Zoology
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Item Comparative Effect of Parasitism of Ciliated Protists Associated with Selected Vector Mosquito Larvae in Selected Rice Field Habitats in Ganewatte, Kurunegala District, Sri Lanka(Institute of Biology Sri Lanka, 2021-09) Wijesinghe, S.; Amarasinghe, L.D.Mosquito breeding sites provide habitats for diversifying naturally occurring microbiota and favour different types of interactions including parasitism. This study was carried out to determine the natural occurrence of ciliated protist parasites associated with selected vector mosquito species inhabiting rice fields in Ganewattha area in Kurunegala district in Sri Lanka and to compare their parasitic effects on the selected vector mosquito larvae. Mosquito samples were collected from five rice field sites during the period from June to December 2020. The samples were observed for epibionts/parasitic infections under the microscope. Moribund or dead mosquito larvae in each sample collection were observed for internal parasitic infections. A comparative study was carried out to determine the lethal effect of ciliated organisms on Culex tritaeniorhynchus (n=50) and Culex gelidus larvae (n=50) in replicated trials (R=3). The minimum number of V. microstoma that cause a lethal effect on Cx. tritaeniorhynchus third instar larvae (n=100) was determined by a bioassay with ten replicates and two controls per each replicate. A total of 1650 third instar mosquito larvae of Culex tritaeniorhynchus (62.8%) and Culex gelidus (37.2%) were collected in this study. Ciliated protists namely Vorticella microstoma, Zoothamnium spp. and Chilodonella spp. associated with both species of mosquito larvae were identified. Results revealed that V. microstoma has the potential of infection to cause 71.33 (±5.23) mean percentage mortality of Cx. tritaeniorhynchus larvae. A minimum of 1000 V. microstoma is required to kill a third instar larva of Cx. tritaeniorhynchus at 69.60 (±2.40) hours of exposure. Culex gelidus larvae showed only 41.33 (±3.43) mean percentage mortality. This study concludes that V. microstoma is the most successful ciliated parasite as a killing agent of Culex tritaeniorhynchus vector mosquito larvae. Their abundance and effectiveness may contribute to develop them as an effective biocontrolling agent in the future.Item Diversity of midgut bacteria in larvae and females of Aedes aegypti and Aedes albopictus from Gampaha District, Sri Lanka(Parasites & Vectors volume 14, 2021) Ranasinghe, K.; Gunathilaka, N.; Amarasinghe, L.D.; Rodrigo, W.; Udayanga, L.Abstract Background: The midgut microbiota of mosquitoes maintain basal immune activity and immune priming. In recent years, scientists have focused on the use of microbial communities for vector control interventions. In the present study, the midgut bacteria of larvae and adults of Aedes aegypti and Ae. albopictus were assessed using both fieldcollected and laboratory-reared mosquitoes from Sri Lanka. Methods: Adults and larvae of Ae. aegypti and Ae. albopictus were collected from three selected areas in Gampaha Medical Officer of Health area, Gampaha District, Western Province, Sri Lanka. Bacterial colonies isolated from mosquito midgut dissections were identified by PCR amplification and sequencing of partial 16S rRNA gene fragments. Results: Adults and larvae of Ae. aegypti and Ae. albopictus harbored 25 bacterial species. Bacillus endophyticus and Pantoea dispersa were found more frequently in field-collected Ae. aegypti and Ae. albopictus adults, respectively. The midgut bacteria of Ae. aegypti and Ae. albopictus adults (X2 = 556.167, df = 72, P < 0.001) and larvae (X2 = 633.11, df = 66, P < 0.001) were significantly different. There was a significant difference among the bacterial communities between field-collected adults (X2 = 48.974, df = 10, P < 0.001) and larvae (X2 = 84.981, df = 10, P < 0.001). Lysinibacillus sphaericus was a common species in adults and larvae of laboratory-reared Ae. aegypti. Only P. dispersa occurred in the field-collected adults of Ae. aegypti and Ae. albopictus. Species belonging to genera Terribacillus, Lysinibacillus, Agromyces and Kocuria were recorded from Aedes mosquitoes, in accordance with previously reported results. Conclusions: This study generated a comprehensive database on the culturable bacterial community found in the midgut of field-collected (Ae. aegypti and Ae. albopictus) and laboratory-reared (Ae. aegypti) mosquito larvae and adults from Sri Lanka. Data confirm that the midgut bacterialItem 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 Microbiota Diversity associated with Mosquito Breeding Habitats in Kegalle District, Sri Lanka(2021-07) Ranasinghe, H.A.K.; Amarasinghe, L.D.The distribution, abundance, and individual fitness of mosquitoes are known to be dependent on associated microbiota composition with developing larvae. Identification of such naturally occurring microbiota and their interactions on mosquito larvae, in terms of parasitic, pathogenic, competitive or predatory organisms against larvae is beneficial. Such agents can be used for potential larval controlling approaches, in an environmental- friendly manner. Thus, the present study aimed to investigate the diversity of microbiota associated with mosquito larval habitats. Sampling was performed from a variety of breeding habitats in Kegalle district, Sri Lanka. Microbiota in water samples were preserved using Rose Bengal solution and Lugol‟s iodine, and were identified observing under the microscope, using standard identification keys. A variety of mosquito breeding habitats indicated the presence of 37 microbiota species under 9 phyla, belong to; Amoebozoa, Arthropoda, Ciliophora, Charophyta, Chlorophyta, Cyanobacteria/ Cyanophyta, Euglenozoa, Ochrophyta/ Heterocanthophyta and Rotifera. Except in coconut shells, every breeding habitat type investigated had the prevalence of rotifers, at least with one species. Thus the phylum Rotifera displayed the highest percentage of abundance (30.83%) of total microbiota. Species under phylum Charophyta had the lowest abundance among recorded (2.19% of total microbiota). Philodina citrina and Euglena pisciformis were found as species showing all three categories of abundance types; constant, common and accidental/or rare. Although the highest number of microbiota species were recorded from paddy field breeding habitats, all the species were existed as accidental or rare species in the habitat type according to their abundance. Only ponds and tree holes were recorded with beta diversities over 50% (high heterogeneity) in microbiota composition among the systems. Paddy fields, marshy lands, blocked drainages, metal containers, and leaf axils had beta diversities between 20 and 50%, indicating intermediate heterogeneity. The rest of the other habitats had beta diversities below 20%, indicating low heterogeneity. Paddy fields exhibited the highest gamma diversity (16) and Shannon-Weiner diversity (52.17) values. From the microbiota species recorded, Zoothamnium sp. was identified as an epibiont in Culex gelidus and Culex tritaeniorhynchus mosquito larvae. Updated information from the present investigation would be facilitated for implementing appropriate vector control interventions.Item Density and diversity of mosquito larvae associated with rice field and marshland habitats in two climatically different areas in Sri Lanka(International Journal of Entomological Research, 2014) Amarasinghe, L.D.; Weerakkodi, W.G.I.S.Rice field and marshland habitats have significant influence on production of mosquito larval populations including vector mosquitoes and hence the disease transmission. Study revealed that mosquito larval density in rice fields of two climatic regions were significantly different and that of rice fields in semi dry zone are more diverse than those of wet zone (H’ semi dry zone = 1.48; H’ wet zone = 1.35). Marshland habitats in wet zone were represented mainly by Culex gelidus. Both Culex gelidus and Culex tritaeniorhynchus larvae were highly available in rice fields of two climatic regions. They were mainly associated with high Total Dissolved Solids, (TDS) ≥10.00 mg/L, pH level of 6-8, low Dissolved Oxygen, (DO) 5.0 – 6.0 mg/L, low nitrate level, ≤ 5.0 mg/L and low phosphate level, ≤ 1.0 mg/L. However, they could tolerate a range of Biological Oxygen Demand (BOD) level in water. Mosquito larval density in two habitat types in wet zone was not significantly different. Temporal variation of C. gelidus and C. tritaeniorhynchus was positively or negatively correlated with cultivation cycle of rice in semi dry zone area. The main goal of this study was to determine the variation of mosquito larval diversity in the rice field and marshy land habitats in two climatically different areas, wet zone and semi-dry zone in Sri Lanka. Sampling of mosquito larvae was done using standard dipping method.Item Surveillance of Dengue Vector Mosquitoes and Their Abundance in the Kelaniya University Premises(Rajarata University, Sri Lanka, 2010) Wadduwage, P.S.; Amarasinghe, L.D.Item Nematicidal activity of aqueous extracts and dry matter of Tithonia diversifolia, Gliricidia sepium and Tagetes erecta against root-knot nematode, Meloidogyne incognita (Kofoid and White) on tomato (Lycopercicon esculentum Mill.)(Institute of Biology, Sri Lanka, 2015) Premachandra, N.W.; Amarasinghe, L.D.Item Study of diversity and abundance of microfauna and microflora associated with selected mosquito breeding habitats in Gampaha district in Sri Lanka(Institute of Biology, Sri Lanka, 2015) Karunathilake, K.D.K.M.; Amarasinghe, L.D.Item Rice field and marshland inhabiting mosquitoes and some physic-chemical and biological parameters affecting their abundance(Institute of Biology, Sri Lanka, 2013) Weerakkodi, W.G.I.S.; Amarasinghe, L.D.Item Temporal study on vector mosquitoes inhabiting rice fields during Yala season in Kurunegala area of Kurunegala district in Sri Lanka(Institute of Biology, Sri Lanka, 2013) Weerakkodi, W.G.I.S.; Amarasinghe, L.D.