Morphology and phylogeny of Gymnodinium trapeziformesp. nov. (Dinophyceae): a new dinoflagellate from the southeast coast of Iran that forms microreticulate resting cysts

G. Attaran-Fariman, M.F. deSalas, A.P. Negri andC.J.S. Bolch. 2007. Morphology and phylogeny of Gymnodinium trapeziformesp. nov. (Dinophyceae): a new dinoflagellate from the southeast coast of Iran that forms microreticulate resting cysts. Phycologia46: 644–656. DOI: 10.2216/07-05.1A new gymnodinioid dinoflagellate, Gymnodinium trapeziformesp. nov. is described from laboratory cultures established by germination of microreticulate resting cysts collected along the southeast coast of Iran bordering the northern Oman Sea. The vegetative cells are small, biconical to ovoid, with a horseshoe-shaped apical groove that encircles the apex in an anticlockwise direction. Cells have a large tear-shaped nucleus positioned in the right side of the cell that extends from the epicone to the hypocone. Cells of G. trapeziformecan be clearly differentiated from the three other microreticulate cyst-forming gymnodinioids, Gymnodinium catenatum, Gymnodinium nolleri,and Gymnodinium microreticulatumby the shape and position of the nucleus. Cultures established from resting cysts do not produce detectable saxitoxin. The resting cysts of G. trapeziformeare unique in being cubic-trapezoidal in shape with a cyst wall colour that is pale purple-brown, most similar in colour to cysts of G. microreticulatumBolch & Hallegraeff. Comparisons of partial large subunit ribosomal RNA gene sequences demonstrate that G. trapeziformeis allied with, but distinct from (> 12.4% sequence divergence) the other microreticulate cyst-forming gymnodinioid species.