6.1.1.1. General setup

For respiration and energetics measurements the setup has to be adapted according to the questions under investigation, the developmental stage of the bees and the quantity to be measured. In open-flow investigations of insect respiration, different parallel and serial plumbing setups are in use. For general advice see also Lighton (2008) and Lighton and Halsey (2011). In most cases, scientists will be interested in O2 consumption or CO2 production of bees, mostly in comparison to ambient air, rather than in the measurement of absolute concentrations of these gases. Therefore, differential setups, comparing the gas concentration before and after a measurement chamber are the most relevant ones. A differential measurement setup which allows a fast, (semi-) automated switch between different measurement modes (serial or parallel; see sections 6.1.1.3. and 6.1.1.4.), and simultaneous thermographic measurement of body surface temperature is shown in Stabentheiner et al. (2012). However, setups with less automation will normally be sufficient to answer a specific question. In general it has to be noted that respiratory equipment is usually not of a 'buy and go' type. Every measurement situation requires its own adaptations. However, many companies provide solutions and help to fit the experimenter's requirements.

1. Standard conditions: The measurement output of instruments (volume of O2 consumption or CO2 production, or flow rate) usually refers to standard (STPS) conditions (0 °C, 101.32 kPa = 760 Torr).

2. Calculation of O2 consumption (VO2) or CO2 production(VCO2): The difference in concentration measured between the measurement and reference air stream, or before and after a measurement chamber, multiplied by the flow rate, provides the O2 consumption or CO2 production (turnover) of the bee in volume units per time interval (Equation 1).  Table 1 provides a short reference of how to convert STPS volumes to moles or energy and power units.

VCO2 or VO2 = concentration × flow (ppm × ml min-1 × 10-3 = µl min-1)         (Equation 1)

 

Table 1. Quick reference for result calculations and units conversion. # molar volume of an ideal gas at 0 °C and 101.32 kPa (760 Torr or 1 atm) of pressure; ## 21.117/60, ### caloric equivalent of sucrose (21.117 kJ l-1, e.g. during sucrose feeding), use different values on demand (Table 2). 

Desired results in units of VO2 or VCO2

Calculate

nl/min

 

ppm × ml/min

nmol/min

 

ppm × ml/min / 22.414#

 

 

 

Units conversion

 

 

From

To

Calculate

µl/min

nMol/min

µl/min × 44.61497

nMol/min

µl/min

nMol/min × 0.022414

nMol/min

ml/h

nMol/min × 0.0013448

µl O2/min

W (J s-1)

µl/min × 0.35195## × 10-3

µl O2

J

µl × 21.117### × 10-3

 

 

 

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