Aloricate oligotrich ciliates are important components of marine microplankton. This paper summarizes the results of several biodiversity and faunal studies on this group in typical coastal habitats of southern China that were carried out from 2006 to 2016. The main findings are as follows: (1) a total of 39 species belonging to 17 genera, seven families and four orders of aloricate oligotrich (s. l.) ciliates were identified from coastal waters of Zhanjiang, Guangzhou, Shenzhen, Huizhou, and Hong Kong; among these 16 species, four genera, one family and one order were new to science; (2) the order Oligotrichida represents the most abundant taxon with highest species richness and its members are widely distributed in all coastal habitats; the family Strombidiidae and the genus Strombidium comprise the highest proportion of all oligotrichs at family and genus levels, respectively; (3) based on the results of our taxonomic investigations, the biodiversity of oligotrichs in five typical habitats are compared; mangrove wetland possessing the highest species richness of oligotrich ciliates represents a biodiversity hotspot habitat in the southern coast of China; (4) morphologies of 10 poorly known species, namely Pelagohalteria cirrifera, Strombidium conicum, Spirostrombidium schizostomum, Parallelostrombidium paralatum, Omegastrombidium elegans, Varistrombidium kielum, Spirotontonia turbinata, Pelagostrobilidium simile, Strombidinopsis batos, and Strombidinopsis cheshiri are redescribed based on living and protargol-stained specimens, and some new characters are analysed. Improved diagnoses of Strombidium conicum and Strombidinopsis batos are supplied.

Although predation risk exists under natural conditions, its role is usually ignored when evaluating the ecotoxicity of environmental contaminants, and the interaction between predation risk and antibiotic ecotoxicity is not yet clear. To investigate the nonconsumptive effects (NCEs) of predation on the ecotoxicity evaluation of antibiotics, the median lethal concentration (LC₅₀), relative population growth rate (RGR), and activities of three antioxidases were measured in the ciliate Paramecium jenningsi exposed to graded concentrations of the antibiotics nitrofurazone (NFZ) or erythromycin (ERY) in the presence or absence of a predator, i.e., the ciliate Didinium nasutum. The results showed that (1) NCEs significantly reduced the LC₅₀ of NFZ but had no effect on that of ERY; (2) predation pressure alone had no significant effect on the inhibitory rate of the P. jenningsi population, but the interaction with NFZ was synergistic, while that with CRY was additive; (3) the concentrationresponse (i.e., mortality) model for each antibiotic exposure with and without predation pressure differed significantly in the parameter slope; (4) RGRs were significantly reduced by antibiotic exposure or NCEs; only in NFZ-exposed groups did the RGRs decrease linearly with increasing exposure concentration; and (5) the activities of all three antioxidases significantly increased due to NCEs or following exposure to antibiotics. In brief, NCEs were detected in P. jenningsi, and these had additive or synergistic effects on antibiotic ecotoxicity, but their magnitude depended on the properties and exposure concentrations of the antibiotics. Our findings suggest that it is necessary to consider the roles of NCEs in the ecotoxicity evaluation of environmental contaminants.

As the typical periphytic ciliate, the genus Euplotes Ehrenberg, 1830 is highly diversified and commonly observed in marine water. In this study, the living morphology, infraciliature and silverline system of two poorly known Euplotes species, E. neapolitanusWichterman, 1964 and E. antarcticusFenchel and Lee, 1972, isolated from coastal water of southern China, were investigated. The original description of these two species were brief, and thus we provided detailed redescription based on our Chinese population. Their diagnoses were improved by adding some morphology characteristics and their detailed illustrations and photomicrographs were first supplied here. Based on the sufficient justification for identification of our population by morphology, their small subunit ribosomal RNA gene sequences which have been reported were linked to the accurate species name. Phylogenetic analyses showed that these two species cluster with their congeners which shared high morphological similarities with them. In addition, the geographic distribution of the genus Euplotes in coast of southern China was revealed, and the mangrove was considered as the ideal habitat for them by possessing the higher species richness.

Amphileptusis one of the largest genera of pleurostomatid ciliates and its species diversity has been reported in various habitats all over the world. In the present work, we review its biodiversity based on data with reliable morphological records. Our work confirms that there are 50 validAmphileptusspecies, some of which have a wide range of salinity adaptability and diverse lifestyles. This genus has a high diversity in China but this might be because of the relatively intensive sampling. Phylogenetic analyses based on SSU rDNA sequence data verify the non-monophyly of the genusAmphileptus. Furthermore, two new and one poorly knownAmphileptusspecies, namelyA. shenzhenensissp. n.,A. cocoussp. n., andA.multinucleatusWang, 1934, from coastal habitats of southern China were investigated using morphological and molecular phylogenetic methods. These three species are highly similar based on their contractile vacuoles and macronuclear nodules. However, they can be discriminated by details of their living morphology and somatic kineties. We also propose two new combinations,Amphileptus polymicronuclei(Li, 1990) comb. n. (original combinationHemiophrys polymicronucleiLi, 1990) andAmphileptus salimicus(Burkovsky, 1970b) comb. n. (original combinationHemiophrys salimicaBurkovsky, 1970b).

Tintinnid ciliates are a highly diverse and essential group in the marine planktonic microbial loop. However, most of the known tintinnids were recorded only by the lorica characters and very few of them had been studied on their cytological features. In this study, the morphological characters of the lorica, ciliary pattern, nuclear apparatus, ontogenesis, and the molecular phylogeny of two poorly known tintinnid ciliates,Leprotintinnus nordqvisti(Brandt, 1906)Kofoid and Campbell (1929)andL. simplexSchmidt (1902), isolated from coastal waters of southern China, were investigated based on living observation, silver staining, three nuclear ribosomal DNA markers (18S, ITS1-5.8S-ITS2, and 28S genes) and one mitochondrial DNA marker (CO1gene). For the first time, the somatic ciliary pattern of the genusLeprotintinnuswas disclosed,viz., comprising a ventral, a dorsal, and a posterior kinety as well as a right, a left, and a lateral ciliary field. The diagnoses of bothLeprotintinnusspecies were improved and the neotype was assigned. The ontogenesis ofL. nordqvistiwas in enantiotropic division mode with the new dorsal and posterior kineties generatedde novo. The molecular phylogeny confirmed thatLeprotintinnusspecies are closely related to some species ofTintinnopsis,Stylicauda,Rhizodomus, andClimacocylis. The anterior extending of the ventral kinety together with some of the lateral kinety is likely to be a distinguishing feature to determine their systematic relationships. This study also revealed that (i) the lorica ofL. nordqvistiis polymorphic or plastic; (ii)Leprotintinnus tubulosusRoxas (1941)might be a synonym ofL.nordqvisti; (iii)Leprotintinnus neriticussensuYoo et al. (1988)might be a misidentification ofL. simplex.