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Fig. 3. Virtual-reality arena and flight data plotted as a function of open
spiracles in Drosophila. (A) Set-up as described
(Lehmann and Dickinson, 1997 ).
To elicit maximum locomotor performance of the animal, a 30° stripe drum
(BP) displayed in the electronic flight arena was oscillated under open-loop
conditions in a vertical direction around the tethered flying fly. IRD,
infrared diode; PSD, position detector of flight force laser balance; L,
laser; WSA, wing stroke analyser. (B) Wing stroke amplitude, (C) wing stroke
frequency, (D) maximum normalized flight force production, (E) mean lift
coefficient  , and (F) mean drag
coefficient  , based on a quasi-steady
aerodynamic approach, plotted against the number of open thoracic spiracles
(grey). Abdominal spiracles remained unsealed in all experiments. Data
represent mean values of all data points within a flight sequence that fell
within the top 1% of flight force (equal to maximum locomotor capacity of the
fly). Number of tested flies: N=5 (0), N=23 (1),
N=43 (2), N=26 (3) and N=10 (4 open thoracic
spiracles). To distinguish the changes resulting from the modifications of
local spiracle gas conductance from those associated with alterations in total
flight force production, we estimated kinematic and aerodynamic parameters in
unmanipulated animals (see text) within a ±2% range of flight forces
that match the maximum values shown in D (red). Red area in B,C, E,F indicates
±s.d. N=10 flies. See text for details.
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, induced power
requirements are the costs to generate an air downward momentum;
, profile power
requirements are the costs to overcome drag on the beating wings;
, flight muscle
mechanical power output that is equal to the sum of induced and profile power
requirements assuming 100% elastic storage; and
= metabolic power
estimated from measurements of CO2 release through the spiracle.
For more explanations see Fig.
3 legend. Values are means ± s.d. (N=10
flies).
, and the sum of
induced and profile power (Ellington,
1984b
) in performance between unmanipulated flies and animals in which up
to 4 thoracic spiracles have been sealed during flight. The differences are
scaled to the performance of the unmanipulated control group. Performance
scores are plotted against total diffusive area of the animal's abdominal and
thoracic spiracles that may participate in tracheal gas exchange. Due to the
reduction of maximum flight force production with decreasing total spiracle
opening area, data are calculated at 0.29 (493 µm2 total
spiracle area), 0.48 (3780 µm2), 0.74 (5424 µm2),
1.01 (7889 µm2) and 1.36 (10 355 µm2) relative
flight force production for 0–4 thoracic spiracles open, respectively. A
value of 1.0 normalized force means that the fly produces a flight force equal
to body weight. Grey areas in the pictograms indicate maximum total spiracle
opening area available for respiratory gas exchange and red lines indicate
linear regression fits. See legend of Fig.
3 for number of tested flies and text for more explanations.
Values are means ± s.d.
40 s. The area under the curve = CO2
buffer capacity of the tracheal system and haemolymph (light grey). Red line
represents first-order exponential fit to data. (B) CO2 buffer
capacity per gram body mass (35 flight sequences, 6 flies) derived from
estimations of the area under curve after flight stop (as shown in A). Data
are plotted as a function of pre-resting flight force produced during the last
2 s before the animals ceased to fly. Blue line indicates mean value ±
s.d. (shaded grey).