Morphology And Molecular Phylogeny Of The Ciliate Subclasses Peritrichia And Scuticociliatia

Ciliated protozoa are morphologically highly differentiated single-celledeukaryotes. They are essential components in microbial food webs, and play akey role in various ecosystems. In world aquaculture, the pathogenic diseasescaused by Peritrichia and Scuticociliatia have resulted in serious economicloss. Despite their economic and ecological significance, there are limitedstudies on the diversity and pathogenic mechanism of these groups. Thereasons include:1) there are many uncertainties in the taxonomy of thesegroups, and2) there are still many phylogentic discrepancies even based onrecent molecular data.To investigate the issues mentioned above, we collected the parasitc andfree-living peritrich and scuticociliatid ciliates from sites located at Dalian,Qingdao, Fuzhou and Hainan in China during2008-2012. Using modernmorphological and molecular methods, we aimed to solve those confusions inmorphological taxonomy and systematology of deep subclades of thesegroups. We also analyzed sequences of various genetic markers to investigatethe disagreements between different researchers.The results are summarized as following:(1)19ambigous species belonging to12genera were redescribed. Amongthese ciliates,14species are first recorded in China.(2) Based on large number of SSU-Rdna sequences of Peritrichia, andcomparison of different alignment and masking methods, we found thatsupport for and against monophyly of the Peritrichia were highlydependent upon alignment and masking methodologies.(3) The support for and against monophyly of the Peritrichia s.l. were not significant basing on alpha tubulin gene sequences. And the resultshowed alpha tubulin gene was dubious help when inferringphylogenetic relationships.(4) Based on the morphological and molecular data, we redefined thesystemic position of six peritrichous genera. Four families and fourgenera in Mobilida were emended: the genera Leiotrocha, Polycycla andTrichodinopsis were transferred to Urceolaria; and consequently thefamily Leiotrochidae, Polycyclidae and Trichodinopsidae weretransferred to Urceolariidae.(5) The monophyly of the subclass Scuticociliatia was not supported withadding new23scuticociliatid SSU-rDNA sequences. The phylogeneticpositions of11genera, whose assignments were historically unclear,have been studied. These11genera are: Ancistrum, Biggaria, Boveria,Conchophthirus, Cyclidium, Madsenia, Myxophyllum, Mytilophilus,Paralembus, Pseudocyclidium, and Protophyra.(6) A fluorescent probe targeting small subunit ribosomal RNA (SSU-rRNA)was designed and optimized in a fluorescence in situ hybridization (FISH)to detect the pathogenic ciliate Pseudocohnilembus persalinus inaquaculture.Additionally, small subunit rDNA sequences of35peritichous andscuticociliatid species/populations, alpha tubulin gene sequences of threeperitichs, and mitochondrial cytochrome c oxidase subunit Ⅰ gene sequence ofone scuticociliatid species were submitted to the GenBank.