Etymology

Etymology

First attested in English 1539, the word parasite comes from the Medieval French parasite, from the Latin parasitus, the romanization of the Greek "παράσιτος" (parasitos), "one who eats at the table of another"^[2] and that from "παρά" (para), "beside, by"^[3] + "σῖτος" (sitos), "wheat".^[4] Coined in English 1611, the word parasitism comes from the Greek "παρά" (para) + "σιτισμός" (sitismos) "feeding, fattening".^[5]

[edit] Types of parasitism

Parasites are classified based on their interactions with their hosts and on their life cycles.
Parasites that live on the surface of the host are called ectoparasites (e.g. some mites) and those that live inside the host are called endoparasites (including all parasitic worms). Endoparasites can exist in one of two forms: intercellular (inhabiting spaces in the host’s body) or intracellular (inhabiting cells in the host’s body). Intracellular parasites, such as bacteria or viruses, tend to rely on a third organism which is generally known as the carrier or vector. The vector does the job of transmitting them to the host. An example of this interaction is the transmission of malaria, caused by a protozoan of the genus Plasmodium, to humans by the bite of an anopheline mosquito.
An epiparasite is one that feeds on another parasite. This relationship is also sometimes referred to as hyperparasitism which may be exemplified by a protozoan (the hyperparasite) living in the digestive tract of a flea living on a dog.
Social parasites take advantage of interactions between members of social organisms such as ants or termites. In kleptoparasitism, parasites appropriate food gathered by the host. An example is the brood parasitism practiced by many species of cuckoo and cowbird, which do not build nests of their own but rather deposit their eggs in nests of other species and abandon them there. The host behaves as a "babysitter" as they raise the young as their own. If the host removes the cuckoo's eggs, some cuckoos will return and attack the nest to compel host birds to remain subject to this parasitism.^[6] The cowbird’s parasitism does not necessarily harm its host’s brood; however, the cuckoo may remove one or more host eggs to avoid detection, and furthermore the young cuckoo may heave the host’s eggs and nestlings from the nest.
Parasitism can take the form of isolated cheating or exploitation among more generalized mutualistic interactions. For example, broad classes of plants and fungi exchange carbon and nutrients in common mutualistic mycorrhizal relationships; however, some plant species known as myco-heterotrophs "cheat" by taking carbon from a fungus rather than donating it.
Parasitoids are organisms whose larval development occurs inside or on the surface of another organism, resulting in the death of the host.^[7] This means that the interaction between the parasitoid and the host is fundamentally different from that of a true parasite and shares some of the characteristics of predation.
An adelpho-parasite is a parasite in which the host species is closely related to the parasite, often being a member of the same family or genus. An example of this is the citrus blackfly parasitoid, Encarsia perplexa, unmated females of which may lay haploid eggs in the fully developed larvae of their own species. These result in the production of male offspring.^[8] The marine worm Bonellia viridis has a similar reproductive strategy, although the larvae are planktonic.^[9]