The biology and ecology of lotic nematodes

Summary1 Morphological structures for identifying freshwater nematodes, e.g. buccal cavity, sensory receptors, oesophagus, reproductive organs and tail are described. 2 Most freshwater nematodes belong to the Adenophorea and are characterised by the presence of setae, adhesive glands and conspicuous amphids. 3 Methods for collecting nematodes from the sediments of running water (e.g. corer, pumps), within plants and aufwuchs are listed. Methods for fixation, extracting and preparing nematodes for identification are described. 4 Life history parameters (e.g. generation time, eggs per female) are not available for lotic nematodes but are summarised for free‐living nematodes in soil, lakes and seas. Field studies indicate that, in contrast to laboratory experiments with nematode cultures, many species will have a generation time of several months. 5 Abundance and species diversity of nematodes of lotic habitats are provided; more than 100 nematode species inhabit lotic habitats and densities can reach 230 individuals per ml. 6 Links between meiobenthic nematodes and the micro‐ and macrobenthos are unclear at present. Evidence such as the increased bacterial activity due to nematode grazing suggests that such interactions may be significant.