Heterocapsa arctica sp nov (Peridiniales, Dinophyceae), a new marine dinoflagellate from the arctic

]A culture strain labeled CCMP445: Heterocapsa sp. deposited in the Culture Collection of Marine Plankton, Bigelow, ME, was studied by means of light and electron microscopy and is described as a new species, Heterocapsa arctica Horiguchi sp. nov. The cells are elongated, consisting of a large epitheca and a small hypotheca. Each cell possesses a parietal chloroplast with a spherical pyrenoid, the matrix of which is penetrated by many tubular extensions of cytoplasm. Heterocapsa arctica possesses triangular scales typical of the genus. The thecal plate arrangement is Po, cp, 5 ', 3a, 7 '', 6c, 5s, 5 ''', 2 '''', which is identical to that of most of the members of the genus Heterocapsa. However, H. arctica is readily distinguished from all other described species of Heterocapsa by its unique, elongated cell shape.