A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. The biological interaction between the host and the parasite is called parasitism. Parasitism is a type of symbiosis, by one definition, although another definition of symbiosis excludes parasitism, since it requires that the host benefit from the interaction as well as the parasite. In biology and ecology, an organism (in Greek organon = instrument) is a living being. ... 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. ... Parasitism (in Greek: παρασσυτισμός) is an interaction between two organisms, in which one organism (the parasite) benefits and the other (the host) is harmed. ... Common Clownfish (Amphiprion ocellaris) in their magnificent sea anemone (Heteractis magnifica) home. ...

Parasites are generally smaller than their hosts, absorbing nutrients from the host's body fluids, but this is far from a universal strategy. Organisms whose life cycle guarantees the death of the host are not called parasites, but are parasitoids. A few parasites have hosts which are themselves parasites. These are called hyperparasites. Parasitoids differ from parasites in their relationship with the host. ...

Examples

• Endoparasites (endo = within; parasites that live inside their hosts)
  • Plants
    • Rafflesia
  • Animals
    • Acanthocephala
    • Candiru (Vampire fish of Brazil)
    • Clonorchis sinensis (the Chinese liver fluke)
    • Dracunculiasis (Guinea Worm Disease)
    • Enterobius vermicularis
    • Strepsiptera
    • Strongyloides stercoralis
  • Fungi (such as ringworm)
    • Gymnosporangium and other rusts
  • Protists (Protozoa)
    • Malaria (a common blood disease caused by plasmodium)
    • Balantidium coli (the only ciliated protozoan to infect humans)
    • Giardia lamblia (the most common intestinal protozoan in the United States)

• Ectoparasites (ecto = outside; parasites that live on but not within their hosts, for example, attached to their skin)
  • Plants
    • Cuscuta
    • Mistletoe
    • Toothwort
    • The woodrose, Dactylanthus taylorii
  • Animals
    • Hirudinea (some leeches)
    • Phthiraptera (Lice)
    • Siphonaptera (Fleas)
    • Acarina (Ticks)
    • Tantulocarida

Many lifeforms are parasitic only during a part of their lifecycle. Many cuckoos, for example, are brood parasites: their young are parasitic on the host species, but adult cuckoos fend for themselves. In some cases, it may even be useful to view an embryo as a parasite of its mother (see parent-offspring conflict). This usage is controversial when applied to humans because it affects the perceived morality of abortion.[1] (http://www.l4l.org/library/notparas.html) Species Rafflesia arnoldi Rafflesia cantleyi Rafflesia gadutensis Rafflesia hasseltii Rafflesia keithii Rafflesia kerrii Rafflesia manillana Rafflesia micropylora Rafflesia patma Rafflesia pricei Rafflesia rochussenii Rafflesia schadenbergiana Rafflesia speciosa Rafflesia tengku-adlinii Rafflesia tuan-mudae Rafflesia is a genus of parasitic flowers. ... Classes Archiacanthocephala Palaeacanthocephala Eoacanthocephala The Acanthocephala (gr. ... Species Ref: FishBase 2002-08-10 The candirú or canero (Vandellia cirrhosa) is a freshwater fish in the group commonly called the catfishes. ... The Clonorchis sinensis is a human liver fluke in the class Trematoda, Phylum Platyhelminthes. ... Dracunculiasis, more commonly known as Guinea Worm Disease (GWD), is a preventable infection caused by the parasite Dracunculus medinensis. ... Genera The pinworm (Genus Enterobius) is a parasitic roundworm of the phylum Nematoda. ... Families Mengenillidae Mengeidae Stylopidae Bohartillidae Corioxenidae Halictophagidae Callipharixenidae Elenchidae Myrmecolacidae The Strepsiptera are a small (~300 species) order of insects. ... Categories: Animal stubs | Roundworms | Parasitology ... Ringworm, also known as Tinea, is a contagious fungal infection of the skin. ... Species (juniper-hawthorn rust) (juniper-rowan rust) (juniper-hawthorn rust) (juniper-apple rust) (juniper-pear rust) (juniper-quince rust) (Japanese juniper-apple rust) Gymnosporangium is a fungus which infects alternately members of the genus Juniperus (junipers) and members of the family Rosaceae in the subfamily Maloideae (apples, pears, quinces, hawthorns... Red blood cell infected with Malaria (Italian: bad air; formerly called ague or marsh fever in English) is an infectious disease which in humans causes about 500 million infections and 2 million deaths annually, mainly in the tropics and sub-Saharan Africa. ... Species Plasmodium berghei Plasmodium brasilianum Plasmodium chabaudi Plasmodium cynomolgi Plasmodium falciparum Plasmodium gallinaceum Plasmodium knowlesi Plasmodium lophurae Plasmodium malariae Plasmodium ovale Plasmodium vivax etc. ... Balantidium coli is a species of ciliate protozoan, and is the only one that is a pathogen of humans. ... Binomial name Giardia lamblia (Kunstler, 1882) Giardia lamblia (formerly also Lamblia intestinalis) is a protozoan parasite that infects the gastrointestinal tract of humans. ... Species Cuscuta americana Cuscuta applanata Cuscuta approximata Cuscuta attenuata Cuscuta boldinghii Cuscuta brachycalyx Cuscuta californica Cuscuta cassytoides Cuscuta ceanothi Cuscuta cephalanthi Cuscuta compacta Cuscuta coryli Cuscuta corylii Cuscuta cuspidata Cuscuta decipiens Cuscuta dentatasquamata Cuscuta denticulata Cuscuta epilinum Cuscuta epithymum Cuscuta erosa Cuscuta europaea Cuscuta exaltata Cuscuta fasciculata Cuscuta globulosa Cuscuta... Species see text Mistletoe attached to eucalyptus host European mistletoe attached to a Silver Birch. ... Species Lathraea squamaria Toothwort is the popular name for a small British carnivorous plant of curious form and growth, known botanically as Lathraea squamaria, family Scrophulariaceae. ... Binomial name Dactylanthus taylorii The woodrose, Dactylanthus taylorii, is a fully parasitic plant that grows on the roots of certain trees in New Zealand. ... Orders Arhynchobdellida Rhynchobdellida *There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. ... Orders Arhynchobdellida Rhynchobdellida *There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. ... ... For the musician, a member of the Red Hot Chili Peppers, see Michael Balzary. ... Families Tetranychidae - Spider mites Eriophyidae - Gall mites Sarcoptidae - Sarcoptic Mange mites The mites and ticks, order Acarina or Acari, belong to the Arachnida and are among the most diverse and successful of all the invertebrate groups, although some way behind the insects. ... Tantulocarida is a small subclass of the class Maxillopoda (ostracods, copepods, barnacles) that consists of about 1200 species. ... Genera See text. ... Brood parasite is a term specifically applied to birds or insects that leave their eggs in the nests of other birds or insects to be raised. ... Robert Trivers theory of parent-offspring conflict (1974) predicts that because the genetic interests of parents and offspring are not identical, offspring will be selected to manipulate their parents in order to ensure higher investment, and that, conversely, parents will be selected to manipulate their offspring. ...

The term parasite is also used for people who benefit from a relationship, society or system without contributing significantly to it, although they could; however this usage of the term is highly controversial because of its association with Nazism and its various extermination programs. The Nazi Party used a right-facing swastika as their symbol and the red and black colors were said to represent Blut und Boden (blood and soil). ...

See also

• saprophyte
• intestinal parasite

A saprophyte used to be defined as any organism which obtained its energy from decaying animal or vegetable matter. ... Intestinal parasites are parasites that populate the gastro-intestinal tract. ...

References

• Centers for Disease Control and Prevention
  • Division of Parasitic Diseases (http://www.cdc.gov/ncidod/dpd/)
    • DPDx (http://www.dpd.cdc.gov/dpdx/) - Laboratory Identification of Parasites of Public Health Concern - Reference and Training as well as Diagnostic Assistance