Oviposition preferences of dengue vectors;Aedes aegyptiandAedes albopictusin Sri Lanka under laboratory settings

Abstract

Investigations on oviposition behaviour of dengue vectors are critical for effective controlling of vector breeding. Therefore, the aim of the present study was to determine the oviposition behaviour of dengue vectors, Aedes aegypti and Aedes albopictus in Sri Lanka. Batches of 1000 adult mosquitoes (1 : 1, male: female ratio) housed in rearing cages were used for each experimental setup from Ae. aegypti and Ae. albopictus. Oviposition responses with respect to the size of the ovitrap, colours of the ovitrap, water source, sodium chloride (NaCl) concentration and presence/absence of larvae were evaluated by enumerating the number of eggs laid in the ovitraps. The analysis of variance and cluster analysis were used to investigate the significance in the variations among oviposition. The number of eggs laid by both species were improved with the increasing size of ovitraps. Ae. albopictus indicated the highest mean number of eggs in 0.2% of NaCl than in the ovitraps filled with distilled water. However, the egg laying preference was reduced with increasing salinity in both species. Drain water with low dissolved oxygen (DO) level (0.43 ± 0.12 mg l-1) was the preferred water source for both species, while a significantly high oviposition rate was observed in ovitraps with larvae. Black colour ovitraps attracted the majority of gravid females, while white was least preferred. There were no significant variations among oviposition behaviours of Ae. albopictus and Ae. aegypti. The ability of these vectors to breed in waste water with low DO levels may lead them to attain wide dissemination in the natural environment, enhancing their potential threat to human life.

Coagulation-Flocculation: A potential Application for Mosquito Larval Source Management (LSM) with No Insecticide Resistance

“…We speculated in this study mosquitoes' oviposition behavior is mainly in uenced by vision. Studies have shown that yellow is more attractive to Culex pipiens pallens for laying eggs than white [39], which in this experiment after coagulation-occulation, yellow alum oc deposited at the bottom of the ovitrap, which is considered to be nutrient-rich for larvae growing, therefore more female Culex pipiens pallens mosquitoes preferred O1 as breeding sites [40].…”

“…Though in laboratory, coagulant PACl could promote oviposition preference of female Culex pipiens pallens to some extent, however, considering the limitation of laboratory, and actually female Culex pipiens pallens prefer ovitrap in deep color as breeding sites [39], PACl may avoid mosquitoes' oviposition if used out-doors. Still, coagulant modi cation may help to solve.…”

Development of an Alternative Low-Cost Larval Diet for Mass Rearing of Aedes aegypti Mosquitoes In Sri Lanka

“…Collected eggs were transferred to 1 L plastic trays with deoxygenated water in the Arthropod Containment Facility at the MMU and kept for 8 hours (hrs) for hatching. Hatched larvae were counted and transferred into properly labeled plastic trays (40 cm x 30 cm x 5 cm) containing 2 L of distilled water [16]. For the purpose of quality control and maintenance of uniform size of the larvae; a density of 1 000 larvae per tray was maintained.…”

“…Sugar solutions were replaced every two days to avoid any fungal growth inside the cage. Mosquitoes were reared in an environment with a temperature of 26-27 o C and 78-80% RH under 12 hrs light and 12 hrs dark cycle [16].…”

“…The number of eggs laid by the females, 2 days after blood feeding was recorded for the three larval diet treatments, separately. In addition, the collected eggs were hatched and the fertility rates were calculated as the percentage of the number of hatched L 1 larvae to the number of eggs laid [16]. Further, the number of days required to eliminate 50% of the male mosqiuotes emerged from different larval diets were reported as male longevity [20].…”