Oxygen supply through the tracheolar-muscle system does not constrain insect gigantism.
basic_science · Level V
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- Record sourced from PubMed, PMID 41882361.
- Also identified by DOI 10.1038/s41586-026-10291-3.
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Abstract
The idea that atmospheric oxygen has dictated the maximum body size of insects across their evolutionary history is ingrained in popular and scientific literature<sup>1-3</sup>. In Nature 30 years ago, the hypothesis was put forward that a limitation on oxygen diffusion at the level of the tracheoles constrains the maximum body size of insects and that increased atmospheric oxygen concentration in the late Palaeozoic permitted insect gigantism<sup>4</sup>. Here we contest this hypothesis by showing that the relative space occupied by tracheoles in the flight muscle of insects (1) increases by only 1.8-fold over a 10,000-fold body mass range (1,320 micrographs, 44 species, 10 orders), (2) is typically 1% or less in most species, and (3) that this observation holds when we extend our relationship to the long-extinct gigantic dragonfly-like Meganeuropsis permiana (approximately 100 g). The small space requirement and the lack of a strong increase in tracheolar investment with body size, despite clear evolutionary potential to do so, provide convincing evidence that diffusive oxygen transport through the tracheolar-muscle system does not constrain the maximum body size of extant or gigantic prehistoric insects.