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 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 The response of the up-country live wood termite (Postelectrotermes militaris, Desneux, (Isoptera:Kalotermitidae) to termite extracts and roots of plants(Proceedings of the 44th Annual sessions of the Sri Lanka Association for the Advancement of Science, 1988) Thirugnanasuntharan, K.; Amarasinghe, L.D.Item Clonal susceptibility and population dynamics of Tea red spider mite, Oligonychus coffeae Nietner, (Acarina:Tetranichidae)(Proceedings of the 45th Annual sessions of the Sri Lanka Association for the Advancement of Science, 1989) Thirugnanasuntharan, K.; Amarasinghe, L.D.Item Growth-overfishing: a potential danger in Sri Lankan reservoir fishery(Reservoir Fishery Management and Development in Asia, 1988) Amarasinghe, U.S.This publication presents the results of an IDRC-funded workshop held in Kathmandu, Nepal, 23-28 November 1987. Representatives from 15 countries reviewed the status of reservoir fishery research in Asia under the following topics: existing fisheries, limnological aspects, biological and resource aspects, management aspects, and culture. Papers were presented on these topics, but the discussion sessions were the main element of the workshop. Summaries of these discussions as well as a series of general recommendations that were generated during the final discussion are presented in this book. The potential for increased fish production in reservoirs and the need for early involvement of fisheries scientists in the planning and preimpoundment studies before dam construction are emphasized.Item Status of the fishery of Pimbmrettewa wewa, a man-made lake in Sri Lanka(Aquaculture and Fisheries Management, 1987) Amarasinghe, U.S.The status of the fishery of Pimburctlewa wewu, a man-made lake in Sri Lanka, was studied from January 1985 to January 1986. The annual fish yield in the reservoir is 441 kg/ha, one of the highest in the south-east Asian region. Oreochromis mossambicus (Peters) is the dominant species in the fishery and accounted for about 90% by weight of the total catch. Although there were monthly variations in catch per unit effort, the daily catch per fisherman was not adversely affected. A possibility of having a more productive fishery is suggested In reducing The minimum permissible mesh size in the gillnet fishery during the peak recruitment season in May?June. The possible effects of reducing the mush size are discussed. Using the length-frequency data of O. mossambicus, the asymptotic length and the growth constant were estimated to be 39.3cm and 0.34 respectively. The estimates of total mortality (2.42). natural mortality (0?82) and mean selection length (24.6 cm) were based on these growth parameters Yield-per-recruit analysis indicated that the O. mossambictus fishery in the reservoir was optimally exploited.Item Assessment of fishing effort in Parakrama Samudra, an ancient man-made lake in Sri Lanka. Fisheries Research(Fisheries Research, 1986) Amarasinghe, U.S.; Pitcher, T.J.As in most artisanal fisheries, assessment of fishing effort is crucial to the management of the artisanal fishery of Parakrama Samudra, an ancient man-made tropical lake in Sri Lanka. Since there were few similarities between alternative ways of expressing effort for the gill-net cichlid fishery is the lake, this study aimed to find the most effective formulation of catch per unit effort (CPUE). The variability of preliminary estimates showed that, before analysis, the data needed to be stratified for different seasons with low and high water levels, and for three geographically distinct areas of the lake. Standardised catch per man was higher in boats operated by smaller numbers of fishermen, but catch per net did not change with the number of nets per boat, and is therefore recommended as the best measure of CPUE. The measure of fishing effort also needs to take account of fishermen who increased their catch by a water-beating technique. The incidence of beating varied with season and area, but could account for a significant portion of the catch. The highest catch efficiencies derived from one-man boats using this technique. Using this method of assessing effort, total annual yield from Parakrama Samudra was estimated at about 120 kg ha?1, a lower value than previously reported.Item Studies on the Exploitation of minor Cyprinids in Parakrama Samudra, A man-made lake in Sri Lanka, using Gillnets(Journal of National Aquatic Resources Agency Sri Lanka, 1985) Amarasinghe, U.S.Item Estimation of maximum sustainable fish yield and stocking densities of fish fingerlings in fresh water lakes and reservoirs(Stuttgart : E. Schweizerbart'sche Verlagsbuchhandlung, 1964-, 1987) Wijeyaratne, M.J.S.; Amarasinghe, U.S.Item Spatial Changes in Growth and Mortality and Effects on the Fishery of Oreochromis mossambicus (Pisces, Cichlidae) in a Man-made Lake in Sri Lanka(Asian Fisheries Society, 1989) Amarasinghe, U.S.; de Silva, S.S.; Moreau, J.Growth and mortality were estimated from the length-frequency data of Oreochromis mossambicus from the gillnet fishery of Parakrama Samudra, a man-made lake in Sri Lanka, separately for its three basins. The asymptotic length (L?) and the growth constant (K) of O. mossambicus in the northern basin of the lake (34.9 cm and 0.3, respectively) are appreciably different from those in other tow basins (middle basin, L? = 38.8 cm and K = 0.24; southern basins are 2.22, 1.64 and 1.07, respectively. The spatial differences in growth are suggested to be due to different fishing pressure and environmental conditions. Yield-per-recruit analysis indicate that in the populations with low L? and high K, exploitation level should be maintained at a low level. Fish yield could be optimized by increasing the size of first capture and exploitation rate in the population with high L? and low K.