A Study on Resting Cysts of an Oxytrichid Soil Ciliate, Rigidohymena quadrinucleata (Dragesco and Njine, 1971) Berger, 2011 (Ciliophora, Hypotrichia), Including Notes on its Encystation and Excystation Process


Eva Tirjaková

This is the first detailed study on the morphology of the resting cysts of an oxytrichid ciliate, Rigidohymena quadrinucleata. Resting cysts were investigated using light microscopy, SEM and TEM. The cyst wall is composed of four distinct layers (from inside to outside), namely the metacyst, the endocyst, the mesocyst and the ectocyst with spine-like protuberances. The cysts of R. quadrinucleata belong to the kinetosome-resorbing (KR) type, which is typical for oxytrichids. The processes of encystation and excystation were observed only in the light microscopy. During the encystation process, the trophic cell changes in shape and volume due to dehydration, four macronuclear nodules fuse into a compact mass, the ciliature is resorbed and cyst wall is formed. The most significant feature is surface ornamentation and yellowish color of resting cysts. We also focuse for the first time on excystation process of R. quadrinucleata. We identified two excystation modes: (i) standard and (ii) rare mode. The beginning of both excystation is characterised by the formation of excystation vacuole which helps the excysting cell to break the cyst wall. The specimen regenerates within a thin, flexible membrane. During the standard mode, the cell leaves the resting cyst in the membrane that is resorbed in the environment. During the rare mode, the excystation vacuole and the pressure of the regenerating cell break the transparent membrane that remains in the resting cyst. The results suggest that not only ciliate resting cysts, but also the excystation process is much more variable than what literature data indicate. 
Słowa kluczowe: Cyst wall, morphology, Oxytrichidae, resting cyst, ultrastructure

Barrero S. S. (2010) Caracterización filogenética de Phacodinium metchnikoffi: Análisis comparativo de datos morfológicos, morfogenéticos y moleculares. Universidad Comlutense de Madrid. 1–178

Beers C. D. (1945) The excystation process in the ciliate Didinium nasutumJ. Elisha Mitchell Sci. Soc. 61: 264–275

Beers C. D. (1948) Excystation in the ciliate Bursaria truncatellaBiol. Bull94: 86–98

Beers C. D. (1966) The excystation process in the ciliate Nassula ornata Ehrbg. J. Protozool13: 79–83

Benčaťová S., Tirjaková E. (2017) Prvonález druhu Bresslauides terricola (Foissner, 1987) Foissner, 1993 (Ciliophora, Colpodea) na Slovensku – cystické štádiá, en- a excystácia. Folia Faun. Slovaca 22: 31–40

Benčaťová S., Tirjaková E., Vďačný P. (2016) Resting cysts of Parentocirrus hortualis Voss, 1997 (Ciliophora, Hypotrichia), with preliminary notes on encystation and various types of excystation. Eur. J. Protistol. 43: 295–314

Berger H. (1999) Monograph of the Oxytrichidae (Ciliophora, Hypotrichia). Monogr. Biol78: 1–1080

Berger H. (2011) Monograph of the Gonostomatidae and Kahliellidae (Ciliophora, Hypotricha). Monogr. Biol. 90: 1–741

Berger H., Foissner W. (1997) Cladistic relantionships of oxytrichid hypotrichs (Protozoa, Ciliophora). Arch. Protistenk. 148: 125–155

Bourland W. A., Wendell L., Hampikian G., Vďačný P. (2014). Morphology and phylogeny of Bryophryoides ocellatus n.g., n. sp. (Ciliophora, Colpodea) from in situ soil percolates of Idaho, U.S.A. Eur. J. Protistol. 50: 47–67

Calvo P., Torres A., Navas P., Perez-Silva J. (1983) Complex carbohydrates in the cyst wall of Histriculus similisJ. Gen. Microbiol. 129: 829–832

Calvo P., Torres A., Perez-Silva J. (1986) Ultrastructural and cytochemical study of the encystment in the hypotrichous ciliate Histriculus similisArch. Protistenkd132: 201–211

Delgado P., Calvo P., Torres A. (1987) Encystment in the hypotrichous ciliate Paraurostyla weissei: ultrastructure and cytochemistry. J. Protozool. 34: 104–110

Foissner W. (1984) Infraciliatur, Silberliniensystem und Biometrie einiger neuer und wenig bekannter terrestrischer, limnischer und mariner Ciliaten (Protozoa: Ciliophora) aus den Klassen Kinetofragminophora, Colpodea und Poluhymenophora. Stapfia 13: 1–165

Foissner W. (1989) Morphologie und Infraciliatur einiger neuer und wenig bekannter terrestrischer und limnischer Ciliaten (Protozoa, Ciliophora). Sber. ӧst. Akad. Wiss. 196: 173–247

Foissner W. (1993) Colpodea (Ciliophora). Protozoenfauna 4: 1–798

Foissner W. (1997) Soil ciliates (Protozoa: Ciliophora) from evergreen rain forests of Australia, South America and Costa Rica: diversity and description of new species. Biol. Fertil. Soils 25: 317–339

Foissner W. (2005) The unusual, lepidosome-coated resting cyst of Meseres corlissi (Ciliophora: Oligotrichea): transmission electron microscopy and phylogeny. Acta Protozool. 44: 217–230

Foissner W., Müller H., Agatha S. (2007) A comparative fine structural and phylogenetic analysis of resting cysts in oligotrich and hypotrich Spirotrichea (Ciliophora). Eur. J. Protistol. 43: 295–314

Foissner W. (2014) An update of basic light and scanning electron microscopic methods for taxonomic studies of ciliated protozoa. Int. J. Syst. Evol. Microbiol. 64: 271–292

Funadani R., Suetomo Y., Matsuoka T. (2013) Emergence of the terrestrial ciliate Colpoda cucullus from a resting cyst: rupture of the cyst wall by active expansion of an excystation vacuole. Microbes Environ. 28: 149–152

Funadani R., Sogame Y., Kojima K., Takeshita T., Yamamota K., Tsujizono T., Suizu F., Miyata S., Yagyu K.-I., Suzuki T., Arikawa M., Matsuoka T. (2016). Morphogenetic and molecular analyses of cyst wall components in the ciliated protozoan Colpoda cucullus Nag-1. FEMS Microbial. Lett. 363: fnw203

Funatani R., Kida A., Watoh T., Matsuoka T. (2010) Morphological events during resting cyst formation in the ciliate Colpoda cucullus. Protistology 6: 204–217

Gu F., Xu J. (1995) A TEM study on pre-excystment cellular structures of Euplotes encysticusCell Res5: 125–133

Gutiérrez J. C., Diáz S., Ortega R., Martín-González A. (2003) Ciliate resting cyst walls: A comparative review. Recent Res. Dev. Microbiol. 7: 361–379

Chen X., Yan Y., Hu X., Zhu M., Ma H., Warren A. (2013) Morphology and morphogenesis of a soil ciliate Rigidohymena candens (Kahl, 1932) Berger, 2011 (Ciliophora, Hypotricha, Oxytrichidae), with notes on its molecular phylogeny based on small-subunit rDNA sequence data. Int. J. Syst. Evol. Microbiol. 63: 1912–1921

Hashimoto K. (1963) Formation of ciliatúre in excystation and induced re-encystment of Oxytricha fallax Stein. J. Protozool. 10: 156–166

Kim Y., Taniguchi A. (1995) Excystation of the oligothric ciliate Strombidium conicumAquat. Microb. Ecol. 9: 149–156

Kumar S., Foissner W. (2015) Biogeographic specializations of two large hypotrich ciliates: Australocirrus shii and A. australis and proposed synonymy of Australocirrus and CyrtohymenidesEur. J. Protistol. 51: 210–228

Kumar S., Bharti D., Marinsalti S., Insom E., La Terza A. (2014) Morphology, morphogenesis, and molecular phylogeny of Paraparentocirrus sibillinensis n. gen., n. sp., a “Stylonychinae Oxytrichidae” (Ciliophora, Hypotrichida) without transverse cirri. J. Eukaryot. Microbiol. 61: 247–259

Li Q., Sun Q., Fan X., Wu N., Ni B., Gu F. (2017) The differentiation of cellular structure during encystment in the soil hypotrichous ciliate Australocirrus cf. australis (Protista, Ciliophora). Animal Cells Syst. 21: 45–52

Martin-González A., Benítez A., Gutiérrez J. C. (1992) Ultrastructural analysis of resting cysts and encystment in Colpoda inflata. 2. Encystment process and a review of ciliate resting cyst classification. Cytobios 72: 93–106

Matsusaka T. (1976) An ultrastructural study of encystment in the hypotrichous ciliate Pleurotricha sp. Kumamoto. J. Sci. Biol. 13: 13–26

Matsusaka T., Noguchi O., Yonezawa F. (1989) Cortical morphogenesis during encystment in a ciliate, Euplotes encysticus Yonezawa, 1985. Eur. J. Protistol. 24: 133–137

McArdle E. W., Bergquist B. L., Ehret Ch. F. (1980) Structural Changes in Tetrahymena rostrata during induced encystment. J. Eukaryot. Microbiol. 27: 388–397

Montagnes D. J. S., Lowe C. D., Poulton A., Jonsson P. (2002) Redescription of Strombidium oculatum Gruber 1884 (Ciliophora, Oligotrichia). J. Eukaryot. Microbiol. 49: 329–337

Mulish M., Hausmann K. (1989) Localization of chitin on ultrathin sections of cysts of two of the ciliated protozoa, Blepharisma undulans and Pseudomicrothorax dubius, using colloidal gold conjugated wheat germ egglutinin. Protoplasma 152: 77–86

Müller H. (2007) Live observation of excystation in the spirotrich ciliate Meseres corlissi. Eur. J. Protistol. 43: 95–100

Nakamura T., Matsusaka T. (1991) Effects of cyst age on excystation of the ciliate Histriculus cavicola (Kahl, 1935) (Ciliophora, Stichotrichia). Eur. J. Protistol. 37: 375–380

Repak A. J. (1968) Encystment and excystation of the heterotrichous ciliate Blepharisma stoltei Isquith. J. Protozool. 15: 407–412

Singh J., Kamra K. (2015) Morphology and molecular phylogeny of an Indian population of Cyrtohymena citrina (Ciliophora, Hypotricha), including remarks onontogenesis of Urosomoida-Notohymena-Cyrtohymena group. Eur. J. Protistol. 51: 280–289

Vďačný P., Foissner W. (2012) Monograph of the dileptids (Protista, Ciliophora, Rhynchostomatia). Denisia 31: 1–529

Verni F., Rosati G. (2011) Resting cysts: A survival strategy in Protozoa Ciliophora. Ital. J. Zool. 78: 134–145

Verni F., Rosati G., Ricci N. (1984) The cyst of Oxytricha bifaria (Ciliata, Hypotrichida). II. The ultrastructure. Protistologica 20: 87–95

Walker G. K., Maugel T. K. (1980) Encystment and excystment in hypotrich ciliates. II. Diophrys scutum and remarks on comparative features. Protistologica 16: 525–531

Walker G. K., Maugel T. K., Goode D. (1975) Some ultrastructural observations on encystment in Stylonychia mytilus (Ciliophora: Hypotrichida). Trans. Am. Microsc. Soc. 94: 147–154

Wang J., Li L., Warren A., Shao Ch. (2017) Morphogenesis and molecular phylogeny of the soil ciliate Rigidohymena quadrinucleata (Dragesco and Njine, 1971) Berger, 2011 (Ciliophora, Hypotrichia, Oxytrichidae). Eur. J. Protistol. 60: 1–12

Czasopismo w darmowym dostępie.

Czasopismo ukazuje się w sposób ciągły on-line.
Pierwotną formą czasopisma jest wersja elektroniczna.