IPRC - 2018

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    Antagonist Potential of Vorticella microstoma on the larval development of Culex gelidus and Aedes aegypti
    (19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Ranasinghe, H.A.K.; Amarasinghe, L.D.
    Selection of effective biological agents which can suppress the growth of immature stages of mosquito vectors has drawn a wide attention in disease control programmes. Vorticella microstoma is a parasitic ciliate which has an ability to parsitize on larval stages of mosquitoes and inhibit their growth. However, the potential antagonist activity has not been evaluated in detail in Sri Lanka. Fifteen each of first, second, and third instar larvae of Cx. gelidus and Ae. aegypti were placed in separate V. microstoma culture bottles at room temperature (27± 2 ºC) and mortality rate of mosquito larvae was observed after 48 h. Bioassay was done in completely randomized design with controls. The first, second, and third instar larvae of Cx. gelidus were allowed to be infested with the trophont stage of V. microstoma. Heavily infested larvae with V. microstoma were identified by the presence of parasites attached all over the body surface. V. microstoma trophonts did not usually attach to siphon region of mosquito larvae when they are alive. None of the instar levels of Ae. aegypti showed susceptible to infection with V. microstoma. In the first instar larvae of Cx. gelidus, thorax and the abdominal segments had the attachment of 30–35 trophonts of V. microstoma, whereas 2–4 trophonts had attached to the anal papillae. Higher densities of V. microstoma were found in abdominal segments of second instar larvae of Cx. gelidus, whereas total of 45–50 trophonts had attached to thoracic region and abdominal segments. Fifty to fifty-five trophonts of V. microstoma had attached to third instar larvae of Cx. gelidus, with higher densities in the anal papillae followed by abdominal segments; in the anal papillae, 20–25 trophonts were found to be attached. V. microstoma infection was positively correlated with the body size of mosquito larvae. The percentage mortality of the first, second, and third instar larvae of Cx. gelidus did not significantly differ from each other (One-Way ANOVA: IBM SPSS Statistic Software, P<0.05). Therefore, the study results would be a new avenue to work on environmentally agreeable manner in reducing the Cx. gelidus vector mosquito populations.
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    Identification of Volatile Compounds in Different Parts of the Brinjal Plant (Solanum melongena)
    (19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Nusra, M.S.F.; Paranagama, P.A.; Amarasinghe, L.D.; Udukala, D.N.
    Plants synthesize and emit a large variety of volatile compounds, which produce a wide range of behavioral responses in insects. In some plants, these volatile organic compounds are the key compounds that are involved in attraction of insect pests. In addition, the synergism between insect pheromones and plant volatiles can increase the attraction of insect pest, offering new strategies for the development of more effective and reliable pest control programs. Volatile mediated foraging behavior is important in insect pests when they target host plants. The volatiles of brinjal may be functionally more important in host-finding behavior of their insect pest. Samples of brinjal plant leaves, fruits, shoots and flowers were collected from the unsprayed brinjal field. Steam distillation method was used to extract the volatiles from shade dried brinjal leaves, shoots, flowers and fresh fruits. The small pieces of the plant material were subjected to steam distillation for 4 hours at a distillation rate of 50 ml/hour. In this study, gas chromatography coupled with mass spectrometry technique was used for the identification of volatiles extracted from host plant brinjal. The GC oven was programmed at an initial oven temperature of 40 0C increased at a rate of 1 0C/min to 50 0C, then increased at a rate of 4 0C/min to 210 0C, and then raised at a rate of 8 0C/min to a final temperature of 230 0C. The MS data of eluted compounds were acquired and identified by the comparison of their retention times to those of authentic standards and with mass spectra from NIST library. Results indicated that brinjal plant produces 1-Methyl-5,8-dimethoxy-1,2,3,4-tetrahydro-1,4-iminonaphthalene, Benzyl alcohol, Phenylethyl Alcohol, Benzeneacetaldehyde, Butylated hydroxytoluene and Methyl salicylate from leaves; Butylated hydroxytoluene, n-Octyl formate, Butyl phthalate and 1,3-Dioxolane, 2-(methoxymethyl)-2-phenyl from fruits; Benzyl alcohol, 1,6-Octadien-3-ol, 3,7-dimethyl, Butylated hydroxytoluene, Hydroquinone and Methyl salicylate from shoots; and 1,6-Octadien-3-ol, 3,7-dimethyl, Methyl salicylate, Butylated hydroxytoluene, Hydroquinone and Benzyl alcohol from flowers as major compounds
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    Oviposition Preference of Aedes albopictus (Diptera: Culicidae) at Domestic and Peri-Domestic Settings in Gampaha Medical Officer of Health (MOH) of Sri Lanka
    (19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Dalpadadoa, C.P.R.D.; Amarasinghe, L.D.; Bandaranayake, W.A.C.L.
    There are varying ranges of water filled man-made and natural container habitats with varying physico chemical parameters available for the breeding of Aedes mosquitoes. House to house cross-sectional entomological survey was carried out monthly in Gampaha MOH area from April 2017 to June 2018 in order to investigate oviposition preference of dengue vector mosquitoes in domestic and peri-domestic areas. Larval collections were done indoors and outdoors using random sampling technique for minimum 100 houses within a radius of 300 m and potential breeding places in each site were identified and categorized accordingly. Out of 1500 premises examined, 17.4% (n= 261) premises were found positive for Ae. albopictus and Ae. aegypti was not recorded during the study period. The House Index (HI), Container Index (CI), and Breteau Index (BI), varied from 3 - 39, from 5.4 - 44.4, and from 4 - 67, respectively during the study period and there was a strong correlation between the HI and the number of dengue patients reported in Gampaha MOH area according to pearson correlation analysis. (r = 0.64). Overall 2828 potential breeding places were examined in which 18.2% (n=405) containers were found positive for Ae. albopictus larvae. The result indicates that most of these positive breeding places were located outdoors 91.2% (n=369) and only 8.8 %( n=36) positive breeding places were located indoor which includes non- used cisterns/ commodes and refrigerator trays. There were 26.5% (n=750) discarded receptacles, 22.6% (n=640) temporary removal items, 13.2% (n=373) natural breeding places, 8.6% (n=242) water storage items, 8.3% (n=235) covering polythenes, 6.2% (n=176) pet feeding cups, 4.8% (n=136) ornamentals, 2.8% (n=78) tyres, 2.4%( n=68) non used cisterns and commodes and 1.9%( n=53) refrigerator trays. Results Indicates that tyres (51.9%), non- used cisterns/commodes (47.7%), ornamentals (26.2%) were the most preferred breeding localities forAe. albopictus followed by discarded receptacles (24.3%) irrespective to the number of potential breeding places found. According to the results CI for discarded items, temporary removals and covering items increased drastically prior to dengue epidemics and four to five weeks lag period was identified between increased container index and increased number of dengue patients. Non- used cisterns/commodes and natural breeding places showed year around productivity and positivity for Ae. albopictus which indicated that they contributed to maintain and survival of mosquito vector population between intermediate dry periods. Therefore, this study emphasizes the control of mosquito breeding in key breeding places such as non-used cisterns, commodes and, natural breeding places may be beneficial to reduce vector densities during dry period hence, leading to reduce the spreading mosquito vectors in to other made artificial containers during rainy season leading to major out breaks