Biology Department, Missouri University of Science and Technology, United States.
Biology Department, Missouri University of Science and Technology, United States.
J Insect Physiol. 2020 Jan;120:103988. doi: 10.1016/j.jinsphys.2019.103988. Epub 2019 Nov 28.
The metabolic cost of growth, which quantifies the amount of energy required to synthesize a unit of biomass, is an important component of an animal's ontogenetic energy budget. Here we investigated this quantity as well as other energy budget variables of the larvae of a holometabolous insect species, Vanessa cardui (painted lady). We found that the high growth rate of this caterpillar cannot be explained by its metabolic rate and the percentage of the metabolic energy allocated to growth; the key to understanding its fast growth is the extremely low cost of growth, 336 Joules/gram of dry mass. The metabolic cost of growth in caterpillars is 15-65 times lower than that of the endothermic and ectothermic species investigated in previous studies. Our results suggest that the low cost cannot be attributed to its body composition, diet composition, or body size. To explain the "cheap price" of growth in caterpillars, we assumed that a high metabolic cost for biosynthesis resulted in a high "quality" of cells, which have fewer errors during biosynthesis and higher resistance to stressors. Considering the life history of the caterpillars, i.e., tissue disintegration during metamorphosis and a short developmental period and lifespan, we hypothesized that an energy budget that allocates a large amount of energy to biosynthesizing high quality cells would be selected against in this species. As a preliminary test of this hypothesis, we estimated the metabolic cost of growth in larvae of Manduca sexta (tobacco hornworm) and nymphs of Blatta lateralis (Turkestan cockroach). The preliminary data supported our hypothesis.
生长代谢成本（growth metabolic cost），即合成单位生物量所需的能量，是动物个体能量预算的重要组成部分。在这里，我们研究了鳞翅目完全变态昆虫烟粉蝶幼虫（Vanessa cardui）的这一数量以及其他能量预算变量。我们发现，这种毛毛虫的高生长率不能仅用其代谢率和代谢能量分配给生长的百分比来解释；理解其快速生长的关键是极低的生长成本，为 336 焦耳/克干物质。与之前研究的恒温动物和变温动物相比，毛毛虫的生长代谢成本低 15-65 倍。我们的研究结果表明，这种低成本不能归因于其身体成分、饮食成分或体型。为了解释毛毛虫生长的“低成本”，我们假设生物合成的高代谢成本导致了细胞的“高质量”，这使得细胞在生物合成过程中错误更少，对胁迫的抵抗力更高。考虑到毛毛虫的生活史，即变态过程中的组织解体以及短暂的发育期和寿命，我们假设在该物种中，将大量能量分配给合成高质量细胞的能量预算将受到选择压力的影响。作为对该假设的初步检验，我们估计了烟粉蝶幼虫（Manduca sexta）和褐蜚蠊若虫（Blatta lateralis）的生长代谢成本。初步数据支持了我们的假设。
