Abstract

Two tintinnid species with stout campanulate loricae were collected from coastal waters of the Yellow Sea, South Korea. These species were identified as Tintinnopsis fimbriata Meunier, 1919 and T. uruguayensis Balech, 1948. The loricae morphology of fixed cells from both species was examined under light and scanning electron microscopes. Also, the phylogenetic positions of the two species were inferred using the gene sequences from SSU rDNA, ITS1, 5.8S rDNA, and ITS2. They share very similar loricae that consist of an obconical collar, a globular bowl, and a cylindrical posterior process. However, T. fimbriata can be distinguished from T. uruguayensis by the lorica size (61-71×34-41 μm vs. 52-61×23-29 μm) and the ratio of lorica length to collar opening diameter (1.6-1.8 vs. 1.9-2.7). The two species showed high similarity to each other as follows: 99.86% (2 nucleotide differences) in SSU rDNA and 99.76% (1 nucleotide difference) in ITS1-5.8S rDNA-ITS2. Given the morphological and molecular similarities between the Korean T. fimbriata and T. uruguayensis, as well as the discrepancies between the neotype of T. fimbriata and its original description (e.g., posterior process of the lorica), further studies are required to clarify their conspecificity or the potential existence of sibling species.