Report and Phylogeny of a Novel Euplotes Species from China:E.mazeii n.sp.,and Review of E.balteatus(Alveolata,Ciliophora)

The freshwater species,Euplotes mazeii n.sp.,and the marine species,E.balteatus(Dujardin,1841)Diesing,1850 were collected from China and investigated based on their living morphology,ciliary pattern,and small subunit ribosomal RNA(SSU rRNA)gene sequence data.Euplotes mazeii n.sp.was characterized by its small cell size((40-55)μm×(25-35)μm),nine frontoventral cirri,one marginal and two caudal cirri,seven dorsal kineties,and a double-eurystomus type of dorsal silverline system.Phylogenetic analyses based on molecular data confirmed the branching position of this new taxa within the genus Euplotes,with 5.01%(84 nucleotides)sequence variation,supporting the identification of a new species.We re-examined all described and supposedly conspecific populations and give a review of Euplotes balteatus.E.balteatus has been reported frequently;however,E.balteatus sensu Agamaliev,1968 is different from other populations in the number of marginal cirri or the type of silverline system,which suggests there might be a misidentification.The SSU rRNA gene sequences of two populations of E.balteatus from the studies of Chen et al.(2013)and Pan et al.(2012)differ from each other by more than 135 nucleotides,implying that the identity of the species currently associated with the SSU rRNA gene sequence in molecular databases requires further confirmation.

Comparative genome analysis of three euplotid protists provides insights into the evolution of nanochromosomes in unicellular eukaryotic organisms

One of the most diverse clades of ciliated protozoa,the class Spirotrichea,displays a series of unique characters in terms of eukaryotic macronuclear(MAC)genome,including high fragmentation that produces nanochromosomes.However,the genomic diversity and evolution of nanochromosomes and gene families for spirotrich MAC genomes are poorly understood.In this study,we assemble the MAC genome of a representative euplotid(a new model organism in Spirotrichea)species,Euplotes aediculatus.Our results indicate that:(a)the MAC genome includes 35,465 contigs with a total length of 97.3 Mb and a contig N50 of 3.4 kb,and contains 13,145 complete nanochromosomes and 43,194 predicted genes,with the majority of these nanochromosomes containing tiny introns and harboring only one gene;(b)genomic comparisons between E.aediculatus and other reported spirotrichs indicate that average GC content and genome fragmentation levels exhibit interspecifc variation,and chromosome breaking sites(CBSs)might be lost during evolution,resulting in the increase of multi-gene nanochromosome;(c)gene families associated with chitin metabolism and FoxO signaling pathway are expanded in E.aediculatus,suggesting their potential roles in environment adaptation and survival strategies of E.aediculatus;and(d)a programmed ribosomal frameshift(PRF)with a conservative motif 5′-AAATAR-3′tends to occur in longer genes with more exons,and PRF genes play an important role in many cellular regulation processes.

Integrative studies on the taxonomy and molecular phylogeny of four new Pleuronema species(Protozoa,Ciliophora,Scuticociliatia)

The ciliate genus Pleuronema comprises approximately 30 nominal species and has been reported in freshwater,brackish water,and marine habitats.Nevertheless,recent studies have indicated that there might be a large undiscovered species diversity.In the present work,four new Pleuronema species,namely P.foissneri sp.nov.,P.parasmalli sp.nov.,P.parasalmastra sp.nov.,and P.paraorientale sp.nov.,collected from Shenzhen,southern China,was investigated using taxonomic methods.The diagnosis,description,comparisons with morphologically related species and detailed morphometric data are supplied for each.The small subunit ribosomal RNA(SSU rRNA)gene of the four new species is sequenced and their molecular phylogeny is analyzed.The SSU rRNA gene tree shows that Pleuronema is polyphyletic comprising several separate clades.All four new species cluster consistently with P.orientale KF206429,P.puytoraci KF840520 and P.setigerum FJ848874 within the core Pleuronematidae+Peniculistomatidae clade.Phylogenies of Pleuronematidae-related taxa are also discussed.

Ontogenesis and systematic position of a new hypotrichous ciliate,Chaetospira sinica sp.nov.,with an improved diagnosis of the poorly defined family Chaetospiridae Jankowski,1985(Protozoa,Ciliophora,Hypotrichia)

Ciliates are unique single-celled organisms that play important roles in ecological,environmental,evolutionary,and ontogenetic research.In the present study,phylogenetic analyses based on 18S rRNA gene sequence data reveal that Chaetospira sinica sp.nov.clusters with Stichotricha aculeata with strong to full support(97%ML,1.00 BI),but is not closely related to members of Spirofilidae Gelei,1929 to which Chaetospira and Stichotricha have previously been assigned.Phylogenetic analyses,together with morphological and morphogenetic data from Chaetospira sinica sp.nov.,support the validity of family Chaetospiridae Jankowski,1985.Chaetospira and Stichotricha are here assigned to the family Chaetospiridae,the improved diagnosis of which is as follows:non-dorsomarginalian Hypotrichia with flask-shaped body;oral region extending along narrow anterior neck region;lorica usually present;two ventral and two marginal cirral rows,all distinctly spiraled or obliquely curved;pretransverse and transverse cirri absent.The basic morphogenetic features in C.sinica sp.nov.can be summarized as:(1)the oral primordium for the opisthe develops de novo and the parental adoral zone is completely retained by the proter;(2)all ventral cirral anlagen and marginal anlagen developed intrakinetally;(3)three dorsal kineties anlagen formed intrakinetally in each daughter cell;and(4)macronuclear nodules fuse into a single mass.Exconjugant cells were also isolated and their morphologic and molecular data are provided.

A new hypotrich ciliate,Oxytricha xianica sp.nov.,with notes on the morphology and phylogeny of a Chinese population of Oxytricha auripunctata Blatterer&Foissner,1988(Ciliophora,Oxytrichidae)

The morphology and infraciliature of the new hypotrichous ciliate,Oxytricha xianica sp.nov.,and a Chinese population of Oxytricha auripunctata Blatterer&Foissner,1988,are investigated using live observation and protargol staining.Oxytricha xianica sp.nov.is defined by the body size 85-130µm×30-50µm in vivo,the typical oxytrichid 18 frontoventral-transverse cirri,cortical granules absent,undulating membranes reduced or absent,three caudal cirri,dorsal kineties in Oxytricha pattern,and two ellipsoidal macronuclear nodules.The Chinese population of O.auripunctata differs slightly from other populations in the arrangement and color of cortical granules and position of anterior end of dorsal kinety 4.Phylogenetic analyses based on SSU-rDNA sequences support the assertion that O.auripunctata belongs to Oxytricha and Oxytrichidae.

Does the Gonostomum-patterned oral apparatus in hypotrichia carry a phylogenetic signal?Evidence from morphological and molecular data based on extended taxon sampling using three nuclear genes(Ciliophora,Spirotrichea)

The classification of hypotrichs based on the gonostomatid oral structure is widely accepted,but the phylogenetic signal of this character is unknown.Here,we infer the species phylogeny of those gonostomatids for which molecular data are available,plus26 new sequences of SSU-rDNA,ITS1-5.8 S-ITS2 and LSU-rDNA genes.The results indicate that:(i)the endoral is more phylogenetically informative than the paroral;(ii)the structure of the endoral and the Gonostomum-pattern adoral zone of membranelles are plesiomorphies for the hypotrichs sensu stricto;(iii)the group of species possessing these features is monophyletic in all our phylogenetic analyses,except that for the SSU-rDNA;(iv)Schmidingerotrichidae is monophyletic in all trees,suggesting that it is a well-defined family;(v)the Gonostomatidae is polyphyletic in the SSU-rDNA and ITS1-5.8 S-ITS2 trees,with Gonostomum,Cladotricha,Cotterillia,Metagonostomum,Paragonostomum and Wallackia distributed among separate clades,but monophyletic in the LSU-rDNA and concatenated trees;(vi)higher hypotrich taxa such as core urostyloids and core sporadotrichids/stichotrichids might have evolved from species that possessed a gonostomatid oral apparatus.