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ZOOSPOROGENESIS, MORPHOLOGY, ULTRASTRUCTURE, PIGMENT COMPOSITION, AND PHYLOGENETIC POSITION OF TRACHYDISCUS MINUTUS (EUSTIGMATOPHYCEAE, HETEROKONTOPHYTA)1
Article first published online: 6 JAN 2012
© 2011 Phycological Society of America
Journal of Phycology
Volume 48, Issue 1, pages 231–242, February 2012
How to Cite
Přibyl, P., Eliáš, M., Cepák, V., Lukavský, J. and Kaštánek, P. (2012), ZOOSPOROGENESIS, MORPHOLOGY, ULTRASTRUCTURE, PIGMENT COMPOSITION, AND PHYLOGENETIC POSITION OF TRACHYDISCUS MINUTUS (EUSTIGMATOPHYCEAE, HETEROKONTOPHYTA). Journal of Phycology, 48: 231–242. doi: 10.1111/j.1529-8817.2011.01109.x
Received 8 October 2010. Accepted 28 July 2011.
- Issue published online: 1 FEB 2012
- Article first published online: 6 JAN 2012
- 18S rRNA;
- Goniochloris sculpta;
- lipid bodies;
- photosynthetic pigments;
- Trachydiscus minutus;
The traditional order Mischococcales (Xanthophyceae) is polyphyletic with some original members now classified in a separate class, Eustigmatophyceae. However, most mischococcalean species have not yet been studied in detail, raising the possibility that many of them still remain misplaced. We established an algal culture (strain CCALA 838) determined as one such species, Trachydiscus minutus (Bourr.) H. Ettl, and studied the morphology, ultrastructure, life cycle, pigment composition, and phylogeny using the 18S rRNA gene. We discovered a zoosporic part of the life cycle of this alga. Zoospore production was induced by darkness, suppressed by light, and was temperature dependent. The zoospores possessed one flagellum covered with mastigonemes and exhibited a basal swelling, but a stigma was missing. Ultrastructural investigations of vegetative cells revealed plastids lacking both a connection to the nuclear envelope and a girdle lamella. Moreover, we described biogenesis of oil bodies on the ultrastructural level. Photosynthetic pigments of T. minutus included as the major carotenoids violaxanthin and vaucheriaxanthin (ester); we detected no chl c. An 18S rRNA gene-based phylogenetic analysis placed T. minutus in a clade with species of the genus Pseudostaurastrum and with Goniochloris sculpta Geitler, which form a sister branch to initially studied Eustigmatophyceae. In summary, our results are inconsistent with classifying T. minutus as a xanthophycean and indicate that it is a member of a novel deep lineage of the class Eustigmatophyceae.