Home / Non-PS_Flagellates_and_Ciliates / Ciliates / Mesodinium
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Name derivation:
Classification:
Order Cyclotrichiida; Family Mesodiniidae. Synonym: Myrionecta rubra Lohmann 1908. Previously Mesodinium was thought to be a phytoplankter because of its red photopigment, now known to be phycoerithrin and alloxanthin produced by its cryptomonad endobiont. Ciliates that harbor chloroplasts in their endobionts are called 'plastidic ciliates'.
Morphology:
Unicellular ciliate, 20 x 50 um. Has an equatorial ‘belt’ of cilia that causes it to ‘jump’ or swim with a 'jumping motion', perhaps to enhance phosphate uptake, while predator avoidanc is ruled out based on physical models (Jiang 2011). Mesodinium rubrum contains a single branched cryptophyte symbiont with many chloroplasts, mitochondria, nucleomorphs, an endoplasmic reticulum, and one nucleus. The endobiont occupies more than a thrid (36%) of the volume of the ciliate host cell. In addition to photosynthate the ciliate requires prey ingestion of <1 cell per generation (Hansen and Fenchel 2006).
Similar genera:
Importance:
A rare secondarily-photosynthetic ciliate. The photosynthetic apparatus is a plastid derived from phagotrophic intake of a cryptomonad (Santore 1984). The photosynthetic activity of Mesodinium rubrum may be the highest measured in any aquatic organism, with a productivity of > 2 g C m^-3 (Smith and Barber 1979). Forms ‘red tides’ when in bloom proportions due to the pigments of the cryptomonads the ciliate cells have consumed.
Habitat:
Marine, widely distributed in temperate to tropical waters. Requires light for maintenance and activity of its endobiontic cryptomonad cells. Distribution, history of classification, abundance and endobiont photosynthetic activity has been reviewed by Crawford (1989).
References:
Crawford, D.W. 1989. Mesodinium rubrum: the phytoplankter that wasn’t. Mar. Ecol. Prog. Ser. 58:161-174. Hansen, P.J., and T. Fenchel 2006. The bloom-forming ciliate Mesodinium rubrum harbours a single permanent endosymbiont. Mar. Biol. Res. 2006(2):169-177. Jiang, H. 2011. Why does the jumping ciliate Mesodinium rubrumpossess an equatorially located propulsive ciliary belt? J. Plankton Res. 33:998-1011. Smith, W.O., and R.T. Barber 1979. A carbon budget for the autotrophic ciliate Mesodinium rubrum. J. Phycol. 15:27-33.