A. Faunistics, biogeography and ecology of free-living Plathelminthes
Free – living Plathelminthes (Microturbellaria) live within water films associated with soil particles. Our knowledge on these species is limited, as these are poor in characteric signs and difficult to investigate. About 30 species are known from soils of Central Europe; the number of unidentified species may be manifold higher. The ongoing faunistic investigations deal with Plathelminthes – communities in deciduous forests of Central Europe with a focus on Eastern Germany . The diversity of the species, their correlation with different types of soil strata and specific habitats and the seasonal variations of the communities are investigated over the year. From 2011, further habitats (coniferous forest, grassland, sandy soil, post mining landscape, mofette fields) were recorded. From 2014 on we want to compare differences between fauna of Plathelminthes focussing on biogeographic and climatic aspects.Therefor we will set a West-East-Gradient from Belgium/Northern France to Lusatia. Further investigations are provided a deeper insight into the function of Plathelminthes within the soil – food – web. Our results show that Turbellaria feed e.g. on Nematodes, Thekamobae and rotifers. The role as predators is to quantify with selected species of Plathelminthes and Nematodes.
B. Evolutionary and functional-morphologic investigations
Plathelminthes are poor in submicroscopic characters. Characters relevant for their evolution, however, can be found in their internal organs. We investigate the male and femal sexual organs, protonephridias, different sensory organs and epidermal and neodermal layers. The investigations are carried out in cooperation with colleagues from abroad. Further investigations will focus on the transition from a free living to a parasitic way of live. Not only ultrastructural investigations allow us to recognize steps in evolution, but may additionally contribute to our understanding of the physiology of these organisms. Investigations of the canals of the sexual organs help to understand the transport of semen and eggs. Dermal glands make us understand the rapid attachment to the substrata. Investigations of excretion organs show the transport of metabolic waste and water. Thus, we may be able to correlate morphological adaptation to functional and vice versa.
C. Methods for extraction of free – living Plathelminthes from soil samples
Methods for quantitative extraction of free – living Plathelminthes from soil samples have long been not quantitative. So we compared different methods for most efficient extraction. We found that magnesiumchlorid anaesthesia is not applicable to terrestrial ecosystems. Salt water ice extraction does enrich Plathelminthes quantitatively in correlation with the salt concentration. A versatile and time wise way of extraction of Turbellaria from forest soils is the extraction with gaze-bags using fresh water. Further investigations on this focus are in progress.