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Name derivation: |
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Named after Cesare Emiliani. Previously called Coccolithus ("Stone kernel"). Emiliani as a geologist contributed much to the understanding of cyclic glacial periods during the past ~ 1 million years. The common species is E. huxleyi, known by the coccolith jockeys as "Ehux" (see, for example, Toby Tyrrell's page).
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Classification: |
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Emiliania W.W.Hay and H.P.Mohler 1967; 1 of 7 species descriptions is currently accepted taxonomically (Guiry and Guiry 2013).Order Isochrysidales; Family Noëlaerhabdaceae |
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Morphology: |
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Non-flagellate unicells (5 - 10 µm diameter; 158 – 218 µm3 volume) covered with complex rivet-shaped calcareous coccoliths in the diploid stage of the life cycle, but biflagellate smaller unicells (45 – 47 µm3 volume) covered with noncalcareous organic scales in the haploid stage (Kilb and Strom 2013). online video of coccolith formation. |
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Similar genera: |
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Habitat: |
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Marine plankton. When blooming a type of 'whiting' of large oceanic areas is visible from satellites (see image 4 above). This reflectance of the calcite coccoliths is similar to lake 'whiting' (as in Lake Michigan, Lake Erie (USA), and many alpine lakes in Europe where calcite marl crystals form when daily photosynthesis elevates the pH, causing a shift in the dissolved inorganic carbon (DIC) equilibrium toward the relatively insoluble calcium carbonate. Accumulation
of coccolith fossils has created the extensive
chalk cliffs in Germany (more than 161 m high in the above-sea-level portion)
and England (more than 106 m high). The oldest chalk sediments were deposited
during the Cretaceous, Latin for chalk
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In at least one specific predator (the ciliate Strombidinopsis acuminatum) – prey (the coccolith Emiliania huxleyi) interaction, the haploid stage of E. huxleyi had an inducible predator defense that reduced predation by 25 – 43%, comparing ‘naďve’ (higher loss to predator) and ‘predator-exposed’ haploid cells. In contrast the coccolith-covered diploid cells did not have inducibility and were ingested at ~50% the rate of the haploid cells (on a cell per ciliate basis in 30 minutes (Kolb and Strom 2013). The authors noted the specificity of the defense, as there was no inhibition of the predator feeding on an alternate prey, Heterocapsa triquetra (a dinoflagellate), suggesting a cell surface-based mechanism rather than an ‘infochemical’ released by haploid E. huxleyi cells into the water medium. |
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References: |
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Guiry, M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 30 April 2013. Kolb, A., and S. Strom 2013. An inducible antipredatory defense in haploiod cells of the marine microalga Emiliania huxleyi (Prymnesiophyceae). Limnol. Ocenogr. 58(3):932-944. |
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