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Two Size-Selective Mechanisms Specifically Trap Bacteria-Sized Food Particles in Caenorhabditis elegans

Christopher Fang-Yen, Leon Avery and Aravinthan D. T. Samuel
Proceedings of the National Academy of Sciences of the United States of America
Vol. 106, No. 47 (Nov. 24, 2009), pp. 20093-20096
Stable URL: http://www.jstor.org/stable/25593329
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Two Size-Selective Mechanisms Specifically Trap Bacteria-Sized Food Particles in Caenorhabditis elegans
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Abstract

Caenorhabditis elegans is a filter feeder: it draws bacteria suspended in liquid into its pharynx, traps the bacteria, and ejects the liquid. How pharyngeal pumping simultaneously transports and filters food particles has been poorly understood. Here, we use high-speed video microscopy to define the detailed workings of pharyngeal mechanics. The buccal cavity and metastomal flaps regulate the flow of dense bacterial suspensions and exclude excessively large particles from entering the pharynx. A complex sequence of contractions and relaxations transports food particles in two successive trap stages before passage into the terminal bulb and intestine. Filtering occurs at each trap as bacteria are concentrated in the central lumen while fluids are expelled radially through three apical channels. Experiments with microspheres show that the C. elegans pharynx, in combination with the buccal cavity, is tuned to specifically catch and transport particles of a size range corresponding to most soil bacteria.

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