A New System for Continuous Respirometry of Small Air-Breathing Invertebrates Under Near-Natural Conditions

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Abstract
1. A new system of respirometry for long-term experiments on small air-breathing invertebrates is described for use in work where changing temperature conditions are essential. There is no reason why the same system should not be used for larger animals. 2. The respirometer is of the Barcroft, compensating type, isolated from the atmosphere, and has provision for temperature equilibration in the two vessels. 3. Oxygen is automatically replenished by electrolysis of copper sulphate solution in the chamber as it is used by the animal and the rate of replenishment is recorded. 4. The main features in design of such an apparatus, its limitations and accuracy are discussed. The accuracy is comparable with that of a Warburg respirometer and the sensitivity, at better than 0.1 mm.3 of oxygen/hour, is about ten times as great. 5. A special control and recording system has been developed in order to reduce expense and simplify the interpretation of the data from six respirometers over long periods. 6. It is shown that the errors arising from temperature changes can be reduced to acceptable levels for most purposes. The apparatus is therefore suitable for use in the study of acclimatization and of responses to rhythmical temperature changes. 7. Examples of respiration records are given which illustrate the possibilities of being able to follow respiration rates through several diurnal cycles. 8. Practical details of construction are given in the appendices.