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

Abstract

Naidlds 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 Oiaetogaster spp., are mainly predaceous, and C. Hmnaei 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 pcriphyton 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 coarse substrates but rarely penetrate below 6 cm in mud. The principal factor limiting both depth penetration and the dominance of naidids in fine substrates is probably oxygen availability.Naidids reproduce both asexually and sexually, the former method predominating k>r most of the year. Asexual reproduction usually involves the budding-off of zooids but a few species fragment. Sexual reproduction is often infrequent; populations of some species produce few or no sexually mature mdividuals. In mature worms asexual reproduction virtually ceases. In populations that produce mature individuals there is apparently one sexual generation a year, usually occurring during the summer and autumn. Adults die soon after laying their cocoons.In general, naidids are most abundant during the summer months when rates of growth and asexual reproduction are stimulated by hi^er temperatures and a plentiful supply of food. A few species, however, e.g. Nais elinguis and Paranais litoralis, are more abundant in the spring.The response of naidid species to different kinds of pollution is varied but generally organic enrichment of rivers which have stony substrates results in a considerable (ten-to twenty-fold) increase in naidid abundance. Mi/s e//«p«s, N. barbata, N. communis, N. variabilis. and Chaetogaster diaphanus are often •Present address: Thames Water Authority, Reading HridKe House. Reading, Berkshire. Correspondence: M. A. Learner,

Population dynamics of free-swimming Annelida in four Dutch wastewater treatment plants in relation to process characteristics

“…Therefore, the stable food supply and temperatures could explain the absence of annual growth patterns in the WWTPs. This was also supported by asexual reproduction of the species in our research, which usually indicates favourable conditions like food availability, higher temperatures and low NaCl concentrations (Learner et al, 1978;Loden, 1981). In addition, top-down predation as observed in field situations by, for example, fishes (Wallace & Webster, 1996) is virtually absent from WWTPs, which is another explanation for the seemingly random population dynamics.…”

Oligochaete assemblages of Swiss Alpine lakes

“…Not surprisingly, Lumbriculidae and Tubificinae are known to prefer fine sediments (Dumnicka 1994;Verdonschot 2001) and were generally more abundant along the lake littorals where such substrates are more likely to occur, while Naidinae, which seemed to prefer coarse substrates (Learner et al 1978), were more frequently found in the lake outlets. Otherwise, the distribution of Enchytraeidae seemed to be determined by parameters other than substrate type and current velocity, because they could be numerically important in both littoral and outlet samples.…”

Colonization by oligochaetes (Annelida: Clitellata) in decomposing leaves ofEichhornia azurea(SW.) Kunth (Pontederiaceae) in a neotropical lentic system

“…of these sub-families can be attributed to their lifestyles. Various species of Naidinae and Pristininae can disperse actively in the water column (Learner et al, 1978) and can thus more easily colonize different habitats, including decomposing organic material. In contrast, the Tubificinae live in direct contact with the substrate (Elissen et al, 2008) and are slow colonizers (Levin et al, 1996).…”