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I want to measure metabolism in tardigrades (a jar of 30 tardigrades). I know that an easy way to measure metabolism is heat loss; I can just measure the temperature of the water before and after a certain period of time and take the difference. I have a few questions:

1) Is this a viable way?

2) Do I need to put the tardigrades in a controlled system (or is the outside environment a constant)?

3) Will the measurements be really really small (so I would need a very precise thermometer?)

4) How long should I wait between the two measurements?

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1 and 2) You need to build/use a calorimeter : http://en.wikipedia.org/wiki/Calorimeter Different types exist, depending on your constraints.

3 and 4) It will depend on the size of your system.

If you decide to use an adiabatic calorimeter: First have an estimate of their metabolism (see e.g. [1]), then divide the energy spent over the duration you think you'll use by the heat capacity of the water volume you have, you get the temperature elevation.

If you use a flux calorimeter, then you don't multiply by the duration but check that the calorimeter will be sensitive enough.

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  • $\begingroup$ Do these cold-blooded critters emit heat at all you think? +1 for your calorimeter idea. Nice one. $\endgroup$ – AliceD Feb 2 '15 at 13:02
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    $\begingroup$ @ChrisStronks: they cannot live and emit no heat at all. Any process will generate some heat, be it only by molecular friction in flows. "Cold-blooded" is misleading, as it rather means that they have no thermal homeostasis target that they'd maintain by internal metabolic processes. $\endgroup$ – Joce Feb 2 '15 at 14:20

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