Colonial Organisms

Colonial Organisms


aquatic organisms, characterized by asexual (vegetative) reproduction, that remain united with the daughter and subsequent generations and form a more or less complex union, or colony. Among colonial plants are various unicellular algae, including blue-green, green, golden-brown, yellow-green, diatomaceous, dinoflagellate, and euglenoid. Depending on the method of formation (reproduction by zoospores or autospores), the colonies are either zoosporic or autosporic.

Colonial animals predominantly include marine invertebrates and lower chordates. Many unicellular animals, or protozoans, are colonial organisms, such as several flagellates, radiolarians, and infusorians. Other colonial invertebrates include many sponges and the majority of coelenterates (including siphonophores). Bryozoans, entoprocts, Rhabdopleura (order Pterobranchia), almost all hydrozoans, many coral polyps and many polypous generations of various scyphozoans are colonial organisms. Synascidiaepyrosomata, salps, and Doliolidae are examples of colonial lower chordates. The extinct graptolites were colonial animals.

Some colonial animals are sessile, such as bryozoans, hydrozoans, coral polyps, and synascidians. These colonies are usually permanently attached to the substrate and have a more or less developed skeleton. Colonial Radiolaria, Siphonophora, Pyrosomata, Doliolidae, and Salpidae, which live in the depths of the sea, are usually semitransparent and lack skeletons.

Many colonial organisms are metagenetic: there is alternation of asexual and sexual generations. Colonial organisms were the intermediate link in the development of multicellular animals from unicellular animals.


References in periodicals archive ?
Because sessile, colonial organisms cannot avoid the path of mobile fishing gear nor can they quickly immigrate into recently disturbed areas, they may be more adversely affected by bottom fishing than motile species.
Although no other research on Georges Bank has examined long-term patterns of recovery from disturbance among epifauna, our results are similar to those of two studies conducted at Cashes Ledge (located 130 km east of Gloucester, MA) on the colonization of artificial and disturbed natural substrate by colonial organisms over a period of less than two years (Sebens et al.
Metazoan organisms are easy to individuate on this basis, but a variety of biological entities challenge the concrete notion of individuality; for example, some fungi and colonial organisms which lack obvious boundaries.

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