Influence of rearing-water temperature on life stages’ vector attributes, distribution and utilisation of metabolic reserves in Culex quinquefasciatus (Diptera: Culicidae): implications for disease transmission and vector control

Abstract

Background: This study aims at determining the effects of rearing water temperature on immature development, adult vectorial attributes and teneral accumulation in Culex quinquefasciatus (Cx. quinquefasciatus) mosquitoes. Immature life stages of the species were reared (to adulthood) in water media with temperature regimens of 28, 30, 32 and 34 °C generated and maintained by digital electrical thermostats. Immature and adult vectorial attributes (i.e. duration of development, growth rates, immature and adult survivorship, emergence rates and adult longevity), and rates of accumulation, distribution and utilisation (for pupation and eclosion) of teneral reserve (lipid, glucose, glycogen and protein) by life stages of the species were determined. Result: Results revealed significant negative effects of temperature increase on all parameters measured. Among these, only rate of larval growth (range = 0.0589 ± 0.0017 to 0.0930 ± 0.0003 mg/day) increased with temperature rise; others reduced with rise in temperature. Total immature duration (9.75 ± 0.09 to 6.43 ± 0.11 days), immature survivorship (94.01 ± 0.18 to 73.26 ± 3.72%), total emergent adults (72.00 ± 2.14 to 14.50 ± 2.67 adults/100 larvae), percentage of emergence, adult daily survivorship (76.86 ± 1.87 to 63.66 ± 0.18%) and post-emergence longevity (23.91 ± 2.97 to 16.90 ± 1.97 days) reduced with increase in temperature. Accumulation of teneral components increased across larval instars, but decreased with temperature rise and at metamorphosis (pupation and eclosion). Immature composition for lipid, glucose, glycogen and protein ranged, respectively, from 9.79 ± 1.05 to 20.07 ± 0.33, 8.49 ± 0.44 to 14.33 ± 0.44, 28.19 ± 2.34 to 42.87 ± 0.12 and 24.11 ± 0.71 to 35.55 ± 0.15 μg/mosquito. While, adult values for these ranged from 7.53 ± 0.40 to 20.66 ± 0.61, 7.45 ± 0.87 to 13.86 ± 0.83, 22.63 ± 0.85 to 33.64 ± 0.79, and 17.81 ± 1.02 to 31. 45 ± 1.40 μg/mosquito, respectively. Glycogen and protein had the highest rates of accumulation, while metabolic reserves utilised for pupation and eclosion varied significantly with temperature change. Conclusion: This study revealed significant effects of temperature on the entomological parameters measured. Vectorial fitness indices, such as duration of immature development and survivorship, emergence rates, adult survivorship and longevity, and teneral accumulation and utilisation, tend to reduce with increase in temperature, while larval growth rates increased with temperature rise. The information generated is vital for developing temperature-based models and life-stage control strategies.