Abstract
Background: As dominant components of planktonic microeukaryotes, the tintinnine ciliates act as a trophic link between microbial food web and traditional planktonic food chain in aquatic ecosystems. However, traditionally the taxonomy and systematics of tintinnines have been based on the lorica. It is now accepted that lorica features alone are insufficient and that cytological and molecular information are also needed. The systematics of the genera Tintinnopsis and Amphorellopsis is ambiguous, mainly due to the lack of ciliary and molecular information on their type species, T. beroidea and A. acuta.
Result: In the present study, specimens of both species were collected from coastal waters of Qingdao, China. The morphology of each was investigated based on observations of live and protargol-stained specimens, and their SSU rDNAand LSU rDNA-based phylogenies were analyzed. Tintinnopsis beroidea presents the genus-typical ciliature. The somatic kineties in Amphorellopsis acuta were found to be evenly distributed without differentiation into distinct ciliary fields. The phylogenetic analyses revealed that Tintinnopsis is non-monophyletic, and that T. beroidea has a close relationship with T. nana and T. baltica. The monophyly of Amphorellopsis is also not supported by SSU rDNA analysis.
Conclusion: This study first reveals the ciliary pattern and two nuclear rRNA gene sequences of two tintinnine type species, and thus expands knowledge and database of tintinnines. Amphorellopsis represents an intermediate lineage between tintinnines (loricate form) and aloricate choreotrichids. (c) 2020 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).