Morphology and molecular phylogeny of a new soil stichotrichid ciliate, Circinella granulifera sp. nov. (Alveolata, Ciliophora)

The morphology and molecular characterisation of a novel soil stichotrichid ciliate, Circinella granulifera sp. nov ., discovered in Ganzhou, southeastern China, were investigated using light microscopy of live and protargol-impregnated specimens, as well as ribosomal gene sequencing methods. The new species can be recognised by having a cell size of 115–130 × 10–15 µm in vivo , a vermiform body with a narrowly rounded anterior end and a tapered posterior portion that is consistently curved leftwards; a body only slightly dorsoventrally flattened in the frontal region; a single contractile vacuole positioned at about mid-body near the left margin; colourless cortical granules about 0.8 μm in diameter and arranged in rows of varying lengths; an adoral zone occupying about 1/10 of the body length and composed of 10 membranelles on average; three frontal membranelles in the distal portion which are separated by a distinct gap from ventral membranelles in the proximal portion; invariably three frontal cirri and one buccal cirrus; one frontoventral row of about seven cirri; one left and one right marginal row with 36–55 cirri and 48–70 cirri, respectively; one dorsal kinety with about 17 dikinetids; and on average 17 macronuclear nodules and two micronuclei. Phylogenetic analyses based on small subunit ribosomal RNA gene sequences showed that Circinella granulifera sp. nov . clusters with Kahliella matisi with moderate to high support, suggesting that Circinella should be assigned to or closely related to the family Kahliellidae Tuffrau, 1979.