Responses to Alteration of Atmospheric Oxygen and Social Environment Suggest Trade-Offs among Growth Rate, Life Span, and Stress Susceptibility in Giant Mealworms (Zophobas morio)

Abstract

Growth rate, development time, and response to environmental stressors vary tremendously across organisms, suggesting trade-offs that are affected by evolutionary or ecological factors, but such trade-offs are poorly understood. Prior studies using artificially selected lines of Manduca sexta suggest that insects with high growth rates, long development time, and large body size are more sensitive to hypoxic or hyperoxic stresses, such as reactive oxygen species (ROS) production, but the mechanisms and specific life-history associations remain unclear. Here, we manipulated the social environment to differentiate the effects of size, growth rate, and development time on oxygen sensitivity of the giant mealworm, Zophobas morio. Crowding reduced growth rates but yielded larger adults as a result of supernumerary molts and longer development times. The juvenile performance (growth rate, development time, adult mass) of crowd-reared mealworms was less sensitive to variation in atmospheric oxygen than it was for individually reared animals, consistent with the hypothesis that high growth rates are associated with increased sensitivity to ROS. Life span in normoxia was extended by crowd rearing, perhaps due to the larger size and/or increased resources of the larger adults. Life spans of crowd-reared animals were more negatively affected by hypoxia or hyperoxia than life spans of individually reared animals, possibly due to the longer total stress exposure of crowd-reared animals. These data suggest that animals with high growth rates experience a negative trade-off of performance with greater sensitivity to stress during the juvenile phase, while animals with long development times or life spans experience a negative trade-off of greater susceptibility of life span to environmental stress.

White Paper: An Integrated Perspective on the Causes of Hypometric Metabolic Scaling in Animals

“…Kearney and White suggested that if this hypothesis is correct, ultimate size and growth rate in animals should be directly proportional to blood oxygen levels ( Kearney and White 2012 ). Most animals that have been tested are smaller when developing in hypoxia, but this generally occurs via hormonally mediated mechanisms rather than oxygen-limitation of metabolic rate, and hyperoxia rarely increases animal body size ( Owerkowicz et al 2009 ; Wang et al 2009 ; Harrison et al 2015 ; VandenBrooks et al 2020 ). Kearney and White also suggested that this theory predicts that exercise training should reduce the scaling exponent, and that the thermal tolerance zone for aerobic respiration should be inversely related to body size ( Kearney and White 2012 ).…”

Effects of diet and feed composition on antibacterial activity of hemolymph of saproxylic beetles: A case study of Zophobas atratus (Coleoptera: Tenebrionidae)

“…Z. atratus are found in tropical regions of the Central and Southern America, while larvae (saproxylic beetles) are trophically associated with large timber remnants of hard wood, and there is indication to feeding by bat excretions (Tschinkel, 1981(Tschinkel, , 1984Marcuzzi, 1984). The species has currently been brought to different regions of Europe and Asia, and beetle larvae are used as animal feed in insectaries and zoos, or as a model object in research to solve various problems (Bulet et al, 1991;Yuan et al, 2012;Fursov & Cherney, 2018;VandenBrooks et al, 2020).…”