Zoology
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Item Potential of aquatic carnivorous plants; Utricularia vulgaris and Utricularia reticulata as biological control agents for the larval stages of dengue vector, Aedes aegypti(2021-09) Perera, K.R.N.; Gunathilaka, P.A.D.H.N.; Amerasinghe, L.D.; Udayanga, N.W.B.A.L.Species in the genus Utricularia are aquatic carnivorous plants that are known as bladderworts. They have the potential to trap a wide range of prey, causing the prey die due to anoxia. This study was conducted to assess the effectiveness of bladderworts as controlling agents of Aedes aegypti larvae. Utricularia vulgaris and U. reticulata species were collected from natural water bodies in Dankotuwa and Kandy, respectively. The experiment was set with 10 larvae of Ae. aegypti (early [i & ii] and late [iii & iv] instars, separately) in 250 mL of water with bladderwort containing approximately 100 bladders. The experiment was repeated 50 times for both plant species to achieve a total sample size of 500 mosquito larvae each from early and late instars. A control test was performed without plant species at each setup. The survival of larvae was recorded daily until death or adult emergence and only the larvae found whole or partially inside the bladders were attributed to predation. The cox-regression and Mantel-Cox log-rank test was used to assess the larval survival probability. The highest predation by both U. vulgaris (97.8%; n= 489) and U. reticulata (82.8%; n= 414) was observed in early instars. The mortality due to predation by U. vulgaris was significantly higher (HR=60.71, CI; 5.69–999.25, P<0.05) than U. reticulata. The mortality rates of late instars were low in both U. vulgaris (82.6%) and U. reticulata (74.8%). The highest predacious efficacy was detected from U. vulgaris (HR=45.02; CI: 5.96– 850.51, P<0.05) even in late instar stages. Overall, >70% of cumulative predation was evident within 72 hours of exposure for early and late instars in both species. Hence, the adults emerge from the breeding site could be minimal. Therefore, U. vulgaris and U. reticulata can be used as potential bio-control agents for Ae. aegypti larvae.Item Molecular Characterization of Midgut Bacteria in Larval and Adult Stages of Aedes albopictus in Gampaha District, Sri Lanka(Institute of Biology Sri Lanka, 2021-09) Ranasinghe, H.A.K.; Gunathilaka, P.A.D.H.N.; Amarasinghe, L.D.; Rodrigo, W.W.P.Bacterial species that are acquired from the aquatic larval and adult stages are established in the midgut of mosquitoes, exhibiting different functional tasks retaining in the gut as symbiotic species. The present study aimed on screening of midgut bacteria of larval and adult Ae. albopictus, as a fundamental pre-requirement to support the Sterile Insect Technique (SIT) and Incompatible Insect Technique (IIT) approaches which are in progress, in Sri Lanka. In novel techniques such as SIT, IIT or the use of genetically modified mosquitoes need artificial rearing of the life cycle stages of disease vectors followed by open releases into the environment and thereby reduce vector densities through population replacement or suppression. Sampling sites included Brandiyamulla, Gampaha, and Miriswaththa in Gampaha Medical Office of Health (MOH) area of Sri Lanka. Unfed adults and 3rd instar larvae, 250 in number were sacrificed using a cold shock and 70% Ethanol respectively. 70% ethanol followed by phosphate buffer saline (PBS) were used for surface sterilization. A homogenized lysate was prepared in sterile PBS (250μL), by pooling dissected midguts of ten individuals of larvae/adult mosquitoes. A dilution series (100- 10-7) was made from lysate and 100 μL from each dilution was plated on Plate Count Agar and pure cultures for each microbe were obtained. Isolated bacteria were subjected to 16S rRNA amplification. A total number of 6 bacterial strains (Microbacterium trichothecenolyticum, Kocuria kristinae, Elizabethkingia miricola, Staphylococcus sciuri, Pantoea dispersa, Neisseria flavescens) were identified from 5 bacterial families; Flavoacteriaceae (22.05%), Neisseriaceae (11.76%), Micrococcaceae (10.29%), Staphylococcaceae (14.70%), and Erwiniaceae 35.29%) from field-collected adults, while 6 strains (Agromyces sp., Microbacterium paraoxydans, Microbacterium sp., Bacillus megaterium, Bacillus nanhaiensis, Bacillus sp.) were identified from the field-captured larvae. Species composition of gut microbes isolated from larvae was dominated by family Bacilliaceae (76.76%). Pantoea dispersa and Bacillus megaterium were the most prominent bacterial species isolated from midgut of adults and larvae respectively. Microbacterium genera was found as common for both adults and larvae, although no common bacteria were found up to species level. Midgut bacteria belonged to Bacteroidetes (Elizabethkingia miricola) and Proteobacteria (Pantoea dispersa, Neisseria flavescens) were only recorded from the midgut of adults. Larvae and adults in Ae. albopictus denoted different midgut bacterial species.Item Knowledge, Attitude and Practices (KAPs) based risk factors for dengue in the Gampola Medical Officer Health area, Kandy District, Sri Lanka(Sri Lanka Association for the Advancement of Science, 2016) Udayanga, N.W.B.A.L.; Gunathilaka, P.A.D.H.N.; Iqbal, M.C.M.; Kusumawathie, P.H.D.; Najim, M.M.M.; Amarasinghe, U.S.; Abeyewickreme, W.Item Geographic, Economic and Socio-cultural factors defining risk of dengue transmission in Kelaniya, Sri Lanka(Journal of Experimental Biology and Agricultural Sciences, 2014) Nadeeka, P.V.J.; Gunathilaka, P.A.D.H.N.; Amarasinghe, L.D.