From Big Medical Encyclopedia

COMMENSALISM (Latin the com-prefix jointly, together + mensa a table) — one of forms of coexistence (symbiosis) of organisms of different types which is characterized by the fact that one organism (commensal) profits from other organism (food, protection, etc.) without doing it harm. To. is intermediate between parasitism (see) and a mutualism — mutually advantageous existence of two types of organisms (see. Symbiosis ).

As well as other forms of symbiosis, To. arose in the course of natural selection. Transition to To. was followed by change of behavior of commensal, its morphology etc. So, e.g., at clingfishes special suckers by means of which they keep on a body of the owner were created; at ants of Formicoxenus nitidulus and Solenopsis fugas ability to a mimicry was developed.

Commensals eat the remains of food or waste of life activity of an organism owner. At the same time extent of contact can be very various. Depending on extent of communication with an organism owner of commensals it is accepted to divide into three groups. Carry soobitatel on the house (a so-called sinoykiya) to the first. Commensal constantly lives near the owner and eats the remains of his food, excrement, and sometimes and corpses. The Annelida of the sort Nereis living in a sink of cancer hermit and eating the remains of its food can be an example of a sinoykiya. The second group of commensals combines constant or temporary inhabitants of a body surface of the owner (a constant or temporary epioykiya). The clingfishes who are attached to leather of sharks and eating the remains them are an example of a temporary epioykiya write. These fishes can be attached also to the bottom of the ship, eating garbage from the vessel. Sea acorns (Balanus) which are attached to stones or to a surface of sinks of mollusks or armors of crabs are other example of it like relationship. There can be and specific (on the owner) commensals, napr, the sedentary cancroid Coronula diadema living only on leather of whales.

Carry to the third group the commensals living in shank bores of an organism of the owner (entoyka). A significant amount of the protozoa, bacteria and other animals and vegetable organisms who are in usual conditions commensals lives in intestines of mammals and the person. However these harmless inhabitants of perigastriums of the owner under certain conditions can pass to position of parasites, becoming pathogenic. E.g., the activator of a candidiasis a fungus of Candida albicans, usually vegetans on fruits, vegetables and fruit, can a long time (sometimes all life of the individual) to be in microbic associations on skin and mucous membranes of the person and to behave as usual commensal. However in certain conditions (e.g., at disturbance of exchange, defective food or at a lack of vitamins, at hormonal insufficiency, abuse of antibiotics etc.) the fungus gains pathogenic value and causes diseases with damage of skin, mucous membranes and internals (see. Candidiasis ). Other example of change of nature of relationship is [[ | prick KOLI-INFEKTSIYA - an infection ]] (see), caused by colibacillus (Escherichia) — one of main types of normal intestinal microflora of the person, typical commensal. Getting into bodies and cavities of the person, colibacilli cause inflammatory processes there. At dysbacteriosis virulence of colibacillus increases. The reasons causing these changes have endogenous character; they are similar to the reasons causing Candidiasis.

Also transitional forms K. Tak, by an example of transition from the second group K are had. to the third the small fish of Trachichtes living between feelers actinium and using a part of its production is. Oyster crabs (Pinnotheres ostreum), a small ugrepodobny small fish of the sort Tieraster and a shrimp find a shelter and food in a perigastrium of holothurias to themselves.

Bibliography: Beklemishev V. N. Biocenological fundamentals of comparative parasitology, M., 1970, bibliogr.; D V. A au gel. General protistology, M., 1951, bibliogr.; Mayr E. Populations, types and evolution, the lane with English, M., 1974, bibliogr.; Pavlovskiye.N. A problem of parazitotsenoz, intraspecific and their trans-species ratios with an organism of owners, value of a problem for clinic of internal and infectious diseases, Izv. Academy of Sciences of the USSR, it is gray. biol., No. 3, page 25, 1955.

A. N. Alekseev.