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Microstome--macrostome transformation in the polymorphic ciliate Tetrahymena vorax leads to mechanosensitivity associated with prey-capture behaviour.

Abstract

Ciliates feed by phagocytosis. Some ciliate species, such as Tetrahymena vorax, are polymorphic, a strategy that provides more flexible food utilization. Cells of the microstomal morph of T. vorax feed on bacteria, organic particles and organic solutes in a non-selective manner, whereas macrostome cells are predators that consume specific prey ciliates. In the present study, we investigated a possible correlation between phagocytosis and mechanosensitivity in macrostome T. vorax. Microstome cells seem to be insensitive to mechanical stimulation whereas macrostome cells depolarise in response to mechanical stimulation of the anterior part of the cell. The amplitude of the receptor potential induced by either a prey ciliate or a 5 μm push by a glass needle was sufficient to elicit a regenerative Ca²⁺ spike. The difference in mechanosensitivity of the two forms correlates with the swimming behaviour when hitting an obstacle; microstome cells swim alongside the obstacle whereas macrostome cells swim backwards, turn and resume forward swimming. Macrostome cells prevented from backward swimming and the subsequent turn failed to capture prey cells in their pouch. Macrostome cells consumed heterospecific prey ciliates preferentially over conspecific microstome cells. This selectivity is not due to electrical membrane responses elicited by physical contact. Both microstome and macrostome cells accumulated in an area containing putative substances released from heterospecific prey ciliates, but the substances did not elicit any electrophysiological membrane responses. We conclude that the mechanosensitivity of macrostome cells is associated with the prey-capture behaviour, whereas the selective phagocytosis is probably due to chemo-attraction to heterospecific prey ciliates.

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  • Publisher Full Text

    • Authors

    Grønlien HK, Hagen B, Sand O

    Institution

    Department of Molecular Biosciences, University of Oslo, Blindern, N-0316 Oslo, Norway. heidi.k.gronlien@hiof.no

    Source

    The Journal of experimental biology 214:Pt 13 2011 Jul 1 pg 2258-66

    MeSH

    Food Chain
    Locomotion
    Mechanoreceptors
    Membrane Potentials
    Phagocytosis
    Tetrahymena

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    22799008