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Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice of certain animals of feeding on blood (from the Greek words αἷμα ''haima'' "blood" and φάγειν ''phagein'' "to eat"). Since blood is a fluid tissue rich in nutritious proteins and lipids that can be taken without enormous effort, hematophagy has evolved as a preferred form of feeding in many small animals such as worms and arthropods. Some intestinal nematodes, such as Ancylostomids, feed on blood extracted from the capillaries of the gut and about 75 percent of all species of leeches (e.g. ''Hirudo medicinalis''), a free-living worm, are hematophagous. Some fish, such as lampreys and candirus, and mammals, especially the vampire bats, and birds, such as the vampire finches, hood mockingbirds, and oxpeckers, also practise hematophagy. ==Mechanism and evolution== These hematophagous animals have mouth parts and chemical agents for penetrating vascular structures in the skin of hosts, mostly of mammals, birds, and fish. This type of feeding is known as phlebotomy (from the Greek words, ''phleps'' "vein" and ''tomos'' "cutting"). Once phlebotomy is performed (in most insects by a specialized fine hollow "needle," the proboscis, which perforates skin and capillaries; in bats by sharp incisor teeth that act as a razor to cut the skin), blood is acquired either by sucking action directly from the veins or capillaries, from a pool of escaped blood, or by lapping (again, in bats). In order to overcome natural hemostasis (blood coagulation), vasoconstriction, inflammation, and pain sensation in the host, biochemical solutions in the saliva for instance, for pre-injection, anesthesia and capillary dilation have evolved in different hematophagous species. Anticoagulant medicines have been developed on the basis of substances found in the saliva of several hematophagous species such as leeches (hirudin). Hematophagy can be classified into obligatory and optional practice. Obligatory hematophagous animals do not have any other type of food besides blood; one such species is ''Rhodnius prolixus'' (an assassin bug from South America). This contrasts with optional hematophages, like the many mosquitoes species, such as ''Aedes aegypti'', which may also feed on pollen, fruit juice, and other biological fluids. Sometimes only the female of the species is a hematophage (this is essential for egg production and reproduction). Hematophagy has apparently evolved independently in many disparate arthropod, annelid, nematode and mammalian taxa. For example Diptera (insects with two wings, such as flies) have eleven families with hematophagous habits (more than half of the 19 hematophagous arthropod taxa). About 14,000 species of arthropods are hematophagous, even including some genera that were not previously thought to be, such as moths of the genus ''Calyptra''. Several complementary biological adaptations for locating the hosts (usually in the dark, as most hematophagous species are nocturnal and silent, in order to avoid detection and destruction by the host) have also evolved, such as special physical or chemical detectors (for sweat components, CO2, heat, light, movement, etc.). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hematophagy」の詳細全文を読む スポンサード リンク
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