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SHORT
CO
;
tlMUNICATION
Effect of Petroleum Effluent Pollution on Carbohydrate
Reserves of The Nile Tilapia,
Oreochromis niloticus
(L.)
*Omoregie, E; Ufodike, E. B. C. and Onwuliri, C.
O
;
E
.
Department of Zoology, University of [o«, P. M. B. 2084,105, Nigeria.
"Present address:
Centre for the Economics and Management of Aquatic Resources,
University of Portsmouth,
Portsmouth, Southsea,
P04 BJF, United Kingdom.
Abstract
The effect of petroleum effluent pollution on the plasma glucose, liver and muscle glycogen of the Nile tilapia, Oreochromis
niloticus (L.) were investigated. The results obtained shows evidence of stress and impairment of carbohydrate metabolism
in fish obtained from down stream of the polluted river. The affected fish showed hypoglyca~mic response and liver and
muscle glycogen depletion.
Key words: Toxicology, carbohydrates reserves, tilapia, petroleum, pollution, Oreochromis niloiicus, fish
Resume
Les effets causes par la pollution d'effluents du petrole sur Ie plasma glucose, Ie foie et les muscles glycogenes de Tilapia
de Nil Oreochromis niloiicus (L) ont ete enquetes, Les resultats obtenus montrent une evidence de tension et un affaiblissement
du metabolisme de hydrate de carbone dans les poissons provenant de l'aval des rivieres polluees. Les poissons affectes
ont montre une reaction hypoglycernique, un foie et des muscles glycogenes reduits.
Mots des: Toxicologie, carbohydrates, Tilapia, petro le, pollution, Oreocnromi« niloticus, poisson
Introduction
One of the most important environmental factors
acting as "stressor" to fish is pollution. There are
many potential pollutants whose occurrence causes
a reduction in the quality of the aquatic environment.
Contamination of the aquatic environment by
petroleum and petroleum effluent, whether as a
consequence of acute or chronic events constitutes
an additional source of stress for aquatic organisms.
To obtain an adequate overall view of the impact of
petroleum pollution on fish production, it is necessary
to accept the broad GESAMP (1980) findings which
included petroleum products as major toxicantte
aquatic life. .,
Individual components of petroleum has been
reported by different authors to have varying
toxicological effects on fish at sublethal
concentrations, death of fish have also been reported
at various acute concentrations. Baker (1979)
observed that the toxicity of refinery effluent is further complicated by the presence of hydrocarbon
breakdown products, unidentified components and
interactions among various components.
Changes in carbohydrate metabolism occurs in
Effect of Petroleum Effluent Pollution
(1967), reported the secretion of catecholamine and
adrenocortisoid in stressful conditions by fish. This leads to marked changes in the carbohydrates reserves which according to Wedemeyer et al. (1984), causes hyperglycaemia. It is important to note that fish increase their metabolic rate to metabolize and excrete aromatic hydrocarbons, and consequently, allocating more energy to homeostatic maintenance than storage, hence depletion in liver and muscle
gl ycogen of exposed fish.
Oreochromis niloticus commonly referred to as the Nile tilapia are conspicuous members of the
freshwater fauna in the tropics, where water temperatures are suitable for their growth and reproduction. Stickney (1979), reported that several species of tilapia, including O. niloticus are able to survive well at dissolved oxygen concentrations as low as Img Zl, and continue to grow rapidly if the exposure period is not prolonged. The fish is well suitable for pond culture in the tropics, where it attains maturity in less than 6 months.
Scientific information on the effects of sublethal exposure of most of the several Nigerian freshwater fish species to petroleum and its effluent is scarce. Most available information on the effects of petroleum pollution in NIgeria is restricted. to the socio-economic
impact of petroleum pollutionon the general aquatic environment (Oladimeji, 1987). The objective of this investigation is to evaluate the effect of petroleum effluent on the carbohydrate reserves in the blood, liver and muscles of O. niloticus in a polluted freshwater body.
Material and Methods
The petroleum effluent polluted. freshwater used for this investigation is River Kaduna, in Kaduna, Kaduna State, Nigeria. This River has been reported by several authors to receive petroleum effluent from the Kaduna Refinery and Petrol-Chemical Company, a division of the Nigerian National Petroleum Company (NNPC). Oladimeji (1987) reported that the river contains high levels of several breakdown.
products of petroleum. _.
For the purpose of this investigation, two stations on the river were selected for the collection of 0. niloiicus sampled. The first station was situated above the point of introduction of the eJ£luent while the second station was below the point of introduction.
O. niloticus of three different sizes were collected by cast netting from the different sampling stations, from where they were transported to the laboratory. In the laboratory, they were sorted into three different sizes (standard length) as tc;,'ows: Juveniles: 3cm -
4.9cm; Sub-adults: Scm - 9.9cm; Adults: lOcm and
above.
Discov, innov., 2000; 12 (1/2) 27
The plasma glucose, muscle and liver glycogen of the fish samples were determined using the anthrone method as modified for use in fish tissues by Wedemeyer and Yasutake (1977). For the plasma glucose, blood from the fish were collected into heparinized micro test-tubes by cardiac puncture technique, according to methods described by Blaxhall and Daisley (1973). Collected blood was centrifuged immediately using haematocrit
centrifuge at 3000 revolution per minute (rpm) for 5
minutes to obtain the plasma.
Three samples from each fish were analysed for all the parameters and the mean values were then subjected to statistical analyses using the Duncan
- multiple range F-test.
Result
Mean values of the plasma glucose, muscle and liver glycogen of O. niloticus from both stations of the river are presented in Figures I, 2 and 3 respectively.
Figure 1: Mean plasma glucose of Oreochromis niloticus from
28 Discov. innov., 2000; 12 (1/2) Effect of Petroleum Effluent Pollution
1.60
~120
1
s
1.00
00
1
0.
80!
0.60
§
o.~o :r
0.20
0.00
. Sut.-odulls
.-.- ____________________________________________ . ___________ ._ .. .I
Figure S: Mean liver glycogen of Oreochromis niloticus from
River Kaduna, Nigeria .
Statistical analyses of the results indicated that there was a significant decrease (P> 0.05) in the values of plasma glucose of all the three different sizes of fish from downstream when compared with values of fish from upstream. Values of liver glycogen shows a significant decrease (P > 0.05) only in the juveniles and sub-adults fish from downstream when
compared. with values of fish from upstream. Though there was a reduction in the mean values of liver glycogen from 1.34
mg
Zg? (±·p.04) to 1.14 mg/g'!(± 0.01) in the adult groups, this was however not a significant reduction at O.OSlevel of probability. Values of the muscle glycogen shows significant decrease (P > 0.05) only in the adult groups of fish from downstream when compared with values of fish from upstream.
Discussion
The trends of results from this investigation shows evidence of stress and impairment of carbohydrate metabolism in O. niloticus as a result of the presence of petroleum effluent in the study area. The
significant reduction in the plasma glucose of fish from the polluted portion .of the river indicated a situation of hypoglycaemic response of the fish to the toxic environment. This according to Oladimeji
and
Ologunrneta (1987),
is probably due toinefficient absorption of soluble glucose from the intestine as a result of the constant swallowing of sublethal levels of the breakdown product of
usually show hyperglycaemic response when in toxic environment. The significant reduction in the muscle and liver glycogen contents of the adult and all three different sizes of fish respectively from the polluted part of the river also confirmed that the fish were severely stressed and metabolism of
carbohydrates was impaired. As noted earlier, fish increased their metabolic rates to metabolize and excrete aromatic hydrocarbons and consequently, allocate more energy to homeostatic maintenance than storage, hence reduction in stored energy food reserves. Increase in metabolic rate in response to hydrocarbon pollution has been demonstrated by Brocken and Bailey (1973), in the striped bass,
Marone saxatitis and chinlook salmon, Oncorhynchus tshawytscha; by Anderson et al. (1974), in sheepshead minnow, Cyprinodon oariegatus, and is suggested by Sabo and Stegemann (1977), in their hepatic lipid studies on mummichog, Fundulus heierocliius, The accumulation of petroleum components by the fish from' the polluted part of River Kaduna also accounted for the severe reduction in the muscle and liver glycogen reserves in these groups of fish. This is in agreement with the report of Wedemeyer et al.
(1984). These workers also reported that one of the secondary tissue responses that reflect the effects of acute stressors include depletion of muscle and liver glycogen. Adebruin (1976), reported that liver glycogen depletion may result from the activation of enzymatic activities in the liver such as action of specific phosphatase or phosphorylase. Oladimeji and Ologunmeta (1987), also reported that depletion of muscle and liver glycogen in fish may be due to inefficient absorption of soluble glucose from the intestine as a result of stress. The impairment of gaseous exchange efficiency of gills of fish due to the presence of toxic substances in their environment (Omoregie and Ufodike, 1991) could also be among the severe factors that have accounted for the impairment of carbohydrate metabolism.
References
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