Limnodrilus amblysetus sp.nov. (Tubificidae) is described and compared with other Chinese Limnodrilus species as well as Limnodrilus silvani which is recorded from California and Oregon, U.S.A. The presence of other previously known Chinese species is confirmed. Polymorphism in the development of dorsal chaetae, already known for the Naididae and for Tubificinae (Tubificidae), is now suspected for Rhyacodrilinae (Tubificidae). The oligochaete fauna of China resembles that of India, Japan,and the eastern Soviet Union. Some tropical and subtropical Naididae may yet be discovered from the southern provinces, some cold-water Tubificidae and Lumbriculidae from the northeast and those elevated parts of the far west of China that are not deserts.
The enigmatic Ilyodrilus masrix Brinkhurst, 1978, and Tectidrilus achaetus sp.nov. are described from the Guangzhou Reach of Pearl River, southern China. The first species is characterized by its greatly enlarged, eversible, feeding apparatus, and was previously known only from British Columbia, Canada. Tectidrilus achaetus is unique within the Tubificidae by lacking setae. A slightly modified definition of the, otherwise marine, genus Tectidrilus Erstus, 1982 is provided.
A new genus and species of freshwater heteronemertean, Amniclineus zhujiangensis, from the Zhujiang (Pearl River), People's Republic of China, is described and illustrated. The species is placed in the family Lineidae along with the existing freshwater heteronemertean taxa, with which its anatomy is compared.
The species composition, distribution and abundance of the Tubificidae (8 spp.) and Naididae (at least 4 spp.) in the Guangzhou reach of the Lower Pearl River were investigated. Limnodrilus spp. (particularly L. hoffmeisteri) constitutes the greatest part in nearly all samples, which were taken in both clean and polluted parts of the reach. In the polluted sites, total oligochaete densities reach values of up to 700 000 ind. m-2. The importance and problems of using oligochaetes as indicators of organic pollution are discussed.
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