Maximum metabolic rate, relative lift, wingbeat frequency, and stroke amplitude during tethered-flight in the adult locustLocusta migratoria

Abstract

. The modest flight metabolic rate of locusts is unlikely to be an artefact of individuals failing to exert themselves, because mean maximum lift was not significantly different from that required to support body mass (95±8%), mean wingbeat frequency was 23.7±0.6Hz, and mean stroke amplitude was 105±5deg in the forewing and 96±5deg in the hindwing -all of which are close to free-flight values. Instead, the low cost of flight could reflect the relatively small size and relatively modest anatomical power density of the locust flight motor, which is a likely evolutionary trade-off between flight muscle maintenance costs and aerial performance.

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.…”

“…Earlier respirometry studies on adult locusts conducted at 35°C showed that the flight muscle consumes a maximum of 967±76mol O 2 h -1 g -1 body mass during tethered-flight exercise (Snelling et al, 2012), whereas the hopping muscles consume a maximum of 158±8mol O 2 h -1 g -1 during jumping exercise (Snelling et al, 2011a). Therefore, the difference in aerobic capacity between the flight and hopping muscles is 6.1-fold (Table2).…”

“…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.…”