Abstract
BackgroundHeterotrichous 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.ResultsThe 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.ConclusionsModern 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.
Highlights
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
The heterotrichs are characterized by their typically large body size, somatic kineties composed of dikinetids with postciliodesmata and a prominent oral apparatus composed of a paroral membrane and an adoral zone of membranelles [1, 2]
Diagnosis Body about 400–800 × 30–50 μm in vivo, slightly contractile, slender with a conspicuously pointed caudal region; macronucleus sausage-shaped; pellicle with rod-shaped, dark-brownish cortical granules and rod-shaped mitochondria (?); 25–37 somatic kineties, several of which are shortened forming a suture near posterior end of body; 76–174 adoral membranelles; paroral membrane fragmented, comprising 29–75 pieces; marine habitat
Summary
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. Species identification and phylogenetic relationships of heterotrichs remain challenging due to the lack of accurate morphological information and insufficient molecular data. Members of the ciliate class Heterotrichea Stein, 1859 are found in a wide range of aquatic biotopes. Only G. lanceolata has been investigated using modern methods while its congeners remain insufficiently described [5, 6]
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