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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1529

Ramesh D. Gulati, Jolanta Ejsmont-Karabin, and G. Postema; Feeding in Euchlanis dilatata lucksiana Hauer of filamentous cyanobacteria and a prochlorophyte. Hydrobiologia 255/256:269-274, 1993

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Ingestion and assimilation rates of Euchlanis dilatata lucksiana Hauer, isolated from Lake Loosdrecht (The Netherlands) and cultures on lake water (seston under 33 µm), were measured in the laboratory using the [14]C-tracer technique. The five taxa used as tracer foods, together with 6-7 mgC l-1 of lake seston in each case, induced four species of filamentous cyanobacteria (Oscillatoria redekei, O. limnetica, Aphanizomenon flos-aquae, Anabaena PCC 7120) and a prochlorophyte (Prochlorothrix hollandica). Except Anabaena, they are all commonly encountered in eutrophic Loosdrecht lakes, including Lake Loosdrecht, and their dimensions ranged between 150 and 250 µm in length and 2 and 3.5 µm in width. The small and large Euchlanis used as experimental animals had mean lengths of 217-223 µm and 276-305 µm, respectively. Euchlanis fed on all the taxa offered as food. Clearance rates ranged from 51 to 99 µl ind-1 day-1 for the large animals and from 22 to 41 µl ind.-1 day-1 for the small animals. The highest ingestion rate observed, 1.7 µg ind.-1 day-1, was for the large animals feeding on Aphanizomenon. The daily ration for both size classes far exceeded 100% of body weight, reaching up to 690% for the small animals feeding on Aphanizomenon. The small animals generally appeared to assimilate the ingested food more efficiently (assimilation efficiencies: 37-100%) than the large animals (34-77%). Compared with an earlier study in which only lake seston (<33 um) was used as food, the specific clearance rates of Euchlanis on the cyanobacteria and Prochorothrix were generally somewhat lower.