Evaluation of Critical Larval Habitat Physico-chemical Factors on Embryonic Development and Adult Fitness of Culex quinquefasciatus mosquitoes (Diptera: Culicidae)

Abstract

This study was carried out to evaluate the influence of selected physico-chemical factors (water temperature, pH and hardness) on duration of embryogeny, egg hatchability, and adult fitness (Wing Length and Fluctuating Asymmetry) of Culex quinquefasciatus mosquitoes under laboratory conditions. Freshly laid egg rafts of this mosquito species were exposed to different levels of these factors. Four temperature regimens (i.e., 28, 30, 32 and 34oC), seven pH levels (i.e., 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 and 10.0) and seven water hardness levels (10, 50, 100, 150, 200, 250, and 300 mg/L of CaCO3) were independently tested on the egg rafts. The temperatures were regulated using thermostat, while pH and water hardness levels were maintained following standard procedures. The results revealed significant effects (p<0.05) of these physico-chemical factors on the entomological parameters measured. The duration of embryogeny varied significantly with values ranging from 19±1 to 24±4, 20±1 to 26±3 and 18±3 to 37.00±9.00 hours, respectively, for temperature, pH and Hardness. Egg hatchability rates fluctuated among the different treatments of a factor: temperature (77.13±48.46 to 204.75±20.27 larvae/egg raft), pH (113.25±13.92 to 218.75±22.34 larvae/egg raft) and water Hardness (98±12.13 to 214±10.22 larvae/egg raft). Wing length and fluctuating asymmetry also showed significant variation among the factors tested and between treatments of each factor. This study revealed profound effects of the physiochemical factors tested on the development and fitness of Cx. quinquefasciatus under laboratory conditions and could be employed in mosquito vectors control strategy.