Parasitism is an interaction between two organisms, in which one organism (the parasite) benefits and the other (the host) is harmed, though usually without killing the host. Parasitism can be considered a special case of predation since in both interactions one species acquires biomass directly from another. In parasitism, the relationship between the two organisms is particularly close (the parasite typically lives within or upon the host), making it a form of symbiosis. (Various forms of "social parasitism", kleptoparasitism, and "cheating parasitism", as discussed below, are characterized by a less close association between parasite and host, however.) Classically, the distinction between parasites and pathogens was methodological: parasites were symbionts that could not be kept alive outside the host, unlike bacteria, for example, which could be cultured in a laboratory. Biological interactions result from the fact that organisms in an ecosystem interact with each other, in the natural world, no organism is an autonomous entity isolated from its surroundings. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ... This snapping turtle is trying to make a meal of a Canada goose, but the goose is too wary. ... Common Clownfish (Amphiprion ocellaris) in their magnificent sea anemone (Heteractis magnifica) home. ... A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ... Subgroups Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular: bacterium) are a major group of living organisms. ... Biochemistry laboratory at the University of Cologne. ...

Types of parasitism

Parasites that live inside the body of the host are called endoparasites (e.g., hookworms that live in the host gut) and those that live on the outside are called ectoparasites (e.g., mosquitos). An epiparasite is a parasite that feeds on another parasite. Many endoparasites acquire hosts by passive mechanisms, such as the nematode Ascaris lumbricoides, an endoparasite of the human intestine. A. lumbricoides produces large numbers of eggs which are passed from the host's digestive tract into the external environment, relying on other humans to inadvertently ingest them in places without good sanitation. Ectoparasites, on the other hand, often have elaborate mechanisms and strategies for finding hosts. Some aquatic leeches, for example, locate hosts by sensing movement and then confirm their identity through skin temperature and chemical cues before attaching. Classes Adenophora    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms (Phylum Nematoda) are one of the most common phyla of animals, with over 20,000 different described species. ... Binomial name Ascaris lumbricoides Ascaris lumbricoides is a human parasitic roundworm, which causes the disease of ascariasis. ... The intestine is the portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. ... An average Whooping Crane egg is 102 mm long, and weighs 208 grams In some animals, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ... Orders Arhynchobdellida or Rhynchobdellida There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. ...

Necrotrophs are parasites that use another organism's tissue for their own nutritional benefit until the host dies from loss of needed tissues or nutrients. Necrotrophs are also known as parasitoids. Biotrophic parasites cannot survive in a dead host and therefore keep their hosts alive. Many viruses, for example, are biotrophic because they use the host's genetic and cellular processes to multiply. Parasitoids differ from parasites in their relationship with the host. ...

Some parasites are social parasites, taking advantage of interactions between members of a social host species such as ants or termites to their detriment. Kleptoparasitism involves the parasite stealing food that the host has caught or otherwise prepared. A specialized type of kleptoparasitism is brood parasitism, such as that engaged in by many species of cuckoo. Many cuckoos use other birds as lifetime "babysitters": cuckoo young are raised and fed by adults of the host species, but adult cuckoos fend for themselves. Ants are one of the most successful groups of insects in the animal kingdom. ... Families Reticulitermes spp. ... Kleptoparasitism (literally, parasitism by theft) is a form of feeding where one animal takes prey from another that has caught, killed, or otherwise prepared it. ... Brood parasites are a sub-category of kleptoparasite occurring among birds or insects, that lay their eggs in the nests of other species to be raised by the host. ... Genera See text. ...

Cheating or exploitation types of parasitism are often found in situations where there are generalized non-specific mutualisms between broad classes of organisms, such as mycorrhizal relationships between plants and many types of fungi. Some myco-heterotrophic plants behave as "mycorrhizal cheaters", establishing mycorrhiza-like interactions with a fungal symbiont, but taking carbon from the fungus (which the fungus, in turn, gets from other plants) rather than donating carbon. Cheating, also known as exploitation, between organisms is a form of parasitism or specialized predation in which an organism engages in what appears to be a mutualistic relationship with another organism, but does not in fact provide any benefit to the other organism. ... In biology, mutualism is an interaction, special connection between two or more species where both species derive benefit. ... A mycorrhiza (typically seen in the plural form mycorrhizae meaning fungus roots) is a distinct type of root symbiosis in which individual hyphae extending from the mycelium of a fungus colonize the roots of a host plant. ... u fuck in ua ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Monotropastrum humile, an obligate myco-heterotroph. ...

Evolutionary aspects

Biotrophic parasitism is an extremely successful mode of life. Depending on the definition used, as many as half of all animals have at least one parasitic phase in their life cycles, and it is also frequent in plants and fungi. Moreover, almost all free-living animals are host to one or more parasite taxa. Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... A taxon (plural taxa), or taxonomic unit, is a grouping of organisms (named or unnamed). ...

The hosts of parasites often evolve elaborate defensive mechanisms as well. Plants often produce toxins, for example, which deter both parasitic fungi and bacteria as well as herbivores. Vertebrate immune systems can target most parasites through contact with bodily fluids. Many parasites, particularly microorganisms, evolve adaptations to a particular host species; in such specific interactions the two species generally coevolve into a relatively stable relationship that does not kill the host quickly or at all (since this would be detrimental for the parasite as well; but see parasitoid). Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern... The venom of the black widow spider is a potent latrotoxin. ... Divisions Chytridiomycota Deuteromycota Zygomycota Glomeromycota Ascomycota Basidiomycota A fungus (plural fungi) is a eukaryotic organism that digests its food externally and absorbs the nutrient molecules into its cells. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... A deer and two fawns feeding on some foliage In zoology, an herbivore is an animal that is adapted to eat primarily plant matter (rather than meat). ... Classes and Clades Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... The immune system is the system of specialized cells and organs that protect an organism from outside biological influences. ... This article or section is in need of attention from an expert on the subject. ...

Sometimes, the study of parasite taxonomy can elucidate how their hosts are similar or related. For instance, there has been a dispute about whether Phoenicopteriformes (flamingos) are more closely related to Ciconiiformes (storks and related groups) or to Anseriformes (waterfowl and allies). Flamingos share parasites with ducks and geese, so these groups are thought to be more closely related to one another than either is to storks. Modern DNA methods, however, have shown that flamingos are not closely related to either. For the American doo-wop group, best known for I Only Have Eyes for You (1959), see The Flamingos. ... Families Ardeidae Cochlearidae Balaenicipitidae Scopidae Ciconiidae Threskiornithidae Traditionally, the order Ciconiiformes has included a variety of large, long-legged wading birds with large bills: storks, herons, egrets, ibises, spoonbills, and several others. ... Families Anhimidae Anseranatidae Anatidae †Cnemiornithidae †Dromornithidae †Presbyornithidae The order Anseriformes contains about 150 species of birds in three families: the Anhimidae (the screamers), Anseranatidae (the Magpie-goose), and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans. ...

It is important to note that "benefit" and "harm" in the definition of parasitism apply to lineages, not individuals. Thus, if an organism becomes physically stronger as a result of infection but loses reproductive capabilities (as results from some flatworm infections of snails), that organism is harmed in an evolutionary sense and is thus parasitized. The harm caused to a host by a parasite can take many forms, from direct pathology, including various specialized types of tissue damage, such as castration, to more subtle effects such as modification of host behaviour. Classes The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ... The name snail applies to most members of the molluscan class Gastropoda that have coiled shells. ... Pathology (from Greek pathos, feeling, pain, suffering; and logos, study of; see also -ology) is the study of the processes underlying disease and other forms of illness, harmful abnormality, or dysfunction. ...

Parasites in fiction

Parasites living in or off humans are a favorite theme in the science fiction and horror genres, particularly in the subgenre of body horror. The fear of the human mind and body being used in such a way by another being is an understandably disturbing idea. In such work, the parasite often is responsible for a metamorphosis of the host, or takes control of the host mentally. Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... DVD cover showing horror characters as depicted by Universal Studios. ... Body horror is term applied to works of horror based on a sense of physical wrongness in the body. ... Metamorphosis has several meanings: Look up Metamorphosis in Wiktionary, the free dictionary For metamorphosis as it applies to animals (biology) see Metamorphosis (biology) In geology, metamorphosis refers to the changes undergone by metamorphic rock due to geological processes. ...

Examples of works with this theme would be Carl Zimmer's book Parasite Rex [1], several of the films of David Cronenberg (particularly Shivers), the Alien series of films, and the televistion series Stargate. Carl Zimmer Carl Zimmer is a popular science writer and weblogger, especially regarding the study of evolution. ... David Cronenberg at Cannes 2002 David Paul Cronenberg OC (born March 15, 1943 in Toronto, Ontario) is a Canadian film director and occasional actor. ... Shivers (also known as The Parasite Murders, or They Came from Within) is a 1975 Canadian horror film written and directed by David Cronenberg. ... The science fiction/horror film Alien (1979), directed by Ridley Scott, has become quite influential and has spawned several sequels and imitators. ... Stargate SG-1 (sometimes written Stargåte to mimic the title art, and popularly abbreviated as SG-1) is an American television series based upon the 1994 science fiction film Stargate. ...

See also

• List of parasitic organisms
• Parasitic wasp
• Intestinal parasite
• Macroparasite
• Malarial parasite
• Myco-heterotrophy
• Parasitoid
• Successful parasite
• Superparasitism
• Teratology

Parasitism. ... The term parasitic wasp refers to a large, artificial assemblage of Hymenopteran superfamilies which are primarily parasitoids of other animals, mostly other arthropods. ... Intestinal parasites are parasites that populate the gastro-intestinal tract. ... Macroparasites are parasites that are large enough to be seen with the naked eye and are the opposite of microparasites which cant. ... Red blood cell infected with malaria Of all the infectious diseases: malaria (from the Italian mal laria, meaning bad air ) has affected the most number of peple. ... Monotropastrum humile, an obligate myco-heterotroph. ... This article or section is in need of attention from an expert on the subject. ... When host larvae, e. ... Teratology (from the Greek teras (genitive teratos), meaning monster, and logos meaning study) is the medical study of teratogenesis or grossly deformed individuals. ...

External links

• Parasites and Parasitological Resources
• Aberystwyth University: Parasitology – class outline with links to full text articles on parasitism and parasitology.
• KSU: Parasitology Research - parasitology articles and links.
• Medical Parasitology – online textbook.
• Division of Parasitic Diseases, Centers for Disease Control and Prevention