Species Diversity And Molecular Phylogeny Of Periphyton Ciliates In The Littoral Zone Of Yantai

Ciliates as the most morphorlogically complex and highly differentiated taxon among unicellular eukaryotes belong to Protozoa,Ciliophora.Ciliated protozoa is an important group in function of energy flow and element cycling.As a kind of favorable model organism,ciliate has been wildly used in the fields of cell biology,molecular biology and molecular systematic,especially in the biogenesis and evolution.Twenty species of periphyton ciliates?involving three classes,eight orders and sixteen genera?were identified by traditional morphology including a new species.Molecular phylogenetic studies were also carried out on the related groups.The main research results are as follows:1.A new species of sessile peritrichs,Zoothamnium palmphlatum n.sp.,was found in Guangdang River.Its morphological definition described as follows: A typical colony is up to 1.3 mm high,which are arranged with highly developed and alternately branched stalk.Mature zooids are 71⁸6 × 33⁴9 ?m in vivo,with double-layered peristomial lip.A single contractile vacuole is located in the apical body portion.The macronucleus is C-shaped and transversely oriented.The silverline system consists of closely spaced transverse lines,i.e,74-102 silverlines extend between the peristome and the aboral trochal band and 35-45 silverlines between the aboral trochal band and the scopula.P3 are composed of two parallel kinetosomal rows of equal length.Besides,we compared 25 regions of the secondary structure of this new species with those of its morphological similarity species and the species with the highest sequence similarity,and obtained the following viewpoints:?1?Sequence similarity may not determine the similarity of the secondary structure.?2?18S rDNA secondary structure could be an informative character for analyzing evolutionary relationships within the genus Zoothamnium.Furthermore,some particular regions exhibit species-dependant diversity in secondary structure,which indicates their potential significance for species identification.2.The phylogenetic and secondary structure analysis of three clades of Zoothamniidae?Zoothamnium clade I,clade II and clade III?,two clades of Epistylididae?Epistylis clade I,clade II?,Vaginicolidae,Operculariidae and suggest that:?1?Three clades of Zoothamniidae can be distinguished by H10,H25 and H47 regions;?2?Two clades of Epistylididae can be distinguished by E10₁,H10,H12,H17 and H37 regions;?3?Zoothamnium clade III and Epistylis clade II can be distinguished by E23₁-2 andH44 regions;?4?Vaginicolidae,three clades of Zoothamniidae and Epistylis clade II can be distinguished by E10₁ regions;?5?Epistylis clade I,Operculariidae and the others can be distinguished by H10 region.In this study,combined with phylogenetic position,we summarize the differential secondary structure regions and find that it is a good marker for the differentiation of the peritrichs groups.In addition,morphologically study of a new species of Zoothamnium was also included,which increased the species diversity and molecular data of the genus.