Ref ID : 7109
Takayama Haruyoshi and Matsuoka Kazumi; [A Reassessment of the Specific Characters of Gymnodinium mikimotoi Miyake et Kominami ex Oda and Gymnodinium nagasakiense Takayama et Adachi]. Bulletin of Plankton Society of Japan 38(1):53-68, 1991
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Gymnodinium nagasakiense Takayama et Adachi was collected from seven embayments along the west Japan as well as Gokasho Bay. The latter is the type locality of Gymnodinium mikimotoi Miyake et Kominami ex Oda. The morphological and physiological features of the two species are herein reassessed on the basis of light and scanning electron microscope observations along with a detailed literature survey. Both species are characterized by the following features. (1) Each species is approximately the same size in cell length, width and thickness. (2) Their cells are both flattened dorso-ventrally. (3) Their nuclei are ellipsoidal and located in the left lobe of the cell. (4) The epicone of each species has a linear apical groove, which was previously misunderstood to be an extension of the sulcus into the epicone. (5) Their cingular displacements are relatively large, approximately one fifth of the cell length. (6) Numerous chloroplasts are randomly distributed in the cell. (7) Both species make red tides not only in the spring-summer but also in the winter. As a result, we conclude that G. mikimotoi is conspecific with G. nagasakiense and that the former is a senior synonym for the latter. The cingular displacement of this species varies from one ninth to one quarter of the cell length. However, most cells observed in this study and in former records have the displacement in less than one fifth of the cell length. This feature suggests that it should belong to Gymnodinium rather than Gyrodinium on the basis of the criterion for both genera. As a result of re-evaluation of description of this species in red tide records, the geographical distribution of G. mikimotoi is wider than in the previous reports.