ASRS 2025 http://ir.lib.seu.ac.lk/handle/123456789/7862 2026-04-21T11:41:35Z 2026-04-21T11:41:35Z Hansamali, S. Vinobaba, M. Udayakantha, W. S. http://ir.lib.seu.ac.lk/handle/123456789/7878 2026-04-21T10:29:42Z 2025-10-30T00:00:00Z

Title: Ant (Hymenoptera, Formicidae) diversity across four selected habitats in Batticaloa District, Sri Lanka Authors: Hansamali, S.; Vinobaba, M.; Udayakantha, W. S. Abstract: Ant diversity in the eastern part of Sri Lanka remains poorly studied. This study aimed to assess worker ant diversity across four different habitats in Batticaloa District in the eastern part of Sri Lanka: Cashew Forest Area (CFA) and Crop Farm at the Faculty of Agriculture (FOA), Iluppadichenai Bare Land (IBL), and Kallady Beach (KB), from August to October 2024. Ant sampling was conducted along three 100 m transects per site using a combination of honey baiting, leaf litter sifting, soil sifting, and pitfall trapping. Honey bait samples were collected after one hour, and pitfall traps were retrieved after three hours. All specimens were preserved in 70 % ethanol and Ants in each collection were sorted and identified to the furthest possible taxonomic levels under a low power stereo-microscope (Motic SMZ-140) at suitable magnifications in the laboratory. Total of 26 ant species belonging to 15 genera across four subfamilies Dolichoderinae, Formicinae, Myrmicinae, and Pseudomyrmecinae, were identified. Six ant species, Oecophylla smaragdina Fabricius, 1775, Polyrhachis punctillata Roger, 1863, Monomorium pharaonis (Linnaeus, 1758), Monomorium sahlbergi Emery, 1898, Solenopsis geminata (Fabricius, 1804), and Tetramorium bicarinatum (Nylander, 1846), were commonly found across all four habitats. With the presence of Tetraponera allaborans (Walker, 1859), the Subfamily Pseudomyrmecinae was recorded for the first time from the Batticaloa District. Statistical analysis using the Chi-Square test (χ² = 3.2972, p = 0.348) indicated no significant difference in species distribution among the sites. The study highlights the effectiveness of multi-method sampling in capturing ant diversity and contributes baseline data for future research on ant diversity in eastern Sri Lanka.

2025-10-30T00:00:00Z Thasajini, S. Mondoni, Andrea Wijayasinghe, Malaka M. Gehan Jayasuriya, K. M. G. http://ir.lib.seu.ac.lk/handle/123456789/7877 2026-04-21T10:26:51Z 2025-10-30T00:00:00Z

Title: Seed germination responses of Sri Lankan wild rice species (Oryza nivara and Oryza rhizomatis) under drying and flood conditions Authors: Thasajini, S.; Mondoni, Andrea; Wijayasinghe, Malaka M.; Gehan Jayasuriya, K. M. G. Abstract: Sri Lankan wild rice, Oryza nivara and O. rhizomatis, are two threatened species occurring in habitats characterised by different patterns of dry and wet periods. Both species have dormant seeds at dispersal, and little is known about their germination phenology. The aim of this study was to determine the germination strategies of these species, to contribute to their conservation. We hypothesized that seed germination behaviour is related to their habitat conditions. Germination phenology was studied by evaluating the prevailing environmental conditions that seeds experience after dispersal, i.e., a dry condition followed by a wet condition. Immediately after harvest, seeds were exposed to nine types of dry- storage conditions (0, 2, 4, 6, 8, 10, 12, 18 or 20 months) at 25°C and ~ 60 % RH. Four replicates each of twenty seeds were incubated on moist filter paper at 25°C for 12 hrs/12hrs under light/darkness for germination testing. Twenty seeds with Four replicates were used in the germination test. Seeds retrieved after 6, 8, 18 and 20 months of dry storage, were subjected to 1, 2- and 4-weeks of flood treatment. Seed germination of both species increased with increasing dry-storage periods until 12 months. Under prolonged dry storage, seed germination declined for O. rhizomatis (6 weeks – 44 %) and none of the seeds germinated in O. nivara. In O. rhizomatis, short flooding treatment (1 week) elicited higher germination (64%) compared to just dry-stored seeds, while prolonged flooding (2-4 weeks) had the opposite effect. Conversely, there was not a significant effect of flooding on seed germination for O. nivara. Overall, our results show that prolonged drying breaks dormancy in both species, a strategy to prevent seed germination right after dispersal, when high risk of drought may result in low seedling survival. The species also show distinctive dormancy cycling caused by either prolonged flooding (O. rhizomatis) or drying (O. nivara), which may contribute to their different geographical and ecological distribution. The increase in precipitation expected with climate change may constrain recruitment success due to lack of sufficient dry after-ripening and/or an excess of flooding. This risk might be especially high for the endemic O. rhizomatis. These results can guide conservation and restoration by identifying optimal drying and flooding conditions for seed germination and storage.

2025-10-30T00:00:00Z Thadsana, S. Sudesh Udayakantha, W. http://ir.lib.seu.ac.lk/handle/123456789/7876 2026-04-21T10:22:32Z 2025-10-30T00:00:00Z

Title: Preliminary Inventory ff mosquito diversity In The Kalmunai region and Faculty of Applied Sciences, SEUSL Authors: Thadsana, S.; Sudesh Udayakantha, W. Abstract: Mosquitoes are important vectors of many communicable diseases such as dengue, chikungunya, lymphatic filariasis, and malaria. Assessing mosquito species diversity in specific ecological settings is important for effective surveillance and vector management. The present study investigated mosquito diversity for the first time in two localities of the Ampara District, Sri Lanka. Kalmunai town area and the premises of the Faculty of Applied Sciences, South Eastern University of Sri Lanka, Sammanthurai from 1st November 2024 to 1st April 2025. Ovitraps were prepared using 250 ml plastic cups, half-filled with paddy straw infusions at four concentrations, 100%, 75%, 50%, and 25%, while distilled water served as the control. A small wooden stick was placed in each trap to facilitate oviposition. Ten households in Kalmunai and six localities within the university premises were selected, with five Ovitraps (one for each treatment) deployed at each site. Traps were retrieved after 14 days, and eggs and larvae were incubated under controlled laboratory conditions. Emerging adults were identified to the lowest possible taxonomic level using taxonomic keys. Species richness and relative abundance were analyzed statistically using Shannon–Wiener diversity indices. Nineteen mosquito species belonging to four genera, Aedes, Anopheles, Culex, and Mansonia, were observed in the Kalmunai region, with Aedes aegypti and Aedes albopictus being the most abundant species. In the Faculty area, five species were recorded, with Aedes aegypti dominant, followed by Aedes albopictus and Mansonia uniformis. The species documented during the study, Aedes aegypti, A. albopictus, A. vittatus, A. macdougalli, A. flavipes, A. dorsalis, A. lankaensis, A. lineatopennis, A. vexans, A. seculatus, A. krombeini, Anopheles culicifacies, A. subpictus, A. varuna, Culex quinquefasciatus, C. gelidus, Mansonia uniformis, and M. indicus, constitute the first preliminary inventory of mosquitoes for the region. The Shannon–Wiener diversity index values were 2.76 for the Kalmunai region and 1.48 for the Faculty premises, indicating higher species diversity in the former. Aedes aegypti (34–41%) and Aedes albopictus (28–33%) were the dominant species across both sites.

2025-10-30T00:00:00Z Thomas, I. B. K. Fernandob, S. Abeykoonb, M. R. Jayasinghe, C. D. Abeysinghe, D. T. Senthilnithy, R. http://ir.lib.seu.ac.lk/handle/123456789/7875 2026-04-21T10:17:56Z 2025-10-30T00:00:00Z

Title: Developmental and biochemical disruptions triggered by trace lead exposures in zebrafish (danio rerio) embryos and larvae Authors: Thomas, I. B. K.; Fernandob, S.; Abeykoonb, M. R.; Jayasinghe, C. D.; Abeysinghe, D. T.; Senthilnithy, R. Abstract: Lead is a ubiquitous toxic heavy metal that poses substantial threats to biodiversity and aquatic ecosystems. Despite its critical impacts on the environment and human health, literature on lead-induced toxicities at trace concentrations remains scarce. Hence, this study aimed to elucidate the toxicities induced by trace concentrations of Pb2+ (2.5 – 40.0 µgL−1) on zebrafish embryos and larvae. Embryos at 2 hpf were exposed to a series of Pb2+ concentrations for 24, 48, 72, and 96 hours following the OECD guideline No. 236. Survival, hatchability, lethal concentration 50 (LC50), and toxicological endpoints were determined. A sublethal Pb2+ concentration (8.79 µgL-1) was then employed to assess heart rate, morphological parameters, morphological deformities, and biochemical alterations. The LC50 value decreased from 137.081 ± 62.114 µgL−1 at 24 hpf to 87.863 ± 24.546 µgL−1 at 96 hpf, reflecting increasing toxicity with prolonged exposure. Pb2+ exposure increased embryo coagulation and led to notable declines in survival and hatchability, indicating elevated embryonic sensitivity during early development. Sublethal Pb2+ exposure significantly reduced heart rate at 72 hpf, resulted in marked reductions in multiple morphological parameters (total body length, tail area, and trunk area) and induced substantial morphological deformities, including spine deformity and uninflated swim bladder, both at 96 and 120 hpf. Biochemical analyses revealed elevated liver-specific enzymes (alkaline phosphatase, and glutamate pyruvate transaminase), increased creatinine levels, reduced total protein content, suppressed catalase activity, and lowered T helper 2 cell (IL-10) levels in tissue lysates, implying significant hepatic, renal, oxidative, and immune dysfunction. These findings underscore the severity of lead toxicity at concentrations typically prevailing in the environment and highlight zebrafish utility in assessing environmental contaminants. Nonetheless, further research coupled with molecular-level studies is warranted to elaborate the mechanisms of action of environmental pollutants, including heavy metals at ecologically relevant doses.

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