ABSTRACT
Soil invertebrates are not among the favourite model organisms in physiological and genetic research. Some Collembola come close to Drosophila in suitability for genetic research but they have never reached the same star status. Physiological work on soil invertebrates, although popular in the 1980s, has therefore always remained a bit scanty and incomplete. Whole-body metabolic rate expressed in energy units per time is one of the most informative measures of animal activity since it reflects the totality of processes in the organism that deal with oxygen-fuelled energy metabolism. Metabolism varies with body size and temperature, but in earthworms and oribatids does not show clear trends in relation to ecology, at least not to the state of present analysis. The cold-hardiness literature commonly makes a distinction between freeze-avoidance and freeze-tolerance. Cold hardiness can be measured by survival time under low temperature, but a particularly interesting variable is supercooling point.
