In recent years, Tetrahymena species have been used as model organisms for research in a wide range of fields, highlighting the need for a fuller understanding of the taxonomy of this group. It is in this context that this paper uses living observation and silver staining methods to investigate the morphology and infraciliature of one Tetrahymena species, T. setosa (Schewiakoff 1892 Verh. Naturh. Med. Ver. Heidelb., 4:544) McCoy (1975) Acta Protozool., 14:253; the senior subjective synonym of T. setifera Holz and Corliss (1956) J. Protozool., 3:112; isolated from a freshwater pond in Harbin, north-eastern China. This organism can be distinguished from other described Tetrahymena species mainly by its single caudal cilium, which is about twice the length of the somatic ciliature. While the Harbin isolate appears similar to the population described by Holz and Corliss (1956) J. Protozool., 3:112, an improved diagnosis for T. setosa is given based on the previous descriptions and the Harbin population. In summary, this species can be recognized mainly by the combination of the following characters: body in vivo approximately 40 μm × 25 μm, 21-26 somatic kineties, one to four contractile vacuole pores associated with meridians 6-11 and a single caudal cilium. The small subunit ribosomal (SSU) rRNA gene and the cox1 gene sequences of Harbin population are also characterized in order to corroborate that the isolated species branches in phylogenetic trees as a T. setosa species. The phylogenetic analysis also indicated that sequences of populations of Tetrahymena species should be published with detailed morphological identifications.

No abstract

No abstract

Background Tetrahymenosis caused by about ten parasitic Tetrahymena species belonging to the Phylum Ciliophora has been recognized as an emerging problem inflicting significant economic loss in aquaculture industry in the world. Increasing knowledge and identification of Tetrahymenosis are important. Methods Four parasitic Tetrahymena species were collected from eight commercially farmed fishes in Harbin, northeastern China. Specific oligonucleotide probe and fluorescence in situ hybridization staining was designed and tested. Hoechst33342 staining methods, gene sequencing and phylogenetic analyses were also conducted. Results Tetrahymena pyriformis, T. vorax, T. chironomi and T. bergeri are the four species responsible for Tetrahymenosis in various fishes in Harbin. Taxonomy, diagnosis, diversity, pathogenicity, and histopathology of Tetrahymenosis were supplemented, analyzed and summaried, based on the present and previous work. The term Tetrahymenosis is diagnosised as diseases affecting a number of fishes, crustaceans, mollus, beetle, dragonfly, salmon, slug, midge larvae and freshwater mussel species that caused by ciliates of the genus Tetrahymena which constitutes an abundant group inhabit various aquaculture and natural habitats. Improved classification of parasitic Tetrahymena was provided. Phylogeny of parasitic Tetrahymena species was studied, and an SSU-rDNA targeted oligonucleotide probe labeled with a fluorochrome was designed, and the FISH protocol was optimized for identification of Tetrahymena species, Conclusions The manifestations of histopathology in fish typically include lesions on the body surface, and affected organs include the skin, musculature, viscera, eye socket and spinal cord; masses of ciliates can be detected in copious amount of mucus and between spaces in the damaged tissues. Improved classification of parasitic Tetrahymena is provided: facultatively parasitic forms ( T. pyriformis , T. rostrate , T. bergeri and T. vorax ), facultatively free-living forms ( T. chironomi , T. corlissi, T. rotunda, T. glochidiophila and T. papula ) and parasitic forms ( T. stegomyiae and T. limacis ).The phylogenic results indicate that Tetrahymena spp. belonging to ‘borealis’ group have a greater probability to become parasitism. the method of which can be used for quick and early detection of Tetrahymenosis.