On enchytraeids and naidids: Life history traits and responses to environmental stress

Abstract: My thesis shows that enchytraeids and naidids are sensitive to various forms of environmental stress, which in combination with the wide distribution of both families make them highly suitable for use in risk assessment and soil monitoring. Enchytraeids were subject to chemical stress under both laboratory and field conditions. In laboratory experiments enchytraeids reacted to chemical stress with decreased reproduction and growth. When given the possibility the enchytraeids avoided metal polluted soil. A standardized test based on the enchytraeid Cognettia sphagnetorum was developed to provide a method for monitoring the quality of forest, bog and pasture soils. Exposure of enchytraeids to a fungicide in the field resulted in reduced abundance of the indigenous enchytraeid fauna. The combined stress due to the fungicide and competition from added enchytraeid individuals increased the reduction further. To study possible impacts of forest management on litter fauna in a primary terra firme rain forest in the Amazonas, colonization of leaf litter by oligochaetes (Enchytraeidae, Naididae, Tubificidae) was studied in a litter bag experiment. Naidid worms were the most rapid colonizers and showed the highest reproductive output owing to asexual reproduction. To investigate what factor limits terrestrial naidid population dynamics in tropical soils, population growth of the naidid Pristinella jenkinae was studied in a laboratory experiment. Soil moisture and food abundance were the most important limiting factors.