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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7455

Ishigaki Tetsuji and Terazaki Makoto; Grazing Behavior of Heterotrophic Nanoflagellates Observed with a High Speed VTR System. J.Eukaryot.Microbiol. 45(5):484-487, 1998

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The grazing patterns of heterotrophic nanoflagellates (Cafeteria roenbergensis and Actinomonas mirabilis) were recorded by high speed video micrography. Experiments were carried out at 10, 15 and 25 degrees C at a salinity of 36 psu and at 20 degrees C when the salinity was either 20 or 36 psu. Bacteria entrained in a stream of water generated by flagellar beating were propelled toward the cell body (phase 1). Each bacterium destined for ingestion made contact with the anterior end of the flagellum of Cafeteria or was captured with an actinopod of Actinomonas (phase 2). The captured bacterium was drawn close to the cell body (phase 3) and ingested (phase 4). Cafeteria was observed during 38 grazing events and appeared to have two different patterns of ingestion, "enclosing " and "pocket phagocytosis". The mean time for food capture was 0.10 sec and the subsequent ingestion was complete on average in 1.59 sec. No further bacteria were captured until ingestion was complete. Actinomonas was observed during 27 grazing events in which capture of particles on an actinopod was followed by transport to the cell body and subsequent "enclosing phagocytosis". The mean time to complete grazing was 39.16 sec, which is about 25 times longer than for Cafeteria; the phase of transport to the cell body occupied most of this time. During the grazing cycle, Actinomonas captured other bacteria on the actinopodia, but sometimes released them. Grazing time in Cafeteria was positively correlated with temperature but not correlated with salinity. Grazing behavior in Actinomonas was correlated with neither temperature nor salinity.