New contributions to two ciliate genera (Ciliophora, Heterotrichea) based on morphological and molecular analyses, with description of a new Gruberia species

Abstract

Background Heterotrichous ciliates are common members of microeukaryote communities which play important roles in both the transfer of material and the flow of energy in aquatic food webs. This group has been known for over two centuries due to their large body size and cosmopolitan distribution. Nevertheless, species identification and phylogenetic relationships of heterotrichs remain challenging due to the lack of accurate morphological information and insufficient molecular data. Results The morphology and phylogeny of two heterotrichous ciliates, namely Gruberia foissneri spec. nov. and Linostomella vorticella (Ehrenberg, 1833) Aescht in Foissner et al., 1999, were studied using rigorous methods (living morphology, stained preparations, and small subunit rDNA sequence data). Gruberia foissneri spec. nov. is morphologically very similar to G. uninucleata Kahl, 1932, however, it can be distinguished from the latter by having more ciliary rows (about 32 vs. about 20) and macronuclear shape (sausage-shaped vs. ellipsoid). Based on a combination of previous and present studies, an improved diagnosis of L. vorticella is supplied and several taxonomic anomalies are clarified. In addition, phylogenetic analyses based on SSU rDNA sequence data support the generic assignment of these two species. Conclusions Modern ciliate taxonomy should be performed by means of detailed living observation, stained preparations and molecular information. For those species that have been reported in previous studies, it is necessary to provide as much useful information as possible using state-of-the-art methods in order to resolve taxonomic anomalies.

Taxonomy and SSU rDNA-Based Phylogeny of Two Heterotrich Ciliates (Ciliophora, Heterotrichea) Collected From Subtropical Wetlands of China, Including the Description of a New Species, Linostomella pseudovorticella n. sp.

“…Over the past two decades, the phylogenetic position of this species was gradually revealed ( Foissner et al, 1992 , 1999 ; Lynn, 2008 ). Chi et al (2020) redescribed L. vorticella based on both morphological and molecular information and supplied a taxonomic revision of the genus Linostomella .…”

“…Three populations of L. vorticella have previously been reported with data on the infraciliature, and all three overlap in terms of the number of somatic kineties, i.e., 39–45 in a Rheinland-Pfalz population, 26–45 in a Salzburg population, and 37–51 in a Qingdao population ( Packroff and Wilbert, 1991 ; Foissner et al, 1999 ; Chi et al, 2020 ). Among these three populations, the morphological characters of the Qingdao population were described in the most detail, and the molecular phylogeny of this population was also analyzed based on SSU rDNA sequence data.…”

“…The ciliary pattern and nuclear apparatus were revealed by protargol staining ( Wilbert, 1975 ). Terminology followed Song and Wilbert (1997) ; Rosati et al (2004) , and Chi et al (2020) .…”

“…The Heterotrichea contains 10 families and about 60 genera, several of which are well-known, e.g., Stentor Oken, 1815 and Spirostomum Ehrenberg, 1834. In contrast, some genera are not familiar because they have few species and/or they are difficult to collect, e.g., Linostomella Aescht in Foissner et al, 1999 , Chattonidium Villeneuve, 1937, and Peritromus Stein, 1863 ( Rosati et al, 2004 ; Modeo et al, 2006 ; Chi et al, 2020 , 2021 ).…”

“…The type species, Linostomella vorticella Ehrenberg, 1833 Aescht in Foissner et al, 1999 , has been recorded and redescribed several times since it was first reported by Ehrenberg ( Ehrenberg, 1833 ; Dujardin, 1841 ; Jankowski, 1978 ; Aescht, 2001 ; Rossi et al, 2016 ). Recently, Chi et al (2020) gave a detailed redescription of L. vorticella and investigated its molecular phylogeny based on a population from Qingdao, China.…”