Journal
JOURNAL OF EXPERIMENTAL BIOLOGY
Volume 215, Issue 14, Pages 2524-2533Publisher
COMPANY BIOLOGISTS LTD
DOI: 10.1242/jeb.057141
Keywords
Coleoptera; allometry; insect; oxygen delivery; respiration; trachea; scaling; metabolism
Categories
Funding
- National Science Foundation [IBN-0419704, DEB-0083422]
- University of New Mexico Graduate Research Allocation Committee (GRAC)
- Student Research Allocations Committee (SRAC)
- National Science Foundation
Ask authors/readers for more resources
Constraints on oxygen delivery potentially limit animal body size. Because diffusion rates are highly distance dependent, and because tracheal length increases with size, gas exchange was traditionally thought to be more difficult for larger insects. As yet the effect of body size on critical oxygen partial pressure (P-crit) has not been measured for any clade of insect species for which there are interspecific data on tracheal scaling. We addressed this deficiency by measuring P-crit over a 4150-fold mass range (ratio of largest to smallest species mean) of two families of Coleoptera (Tenebrionidae and Scarabaeidae). We exposed adult beetles to progressively lower oxygen levels and measured their ability to maintain CO2 release rates. Absolute metabolic rates increased hypometrically with beetle body mass (M) at both normoxic (M-0.748) and hypoxic (M-0.846) conditions. P-crit, however, was independent of body size. Maximum overall conductances for oxygen from air to mitochondria (G(O2,max)) matched metabolic rates as insects became larger, likely enabling the similar P-crit values observed in large and small beetles. These data suggest that current atmospheric oxygen levels do not limit body size of insects because of limitations on gas exchange. However, increasing relative investment in the tracheal system in larger insects may produce trade-offs or meet spatial limits that constrain insect size.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available