Ph.D. on Soil fauna drought physiology - acclimation and adaptation to drought in euedaphic Collembola

This Ph.D. project was started December 1st 2008 with Ph.D.-student Dorthe Jensen. The project is rooted in WP2.2 (Soil fauna responses) with links to WP3.2 (Soil fauna community).

Background
Euedaphic (true soil living) collembolans and many mites are water permeable, thus for these and several other soil living invertebrates one of the most important environmental factors is the availability of water in the soil. However, soil invertebrates possess various strategies to acclimate to water deficiency. One of the drought acclimation strategies used by water permeable soil fauna is the ability to tolerate extensive loss of body water. Several euedaphic collembolans overcome such desiccation by absorbing soil pore water vapour driven by hyperosmotic body fluids created from accumulation of low molecular weight organic osmolytes. However, further metabolic changes most probable are crucial to these collembolans during drought acclimation. Such physiological responses may not only increase survival, but also affect the population life history traits and thereby have a great influence on the soil community.

Project
This project includes studies on acclimation and adaptation to drought in euedaphic Collembola. In euedaphic Collembola collected at the Brandbjerg field site drought adaptation and the influence of this adaptation on life history traits such as growth and reproduction will be investigated in laboratory studies. Furthermore, to elucidate which metabolites are involved in drought adaptation in these Collembola, qualitative and quantitative studies on their metabolic profiles will be conducted together with measurements of respiration. 

The most important pathway in the N-metabolism of Collembola seems to be ammonium excretion. However, ammonium is relatively toxic to the organisms themselves, and is therefore excreted as highly diluted urine. Thus, this mode of nitrogen excretion is supposedly dependent on unlimited water access. However, shorter drought periods may halt the excretion of ammonium until the internal water content has been re-established in the Collembola. This project will include investigation of alternative N-metabolic pathways which may be crucial for the Collembola drought acclimation and provide a data basis for the estimation of microarthropods’ contribution to C- and N-cycling of the ecosystem at Brandbjerg.