Critical thermal maximum and water loss in developmental stages of the lesser mealworm Alphitobius diaperinus

摘要

Effect of increasing ambient temperature on water loss and thermosensibility (critical thermal maximum, CT_max) was examined in last instar larvae, pupae and adults of Alphitobius diaperinus (Coleoptera: Tenebrionidae). CT_max was significantly lower in adults and pupae than in last instar larvae (last instar larvae: CT_max = 48.5 ± 0.5°C, pupae: CT_max = 48.0 ± 0.9°C, adult: CT_max = 47.8 ± 1.1°C). Moreover, acclimation had no significant impact on adult CT_max. Water loss was recorded continuously between 20 and 60°C and differed significantly among the three developmental stages. Last instar larvae and adults exhibited similar water losses with a sharp increase above a critical transition temperature (CTT), which is about 40°C. In pupae, a significantly lower rate of water loss was found, even above 40°C. An increase of 10°C (25 - 35°C) induced a 2.0 and 2.6-fold increase of the water loss in pupae and adults of A. diaperinus ( Q₁₀ = 2.05 ± 0.70 and 2.49 ± 1.31, respectively) vs. 3.52 ± 1.27 in larvae. Water loss was strongly increased over the range 35 - 45°C in larvae and adults ( Q₁₀ = 6.85 ± 1.90 and 8.51 ± 2.32). In pupae, Q₁₀ was also increased over the range 35 - 45°C ( Q₁₀ = 3.76 ± 1.83), but less than in pupae and adults. In A. diaperinus pupae, characterized by motionless without feeding ability, lower metabolic rate, better ability to keep the spiracles closed more often thanks to a specific structure, and the cuticular composition (surface lipids and proteins) may explain the reduced water loss[ Acta Zoologica Sinica 52(1):79 – 86 , 2006] .