Morphological and ribosomal DNA-based characterization of six Antarctic ciliate morphospecies from the Amundsen Sea with phylogenetic analyses.

We characterized six tintinnid ciliates from Antarctic waters using molecular markers and morphological traits: Amphorellopsis quinquealata, Codonellopsis gaussi, Cymatocylis convallaria, Cy. calyciformis, Cy. drygalskii, and Laackmanniella prolongata. The 100% similarity in SSU-ITS1-5.8S rDNA-ITS2-partial LSU rDNA sequences among Cy. convallaria, Cy. calyciformis, and Cy. drygalskii is supportive of synonymy. Codonellopsis gaussi and L. prolongata also showed high levels of similarity in SSU rDNA (99.83%) and the D2 domain of LSU rDNA (95.77%), suggesting that they are closely related. Phylogenetic analysis placed Cymatocylis in the Rhabdonellidae, Amphorellopsis in the Tintinnidae and L. prolongata/Co. gaussi within the Dictyocystidae.