Size-selective grazing of bacteria by Bosmina longirostris—an image-analysis study

• Published in: Journal of plankton research 1997-10, Vol.19 (10), p.1477-1493
• Main Authors: Tóth, Lószló G., Kato, Kenji
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Bosmina longirostris; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; Synecology
• ISSN: 0142-7873; 1464-3774
• DOI: 10.1093/plankt/19.10.1477

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. Grazing experiments combined with image analysis confirmed the efficient grazing of B.longirostris on natural bacteria with cell lengths equal to or larger than the intersetular distances of the gnathobasic filter plates. During the experiments, the animals minimized the average cell length of the bacterioplankton assemblages from 0.77–0.96 μm to 0.55–0.68 μm, corresponding to the mean of the filter mesh size on the fine gnathobasic filter plates of the experimental populations. The clearance rates for large, elongated or dividing cells with maximal lengths of 0.88–8.40 μm were 2.3–17.7 times higher than those for small single coccoids with a diameter of