Zoology
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Item Effects of biological and technical factors on brain and muscle cholinesterases in Nile tilapia, Oreochromis niloticus: implications for biomonitoring neurotoxic contaminations(Springer-Verlag., 2008) Pathiratne, A.; Chandrasekera, L.W.H.U.; De Seram, P.K.C.Influence of body length, body weight, gender, sexual maturity, and tissue storage on brain and muscle cholinesterases (ChE) in Nile tilapia was evaluated considering its potential use in biomonitoring neurotoxic contaminations in tropical environments. Results show that ChE activities in both tissues decreased significantly with increased total length (4–24.5 cm) or body weight (1–186 g) of the fish and the relationships were curvilinear. Comparisons of the slopes and elevations of the regression lines of the logarithmic ChE and body size relationships of males with those of females indicated that gender had no significant effect on the body size-specific ChE activities. Response of the ChE of sexually mature males to chlorpyrifos exposure was similar to that of females. Gonadal maturity stage of this fish does not seem to influence ChE activities. Storage of tissues at –80°C for 28 days had no significant effect on ChE activities in the control fish and the fish exposed to carbofuran. However, a partial reactivation of brain ChE activities was observed in the fish exposed to carbosulfan after 28 days of storage. The results emphasize the importance of consideration of body size of the fish and storage time of the tissues in order to formulate accurate conclusions about the neurotoxic chemical exposure when ChE of the fish is used in biomonitoring programs.Item Traditional Practices for Resource Sharing in an Artisanal Fishery of a Sri Lankan Estuary(Asian Fisheries Society, 1997) Amarasinghe, U.S.; Chandrasekera, L.W.H.U.; Kithsiri, H.M.P.In the Negombo estuary of Sri Lanka, there is an artisanal fishery for penaeid shrimp locally known as stake-seine fishery. Stake-seine nets, which can be fixed in specific sites close to the sea mouth, are used for catching shrimp that migrate from the estuary to the sea. According to regulations imposed by the fishing communities, use-rightss in the fishery are granted to descendants of certain fishing families in four villages. Among the stake-seine fishers who are organized into four rural societies, an effective mechanism has been evolved for resource sharing in the fishery over a period of several hundred years. For equity sharing of the resource, different fishing dates are assigned to the four rural societies, and fishing sites are allocated to individual fishers in each society using a lottery system. Sustenance of this traditional practice is due to the fact that the returns from the fishery are significant. Community-based management strategies for the fisheries in developing countries can therefore be defined by adopting relevant mechanisms found in these types of artisanal fisheries.Item Use of biomarkers in Nile tilapia to assess the impacts of pollution in BolgodaLake, an urban water body in Sri Lanka(Environmental Monitoring and Assessment, 2009) Pathiratne, A.; Chandrasekera, L.W.H.U.; Pathiratne, K.A.S.The present study reports the first analysis of water pollutants in Sri Lankan waters using a suite of biomarkers in Nile tilapia (Oreochromis niloticus) residing in Bolgoda Lake which receives urban, industrial and domestic wastes from multiple sources. The fish were collected from the lake in the dry period (April 2005) and wet periods (September 2005, October 2006) and the levels of biomarkers viz. hepatic ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST), metallothioneins, biliary fluorescent aromatic compounds, brain and muscle cholinesterases (ChE) were compared with those of the laboratory reared control fish and the fish obtained from a less polluted water body, Bathalagoda reservoir (reference site). The results revealed that biomarker levels of the fish collected from the reference site were not significantly different from the controls. Hepatic EROD and GST activities in fish from Bolgoda Lake were induced 4.2?16.6 folds and 1.4?3.3 folds respectively compared with the control fish. Analysis of bile in the lake fish revealed recent uptake of naphthalene, pyrene and benzo(a)pyrene type polycyclic aromatic hydrocarbons (PAHs). The induction of EROD activities in feral fish reflects the exposure of fish to aryl hydrocarbon receptor agonists including PAHs present as pollutants in the Bolgoda Lake. Cholinesterase activity in the fish inhabiting one sampling site of Bolgoda Lake was lower (22?40% inhibition) than the activity measured in the control fish indicating the presence of anticholinesterase pollutants in the area. Hepatic metallothionein levels in the lake fish were higher (1.9?3.2 folds) in comparison to the controls indicating metal exposure. The results support the potential use of these biomarkers in Nile tilapia in assessing pollution in tropical water bodies.Item Effect of biological and technical factors on brain and muscle cholinesterases in Nile Tilapia(Oreochromisniloticus): Implications for biomonitoring neurotoxic contaminations(Archives of Environmental Contamination and Toxicology, 2008) Pathiratne, A.; Chandrasekera, L.W.H.U.; de Seram, P.K.C.Influence of body length, body weight, gender, sexual maturity, and tissue storage on brain and muscle cholinesterases (ChE) in Nile tilapia was evaluated considering its potential use in biomonitoring neurotoxic contaminations in tropical environments. Results show that ChE activities in both tissues decreased significantly with increased total length (4?24.5 cm) or body weight (1?186 g) of the fish and the relationships were curvilinear. Comparisons of the slopes and elevations of the regression lines of the logarithmic ChE and body size relationships of males with those of females indicated that gender had no significant effect on the body size-specific ChE activities. Response of the ChE of sexually mature males to chlorpyrifos exposure was similar to that of females. Gonadal maturity stage of this fish does not seem to influence ChE activities. Storage of tissues at ?80?C for 28 days had no significant effect on ChE activities in the control fish and the fish exposed to carbofuran. However, a partial reactivation of brain ChE activities was observed in the fish exposed to carbosulfan after 28 days of storage. The results emphasize the importance of consideration of body size of the fish and storage time of the tissues in order to formulate accurate conclusions about the neurotoxic chemical exposure when ChE of the fish is used in biomonitoring programs.Item Effects of waterborne cadmium on biomarker enzymes and metalothioneins in Nile tilapia, Oreochromis niloticus(Journal of National Science Foundation of Sri Lanka, 2008) Chandrasekera, L.W.H.U.; Pathiratne, A.; Pathiratne, K.A.S.Cadmium is widely used in modern industry and ranks among the most toxic metals in the aquatic ecosystems. In the present study, activities of several biomarker enzymes viz. ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST) and cholinesterase (ChE) were determined in Nile tilapia (Oreochromis niloticus) at different waterborne Cd22+ exposure levels (0, 0.001, 0.005, 0.01, 0.1, and 1 mg/L for 28 days) to evaluate the potential influence of environmental cadmium on these enzymes. In addition, hepatic metallothionein (MT) levels in these fish at different waterborne Cd2+ exposure levels were also studied to evaluate their response to waterborne cadmium exposure. The results revealed that hepatic MT levels in the fish exposed to Cd2+ increased 2-26 fold depending on the exposure level and duration. Hence hepatic MT in Nile tilapia is a sensitive biomarker to indicate cadmium pollution in the natural environments. Continuous exposure of fish to ? 0.01 mg/L of Cd2+ had no significant effect on hepatic EROD, hepatic GST and brain and muscle ChE activities whereas exposure to ? 0.1 mg/L Cd2+ evoked time dependent significant depression of hepatic EROD (41-55%) activity. Brain and muscle ChE activities of the fish exposed to 1 mg/L Cd2+ were depressed to 24-32% and 33-35% respectively. Results revealed that high concentrations of Cd2+ in the natural environments could inhibit the basal activities of the hepatic EROD and brain and muscle ChE in Nile tilapia affecting the normal functioning of these biomarker enzymes and influencing the biomarker response to targeted organic pollutants in the environment.Item Body size related differences in the inhibition of brain acetylcholinesterase activity in juvenile Nile tilapia Oreochromisniloticus by chlorpyrifos and carbosulfan(Ecotoxicology and Environmental Safety, 2007) Chandrasekera, L.W.H.U.; Pathiratne, A.