A Scholander-type respirometer designed for measuring both aerial and aquatic respiration

Abstract

An inexpensive respirometer designed in accordance with the measuring principles of the Scholander constant pressure respirometer is described. An advantage of this respirometer is that gas leakages during the measurements of both aquatic and terrestrial animals are completely prevented. This was achieved by using a magnetically induced rotation of the impeller wheel through a 2 mm thick Perspex wall. The accuracy of the measurements was tested after background correction was made for the oxygen consumption rate caused by microbial populations. It was found by experiment that 1,30 (± 0,11) ml; 3,55 (± 0,20) ml and 4,65 (± 0,21) ml of air dissolved in 900 ml of water at 90%, 73,6% and 62% air saturation respectively. In comparison, these values agree closely with the calculated values. This indicates the effectiveness of agitation by the impeller and an efficient air/water equilibrium. The impeller wheel was designed to reduce excessive splatter, but not to impede the air/water mixing ability. Furthermore, the respirometer was tested for its ability to measure the oxygen consumption rate (VO₂) of the same crab, both when in air and when in water. The results indicate that the mean difference between aerial and aquatic respiration is less than 6%.