A review of the biology of British Naididae (Oligochaeta) with emphasis on the lotic environment

SUMMARY. Naidids live in a wide range of aquatic habitats but are particularly important numerically as part of the benthic fauna of rivers with stony substrates. In general they graze on bacteria and algae although some, particularly Chaetogaster spp., are mainly predaceous, and C. limnaei vaghini is a parasite of molluscs, chiefly Gastropoda. Food selection seems to be based largely on particle size although the food quality of the particles within the appropriate size‐range influences rates of growth and reproduction.Major factors determining the distribution and abundance of naidid species are the nature of the substratum and the presence and kind of vegetation. Plants with a highly dissected form, a thick growth habit, and which permit the greatest periphyton development generally support the most abundant naidid populations. The oligochaete fauna of coarse substrates (stones and gravels) is often dominated by the Naididae but both species‐richness and abundance of naidid populations are generally reduced where fine substrates (silts and muds) occur. The occurrence of worms within the substratum is also determined by its nature; naidids penetrate to depths of 20–70 cm in