抄録
The change in ciliate populations was investigated in bottom sediment at a place 2 km upstream from the Marukobashi Bridge of the Tamagawa River about once a month from April 1976 to May 1978. The numbers of viable heterotrophic bacteria, diatoms and flagellates as foods of ciliates were also counted. A similar pattern of the seasonal change in ciliate populations was observed for two years. In winter Paramecium caudatum, P. trichium, Colpidium colpoda and Chilodonella cucullulus dominated. The number of each species was 103-104 cells per ml of sediment. Perispira ovum increased up to 103 cells per ml at the end of winter. From spring to early summer Spirostomum spp. dominated, and their number increased up to 103 per ml. From summer to autumn Loxodes spp. and P. caudatum were predominant. The number of each species was 102-103 per ml. Frontonia leucas also appeared in summer. Stentor, Metopus es, Litonotus and Acineria did not change seasonally. Interspecific relations, such as predation (of Perispira and Loxodes on Euglena and diatoms, respectively) and competition (between bacteria-feeding ciliates and metazoa such as oligochaetes and diptera larvae), may be some of the important factors controlling the seasonal change in ciliate populations.
