Effects of chronic hypoxia, normoxia and hyperoxia on larval development in the beetle Tenebrio molitor

The effect of chronic hypoxia and hyperoxia on survival, developmental time, body mass, growth and moulting in Tenebrio molitor larvae were studied. Larvae were reared from eggs to pupae at 25°C, 70% relative humidity, in 3 different oxygen environments: normoxia (21%), hypoxia (10%) and hyperoxia (40%) balanced by nitrogen (at sea level). 20% of larvae in hypoxia, and 96% in normoxia and hyperoxia survived to pupation. It was estimated that hypoxic, normoxic and hyperoxic larvae moulted 12.3, 5.8 and 3.9 times, respectively, between day 38 and the beginning of pupation. Body mass growth patterns were fitted to 3rd degree polynomial equations. The lowest growth rate was found in the hypoxic group. No differences in growth rate during the steep mass increase phase were found between the hyperoxic and the normoxic larvae. Despite a low total number of moults in hyperoxia, larvae finally reached a body mass similar to those reared in normoxia. This suggests that oxygen availability affects moulting. Our results indicate that the trigger for moulting is related to the atmospheric oxygen availability and to the size of the tracheal system, which must supply sufficient oxygen to meet tissue demands.