Scaling of resting and maximum hopping metabolic rate throughout the life cycle of the locust Locusta migratoria

Abstract

Secondly, a recent comparative analysis concludes that insect metabolic rate does scale with a k-power exponent (Riveros and Enquist, 2011), and the authors use this as evidence to provide broad . Increasing body mass by 20-45% with attached weights did not increase mass-specific MM O2 significantly at any life stage, although mean mass-specific hopping M O2 was slightly higher (ca. 8%) when juvenile data were pooled. The allometric exponents for all measures of metabolic rate are much greater than 0.75, and therefore do not support West, Brown and Enquist's optimised fractal network model, which predicts that metabolism scales with a 3 ⁄ 4-power exponent owing to limitations in the rate at which resources can be transported within the body.

Symmorphosis and the insect respiratory system: a comparison between flight and hopping muscle

“…There was also no significant difference between the body mass of adult locusts used in the present study and those used in earlier respirometry experiments (ANOVA, P0.21) (Snelling et al, 2011a;Snelling et al, 2012). Nevertheless, body-mass-specific values are presented (except for volume density, surface density and thickness estimates).…”

“…The flight muscles contain predominantly fast phasic-type fibres (Kutsch and Usherwood, 1970;Mizisin and Ready, 1986;Wilson and Weis-Fogh, 1962), whereas the hopping muscles contain a mixture of fast phasic-type, slow tonic-type and intermediate-type fibres (Cochrane et al, 1972;Hoyle, 1978). Earlier respirometry revealed that the maximum oxygen consumption rate of adult hopping muscles during jumping exercise averages 158molh -1 g -1 body mass (Snelling et al, 2011a), whereas the flight muscle consumes a maximum of 967molh -1 g -1 during tethered-flight exercise (Snelling et al, 2012). According to the principles of symmorphosis, the 6.1-fold difference in aerobic capacity between the hopping and flight muscles should be matched by an equivalent difference in the overall volume, surface area and anatomical diffusing capacity of the tracheoles in the two muscles, and also in the total volume and inner membrane surface area of the mitochondria in the two muscles.…”

“…Gregarious-phase locusts L. migratoria (Linnaeus 1758) were reared at 33±1°C, under a 12h:12h light-dark cycle, with ad libitum access to seedling wheatgrass and wheat germ, as previously described (Snelling et al, 2011a). Newly emerged adults were identified from the breeding colony and were placed into separate plastic terraria with other adults of similar age.…”

“…Morphometric analysis of the metathoracic femurs (hopping leg femurs) was conducted on adult locusts (N3 individuals) 3-4days post-final moult, which is sufficient time for the exoskeleton to stiffen while minimising compression of the tracheal system due to growth (Greenlee and Harrison, 2004;Queathem, 1991). All locusts were fasted 6-10h prior to tissue fixation consistent with earlier respirometry studies (Snelling et al, 2011a;Snelling et al, 2012).…”

“…) corrected to 35°C using Q 10 1.1 (Bartels, 1971), consistent with the temperature at which respirometry was performed (Snelling et al, 2011a;Snelling et al, 2012). The sum of the lateral diffusing capacities of each trachea size class provided an overall estimate of the lateral diffusing capacity of the entire tracheal system associated with the flight muscle/both hopping muscles in each locust.…”