Three Redescriptions in Tintinnopsis (Protista ：Ciliophora: Tintinnina) from Coastal Waters of China, with Cytology and Phylogenetic Analyses Based on Ribosomal RNA Genes

Abstract

Background: The taxonomy of tintinnine ciliates is vastly unresolved because it has traditionally been based on the lorica (a secreted shell) and it has only recently incorporated cytological and molecular information. Tintinnopsis, the most speciose tintinnine genus, is also the most problematic: it is known to be non-monophyletic, but it cannot be revised until more of its species are studied with modern methods.Results: Here, T. hemispiralis Yin, 1956, T. kiaochowensis Yin, 1956, and T. uruguayensis Balech, 1948, from coastal waters of China, were studied. Lorica and cell features were morphometrically investigated in living and protargol-stained specimens, and sequences of three ribosomal RNA (rRNA) genes were phylogenetically analyzed. The three species show a complex ciliary pattern (with ventral, dorsal, and posterior kineties and right, left, and lateral ciliary fields), but differ in lorica morphology, details of the somatic ciliature and rRNA gene sequences. Tintinnopsis hemispiralis is further distinguished by a ciliary tuft (a ribbon of very long cilia originating from the middle portion of the ventral kinety and extending out of the lorica) and multiple macronuclear nodules. Both T. kiaochowensis and T. uruguayensis have two macronuclear nodules, but differ in the number of somatic kineties and the position of the posterior kinety. Two neotypes are fixed for T. hemispiralis and T. kiaochowensis to stabilize the species names objectively, mainly because of the previous unavailability of type materials. By phylogenetic analysis and comparison with closely-related species, we infer that the ciliary tuft and details such as the commencement of the rightmost kinety in the lateral ciliary field are synapomorphies that may help clarify the systematics of Tintinnopsis-like taxa.Conclusion: The redescriptions of three poorly known Tintinnopsis species, namely T. hemispiralis, T. kiaochowensis, and T. uruguayensis firstly revealed their ciliary pattern and rRNA sequences. This study expands knowledge and database of tintinnines and helps in identifying potential synapomorphies for future taxonomic rearrangements.

Integrative Taxonomy and Molecular Phylogeny of Three Poorly Known Tintinnine Ciliates, with the Establishment of a New Genus (Protozoa; Ciliophora; Oligotrichea)

“…nov. can differ from A. karajacensis comb. nov. by the shape of lorica, the numbers of macronuclear nodules and collar membranelles as well as the details about somatic ciliary rows ( [42] and present study). A. subacuta comb.…”

“…nov. and A. gracilis (Kofoid & Campbell, 1929) comb. nov. resemble our specimens not only in the unique most complex type of ciliary pattern, but also in the presence of multiple macronuclear nodules [42,46,52]. However, both A. hemispiralis comb.…”

“…A. hemispiralis comb. nov. is distinguished from our specimens by the presence of 3-5 spiral striations in the collar of the lorica (vs. absence), and the commencing position of the ventral kinety (anteriorly to second kinety vs. rst kinety of right ciliary eld) as well the length of the ventral kinety (extending to posterior one quarter to one third of cell proper vs. terminating at the middle portion of cell proper) [42]. Furthermore, the SSU rDNA sequences of A. subacuta comb.…”

“…Tintinnopsis subacuta was described to have these two distinctive features by Pierce [46] and Mühlthaler et al [52]. Most recently, this unique, elongated ciliary tuft was also recognized in T. hemispiralis by Bai et al [42]. Considering these remarkable divergences that differ from the other Tintinnopsis species, we thus establish a new genus for the four species with the two synapomorphies by splitting them from the problematic genus Tintinnopsis.…”

“…Members of the genus can be recognized by an agglutinated and hard lorica; however, species determination remains very confused because many species overlap too much in terms of lorica size and shape. Up to now, only 17 species have been investigated within the genus regarding cell features [36][37][38][39][40][41][42][43][44][45][46][47]. On the other hand, the SSU rDNA sequences are available for 22 species of Tintinnopsis in the GenBank.…”