ICAPS 2023

Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/26832

Browse

Now showing 1 - 2 of 2

Comparative Effect of Nanoparticles of Sliver, Europium Doped ZnO and CaF2 on Aedes aegypti and Daphnia magna
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Kumarasinghe, G. D. S. S.; Amarasinghe, L. D.; De Silva, C. R.
Aedes aegypti mosquitoes are responsible for transmitting dengue fever. Using nanoparticles is a better suggestion to combat vector mosquito spread. Daphnia magna is the keystone species in freshwater food webs. The sensitivity of Daphnia magna to low metal concentrations underscores its importance in evaluating the impact of nanoparticles on the ecosystem. This study examined the impact of Silver, ZnO, CaF2, Europium-doped ZnO, and CaF2 nanoparticles on Aedes aegypti larvae and adult Daphnia magna. The batch of 25 third instar larvae of Aedes aegypti and the batch of 25 adult Daphnia magna were exposed to each nanoparticle in a concentration series for 24 and 48 hours. For Aedes aegypti, nanoparticles of ZnO and CaF2 at 20 mg/L, 40 mg/L, 60 mg/L, 80 mg/L, and 100 mg/L; nanoparticles of Europium-doped ZnO and CaF2 at 50 mg/L; and Silver nanoparticles at 1 mg/L, 2 mg/L, 3 mg/L, 4 mg/L, and 5 mg/L. For the Daphnia magna, ZnO nanoparticles at 0.2 mg/L, 0.4 mg/L, 0.6 mg/L, 0.8 mg/L, and 1 mg/L; Europium-doped ZnO nanoparticles at 0.5 mg/L; CaF2 nanoparticles at 1 mg/L, 2 mg/L, 3 mg/L, 4 mg/L, and 5 mg/L; Europium-doped CaF2 nanoparticles at 4 mg/L; and Silver nanoparticles at 2.36 mg/L. The percentage mortality of Aedes aegypti larvae and Daphnia magna was calculated for each nanoparticle. The study revealed that nanoparticles of ZnO and CaF2 did not affect Aedes aegypti larvae but caused significant mortality in Daphnia magna. LC50 value at 24 hours for ZnO nanoparticles was 0.51 mg/L, while for CaF2 nanoparticles, it was 4.44 mg/L. The study also revealed that increasing europium doping in ZnO and CaF2 nanoparticles led to higher Daphnia magna mortality. The study revealed that exposure to silver nanoparticles for 24 hours significantly increased Aedes aegypti larvae mortality rates. LC50 value was 2.36 mg/L. All Daphnia magna were dead within 24 hours of exposure to silver nanoparticles. The study concludes that ZnO and CaF2 nanoparticles did not affect Aedes aegypti larvae. Silver nanoparticles showed lethal effects but cannot be recommended for Aedes aegypti control due to being toxic to Daphnia magna, a keystone species in aquatic ecosystems.
The effect of egg desiccation period on the hatching success, morphometrics of emerged larvae and F1 generation adults of Aedes aegypti and Aedes albopictus (Diptera: Culicidae)
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Kumari, A. G. Y. G.; Dalpadado, R.; Amarasinghe, L. D.
Dengue is a seasonal vector-borne disease that is transmitted by female Aedes aegypti and Aedes albopictus mosquitoes. One of the most significant challenges in controlling these mosquitoes is the ability of Aedes eggs to withstand prolonged desiccation. This study aimed to investigate the effect of egg desiccation on the hatchability, larval and adult morphometrics, and duration of adult emergence of Ae. aegypti and Ae. albopictus. The Aedes eggs were collected from the field using oviposition traps and soaked in larval-rearing trays. Hatched larvae were reared with fish feed. They were differentiated into Ae. aegypti and Ae. albopictus and transferred to separate pupalrearing containers. The resulting adult mosquitoes were provided with a sugar solution and a cattle blood meal using a membrane feeding system. They were allowed to lay eggs on cloth strips. Initially, the hatchability of fresh eggs was calculated for two species. The head length and total length of the fourth instar larvae and head, thorax, abdomen, total length, wing length, and wing width of adults of both species that emerged from fresh eggs were measured. The days needed for adult emergence from fresh eggs were counted. Subsequently, other egg sheets were air dried and stored within the insectary (at 27±2°C and 75±5 % humidity), and monthly measurements of the aforementioned parameters were collected for eggs subjected to desiccation over six months. According to the results, the hatchability of both Ae. aegypti and Ae. albopictus decreased with increasing egg desiccation periods. The hatchability of Ae. aegypti and Ae. albopictus eggs was highest (75.0±0.6% and 58.3±0.3% respectively) when the eggs were fresh, and lowest (22.0±1.2% and 13.3±0.9% respectively) when they were desiccated for six months. There was a strong negative correlation between hatchability and the desiccation period of both Ae. Aegypti and Ae. albopictus (Pearson's correlation, p<0.05, R2 = 0.840 and R2 = 0.957 respectively). Pearson's correlation also indicated a strong negative correlation between egg desiccation period and head length (p<0.05, R2 = 0.875 for Ae. aegypti and R2 = 0.846 for Ae. albopictus), as well as total length (p<0.05, R2 = 0.812 for Ae. aegypti and R2 = 0.888 for Ae. albopictus) of the fourth instar larvae. The adult emergence was delayed with increasing egg desiccation periods, with the longest duration (Ae. aegypti; 15.0 ± 0.2 days and Ae. albopictus; 26.0 ± 0.2 days) observed when eggs were desiccated for six months. However, no significant differences were found in the morphometrics of adult mosquitoes of both species that emerged from desiccated eggs (one-way ANOVA, p > 0.05). In conclusion, the study showed that prolonged egg desiccation reduced hatchability, delayed adult emergence, and negatively affected the morphometrics of fourth instar larvae of Ae. aegypti and Ae. albopictus. However, the morphometrics of the F1 generation adult mosquitoes were not significantly different from those of fresh eggs, suggesting that the egg desiccation period does not negatively affect the overall morphometrics of adult Aedes mosquitoes.