AME 67:177-187 (2012)  -  DOI:

Plastid retention, use, and replacement in a kleptoplastidic ciliate

D. M. Schoener*, G. B. McManus

Department of Marine Sciences, University of Connecticut, Groton, Connecticut 06340, USA

ABSTRACT: The marine oligotrich ciliate Strombidium rassoulzadegani retains and utilizes the chloroplasts of its algal food. It does not appear to be able to induce its captured plastids to divide, and so the plastids must be replaced with new ones from recently ingested food. We measured the plastid replacement rate of S. rassoulzadegani, its growth and feeding rates, chlorophyll retention, and mortality when starved, and determined whether the ciliate showed differential grazing or plastid retention when presented with different algal foods. S. rassoulzadegani had similar mortality rates when starved following growth on either Tetraselmis chui or Rhodomonas lens. When presented with a source for new plastids, the ciliate can incorporate its first new plastid within 30 min and completely replace all of its plastids within 48 to 72 h. S. rassoulzadegani did not show a preference for either Tetraselmis or Rhodomonas when grazing. However, it did preferentially acquire the Tetraselmis-derived plastids. Our results contrast with those for other mixotrophic ciliates; for example, Mesodinium rubrum can maintain its plastids for extended periods of time (weeks), while Strombidium capitatum can quickly lose (40 h) and replace (9 h) its prey-derived plastids. S. rassoulzadegani also seems to be able to grow more efficiently when grazing on Tetraselmis than on Rhodomonas. S. rassoulzadegani may contribute to the primary production in the tide pools where it is found and by using autotrophic and heterotrophic nutritional strategies may be able to survive changes in food availability.

KEY WORDS: Kleptoplasty · Mixotrophy · Growth efficiency · Ciliate

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Cite this article as: Schoener DM, McManus GB (2012) Plastid retention, use, and replacement in a kleptoplastidic ciliate. Aquat Microb Ecol 67:177-187.

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