0.43 - 0.97 µm
||Cladocera Bosmina longirostris
||Young KD. The selective value of bacterial shape. Microbiol Mol Biol Rev. 2006 Sep70(3):660-703 DOI: 10.1128/MMBR.00001-06 p.685 right column bottom paragraphPubMed ID16959965
|| To´th, L. G., and K. Kato. 1997. Size-selective grazing of bacteria by Bosmina longirostris—an image-analysis study. J. Plankton Res. 19: 1477–1493 link
||Primary source  abstract: "Image analyses on the filtering apparatus of Bosmina longirostric showed that the filter mesh is finer on the gnathobasic filter plates of the second and third trunk limbs (ranges from 0.43 to 0.97 μm) and coarser for the outer ones of the third limb (ranges from 0.5 to 1.36 μm), and the intersetular distances increase with body length."
||P.685 right column bottom paragraph: "The short of it: selection for small cells. The opposite side of the bimodal effect is the selection for cells too small to be captured by particular protists. For example, the cladoceran predator Bosmina longirostris inhales bacteria through a filter with a mesh size of 0.43 to 0.97µm. Bacteria equal to or exceeding these lengths are captured most efficiently, but smaller coccoid cells escape, so that prolonged grazing reduces the average size of the survivors (primary source). Rods in the process of cell division and spirillum-shaped bacteria are captured twice
as well as single cells, indicating that bacterial size selection is due to physical capture by the filtering apparatus and not by surface properties of the prey (primary source). The effect is not confined to filter feeders, because grazing by the mixotrophic flagellate Ochromonas also selects for cells of less than 0.9µm in diameter (ref 259)."