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.