title: Dynamics of Sequestered Cryptophyte Nuclei inMesodinium rubrumduring Starvation and Refeeding.
abstract: The marine mixotrophic ciliateMesodinium rubrumis known to acquire chloroplasts, mitochondria, nucleomorphs, and nucleus from its cryptophyte prey, particularly from species in the genera,GeminigeraandTeleaulax. The sequestered prey nucleus and chloroplasts are considered to support photosynthesis ofM. rubrum. In addition, recent studies have shown enlargement of the retained prey nucleus in starvedM. rubrumand have inferred that enlargement results from the fusion of ingested prey nuclei. Thus far, however, little is known about the mechanism underlying the enlargement of the prey nucleus inM. rubrum. Here, we conducted starvation and refeeding studies to monitor the fate of prey nuclei acquired byM. rubrumwhen feeding onTeleaulax amphioxeiaand to explore the influence of the retained prey nucleus on photosynthesis ofM. rubrum. Results indicate that enlargement of the prey nucleus does not result from fusion of nuclei. Furthermore, the enlarged prey nucleus does not appear to divide during cell division ofM. rubrum. The presence of a prey nucleus significantly affected photosynthetic performance ofM. rubrum, while the number of retained chloroplasts had little influence on rate of carbon fixation. We interpret results within the context of a model that considers the dynamics of ingested prey nuclei during division ofM. rubrum.
authors.affiliation: Marine Biological Section, Department of Biology, University of Copenhagen Helsingør, Denmark.
authors.forename: Miran
authors.initials: M
authors.lastname: Kim
authors.affiliation: Marine Biological Section, Department of Biology, University of Copenhagen Helsingør, Denmark.
authors.forename: Kirstine
authors.initials: K
authors.lastname: Drumm
authors.affiliation: Marine Biological Section, Department of Biology, University of Copenhagen Copenhagen, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Daugbjerg
authors.affiliation: Marine Biological Section, Department of Biology, University of Copenhagen Helsingør, Denmark.
authors.forename: Per J
authors.initials: PJ
authors.lastname: Hansen
keywords: Teleaulax amphioxeia; nucleus enlargement; photosynthesis; sequestered chloroplasts; sequestered nucleus