title: Cryptophyte algae are robbed of their organelles by the marine ciliate Mesodinium rubrum.
abstract: Mesodinium rubrum (Lohmann 1908) Jankowski 1976 (= Myrionecta rubra) is a common photosynthetic marine planktonic ciliate which can form coastal red-tides. It may represent a 'species complex' and since Darwin's voyage on the Beagle, it has been of great cytological, physiological and evolutionary interest. It is considered to be functionally a phytoplankter because it was thought to have lost the capacity to feed and possesses a highly modified algal endosymbiont. Whether M. rubrum is the result of a permanent endosymbiosis or a transient association between a ciliate and an alga is controversial. We conducted 'feeding' experiments to determine how exposure to a cryptophyte alga affects M. rubrum. Here we show that although M. rubrum lacks a cytostome (oral cavity), it ingests cryptophytes and steals their organelles, and may not maintain a permanent endosymbiont. M. rubrum does not fall into recognized cellular or functional categories, but may be a chimaera partially supported by organelle robbery.
authors.affiliation: University of Maryland, Center for Environmental Science, Horn Point Laboratory, Cambridge 21613, USA. gustafsn@hpl.umces.edu
authors.forename: D E
authors.initials: DE
authors.lastname: Gustafson
authors.forename: D K
authors.initials: DK
authors.lastname: Stoecker
authors.forename: M D
authors.initials: MD
authors.lastname: Johnson
authors.forename: W F
authors.initials: WF
authors.lastname: Van Heukelem
authors.forename: K
authors.initials: K
authors.lastname: Sneider
mesh_terms: D000818:Animals; D002734:Chlorophyll / Q000378:metabolism; D016798:Ciliophora / Q000502:physiology*; D056890:Eukaryota / Q000502:physiology*; D015388:Organelles; D010788:Photosynthesis; D010839:Phytoplankton / Q000502:physiology*; D013559:Symbiosis
chemical_list: D002734:Chlorophyll