Scaling of gas exchange cycle frequency in insects

Abstract

Previously, it has been suggested that insect gas exchange cycle frequency ( f C ) is mass independent, making insects different from most other animals where periods typically scale as mass −0.25 . However, the claim for insects is based on studies of only a few closely related taxa encompassing a relatively small size range. Moreover, it is not known whether the type of gas exchange pattern (discontinuous versus cyclic) influences the f C –mass scaling relationship. Here, we analyse a large database to examine interspecific f C –mass scaling. In addition, we investigate the effect of mode of gas exchange on the f C –scaling relationship using both conventional and phylogenetically independent approaches. Cycle frequency is scaled as mass −0.280 (when accounting for phylogeneticnon-independence and gas exchange pattern), which did not differ significantly from mass −0.25 . The slope of the f C –mass relationship was shallower with a significantly lower intercept for the species showing discontinuous gas exchange than for those showing the cyclic pattern, probably due to lower metabolic rates in the former. Insects therefore appear no different from other animals insofar as the scaling of gas exchange f C is concerned, although gas exchange f C may scale in distinct ways for different patterns.

Allometric scaling of discontinuous gas exchange patterns in the locust Locusta migratoria throughout ontogeny

“…Using an allometric approach, we found that despite overall CO 2 production rate scaling near-isometrically with body mass, 0.95±0.09, the duration of the DGC cycle is significantly longer in older locusts, scaling with body mass raised to the power of 0.22±0.17 in normoxia (Fig.2, Table1). Thus, the scaling of locust DGC frequency is -0.22±0.17, which aligns closely with the metaanalysis that derived an exponent of -0.20 across 49 insect species (Terblanche et al, 2008).…”

“…Another study that analysed gas exchange patterns in scarab beetles found that the C, F and O phase durations all scale invariantly with body mass, but that total DGC duration is significantly shorter in larger beetles, and thus DGC frequency increases with body mass, scaling with an exponent of M b 0.56 , but this was only over an approximately fourfold range in body mass (Davis et al, 1999). And contradicting all these studies, a recent meta-analysis of 49 insect species found that larger insects tend to have longer DGCs, and thus DGC frequency decreases with body mass scaling with an exponent of M b -0.20 (Terblanche et al, 2008).…”

Mass scaling of metabolic rates in carabid beetles (Carabidae) – the importance of phylogeny, regression models and gas exchange patterns

“…Overall, our results and emerging evidence from other studies suggest that the heterogeneity of scaling exponents is a fact, and deviations in scaling exponents from 0.67 or 0.75 must be treated as a rule rather than an exception. Numerous factors affecting scaling exponent and intercept estimation have been recognized based on real biological datasets (Capellini et al, 2010;Ehnes et al, 2011;Terblanche et al, 2008b;White and Kearney, 2014;White and Seymour, 2005b) or randomly generated datasets (Hui et al, 2010;Kilmer and Rodriguez, 2017;Warton et al, 2006). Here, we provided a coherent dataset that permitted the testing of factors discussed frequently in literature, e.g.…”

Peer Review #2 of "Larval exposure to field-realistic concentrations of clothianidin has no effect on development rate, over-winter survival or adult metabolic rate in a solitary bee, Osmia bicornis (v0.1)"

“…The factors underlying switches between continuous and discontinuous patterns of gas exchange in insects are still widely debated (e.g. Contreras & Bradley, 2009), and so the reason why female bees were less likely to engage in discontinuous gas exchange is not clear, though could be related to sex-specific differences in body mass causing females to produce more CO 2 at rest (Terblanche et al, 2008).…”