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Problems of species in parasitology

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Pasozyty jako naturalny skladnik ekosystemu

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Parasites as a natural element of any ecosystem. The article presents some ideas upon the functioning of the parasite populations and communities in relation to the whole ecosystem. The author underlines that the parasites are one of the natural elements of every biocenosis and their existence submittes to similar ecological rules as the populations and communities of free-living organisms. Colonization of their particular environment (living organism) demands some adaptations allowing to resist immunological defense of the host, and to coexist with other parasite species harboured by the same host, not exploiting the supplies over the host "carying capacity", what could provoke the streng pathogenic eB'ects, including host death. The mechanims maintaning the state of relative stability in host-parasite system are similar as in the case of free-living organisms, and are of both parasite-and host origin. They can confine the number of parasites (elimination of some specimens) or their biomass (growth restraint), limit their fecundity (maturation resttaint), or make particular species to use different supply (niches separation). On the other hand parasite can regulate the demography of host population: restrict their fecundity, or kill their host directly or indirectly (making them an easier prey for predators). The author presents and discusses some examples illustrating the activity of the regulating mechanisms in host-parasite relationship, as well as the role of parasites in energetic ballance of ecosystem and in "engineering of ecosystem".
The article comprises a critical review of the most common ecological terms, used in Anglo-Saxon parasitological literature, with the short definition of each of them, and the propositions of their counterparts in the Polish language.
Referring to a recently published new taxonomy of the tapeworms, changes in generic combinations, for 19 cestode species recorded in Poland, are proposed.
Changes in infection and distribution of parasites in fish of different length (age) were analyzed. It was found that most parasites colonized fish during the first weeks of their sojourn in the ponds, but only some of these species remained in fish in the second and third years of their life. Protozoans appeared to be mainly associated with fry; the occurrence of some dactylogyrids decreased with increasing fish length, others showed the opposite tendency; ectoparasitic crustaceans and leeches showed preference to bigger fish. The probable reasons for these phenomena are discussed.
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