FACTORS AFFECTING FEEDING RATE, REPRODUCTION AND GROWTH OF AN OLIGOCHAETE LUMBRICULUS-VARIEGATUS (MULLER)

Worm density of a deposit feeding oligochaete (Lumbriculus variegatus) did not affect egestion whereas both temperature and sediment type ha d a significant influence. The worms egested less actively at the lowe st temperature (6 degrees C). The egestion rate, expressed as mg dry f eces produced, was highest in the sandy sediment and lowest in the sed iment derived almost exclusively from decaying plant material. The amo unt of dry material and the volume of wet sediment passing through the worms varied between the test sediments; the results are probably dep endent on the chosen unit of measure. Reproduction was significantly d ecreased in sandy sediment with low organic carbon content. Reproducti on was also dependent on the worm size, larger worms reproducing more frequently. Most worms lost weight during the tests, but the loss was lowest in the sediment with the highest organic carbon content.