A New Clade, Based on Partial LSU rDNA Sequences, of Unarmoured Dinoflagellates

Approximately 10^5 species of protists (unicellular eukaryotic microorganisms) are currently known but it is estimated that their diversity is several orders of magnitude higher. In most cases, the organisms lack of a distinctive morphology and cannot be cultured in the lab. 
Consequently, we do not know how many species there are, who they are and how they live. By sequencing their DNA, we are able to characterize this hidden diversity, to fill out the microbial tree of life and to understand the role that microbes play in the environment.

The taxonomy and diversity of dinoflagellates (a group of flagellate protists) has been based on morphological features but molecular data evidence a diversity not reflected by morphological characters and, moreover, their classification is not always supported by genetic analyses. Therefore, many organisms need to be reclassified. In the dinoflagellates group, the order Gymnodiniales comprises organisms with few morphological characters and most species do not grow in cultures. However, the single-cell PCR technique allows sequencing some fragments of DNA from single specimens. The phylogenetic information gives evidence that some morphology-based groups of Gymnodiniales are inconsistent.