title: Ultrastructure observation on the cells at different life history stages of Cryptocaryon irritans (Ciliophora: Prostomatea), a parasitic ciliate of marine fishes.
abstract: Cells of Cryptocaryon irritans at different life history stages were studied using both light and electron microscopy. The characteristics of several organelles were revealed for the first time at the ultrastructural level. It was confirmed that the cytostome of trophonts, protomonts and theronts was surrounded by cilium-palp triplets rather than ciliary triplets. The nematodesmata underlying the circumoral dikinetids were single bundles, whereas these were always paired in Prorodontids. Toxicysts were present in late-stage tomonts and theronts, but were absent in trophonts and protomonts. We posited that toxicysts might play a role in infection and invasion of host-fish tissue by theronts. The adoral brosse was unlike that of any other family of the class Prostomatea based on its location and morphology. Membranous folds were present in trophonts, protomonts and theronts. These folds were longer and more highly developed in C. irritans than in exclusively free-living prostome ciliates suggesting that they might be linked to parasitism in C. irritans. Trophonts, protomonts and theronts had multiple contractile vacuoles. The basic ultrastructure of the contractile vacuole of C. irritans was similar to that of other kinetofragminophoran ciliates. They might play different roles in different stages of the life cycle since their ultrastructure varied among trophonts, protomonts and theronts.
authors.affiliation: School of Life Sciences, East China Normal University,Shanghai,China.
authors.forename: Rui
authors.initials: R
authors.lastname: Ma
authors.affiliation: School of Life Sciences, East China Normal University,Shanghai,China.
authors.forename: Bing
authors.initials: B
authors.lastname: Ni
authors.affiliation: School of Life Sciences, East China Normal University,Shanghai,China.
authors.forename: Xinpeng
authors.initials: X
authors.lastname: Fan
authors.affiliation: Department of Life Sciences,Natural History Museum,London,UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Warren
authors.affiliation: Key Laboratory of East China Sea and Oceanic Fishery Resources Exploitation,Ministry of Agriculture, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences,Shanghai,China.
authors.forename: Fei
authors.initials: F
authors.lastname: Yin
authors.affiliation: School of Life Sciences, East China Normal University,Shanghai,China.
authors.forename: Fukang
authors.initials: F
authors.lastname: Gu
mesh_terms: D058500:Animal Fins / Q000469:parasitology; D000818:Animals; D016798:Ciliophora / Q000254:growth & development* / Q000302:isolation & purification / Q000502:physiology / Q000648:ultrastructure*; D016770:Ciliophora Infections / Q000469:parasitology* / Q000662:veterinary*; D005393:Fish Diseases / Q000469:parasitology; D005880:Gills / Q000469:parasitology; D008018:Life Cycle Stages; D008854:Microscopy, Electron; D015388:Organelles / Q000648:ultrastructure; D010473:Perciformes / Q000469:parasitology*; D014617:Vacuoles / Q000648:ultrastructure
keywords: Cryptocaryon irritans; electron microscopy; life history; organelle; ultrastructure