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Parasite increased trophic transmission (PITT) is a mode of parasite transmission in which the parasite manipulates the behavior of its host to increase transmission success to higher trophic levels.〔 Seppala, O., Valtonen, E. and Benesh, D. (2008). Host manipulation by parasites in the world of dead-end predators: adaptation to enhance transmission?. Proceedings of the Royal Society B: Biological Sciences, 275(1643), 1611-1615.〕 Parasites that use PITT have complex life cycles,〔Mouritsen, K. and Poulin, R. (2003). Parasite-induced trophic facilitation exploited by a non-host predator: a manipulator's nightmare. International Journal for Parasitology, 33(10), 1043-1050.〕 requiring more than one host species to procreate.〔 Sexual reproduction is typically limited to a definitive host, high in the trophic levels.〔Schmidt, G. and Roberts, L. (1985). Foundations of parasitology. St. Louis: Times Mirror/Mosby College Pub.〕 Parasite progeny sequentially infect one or more intermediate hosts, inside which they may undergo asexual reproduction and physiological changes. Trophic transmission often relies on predator-prey relationships,〔Luong, L., Grear, D. and Hudson, P. (2014). Manipulation of host-resource dynamics impacts transmission of trophic parasites. International Journal for Parasitology, 44(10), 737-742.〕 where the parasite can only be transmitted if the host is eaten by a later stage host. Parasitic manipulation of the intermediate host can involve adaptations that make it an easier prey for predators, thereby increasing the transmission rate of the parasite.〔Moore, J. (2002). Parasites and the behavior of animals. Oxford: Oxford University Press.〕〔Lafferty, K. (1999). The Evolution of Trophic Transmission. Parasitology Today, 15(3), 111-115.〕 ==Evolutionary aspects== For complex life cycles to emerge in parasites, the addition of intermediate host species must be beneficial, e.g., result in a higher fitness.〔Trail, D. (1980). Behavioral Interactions between Parasites and Hosts: Host Suicide and the Evolution of Complex Life Cycles. The American Naturalist, 116(1), 77-91.〕〔Brown, S., Renaud, F., Guégan, J. and Thomas, F. (2001). Evolution of trophic transmission in parasites: the need to reach a mating place?. Journal of Evolutionary Biology, 14(5), 815-820.〕 It is probable that most parasites with complex life cycles evolved from simple life cycles.〔Choisy, M., Brown, S., Lafferty, K. and Thomas, F. (2003). Evolution of Trophic Transmission in Parasites: Why Add Intermediate Hosts?. Am Nat, 162(2), 172-181.〕 The transfer from simple to complex life cycles has been analyzed theoretically, and it has been shown that trophically transmitted parasites can be favored by the addition of an intermediate prey host if the population density of the intermediate host is higher than that of the definitive host.〔 Additional factors that catalyze this transfer are high predation rates, and a low natural mortality rate of the intermediate host.〔 Parasites with a single host species are faced with the problem of not being able to survive in higher trophic levels and therefore dying with its prey host. The development of complex life cycles is most likely an adaptation of the parasite to survive in the predator.〔 The development of parasite increased trophic transmission is a further adaptation in relation to a complex life cycle, where the parasite increases its transmission to a definitive host by manipulating its intermediate host.〔 The parasitic manipulation of host behavior is not necessarily an effect of PITT; it could also be a behavioral change induced as a side effect of the infection itself.〔Wobeser, G. (2006). Essentials of disease in wild animals. Ames, Iowa: Blackwell Pub.〕 ==Host and parasite== The coexistence of host and parasite can initiate an evolutionary arms race, resulting in the development of new parasitic strategies and new host defenses. The selective force in susceptible hosts to fight off parasitic infections is often very strong, especially when the parasite kills the host. The parasite is also often strongly affected by selective forces, especially to ensure successful transmission to new hosts and overcome the host’s defenses to survive and reproduce. 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「Parasite increased trophic transmission」の詳細全文を読む スポンサード リンク
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