublethal and lethal concentrations of quinalphos
technical grade and 25% EC to fish Channa punctatus (Bloch).
131
The amount of dissolved oxygen consumption was calculated per gram body weight per
hour.
O2 consumed by fish/
gram body weight/hour =
α-β x N of hypo x 8 x 1000
---------------------------------------------------Vol. of the sample taken x Correction factor x
Wt. of the fish x Time interval for each sample
α = hypo rundown before exposure
β = hypo rundown after exposure
Students’t-test was employed to calculate the significance of the differences between
control and experimental means. P values of 0.05 or less were considered statistically significant
(Fisher, 1950).
RESULTS AND DISCUSSION
The comparative data on the whole animal oxygen consumption of control and
experimental fish, calculated per gram body weight per hour in sublethal and lethal
concentrations of quinalphos technical grade and 25% EC for Channa punctatus was given in the
Table III.1. The results of the experiments and control values are graphically represented in Fig
III.1 by taking time on X axis and the amount of oxygen consumed per gram body weight on Y
axis.
In sublethal concentrations of quinalphos technical grade and 25% EC it was observed
that fish showed similar tendency of increase in oxygen consumption during the initial time of
exposures i.e., 1 to 4 hours and a gradual decrease was observed during the subsequent period of
study. The presence of sublethal concentration of toxicants is inevitable. The toxicant stress in
oxygen consumption makes them less fit and reduces growth due to lack of proper metabolism.
In lethal concentrations of quinalphos technical grade and 25% EC it was observed that fish
showed gradual decrease in oxygen consumption from the starting period of exposure till the end
of the experiment. In controls also, the rate of oxygen consumption was gradually decreased and
this can be attributed to the starved conditions and the reduced metabolic rates of the starved fish
and the reduction is not that significant, than toxicant exposed values.
The initial increase in oxygen uptake may be due to the stress imposed on the fish by the
changed environment making the animal active to combat the stress, thus incurring an increased
energy requirement for the animal. The increase in activity due to stress increases muscular
132
activity and this will result in an increased demand for oxygen. The increase in activity might be
to boost up oxidative metabolism for an increased supply of energy to combat the chemical stress
(David et al., 2003).This probably accounts for an elevation in oxygen consumption. It can be
inferred from the results that, during sublethal exposure to toxicant, the fish may be adapting to
augment the physiological adjustment for elimination of the chemical stress.
Similarly increased oxygen consumption was observed by Shereena et al., (2009) in
Tilapia mossambica exposed to dimethoate, in Channa punctatus (Luther Das et al., 2000;
Veeraiah and Durga Prasad, 1998) in Labeo rohita (Veeraiah, 2002) in Labeo rohita exposed to
cypermethrin, in fingerlings of Cirrihinus mrigal (Rajamannar and Manohar,1992) exposed to
pesticides. in Ophiocephalus punctatus (Sambasiva Rao et al., 1981) exposed to Eisan, elevation
of basal metabolic rate of rainbow trout exposed to permethrin was reported by Kumaraguru and
Beamish (1983).
The decrease in oxygen consumption at the later period appears to be a protective
measure to ensure that there is low intake of the toxic substance. When fish are exposed to
potential toxicants, the chemicals may directly affect metabolic reactions and attribute to
respiratory distress as a consequence of impaired oxidative metabolism. Respiratory distress may
arise as a result of either reduced oxygen diffusion over the gill membranes caused by an
increase in the thickness of the mucous layer covering the secondary lamellae (Jobling, 1994) or
depleted haemoglobin content (Babu et al., 1985, Ramaswamy et al., 1996). According to Patil
et al., (2003) the gill movement increased at the initial phase and gradually decreased towards
the lethal phase (Swaminathan et al., 1987). It is presumed that the toxicant directly or indirectly
affects the respiration of fish (Ramanujam and Ratha, 1980). The rate of oxygen consumed by
the affected fish was very low. Once the respiration of the fish is affected, in turns all the
biological activities of the fish will also be reduced. The decrease in whole animal oxygen
consumption might be due to the damage in the structural integrity of the cells of respiratory
organs ar reported by Saraswathi and Indira (1986). The observed initial increase in oxygen
consumption should be a consequence of a sudden increase in the oxidative metabolism and
mobilization of metabolic reserves as an immediate response to the stress. Subsequent decrease
in oxygen consumption indicates either increased entry of quinalphos molecules or its
accumulation in the body as a function of time.
133
Similarly earlier works have estimated a significant reduction in oxygen consumption by
many fish species under the toxic stress of aquatic pollutants such as insecticides Mushithaq &
Nagarajan (1992), Ramakrishnan & Sivakumar (1993), Anita Susan (1994), Vijayalakshmi
(1994), Ramana Kumari (1999), Veeraiah and Durga prasad (2001), Ramakritinan et al., (2005).
Patil and David (2008) Tilak and Swarna kumari (2009), Tilak and Japamali (2009), Logaswamy
and Remia (2009) and Marigoudar et al., (2009).
In the present study, the control fish behaved in natural manner with well coordinated
movements, but in the toxic environment, fish exhibited irregular, erratic and darting swimming
movements and loss of equilibrium which is due to inhibition of AChE activity leading to
accumulation of acetylcholine in cholinergic synapses ending up with hyperstimulation
(Mushigeri and David, 2005). Throughout the experimental period, the fish showed severe
respiratory distress and rapid opercular movements leading to the higher amount of toxicant
uptake. Increased mucus secretion, higher ventilation volume, laboured breathing and engulfing
of air through the mouth was also observed in fish exposed to both technical grade and 25% EC.
However, the above said changes in the fish were more pronounced in 25% EC than in technical
grade quinalphos. Similar observations were made by Shivakumar and David (2004), Rao et al.,
(2003) and Parma de Croux et al., (2002). Opercular movements increased initially but decreased
steadily in lethal exposure compared to sublethal exposure periods. Increased gill opercular
movements observed initially may possibly compensate the increased physiological activities
under stressful conditions. Gulping air at the surface to avoid contact of medium and swimming
at the water surface was observed in fish exposed to lethal and sublethal concentrations and
continued the same further intensely which is in accordance with the observations made by Ural
and Simsek (2006). Surfacing phenomenon i.e., significant preference of upper layers in exposed
group might be a demand of higher oxygen level during the exposure period (Katja et al., 2005).
The restless and increased opercular movements in the fish exposed to toxicants are
characteristics of fish put to hypoxic condition (David, 1995) resulting in more amount of
toxicants to be brought in contact with the secondary lamellae of the gills causing a greater
damage to the respiratory epithelium, implying impaired O2 uptake. In acute lethal concentration,
a greater damage of the respiratory epithelium as well as its shrinkage, lead to sharp decline in
the O2 uptake rate (Sarkar, 1999). The decrease in O2 consumption in the sublethal concentration
of quinalphos appears to be mainly due to lowering down of energy requirements and if so, such
134
lowering of maintenance energy requirement is to be considered adaptive and even strategic. The
secretion of mucus layer over the gill lamellae has been observed during quinalphos stress. The
coagulation of mucus on the gills caused demolition of various important processes such as gas
exchange, nitrogen excretion, salt balance and circulation of blood. Greater decrease in the rate
of oxygen consumption would be due to internal action of by toxicant altering the metabolic
cycle at sub cellular level (Bradbury et al., 1986) and also due to damage caused to RBC. Similar
observation was made by Deva Prakasa Raju (2000) and Mushigeri and David (2003). The
results observed in the present study were in agreement with Chebbi and David (2009a) where
considerable variation was observed in respiratory rate in freshwater fish, Cyprinus carpio
exposed to quinalphos.
The effect of different organophosphorus insecticides on oxygen consumption has been
studied by many researchers. According to Murty et al., (1984) when methyl parathion and
fensulfothion were exposed to freshwater fish Mystus cavasius, both pesticides at higher
concentrations, affected the oxygen uptake of M. cavasius, with a progressive reduction of the
oxygen consumption with increasing concentration of the pesticide. The highest concentration of
methyl parathion that caused irreversible damage during the period of the respiratory experiment
induced stressed and excited swimming and increased the oxygen uptake. Bakthavathsalam and
Srinivasa Reddy (1985) observed significant change in total oxygen consumption of the
freshwater fish Anabas testudineus exposed to disyston and furadan. Significant increase was
noted after 3 hr of exposure in both the pesticides, their effects varied from one exposure period
to another. In sublethal concentrations of ekalux oxygen consumption rate of the fish
Lepidocephalichthys thermalis decreased by more than 40% with increasing concentration of
pesticides was reported by Palanichamy et al., (1986). When Spangled perch, Leiopotherapon
unicolor, were exposed to concentration of temephos, an organophosphorus insecticide Gehrke
(1988) observed an immediate reduction in ventilation rate and oxygen consumption, and also
reduced heart rate during the second hour of exposure and concluded that effects of exposure to
temephos correspond to cholinesterase inhibition in nerves supplying the respiratory musculature
and the heart. Effect of multiple sublethal concentrations of Phosalone on whole animal and
kidney oxygen consumption in freshwater fish Oreochromis mossambicus, caused a significant
change indicating the presence of hypoxic condition in the biosystem during the toxicity of
phosalone was reported by Reddy et al., (1992). Since AChE is the target enzyme for OP
135
compounds (O’ Brien, 1967), its inhibition should be responsible for decrease in oxygen uptake
in the gill tissue, because accumulation of acetylcholine (Ach) is known to increase vascular
resistance preventing the flow of blood through the gill and also directing the blood away from
the secondary lamellae (Mary 1984), thus diminishing oxygen transport capacity.
Studies on organochlorine pesticides by Devi Swetharanyam (2000) observed
enhancement in the oxygen consumption rate initially in the fishes of sublethal and median lethal
exposures to endosulfan might be due to a sudden response of the fish to the impending toxicity
endosulfan as opined by Sambasiva Rao et al., (1981) and the animal might also try to adjust
with new steady state of metabolism (Jawale, 1985). The present status of the fish may be an
indication of mobilization of metabolic reserves in response to immediate toxic effects (Moorthy
et al., 1985) However the declining respiratory rates recorded in the subsequent periods in
sublethal and median lethal exposures suggest that the fishes could not succeed in their attempts
of boosting oxidative metabolism due to uncoupling of oxidative phosphorylation by the toxicant
(Jhingran, 1983). Ramalingam and Srinivasa Reddy (1982) exposed the fish Colisa lalia to an
organochlorine pesticide, lindane to different concentrations and studied the bimodal respiration
and found total oxygen consumption of fish increased but the dependence on the type of
respiration differed in the different concentrations. Experiments were conducted by Rao et al.,
(1981) to the freshwater fish Macrognathus aculeatum to study the toxicity and metabolism of
endosulfan and the effect of the pesticide on the oxygen consumption revealed that the pesticide,
both at sublethal and lethal concentrations, decreased oxygen consumption. According to Gaindo
et al., (1996) the effects of treatment with sublethal concentrations of organochlorine pesticides
such as lindane, lorsban, chlordane and DDT to shrimp larvae Penaeus vannamei increased the
larval respiratory rate.
Effects of pyrethroid insecticides also revealed the decrease in oxygen consumption
might also be due to disruption of O2 binding capacity of respiratory pigment as evidenced by the
decrease in RBC and Hb content in carp under cypermethrin toxicity (Malla Reddy and
Bashamohideen, 1989). Decreased O2 uptake efficiency was also observed in another species,
Salmo gairdneri, exposed to pyrethroid insecticides (Kumaraguru and Beamish, 1983; Bradbury
et al., 1987a). The change in the level of respiration and ions in the tissues of freshwater fish
Labeo rohita under fenvalerate stress was studied by Malla Reddy and Harold Philip, (1992)
136
which supports the present findings. All the above investigations indicate that O2 consumption a
sensitive indicator of stress in fishes exposed to pollutant is suppressed considerably.
Hypoxic conditions prevail under toxic conditions and a number of poisons existing in
low concentrations in the medium (which were not toxic earlier) become more toxic to the
organism. Hence, the fish breathe more rapidly and the amplitude of respiratory movements will
increase. Mason (1981) observed that the lack of oxygen increases the ventilation volume of
fishes and the cardiac output is reduced. This reduces the rate of passage of blood through the
gills, thus allowing a longer period of time for uptake of oxygen and also conserves oxygen by
reducing muscular work.
The zone of resistance reached when the oxygen tension in the
medium is so low that homeostatic mechanisms of the fish are no longer able to maintain the
oxygen tension in the afferent blood and the standard metabolism begins to fall.
Gills are the major respiratory organs and all metabolic pathways depend upon the
efficiency of the gills for their energy supply and damage to these vital organs causes a chain of
destructive events, which ultimately lead to respiratory distress (Magare and Patil, 2000).
Pronounced secretion of mucus layer over the gill lamellae has been observed during quinalphos
stress. Secretion of mucus over the gill curtails the diffusion of oxygen (David et al., 2002),
which may ultimately reduce the oxygen uptake by the animal. If gills would be destroyed due to
xenobiotic chemicals (Grinwis et al., 1998) or the membrane functions are disturbed by a
changed permeability (Hartl et al., 2001), oxygen uptake rate would even rapidly decreased. In
exposed fish, the reduction in oxygen uptake can be correlated to the extent of damage of gill
epithelium (Tilak et al., 2001a, 2005a). On the other hand, the metabolic rate (in relation to
respiration) of fish could be increased under chemical stress. Kalavathy et al., (2001) reported
that the dimethoate is efficiently absorbed across the gill and diffuse into the blood stream
resulting toxic to fish.
The change in the architecture of gill under quinalphos stress i.e., changes in the gill
surfaces and increased mucus production are consistent with the observed histological effects
such as hyperplasia, necrosis and lamellar aneurysms in the fish Channa punctatus (Bloch)
exposed to sublethal and lethal concentrations of technical grade and 25% EC quinalphos vivid
from Chapter VI and haematological parameters (damage caused to RBC) vivid chapter-IV
would have altered diffusing capacity of gill with consequent hypoxic/anoxic conditions and
thus respiration may become problematic task for the fish. These results suggest that the altered
137
rates of respiration of freshwater fish may serve as a rapid biological monitor of the pesticide
exposure to important components of freshwater. From above discussions and results obtained it
can be concluded that the decrease in oxygen consumption of an organism as a response to the
toxic stress is the cumulative effect of several stages at which the toxicant acts.
All the studies mentioned above indicate a considerable effect of insecticides on oxygen
consumption in different species of fish in lethal as well as sublethal concentrations. The present
study also reveals that commercial formulations 25% EC had more effect than technical grade
due to the active ingredients present in the form of emulsifiable concentration which might be
the reason for more effect in alterations of the oxygen consumption of Channa punctatus
exposed to sublethal and lethal concentrations of quinalphos. The active ingredients mixed in the
formulation 25% EC might be causing cumulative or additive or synergistic toxic action. Hence,
it has a bearing on toxic stress as a result of more oxygen consumption.
138
Table III.1
The amount of oxygen consumed in mg/gr body weight/hr of the fish
Channa punctatus exposed to sublethal and lethal concentrations of
quinalphos technical grade and 25% E.C.
Hours
Control
Technical
Sublethal
%
Change
Technical
Lethal
0
0.789
±0.025
0.774
±0.065
-1.90
0.777
±0.085
2
0.775
±0.045
0.971
±0.211
25.29
4
0.765
±0.078
1.166
±0.014
6
0.754
±0.024
8
%
Change
25% EC
Sublethal
%
Change
25% EC
Lethal
%
Change
-1.52
0.773
±0.158
-2.02
0.779
±0.043
-1.26
0.748
±0.025
-3.48
1.261
±0.054
62.70
0.727
±0.098
-6.19
52.41
0.711
±0.026
-7.05
1.391
±0.087
81.83
0.682
±0.078
-10.84
1.329
±0.145
76.25
0.677
±0.056
-10.21
0.733
±0.095
-2.78
0.638
±0.024
-15.38
0.752
±0.098
0.725
±0.065
-3.59
0.635
±0.189
-15.55
0.689
±0.087
-8.37
0.587
±0.132
-21.94
10
0.712
±0.128
0.642
±0.046
-9.83
0.556
±0.127
-21.91
0.621
±0.052
-12.78
0.495
±0.145
-30.47
12
0.684
±0.076
0.598
±0.031
-12.57
0.493
±0.028
-27.92
0.551
±0.035
-19.44
0.42
±0.014
-38.59
14
0.681
±0.065
0.542
±0.021
-20.41
0.46
±0.065
-32.45
0.512
±0.065
-24.81
0.369
±0.041
-45.81
16
0.679
±0.081
0.505
±0.076
-25.62
0.42
±0.025
-38.14
0.469
±0.079
-30.92
0.323
±0.054
-52.43
18
0.681
±0.155
0.457
±0.142
-32.89
0.398
±0.087
-41.55
0.438
±0.048
-35.68
0.287
±0.011
-57.85
20
0.689
±0.087
0.413
±0.245
-40.05
0.302
±0.056
-56.16
0.404
±0.078
-41.36
0.27
±0.054
-60.81
22
0.691
±0.036
0.396
±0.127
-42.69
0.259
±0.078
-62.51
0.38
±0.064
-45.00
0.219
±0.012
-68.30
24
0.682
±0.011
0.362
±0.104
-46.92
0.237
±0.059
-65.24
0.353
±0.035
-48.24
0.201
±0.021
-70.52
Values are the mean of five observations
Standard Deviation is indicated as (±)
Values are significant at p < 0.05
139
Oxygen consumption in mg/gr body weight/hr
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
1
3
Control
2
4
6
7
8
Technical Sublethal
5
9
11
12
13
14
140
Technical Lethal
Hours of exposure
10
15
17
18
19
25% EC Sublethal
16
20
22
23
24
25% EC Lethal
21
Fig III.1: The amount of oxygen consumed in mg/gr body weight/hr of the fish exposed to sublethal and lethal
concentrations of quinalphos technical and 25%EC