Obligate parasite
An obligate parasite or holoparasite is a
It is advantageous for the parasite to preserve the health of its host when this is compatible with its nutritional and reproductive requirements, except when the death of the host is necessary for transmission.[1]
Species
Obligate parasitism is exhibited in a range of organisms, with examples in
They are unable to complete their development without passing through at least one parasitic stage which is necessary to their life-cycle.Whether one regards viruses as living organisms or not, they cannot reproduce except by means of resources within living cells. Accordingly, it is convenient and customary to regard them as obligate intracellular parasites.
Among the Vespidae family, Vespula austriaca is an example of an obligate reproductive parasite; its common host is Vespula acadica.[3] In the genus Bombus, B. bohemicus is an obligate parasite of B. locurum, B. cryptarum, and B. terrestris.[4]
Host-parasite interaction
Life-cycle
Intermediate or final host
An
Parasitic permanence
Obligate parasites may not necessarily spend all of their time behaving as parasites. When a parasite is permanent, a number of generations occur in or on the host of an infested individual.
Location on host
The parasite may live outside of the host ectoparasite; for example, a tick. Alternatively, the parasite may live within the host endoparasite; for example, the fluke. An obligate parasite that does not live directly in or on the host, but rather acts at a distance – for example, a
Invasion strategies
In order to establish infestation in a susceptible host, obligate parasites must evade defences before, during and after entry into the host.[7] Due to the wide range of obligate parasite types, it is impossible to identify a general invasion strategy. Intracellular parasites use various strategies to invade cells and subvert cellular signalling pathways. Most bacteria and viruses undergo passive uptake, where they rely on the host cell for uptake. However, apicomplexans engage in active entry.[8] One obligate wasp parasite, Polistes atrimandibularis, infiltrates its hosts' colony by modifying its chemical signature to match that of the hosts.[9] This tricks the host wasps into thinking the parasite is one of their own.
Evasion of host defences
A number of obligate intracellular parasites have evolved mechanisms for evading their hosts' cellular defences, including the ability to survive in distinct cellular compartments.[10] One of the mechanisms that hosts employ in their attempt to reduce the replication and spread of pathogens is apoptosis (programmed cell death). Some obligate parasites have developed ways to suppress this phenomenon, for example Toxoplasma gondii, although the mechanism is not yet fully understood.[11]
Manipulation of host behaviour
Changes in a host’s behaviour following infection with obligate parasites are extremely common.
Extended phenotype
In some cases the behaviour we observe in an organism is not due to the expression of its genes, but rather to the genes of parasites infecting it. This behaviour is an extended phenotype.[13]
Evolution of host behaviour manipulation
Three main evolutionary routes have been suggested for the appearance of host behaviour manipulation by parasites. The first is a parasite driven scenario of manipulation, while the second and third are host driven scenarios of manipulation.
- Manipulation sensu stricto (extended phenotype- abhorrent behaviour displayed by parasitised hosts results from the expression of the parasites genes) this capacity could have been the product of natural selection in an ancestral parasite with the trait.[19]
- The mafia-like strategy- retaliation for non-compliance (eg.great spotted cuckoo and magpie) magpies that eject the cuckoos eggs from their nests suffer a much greater rate of cuckoo predation.[19]
- The exploitation of compensatory responses induce host compensatory responses since these may at least partially match with the transmission routes of parasites. E.g. the sexually transmitted ectoparasite Chrysomelobia labidomerae, parasitizing the leaf beetle host Labidomera clivicollis~ infected males exhibit increased sexual behaviour and as a result enhance inter- and intra- sexual contacts (copulation and competition) which provide more opportunities for parasite transmission.[20]
It has been suggested that extended phenotype behaviours are not adaptive, but are Exaptative.[21] While they may have a benefit for the parasitic organism, they did not arise with the intention of this benefit.[20]
Parasitic mimicry in brood parasites
The
Several butterfly species will also exhibit brood parasitic behavior. An example is Niphanda fusca, a butterfly that will release cuticular hydrocarbons (CHCs) to trick the host ant, C. japonicus, into adopting the larva as their own in their own nest. The ant will then raise the larva of the butterfly, feeding it directly from mouth-to-mouth, until it pupates.[26]
It is proposed that this mimicry has evolved through two processes: either as coevolutionary responses to host defences against brood parasites or modifying pre-existing host provisioning strategies.[27] Competition between the parasite and host young for parental resources might lead to exaggeration of the aspects of the signal that most effectively exploit host parents.[28] The parasitic young are likely to experience stronger selection for exaggerated signals than host young, because they are unrelated to the other chicks in the nest and therefore under selection to behave more selfishly.[29]
Evolution of obligate parasitism
Current theory in evolutionary biology indicates that host-parasite relationships may evolve towards equilibrial states of severe disease.[30] This differs from the conventional belief that commensalism is the ideal equilibrium for both the host and parasite.[1]
See also
- Obligate intracellular parasite
- Parasitoid
References
- ^ a b Combes, C. (1997) Fitness of Parasites: Pathology and Selection International Journal for Parasitology 27 (1): 1–10.
- ^ a b Balashov, Yu.S. (2011) Parasitism and Ecological Parasitology. Entomological Review 91 (9): 1216–1223.
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- ^ a b May, R. M. & Anderson, R. M. (1979) Population biology of infectious diseases. Nature 280: 455–461.
- ^ Goodman, B. A. & Johnson, PTJ. (2011) Disease and extended phenotype: Parasites control host performance and survival through induced changes in body plan. PLoS ONE 6(5):1–10.
- PMID 2069674.
- ^ Sibley, L. D. (2004) Parasite invasion strategies. Science 304(5668): 284–253.
- ^ Cervo, Rita (December 2006). "Polistes Wasps and Their Social Parasites: An Overview" (PDF). Ann. Zool. Fennici.
- ^ Hackstadt, T. (1998) The diverse habitats of obligate intracellular parasites. Current Opinion in Microbiology 1: 82–87.
- ^ Laliberté, J. & Carruthers, V.B. (2008) Host cell manipulation by the human pathogen toxoplasma gondii. Cellular and Molecular Life Sciences 65: 1900–1915.
- ^ Poulin, R. (1995) “Adaptive” changes in the behaviour of parasitized animals: A critical review. International Journal for Parasitology 5 (12): 1371–1383.
- ^ a b Hughes, D. (2013) Pathways to understanding the extended phenotype of parasites in their hosts. The Journal of Experimental Biology 216: 142–147.
- ^ Combes, C. (1991) Ethological aspects of parasite transmission. The American Naturalist 138 (4): 866–880.
- ^ McNair D. M. & Timmons E. H. 1977. Effects of Aspiculuris tetraptera and Syphacia obvelata on exploratory behaviour of an inbred mouse strain. Laboratory Animal Science 27:38–42.
- ^ Pullin, R. (1995) “Adaptive” changes in the behaviour of parasitized animals: A critical review. International Journal for Parasitology 25 (12): 1371–1383.
- ^ Berdoy, M.F., Webster, J. P & MacDonald, D. W. (2000) Fatal Attraction in rats infected with Toxoplasma gondii. Proceedings of the Royal Society B 267:1591–1594.
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- ^ a b Adamo, S. A. (2012) The strings of the puppet master: How parasites change host behaviour in Hughes, D.P., Brodeur, J. & Thomas, F. (Eds.), Host Manipulation by Parasites (pp. 36–51).Oxford, UK: Oxford University Press.
- ^ a b Abbot, P. & Dll, L. M. (2001). Sexually transmitted parasites and sexual selection in the milkweed leaf beetle, Labidomera clivicollis. Oikos 92: 91–100
- ^ Gould, S. J. & Vrba, E.S. (1982) Exaptation: a missing term in the science form. Paleobiology. 8:4–15.
- ^ May, R. M., & Robinson, S.K. (1984) Population dynamics of avian brood parasitism. The American Naturalist 126(4):475–494.
- ^ Kilner, R. M., & Davies, N. B. (1999). How selfish is a cuckoo chick? Animal Behaviour 58:797–808.
- ^ Sledge, M.F., Dani, F.R., Cervo, R., Dapporto, L., Turillazzi, S. (2001). “Recognition of social parasites as nestmates: adoption of colony-specific host cuticular odours by the paper wasp parasite Polistes sulcifer”. Proceedings of the Royal Society of London B 268: 2253–2260.
- ^ Cervo, R. (2006). Polistes wasps and their social parasites: an overview. Ann. Zool. Fennici, 43, 531–549.
- PMC 2664337
- ^ Langmore, N. E. & Spottiswoode, C. N. (2012) Visual Trickery in avian brood parasites in Hughes, D.P., Brodeur, J. & Thomas, F. (Eds.), Host Manipulation by Parasites (pp. 36–51).Oxford, UK: Oxford University Press.
- ^ Hauber, M. E. & Kilner, R. M. (2007) Coevolution, communication and host-chick mimicry in parasitic finches: who mimics whom? Behavioral Ecology and Sociobiology 61: 497–503.
- ^ Lichtensten, G. (2001). Low success of shiny cowbird chicks parasitizing rufous-bellied thrushes: chick-chick competition or parental discrimination? Animal Behaviour 61:401–413.
- ^ Ewald, P.W. (1983). Host-parasite relations, vectors, and the evolution of disease severity. Annual Review of Ecology and Systematics 14:465–485.