Specialeforsvar: Kristine Sydow Krogh Pedersen

Foraging ecology and fungus growth optimization in the fungus-growing termite symbiosis

Vejleder: Michael Thomas-Poulsen, Section for Ecology and Evolution

Censor: Bent Petersen Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark

Abstract
Fungus-growing termites are distributed throughout Africa and Asia. They can dominate decomposition of plant material, partly due to their associated mutualist fungus, Termitomyces. Termite workers forage for and ingest plant substrate and after a rapid gut passage the faeces are placed on the young fungus comb. Here Termitomyces decompose lignocellulose, before termites ingest the old comb, containing fungal material and partly degraded plant material. Termite foragers have been found bring back very different substrates. Here it was investigated through video observation of Macrotermes natalensis workers from two castes (major and minor) whether a preference could be found. Given the choice between dung, straw and wood, they showed no preference. Furthermore, division of labour was examined. A strong difference between major and minor workers in handling the substrate was found, namely that major workers were more active than minor workers in substrate handling. The growth of Termitomyces were measured in response to varying concentrations and ratios of protein and carbohydrates (P:C) with the aim to find the diet that gives the most optimal fungal growth. From the termites point of view, optimal growth is high biomass. The highest biomass was obtained at the diet with high concentration of nutrients and P:C of 1:1-1:2. The amount of protein seems to be the limiting factor for Termitomyces when growing on artificial media. Normally Termitomyces are growing on substrate much more poor in protein. This could imply that the substrate provided by the termites are not the most optimal for biomass production.