Description of Prymnesium
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Coccolithophorids, cells sub-spherical to elongate, sometimes compressed, 2 two equal or sub-equal flagella and a flexible non-coiling haptonema, flagella 1 - 1.5 x cell length, haptonema approx. 1/3 to 1/5 the length of the flagella, flagella sometimes with a covering of scales, arising sub-apically from the obliquely truncate apical pole; one flagellum often held closely to the cell body, the other extended away from the cell; haptonema directed forwards during swimming, usually 2 chloroplasts with immersed or bulging pyrenoids; eyespot absent, contractile vacuole sometimes present anteriorly; muciferous bodies often situated peripherally; body scales present, with two or more morphotypes arranged in two or more layers; some species toxic to fish and other gill-breathing animals; some are heterotrophic.
