Contributed by
Igor V. Dovgal, Senior Research Scientist,
Address:
Office address: Department of Invertebrate Fauna and Systematics,
I.I. Schmalhausen Institute of Zoology of the Ukrainian Academy of Sciences
B.Khmelnitsky str.15, 01601- Kiev Ukraine
Phone:(38-044) 235-7053
Fax: (38-044) 234-1569
E-mail: dovgal@dovgal.kiev.ua
http://ln.com.ua/~uudovgal
Sessile protists are principally unicellular organisms that are attached to substrate by special adhesive organelles (such as stalks, etc). These organisms are usually have attached adult stage (trophont) and free-swimming larval stage (swarmer). Two main morphotypes of sessile protists are distinguished (Dovgal, 2000): stalked and flattened on substrate. These protists are inhabited on unanimate substrates (stones, etc) and as commensals or ectoparasites on various water animals and plants.The attached mode of life is rather common among protists. There are sessile species even among foraminifers and radiolarians. There are also many attached species among autotrophic flagellates. The majority of heliozoans and representatives of three orders of flagellates (Choanophlagellata, Bicosoecidae, and Chrysomonadida) are sessile. Attached mode of life is quite characteristic for ciliates. Several high taxa (class Suctorea, subclasses Peritrichia and Chonotrichia, order Pilisuctorida and family Folliculinidae) are include hundreds sessile species. Evidences for an important role of these protists in the fouling communities are not uncommon in the literature (Burkovsky, 1984, Fenchel, 1987). The density of sessile predating suctorian ciliates can comprise 140 million individuals per square meter in rivers (Dovgal, 1990). Under this abundance their are a principal controllers of planktonic ciliates numbers. It should be remarked that the abundance of filter-feeding heterotrophic protists (such as bicosoecids, choanoflagellates and peritrichous ciliates) may be greater (Fenchel, 1987). After I.V. Burkovsky (1984) data the density of sessile ciliates only may comprise up 102-107 individuals per square meter.
Some additional evidence on sessile protists can be found in following review works:
- Burkovsky I.V. 1984. Ecology of free-living ciliates. Moskow: MGU. 208 p. In Russian.
- Dovgal I.V. 1990. Flowage effect on the fouling glasses colonization by Suctoria (Ciliophora). - Hydrobiological journal. 26,N2:37-41 (In Russian).
- Dovgal I.V., Kochin V.A. 1997. Fluid boundary layer as an adaptive zone for sessile protists. - Zurn. obsh. biol. 58, N2. P. 67-74.
- Dovgal I.V. 2000. The morphological and ontogenetic changes in Protista under transition to the sessile mode of life. Zurn. obsh. biol. 61, N3. P. 290-304. (In Russian).
- Dovgal I.V. 2001. Protozoans: inhabitants of the boundary layer. Priroda. N9. P. 73-78. (In Russian).
- Fenchel T. 1987. Ecology of Protozoa. Berlin; Heidelberg etc.: Springer-Verlag. 197 p.
- Railkin A.I. 1998. Colonization processes and defense against biofouling. St. Peterburg: St. Peterburg University. 272 p.
Additional references on sessile protists (In English):
- Dovgal I.V. Some regularities in sessile protists evolution// Study and protection of the animal world on the end of the century. Baku: Elm, 2001. - P. 111-115.
- Febvre-Chevalier C. 1990. Phylum Actinopoda: Class Heliozoa// Handbook of Protoctista. Eds. L. Marulis, J.O. Corliss., M. Melkonian, D.J. Chapman. Boston. P. 347-362.
- Mikrjukov K.A. 2001. Heliozoa as a component of marine microbenthos: a study of heliozoa of the White Sea// Ophelia. Vol. 54, No. 1. P. 51-73.
- Fig. 1. Sessile suctorian ciliates Discophrya elongata on leg of water bug Ranatra linearis (according to Dovgal, 2001).
- The full texts of some I. Dovgal’s article can be obtained at his web-site: http://ln.com.ua/~uudovgal
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