THESIS APPROVAL

Thalassodrilus, Clitellio, Adelodrilus, Phallodrilus and Spiridion may be classified as
marine oligochaetes (Hrabe, 1960). Among the brackish water forms may be
considered several species of Monopylephorus and other such as Tubifex costatus,
Peloscolex benedeni, and several Isochaeta species (Brinkhurst and Simmons, 1968).
At the superficial level, there is an obvious tendency for some naidids and
lumbriculids to occur in stony streams whereas tubuficids, which is frequently limited
to Tubifex tubifex, Peloscolex.ferox and Limnodrilus hoffmeisteri, are more often
found in the softer sediments of river and lake (Brinkhurst and Jamieson, 1971).
Brinkhurst (1964) established that Tubifex tubifex is often found in productive or
polluted lakes, replacing Peloscolex ferox, which is common in oligotrophic or
mesotrophic lakes. All of these three species is always found in mud and debris
substrates (Figure 6). Aulodrilus pluriseta also seems to occur most often in mud rich
in plant fragments, whilst Rhyacodrilus coccineus and the lumbriculid Stylodrilus
heringianus being mostly restricted to sandy sediment (Brinkhurst, 1967).
Figure 6 Colony of Tubificidae in mud and debris substrates.
Source: Pennak (1989)
3. Pollution Biology
The diversity of benthic fauna was severely reduced by the degree of pollution
suffered. Lacking of oxygen and food supply, accumulation of poisonous products of
anaerobic breakdown of organic matter and metabolic wastes are the most limiting
factor. Certain species of aquatic oligochaete have the ability to tolerate under these
conditions (Lerberg et al., 2000). In fact, the distributional patterns of certain
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