Adaptation and Transition into Parasitism from Commensalism: A Phoretic Model

Abstract

A parasite is ``any organism that grows, feeds and is sheltered on or in a different organism while contributing nothing to the survival of its host'' (The American Heritage Dictionary of the English Language). The etymology of the word has its origin in the Greek word parasitos, ``fellow guest.'' Parasitism is an important ecological and evolutionary role assumed by a variety of animals, and it has been suggested that parasitic insects comprise as many as half of all animals living on earth today (Price 1980). While a comparable projection is not yet available for mites, it is clear that the Acari have been particularly prominent in the exploitation of this mode of existence, both as ectoparasites and (to a lesser extent) as endoparasites (e.g. Pneumocoptes = lung parasites of the rodents Peromyscus, Onychomys, and Cynomys; Baker 1951).