Epifluorescent microscopy was employed to compare the bacterial live counts (BC) in the gut of two earthworm species Aporrectodea caliginosa and Lumbricus rubellus, representing different ecophysiological groups. The average number of BC was 10.9 x 10(9) g-1 dry weight in the gut of A. caliginosa, 5.9 x 10(9) in that of L. rubellus, 8.1 x 10(9) in earthworm casts and 6.0 x 10(9) in the soil. The number of BC showed a great seasonal variability in all the materials studied, exhibiting maxima in spring and autumn, and a minimum in summer. The BC increased in number during the passage of food material through the gut of both L. rubellus and A. caliginosa. The difference between BC in fore-gut and hind-gut were significantly higher in L. rubellus (4.2 x 10(9) vs. 8.8 x 10(9)) than that in A. caliginosa (10.3 x 10(9) vs. 13.4 x 10(9)). Interspecific differences in the number of BC may result from the different chemical and microbiological composition of the material consumed by earthworms as related to different feeding habits of both species.

Institute of Soil Biology Czechoslovak Academy of Sciences Ceské Budĕjovice