DNA Analysis of Algal Endosymbionts of Ciliates Reveals the State of Algal Integration and the Surprising Specificity of the Symbiosis.

Many freshwater protists harbor unicellular green algae within their cells, but little is known of their degree of integration and specificity. Using algae-targeted PCR of whole ciliate cells collected at irregular intervals over 15 months from Lake Biwa, Japan, we explored the SSU-ITS rDNA of the endosymbiotic algae and its changes over time, obtaining sequences of algal rDNA fragments from four ciliate species. A high proportion of clonal algae was evident within the ciliate cells.

Vorticella Linnaeus, 1767 (Ciliophora, Oligohymenophora, Peritrichia) is a grade not a clade: redefinition of Vorticella and the families Vorticellidae and Astylozoidae using molecular characters derived from the gene coding for small subunit ribosomal RNA.

Recent phylogenetic analyses of the peritrich genus Vorticella have suggested that it might be paraphyletic, with one Vorticella species - Vorticella microstoma grouping with the swimming peritrichs Astylozoon and Opisthonecta in a distant clade. These results were based on very limited taxon sampling and thus could not be accepted as conclusive evidence for revising the generic classification. We tested paraphyly of the genus Vorticella by making a new analysis with a broad range of samples from three continents that yielded 52 new sequences of the gene coding for small subunit rRNA.

Molecular phylogeny of the family Vorticellidae (Ciliophora, Peritrichia) using combined datasets with a special emphasis on the three morphologically similar genera Carchesium, Epicarchesium and Apocarchesium.

Little is known about the phylogeny of the family Vorticellidae at the generic level because few comprehensive analyses of molecular phylogenetic relationships between members of this group have, so far, been done. As a result, the phylogenetic positions of some genera that were based originally on morphological analyses remain controversial. In the present study, we performed phylogenetic analyses of vorticellids based on the sequence of the small-subunit (SSU) rRNA gene, including one species of the genus Apocarchesium, for which no sequence has previously been reported.

Morphology, morphogenesis and gene sequence of a freshwater ciliate, Pseudourostyla cristata (Ciliophora, Urostyloidea) from the ancient Lake Biwa, Japan.

The urostyloid freshwater ciliate Pseudourostyla cristata was recorded for the first time from Lake Biwa, a 4-million-year-old lake located in Shiga Prefecture, Japan. Its morphology and morphogenesis were investigated using live observation and protargol impregnation, and the SSU ribosomal RNA gene was sequenced. Based on the current observations and previous descriptions, this species is readily recognized mainly by the following characters: body slender or broadly oval to elliptical, and dark grey in color; size in vivo about 170-400 x 40-150 microm; pellicle flexible and contractile, with extrusomes forming a hyaline seam underneath; ciliature comprising about 60-130 adoral membranelles, usually 1 buccal cirrus, 20-24 frontal, 2 frontoterminal, 17-26 pairs of midventral, and 5-16 transverse cirri, 4-6 left and 4-5 right marginal rows, and 8-10 dorsal kineties; 15-83 macronuclear nodules and 2-9 micronuclei; freshwater habitat.

Morphological and molecular characterization of Histiobalantium natans viridis (Ciliophora, Scuticociliatia).

We investigated a Histiobalantium natans viridis population from the ancient Lake Biwa in Japan, using live observation, silver impregnation, and the small subunit rRNA gene sequence. The morphological and molecular data show, with high support, a close relationship of Histiobalantium, Schizocalyptra and Pleuronema, supporting the family Pleuronematidae Kent, whose nearest relatives are the Cyclidiidae Ehrenberg. A family Histiobalantiidae Puytorac and Corliss is not supported, either by the nucleotide sequences or the morphologic data, except for the curious dorsal location of the cytopyge.

A description of Apocarchesium rosettum n. gen., n. sp. and a redescription of Ophrydium eichornii Ehrenberg, 1838, two freshwater peritrichous ciliates from Japan.

This paper includes the proposal of a new genus for a new species of peritrichous ciliate, Apocarchesium rosettum n. gen., n.

Morphology and gene sequence of Levicoleps biwae n. gen., n. sp. (Ciliophora, Prostomatida), a proposed endemic from the ancient Lake Biwa, Japan.

Levicoleps biwae n. gen., n.