Integrative taxonomy and molecular phylogeny of three poorly known tintinnine ciliates, with the establishment of a new genus (Protista; Ciliophora; Oligotrichea)

BACKGROUND

The taxonomic classification of the suborder Tintinnina Kofoid & Campbell, 1929, a species-rich group of planktonic ciliated protistans with a characteristic lorica, has long been ambiguous largely due to the lack of cytological and molecular data for most species. Tintinnopsis is the largest, most widespread, and most taxonomically complex genus within this group with about 170 species occurring in nearshore waters. Previous molecular phylogenetic studies have revealed that Tintinnopsis is polyphyletic.

RESULTS

Here we document the live morphology, infraciliature, gene sequences, and habitat characteristics of three poorly known tintinnine species, viz. Tintinnopsis karajacensis Brandt, 1896, Tintinnopsis gracilis Kofoid & Campbell, 1929, and Tintinnopsis tocantinensis Kofoid & Campbell, 1929, isolated from the coastal waters of China. Based on a unique cytological feature (i.e., an elongated ciliary tuft with densely arranged kinetids) in the former two species, Antetintinnopsis gen. nov. is erected with Antetintinnopsis hemispiralis (Yin, 1956) comb. nov. (original combination: Tintinnopsis hemispiralis Yin, 1956) designated as the type species. Moreover, A. karajacensis (Brandt, 1896) comb. nov. (original combination: Tintinnopsis karajacensis Brandt, 1896) and A. gracilis (Kofoid & Campbell, 1929) comb. nov. (original combination: Tintinnopsis gracilis Kofoid & Campbell, 1929) are placed in a highly supported clade that branches separately from Tintinnopsis clades in phylogenetic trees based on SSU rDNA and LSU rDNA sequence data, thus supporting the establishment of the new genus. One other species is assigned to Antetintinnopsis gen. nov., namely A. subacuta (Jörgensen, 1899) comb. nov. (original combination Tintinnopsis subacuta Jörgensen, 1899).

CONCLUSIONS

The findings of the phylogenetic analyses support the assertion that cytological characters are taxonomically informative for tintinnines. This study also contributes to the broadening of our understanding of the tintinnine biodiversity and evolution.

Morphological redescriptions and neotypification of two poorly known tintinnine ciliates (Alveolata, Ciliophora, Tintinnina), with a phylogenetic investigation based on SSU rRNA gene sequences

Two poorly known tintinnine ciliates collected from the coastal waters of PR China, viz., Codonellopsis mobilis Wang, 1936 and Tintinnopsis chinglanensis Nie & Ch'eng, 1947, were redescribed and neotypified using live observation, protargol staining and SSU rRNA gene sequencing. Ciliature information and SSU rRNA gene sequence data of both species were revealed for the first time and improved diagnoses were given based on the original descriptions and data from the present study. Further phylogenetic analyses inferred from SSU rRNA gene sequences and morphological data suggested that the genus Tintinnopsis is polyphyletic and that the genus Codonellopsis is non-monophyletic. The approximately unbiased test, however, does not reject the possibility that Codonellopsis is monophyletic.