ECOHISTOLOGICAL INVESTIGATION OF THE FEEDING-BEHAVIOR OF THE ENCHYTRAEID ENCHYTRAEUS-CORONATUS (ANNELIDA, OLIGOCHAETA)

Knowledge on the nutritional ecology of enchytraeids is scarce. Theref ore, laboratorial investigations were undertaken to study uptake, fate and digestive processes of different food sources (Penicillium sp., B acillus cereus var. mycoides, Sambucus nigra, rolled oats, soil) by En chytraeus coronatus. Feeding behaviour, cocoon production and mortalit y of the worms were observed with the aid of a light microscope. Ultra histological investigation of the gut and its luminal contents were us ed to recognize; (1) the fate of the food passing the gut, (2) alterat ion of the gut tissues due to the diet. The number of cocoons and adul t worms depended on the diet and decreases from rolled oats < Sambuca nigra < Bacillus cereus < Penicillium. Remnants of food were generally rare but nearly all offered diets except Penicillium were found in th e gut. Because of the small amount of remnants in the gut, preoral dig estion must be assumed. Alteration of the gut epithelia resulting from food quality could not be observed. The only prominent alteration was found in the chloragogenous tissue. Feeding with rolled oats results in a high number of fat vesicles within the chloragogenous cells. The results show that enchytraeids have a widespread nutrient spectrum and are possibly not a member of the group of primary decomposer.