Influence of biological and physicochemical characteristics of larval habitats on the body size of Anopheles gambiae mosquitoes (Diptera: Culicidae) along the Kenyan coast

Background & objectives: The number and productivity of larval habitats ultimately determine thedensity of adult mosquitoes. The biological and physicochemical conditions at the larval habitataffect larval development hence affecting the adult body size. The influence of biological and physicochemicalcharacteristics on the body size of Anopheles gambiae was assessed in Jaribuni village,Kilifi district along the Kenyan Coast.Methods: Ten cages measuring 1 × 1 × 1 m (1 m3) with a netting material were placed in 10 differentaquatic habitats, which were positive for anopheline mosquito larvae. Emergent mosquitoes werecollected daily by aspiration and the wing lengths were determined by microscopy. In the habitats,physicochemical parameters were assessed: pH, surface debris, algae and emergent plants, turbidity,substrate, nitrate, ammonia, phosphate and chlorophyll a content.Results: A total of 685 anopheline and culicine mosquitoes were collected from the emergent cages.Only female mosquitoes were considered in this study. Among the Anopheles spp, 202 were An.gambiae s.s., eight An. arabiensis, two An. funestus, whereas the Culex spp was composed of 214Cx. quinquefasciatus, 10 Cx. tigripes, eight Cx. annulioris and one Cx. cumminsii. The mean winglength of the female An. gambiae s.s. mosquitoes was 3.02 mm (n = 157), while that of An. arabiensiswas 3.09 mm (n = 9). There were no associations between the wing lengths and the environmentaland chemical parameters, except for a positive correlation between wing length of An. gambiae andchlorophyll a content (r = 0.622). The day on which the mosquitoes emerged was not significant forthe anopheline (p = 0.324) or culicine mosquitoes (p = 0.374), because the mosquito emerged fromthe cages on a daily basis.Interpretation & conclusion: In conclusion, there was variability in production of emergent mosquitoesfrom different habitats, which means that there should be targeted control on these habitatsbased on productivity