WHERE TURBELLARIA - CONCERNING KNOWLEDGE AND IGNORANCE OF MARINE TURBELLARIAN ECOLOGY

Present knowledge of marine free-living turbellarians is reviewed in the light of a standard ecological text. Little is known of their ecological adaptations or fitness but they are clearly successful animals. Diversity within communities can be considerable, possibly relating to the small size of individuals and temporal and spatial resource gradients. Little is known about genetic diversity, environmental tolerances and demography. Local distribution patterns are better known but rarely proven with appropriate statistics. New data from work in Northern Ireland on behaviour and habitat choice of Procerodes littoralis and on species richness, population aggregation and microdistribution of meiofaunal turbellarians is presented. Nothing appears known about intra-specific competition but more about inter-specific relationships including responses to biogenic structures. Dietary information is sparse and mostly observational with little known about feeding efficiency. Studies at Sylt have revealed mainly univoltine or polyvoltine annual life cycles partly related to habitat preference and possibly giving some evidence of r and K selection. Factors controlling local abundance are largely uninvestigated and the reasons for the apparent rarity of many species not understood. Lists and counts of turbellarians within particular habitats provide some knowledge of community structure but very few numerical analyses, e.g. of diversity and similarity, exist. Contribution to energy flux and to structuring communities has not been determined in spite of the turbellarians' assumed major role as meiofaunal predators. Nevertheless marine turbellarians appear particularly fitted to studies such as habitat heterogeneity, community stability and biogeography and are surely suitable subjects for field and laboratory experiments. There is no lack of direction for studies to proceed. Impulsion is required.