title: Phylogeny of the Poorly Known Ciliates, Microthoracida, a Systematically Confused Taxon (Ciliophora), with Morphological Reports of Three Species.
abstract: Three species of Microthoracids, Lopezoterenia paratorpens n. sp., Trochiliopsis australis Foissner et al., 1988 and Discotricha papillifera Tuffrau, 1954, collected from Chinese coastal waters, were investigated using live observation and protargol staining methods. Lopezoterenia paratorpens n. sp. was characterized by its squarely shaped cortical papillae and by dorsal kineties which contained loosely distributed basal bodies. Trochiliopsis australis was revealed to have two oral membranelles, which was not recorded in the original report. Phylogenetic analyses were carried out based on SSU rRNA gene sequence data from each of the three species, and on other available data for microthoracids. The results showed that the order Microthoracida is not monophyletic because the family Discotrichidae, which contains L. paratorpens and D. papillifera, forms a clade separated from the "core" Microthoracids clade. The topologies of the ML and BI trees, along with the distinct morphological characteristics found previously, suggest that the family Discotrichidae should not be assigned to the order Microthoracida. We propose to designate a new order, Discotrichida n. ord. which diagnosed as: flattened ciliates with conspicuous cortical papillae on both dorsal and ventral faces, rod-shaped mucocysts, and an asymmetric cytopharyngeal basket. Also, the fact that Leptopharynx clusters with the assemblage including T. australis, and Pseudomicrothorax is located distantly from Leptopharynx indicates that the classification of Pseudomicrothoracidae and Microthoracidae by Foissner (1985) is justified. This article is protected by copyright. All rights reserved.
authors.affiliation: School of Life Science, East China Normal University, Shanghai, 200062, China.|Laboratory of Protozoology, Institute of Evolution and Marine Biodiversity Ocean University of China, Qingdao, 266003, China.
authors.forename: Xinpeng
authors.initials: X
authors.lastname: Fan
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, 201306, China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Pan
authors.affiliation: Marine College, Shandong University at Weihai, Weihai, 264209, China.
authors.forename: Lifang
authors.initials: L
authors.lastname: Li
authors.affiliation: College of Fisheries and Life Science, Shanghai Ocean University, Shanghai, 201306, China.
authors.forename: Jiamei
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Zoology Department, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Khaled A S
authors.initials: KA
authors.lastname: Al-Rasheid
authors.affiliation: School of Life Science, East China Normal University, Shanghai, 200062, China.
authors.forename: Fukang
authors.initials: F
authors.lastname: Gu
keywords: Microthoracida; Morphology; new order; phylogeny; small subunit rRNA (SSU rRNA); systematics