Zoology
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Item A Preliminary Study on the Relationship between Arthropod Diversity and Vegetation Diversity in Four Contrasting Ecosystems in Hanthana Mountain Range of Sri Lanka, during the Post-Monsoon Dry Season(2023) Weerathunga, W. A. Manasee; Athapaththu, A. M. Gihan; Amarasinghe, L. D.This study assesses the relationship between arthropod and vegetation diversity in four ecosystems with different types of vegetation, during a post-monsoonal season. We determined the arthropod diversity in vegetation surrounding an aquatic environment (AQ), a broad-leaved wet, evergreen forest ecosystem (BL), a Pinus caribaea monoculture plantation (PN), and a Pinus plantation artificially enriched with indigenous broad-leaved tree species (PNEN) located in the Hanthana mountain range, Sri Lanka. Arthropods randomly sampled from three randomly selected sites (5 m × 5 m) of each ecosystem were identified up to the highest possible taxa using standard identification keys. Woody and herbal vegetation was identified via a plant census. Arthropod and vegetation diversities were computed separately for each site using the Shannon–Wiener Index (H). Arthropods of 68 species and 43 families were found. AQ had the greatest arthropod diversity (H 2.642), dominated by Olios spp., followed by BL (H 2.444), dominated by a tettigonid species, Oxytate spp. and Psechrus spp. PN was third (H 1.411), dominated by Dicaldispa spp. PNEN had the lowest (H 1.3500), dominated by an ant species. Contrastingly, PNEN had the highest plant diversity (H 2.614) and PN, the lowest (H 0.879). In AQ, BL, and PN, the arthropod diversity was linearly dependent on plant diversity (R2 0.423, p≤ 0.001), whereas it was not so when PNEN was also included (R2 0.008, p≤ 0.001). This shows that higher plant diversity contributes to greater arthropod diversity in ecosystems where human intervention is minimal. But this pattern was not visible in PNEN, which is an artificially created ecosystem.Item Volatiles from host plant brinjal attract the brinjal Fruit and Shoot Borer -Leucinodes orbonalis Guenee(2021) Nusra, M. S. F.; Udukala, D. N.; Amarasinghe, L. D.; Paranagama, P. A.Blinjal Fruit and Shoot Borer- Leucinodes orbo11alis Guenee is a major insect pest on brinjal- Sola11u111 111elo11ge11a worldwide. An effective strategy used in developing pest controlling agents is the synergism between insect pheromones and host plant volatiles, which can increase the attraction of insect pest. The present study was aimed at investigating the chemical consti tuents and attractant effects of the volatiles extracted from different parts of the host plant brinjal on the behavior of ad ult L. orbo11alis. Bioassay using Y-shaped olfactometer revealed that the one-day old virgin female, gravid female and male insects respond positively to the host plant volatiles exU'acted from fruits, leaves and shoots but not to that of flowers. It was shown that the gravid females were significantly attracted to all three volatiles (p < 0.05). Bioassay using X-shaped olfactometer identified that all three types of insects highly preferred the volatiles from fruits (p < 0.05). Gas chromatography-mass specuomeuy analysis of volatiles indicated that brinjal plant produces volatile seconda1y metabolites, which include 2,2' -(Ethane-l ,2-diylbis(oxy))bis(ethane-2,1-diyl) di benzoate (12.11 %), 3,7-dimethylocta-1,6-dien-3-ol (22.38%), Benzyl alcohol (22.9%) and Benzyl alcohol (27.06%) as major constituents from fruits, shoots, leaves and flowers respectively. Responses of insects to the volatiles from host plant in the absence of visual cues direct us to focus on the importance of host plant volatiles to locate the plant. Results of this study emphasize the major role that host plant volatiles play in the attraction of insect pests towards the plant.Item Assessingthe Filariasis Causing Parasites in Adult Mosquitoes and the Vector Mosquito Larval Breeding in Selected Medical Officer of Health Areas in Gampaha District, Sri Lanka(Journal of Tropical Medicine, 2021) Pilagolla, S. A. S.; Amarasinghe, L. D.The present study was conducted to determine the prevalence of filariasis causing parasites in adult mosquitoes and vector mosquito larval breeding in four Medical Officer of Health (MOH) areas in Gampaha district, Sri Lanka. Adult female mosquitoes at their resting places were collected using a prokopack aspirator operated twice a day from 7.00 am to 8.00 am and 8.00 pm to 9 pm in predetermined dates. Microfilarial worms in dissected mosquitoes were morphologically identified. Nine species of mosquitoes, namely, Culex quinquefasciatus, Cx. pipiens, Cx. fuscocephala, Cx. gelidus, Armigeres subalbatus, Mansonia uniformis, Ma. annulifera, Aedes aegypti, and Ae. Albopictus, were captured. A total of 1194 mosquito larvae were collected that belonged into three genera, namely, Culex (62.73%), Armigeres (25.62%), and Mansonia (11.64%), from blocked drains, polluted drains, blocked canals, large polluted water bodies, stagnant water bodies, marsh lands, rice field mudflats, and concrete pits. Large polluted water bodies (Shannon-Wiener diversity index/H’ = 1.5591) were the most diversed habitat type. In breeding water, average pH mainly lied in between 6 and 8 and average dissolved oxygen ranged from 3 to 7 mg/L. Cx. quinquefasciatus and Armigeres subalbatus adult female mosquitoes captured from Kelaniya MOH area were positive for microfilariae and were identified as Wuchereria bancrofti and Dirofilaria repens, respectively. This study concludes possible lymphatic filariasis situation is in extremely very low level persistent (0.06%) where transmission cannot be sustained and is restricted only to isolated pockets in the study area. The zoonotic strains of filariasis causing subcutaneous dirofilariasis in humans by Dirofilaria repens is continuing to survive due to the presence of stray dogs that serve as reservoir hosts.Item Naturally Occurring Microbiota in Dengue Vector Mosquito Breeding Habitats and Their Use as Diet Organisms by Developing Larvae in the Kandy District, Sri Lanka(BioMed Research International, 2020) Ranasinghe, H. A. K.; Amarasinghe, L. D.Naturally occurring microbiota in mosquito larval habitats are among biotic factors which affect the population dynamics of developing larvae. Many microbiota species serve as food items for vector mosquito larvae, and food limitations within habitats adversely affect larval survival, developmental rate, adult fitness, and thereby vector competence. Therefore, identification of microbiota as associates with larvae reveals their relationship between each other as parasites, pathogens, epibionts, or diet organisms. Analysis of associated microbiota species in the dengue vector larval breeding habitats (n = 40) and the mosquito larval gut content were conducted in Kandy District in Sri Lanka. Study revealed that a total of 22 microbiota species belong to nine phyla (Amoebozoa, Bacillariophyta, Ciliophora, Chlorophyta, Sarcodina, Cyanobacteria/Cyanophyta, Euglenozoa, Ochrophyta/Heterokontophyta, and Rotifera) were encountered from different Ae. aegypti mosquito breeding habitats while 26 microbiota species that belonged to ten phyla were recorded from Ae. albopictus mosquito breeding habitats with one additional phylum Arthropoda. Considering Ae. aegypti breeding habitats, only Philodina citrina in low roof gutters existed as constant species. Considering Aedes albopictus breeding habitats, Volvox aureus in plastic containers, Lecane luna in coconut shells, Phacus pleuronectes in concrete slabs, and Pinnularia sp. in tree holes existed as constant species. The rest of the microbiota existed as common or accidental/rare species in a variety of habitat types. The Shannon-Weiner diversity (21.01 and 19.36) and gamma diversity (eight and eight) of the microbiota associated with Ae. aegypti and Ae. albopictus larvae, respectively, in ponds were found to be higher than other types of breeding habitats recorded during the study. Twelve microbiota species were recorded from larval gut analysis as food organisms of both species of mosquito larvae. However, the distribution of gut microbiota species differed between Ae. aegypti and Ae. albopictus (Chi − square = 21:294, P = 0:002). Identification of microbiota as food items of vector mosquito larvae led to a focus on larval food limitation by introducing food competitors, which could be a potential additional tool for integrated vector control approaches within the country.