The predatory or parasitic suctorians are sessile ciliates. However, adult stages do not bear cilia. The ciliated stage is a free‐swimming swarmer, which settles on a substrate or infects a new host organism, loses its cilia and undergoes metamorphosis into the adult form. Many species attach to the substrate by a stalk, or a lorica. Suctorians feed through straight tubular cell extensions called tentacles.

Keywords: protozoa; ciliophora; suctoria

Figure 1.

Light‐micrograph pictures of two suctorians.

A, Tokophrya infusionum: side‐view phase‐contrast micrograph of a live organism with numerous tentacles (t), a stalk (s), an attachment disc (d) and a contractile or pulsating vacuole (pv). Micrograph by Dr Maria A. Rudzinska, reproduced with permission of The Rockefeller University Archives. Bar, 20 μm.

B, Heliophrya erhardi: top‐view dark‐field micrograph of a live organism after feeding. Four bundles of long slender tentacles can be seen. Each tentacle ends in a knob‐like enlargement. Internal cellular structures are obscured by the many food vacuoles that fill the cell body. Bar, 100 μm.

C, Heliophrya erhardi: Top‐view phase‐contrast micrograph of a live organism (after metamorphosis without feeding). This specimen has seven tentacle bundles. The attachment plate protrudes from underneath the cell body and surrounds the cell like a ring (r). Four contractile or pulsating vacuoles (pv) are clearly visible, as is the large irregular macronucleus (ma). Micronuclei (arrowheads) are more difficult to differentiate from small cytoplasmic inclusions. Bar, 50 μm.

Figure 2.

Some details of suctorian cellular organization (all pictures are from Heliophrya erhardi)

A, Structure of pellicle – consisting of cell membrane and two alveolar membranes (between arrowheads) followed by a fibrillar epiplasm (e). The pellicle is traversed by a pit (p). Electron micrograph; bar, 250 nm.

B, Field of kinetosomes adjacent to the epiplasm (e). Electron micrograph; Bar, 100 nm.

C, Longitudinal section through tentacle tip. The axoneme (a) is sectioned longitudinally (see cross‐section in Figure E). Haptocysts (arrows) are arranged at the periphery of the tentacle knob. (Haptocysts are marked only on a portion of the knob, and some haptocysts are outside of the section plane.) Electron‐dense bodies (b) fill the axoneme and the tentacle knob. Electron micrograph; bar, 500 nm.

D, Longitudinal section through haptocyst showing the complex structure of this organelle. Electron micrograph; bar, 200 nm.

E, Cross‐section through a tentacular axoneme within the cell body (see text). This picture also shows ‘dense bodies’ (b) and a ‘vesicle with osmiophilic cap’ (v). Electron micrograph; bar, 250 nm.

F, Light micrograph of reproducing Evaginogenida (e.g: Heliophrya). A large brood cavity (bc) extends through the cell body (see Figure , fourth column). The bean shape of the cavity corresponds to the bean shape of the resulting swarmer after evagination. During reproduction, the normally elongated macronucleus becomes round in preparation for nuclear division (ma). Light micrograph, live organism; bar, 50 μm.

G, The wall of the Evaginogenida brood cavity. Cilia project from the cell body into the lumen of the brood cavity (bc). Most cilia are pictured as cross‐sectional profiles. The arrowhead points to a tentacular axoneme within the cytoplasm. Electron micrograph; bar, 1 μm.

H, Organism forming a cytoplasmic bulge in direction (arrow) of a neighbouring cell (not shown). Bulges from two cells contact and fuse, thereby establishing a cytoplasmic conjugation bridge between the organisms. Light micrograph, phase contrast, live organism; bar, 50 μm.

I, Two conjugating cells of Heliophrya. The two organisms are connected by a conjugation bridge (between arrowheads). Some micronuclei are marked by arrows in one conjugant. Light micrograph, phase‐contrast Feulgen staining. Bar, 50 μm.

J, Higher magnification of a portion of Heliophrya's conjugation bridge at the moment of nuclear exchange and nuclear fusion, the central event in ciliate conjugation. The arrows indicate the direction of movement of one nucleus (migratory nucleus) from one organism into the conjugation partner. Top, nuclear pair at the beginning of fusion. Bottom nuclear pair: fusion nearly completed. Light micrograph, phase‐contrast Feulgen staining; bar, 10 μm.

Figure 3.

Diagrams of modes of reproduction in suctorians (tentacles omitted). Differences are shown between ciliated swarmer formation (reproduction) in Exogenida, Endogenida and Evaginogenida. Within the Exogenida, transitional species can link the closely related modes of reproduction of Exogenida and Endogenida.



Batisse A (1994) Sous‐Class des Suctoria Claparède et Lachmann, 1858. In: Grassé P‐P (ed.) Taité de Zoologie. Anatomie, Systématique, Biologie, vol. 2, part 2, pp. 493–563. Paris, France: Masson.

de Puytorac P, Batisse A, Deroux G et al. (1993) Proposition d'une nouvelle classification du phylum des protozoaires Ciliophora Doflein, 1901. Comptes Rendus Académie Sciences Paris, Série III, Sciences de la Vie 316: 716–720.

Grell KG and Meister A (1984) Beiträge zur Ultrastruktur der Konjugation von Ephelota gemmipara Hertwig (Suctoria). Protistologica 20: 65–86.

Henk WG and Paulin JJ (1977) Scanning electron microscopy of budding and metamorphosis in Discophrya collini (Root). Journal of Protozoology 24: 134–139.

Karakashian SJ, Lanners HN and Rudzinska MA (1984) Cellular and clonal aging in the suctorian protozoan Tokophrya infusionum. Mechanisms of Ageing and Development 26: 217–229.

Lanners HN (1973) Beobachtungen zur Konjugation von Heliophrya (Cyclophrya) erhardi (Rieder) Matthes, Ciliata, Suctoria. Archiv für Protistenkunde 115: 370–385.

Lanners HN (1980) Pronuclei of Heliophrya erhardi Matthes during conjugation and their differential association with coated and uncoated microtubules. Journal of Cell Science 45: 245–255.

Lanners HN and Rudzinska MA (1986) Exchange of pronuclei during conjugation in the suctorian ciliate Heliophrya erhardi is mediated by a microtubule–microfilament network. Protistologica 22: 89–96.

Millecchia LL and Rudzinska MA (1970) The ultrastructure of brood pouch formation in Tokophrya infusionum. Journal of Protozoology 17: 574–583.

Rudzinska MA (1973) Do suctoria really feed by suction? BioScience 23: 87–94.

Rudzinska MA (1980) Internalization of macromolecules from the medium in suctoria. Journal of Cell Biology 84: 172–183.

Small EB and Lynn DH (1985) Phylum Ciliophora Doflein, 1901. In: Lee JJ, Hutner SH and Bovee EC (eds) An Illustrated Guide to the Protozoa. Lawrence, Kansas: Society of Protozoologists.

Sonneborn TM (1978) Genetics of cell–cell interaction in ciliates. In: Lerner RA and Bergsma D (eds) The Molecular Basis of Cell–Cell Interaction, pp. 417–427. New York: Alan R. Liss.

Further Reading

Batisse A (1994) Sous‐Class des Suctoria Claparède et Lachmann, 1858. In: Grassé P‐P (ed.) Taité de Zoologie. Anatomie, Systématique, Biologie, vol. 2, part 2, pp. 493–563. Paris, France: Masson.

Collin B (1912) Étude monographique sur les acinétiens. II. Morphologie, Physiologie, Systématique. Archives Zoologique Expérimentale et Générale 51: 1–457.

Corliss JO (1979) The Ciliated Protozoa: Characterization, Classification and Guide to the Literature, 2nd edn. London: Pergamon Press.

Grell KG (1967) Sexual reproduction in Protozoa. In: Chen T‐T (ed.) Research in Protozoology, vol. 2, pp. 149–213. New York: Pergamon Press.

Grell KG (1973) Protozoology, 3rd edn. Berlin: Springer Verlag.

Small EB and Lynn DH (1985) Phylum Ciliophora Doflein, 1901. In: Lee JJ, Hutner SH and Bovee EC (eds) An Illustrated Guide to the Protozoa. Lawrence, Kansas: Society of Protozoologists.

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Lanners, H Norbert, and Lanners, Ellen B(Jun 2001) Suctorians. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001988]