Zoology
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Item In vitro metabolism of benzene, toluene, and xylene in rat liver(North Dakota State Univ., Fargo (USA)., 1985) Pathiratne, A.A headspace gas chromatographic method was used to study the metabolism of benzene, toluene, and m-xylene in rat liver. Metabolism of benzene was lower than that of toluene, or m-xylene. Investigating metabolic rates of subcellular fractions, it was found that glutathione and glutathione S-transferase in the cytosol are involved in metabolism of benzene and toluene by microsomes. When both benzene and toluene are present in the incubation medium, they act as inhibitors of each others metabolism. Toluene and m-xylene metabolism were induced by the pretreatment of rats with phenobarbital (75 mg/kg), or 3-methylcholanthrene (25 mg/kg), or Aroclor 1254 (75 mg/kg) for 3 days, whereas benzene metabolism was not induced by all pretreatments. Another series of experiments was conducted to compare the effects of benzene, toluene, and xylene pretreatment on liver metabolism. In vivo metabolism of /sup 14/C-toluene and possible covalent binding of /sup 14/C-toluene to microsomes were also investigated. /sup 14/C-toluene when incubated with liver microsomes in the presence of a NADPH generating system formed benzylalcohol and cresols. Some of the radioactivity was covalently bound preferentially to microsomal proteins. The binding process required cytochrome P-450 dependent mixed function oxidases. This study suggests that toluene is metabolized to several reactive intermediates by liver microsomal enzymes and these metabolites are responsible for the covalent binding to macromolecules which represents a subcellular mechanism by which toluene may express its own in vivo toxicity.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 Acetylcholinesterase inhibition and gill lesions in Rasbora caverii, an indigenous fish inhabiting rice field associated waterbodies in Sri Lanka(Kluwer Academic Publishers-Plenum Publishers., 2006) Wijeyaratne, W.M.D.N.; Pathiratne, A.The present study was aimed at applying condition factor (CF), brain acetylcholinesterase (AChE) and gill histology as biomarkers for detecting possible exposure/effect induced by pesticides in fish residing rice field associated waterbodies in Sri Lanka. Biomarkers of an indigenous fish, Rasbora caverii collected from five sampling sites including canals near rice fields, a river and a reservoir (the reference site) were evaluated at four sampling stages covering pesticide application periods during rice cultivation season in 2004. Results indicated that CF of the fish did not show significant alterations regardless of the sampling sites or sampling stages. Site specific differences in AChE activities of the fish were not evident either prior to application of pesticides or at 7 days after Paraquat application to the rice fields. Two days after the application of a mixture of Fenthion and Phenthoate to the rice fields, AChE activity of the fish collected from canals near rice fields was significantly depressed (65–75%) compared to the fish in the reference site. The activities remain depressed to 50–56% even at 65 days after the insecticides application. Laboratory studies showed that prior exposure of R. caverii to Paraquat (2 μg l−1, 7 days) enhanced the extent of inhibition of brain AChE activity induced by Fenthion (3 μg l−1) or a mixture of Fenthion (3 μg l−1) and Phenthoate (5 μg l−1). Gills of fish collected from canals near rice fields exhibited abnormal multiple divisions at the tips of some secondary lamellae in addition to hyperplasia, hypertrophy and club shaped deformities. Results indicate that application of pesticides in rice culture could manifest a threat to native fish populations residing rice field associated waterbodies. The response of brain AChE and histological changes in the gills of R. caverii allowed differentiating sampling sites after insecticide applications to the rice fields. Hence, R. caverii may be considered as a surrogate species in ecotoxicological risk evaluation of agrochemicals in the region.Item Body size-related differences in the inhibition of brain acetylcholinesterase activity in juvenile Nile tilapia (Oreochromis niloticus) by chlorpyrifos and carbosulfan(Academic Press., 2007) Chandrasekara, L.W.H.U.; Pathiratne, A.Influence of body size on inhibition of brain acetylcholinesterase (AChE) activity of juvenile Nile tilapia, Oreochromis niloticus by chlorpyrifos and carbosulfan was investigated concerning its potential use in the biomonitoring of anticholinesterase pesticides in tropical water bodies. Three size groups of fish (fry: 3–4 cm, fingerlings: 6–8 cm, sub-adults: 10–12 cm in total length) were exposed to a series of concentrations of chlorpyrifos (0.5–12 μg L−1) or carbosulfan (1–10 μg L−1), and concentration–response for inhibition and recovery of the AChE enzyme was evaluated in comparison to the controls at different time points, 2, 6, 10, and 14 d. The AChE activities of the control fish followed the order of decreasing activity, fry>fingerlings>sub-adults. AChE activities of the fry were nearly 2-fold higher than that of the sub-adults. Following 48 h of pesticide exposure, the AChE activity of the three size groups of fish decreased significantly in comparison to the respective controls in a concentration-dependent manner. The activity was greatly inhibited in the fry (39–85%) compared to sub-adults (18–47%) exposed to the most of the similar concentrations of the pesticides. Median effective in vivo inhibition concentrations (48 h IC50) of chlorpyrifos for fry, fingerlings, and sub-adult stages were 0.53, 0.75, and 3.86 μg L−1, respectively, whereas the corresponding values for carbosulfan were 3.37, 7.02, and 8.72 μg L−1. When fish were maintained in the initial pesticide medium for 14 days, AChE activity restored gradually depending on the initial pesticide exposure concentration and the size group of the fish. Results indicate that brain AChE of Nile tilapia is a promising biomarker for assessment of anticholinesterase pesticide contaminations in water. However, body size of Nile tilapia should be taken into account when using this biomarker in biomonitoring programmes.Item Ancient Reservoirs of Sri Lanka: A Modern Biological Resource for Assuring Food Security in Rural Communities(University of Kelaniya, 2005) Kularatne, M.G.; Amarasingha, U.S.Reservoir construction in Sri Lanka dates back to times even before the period of written history. In Sri Lanka (64,652 km2), there are over 200 large (750 – 7,793 ha) and medium-sized (250 – 750 ha) reservoirs with a cumulative extent of over 130,000 ha, which support capture fisheries. In addition, there are over 15,000 small (<50 ha) village reservoirs with a total extent of about 39,000 ha. The reservoir density in Sri Lanka (about 2.6 ha for every km2 of island) is one of the highest, if not the highest in the world. Almost entire reservoir resource in Sri Lanka, with the exception of recently constructed hydroelectric reservoirs, supports agricultural food production in the country. As the extent of perennial reservoirs in each district is directly related to per capita freshwater fish consumption, in addition to agricultural production, major perennial reservoirs of Sri Lanka support animal protein production in the form of fish production. This is of particular importance because marine fish consumption is much low in inland districts possibly due to the availability of good quality freshwater fish locally. Also, there is a significant potential for the development of culture-based fisheries in small, village reservoirs of the country. An average fish yield of about 450 kg ha-1 can be achieved during a single culture cycle within a year from the culture-based fisheries in these village reservoirs. However, in order to achieve success of this strategy, a strong extension mechanism is needed to obtain active community participation. As inland fishery is a source of relatively cheap animal protein for rural communities, future prospects of this sector for food security need to be properly understood to give a high priority for inland fisheries research and development in national development plans.Item Promotion of sustainable capture fisheries and aquaculture in Asian reservoirs and lakes(Hydrobiologia, Springer Netherlands, 2001) Amarasingha, U.S.; Dancun, A.; Moreau, J.; Schiemer, F.; Simon, D.; Vijverberg, J.A collaborative international project funded by the European Union’s INCO-DC programme is undertaking limnological, fish biological, environmental and socio-economic research in five tropical lakes and reservoirs in Sri Lanka, Thailand and the Philippines over the period 1998–2001. The aim is to determine their trophic structure and their capacity to sustain both their existing fisheries and present and future aquaculture. In some cases, these activities could potentially be expanded for the benefit of rural communities and of the local market within the bounds of social and environmental sustainability. This paper describes the concepts and methods involved in this innovative multidisciplinary project which aims to integrate limnological, fisheries and socio-economic issues in a comparative approach involving Asian and European research teams.Item Role of fishermen in implementing management strategies in the reservoirs of Sri Lanka(Ottawa : International Development Research Centre, 1988) Amarasingha, U. S.The socioeconomics of six fishing communities in four man-made reservoirs of Sri Lanka was studied to investigate the potential contribution of fishermen to effective management. Adopting illegal fishing methods and changing fishing grounds are two of the socioeeonamic indicators of low incane derived fran the fishery. The fishermen in all six fishing communities were willing to comply with any fishery regulation provided the fishermen unanimously agreed to the regulation. This suggests that effective management strategies, which will contribute to increasing the fishermen's income, can be implemented through properly organized extension societies in the reservoirs of Sri Lanka.Item How effective are the stocking strategies for the management of reservoir fisheries in Sri Lanka, Stocking and Introduction of Fish(Fishing News Books, Blackwell Science, 1998) Amarasingha, U. S.Item Evaluation of the effects of infestation by trematodes and copepods on Catla catla, an Indian carp, cultured in Sri Lanka(Sri Lanka Association for Fisheries and Aquatic Resources, 2004) Wimalawickrama, N.D.; Pathiratne, A.Juvenile stages of Catla catla collected from Udawalawa fisheries station, National Aquaculture Development Authority were found to be infested mainly with Gyrodactylus, digenean metacercarial cysts and Lernaea. In the present study, the intensity of infestation of the parasites and preference sites of the parasites on fish, the oxygen consumption rate, blood haematocrit levels and histological structure of the infested sites of the host fish were examined in comparison to the control fish to evaluate the effects of parasitic infestation(s) on the host fish. All trematodes were recovered from the gills, whereas Lernaea (a copepod) were found attached to the skin and fins of the fish. All Lernaea were adult females of Lernaea cyprinacea. The intensity of Gyrodactylus ranged from 1-2368 individuals per infected fish and the intensities of metacercarial cysts and Lernaea cyprinacea ranged from 1-80 and 1-5 individuals per infected fish respectively. Statistical analysis indicates that Gyrodactylus and metacercarial cysts had no specific preference sites on the gill. Caudal peduncle region of the fish was preferred by Lernaea cyprinacea. Results show that the oxygen consumption rates and blood haematocrit values of the host fish were not affected significantly by the presence of parasites at the current infestation level in spite of histopathological changes induced by the parasites on the infected sites of the fish.Item Cage culture of the snakehead Ophicephalus striatus in a peaty swamp in Sri Lanka In. Zhou, et al. (eds).(Asian Fisheries Society, Manila, Philippines, 1997) Wijeyaratne, M.J.S.