[The importance of environmental factors. 1. Conditions for parasite infection].
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Abstract:
Results of research showing an evident influence of the host's species, strain and age on the biology of the parasite have been presented. Various Hymenolepididae and Amidostomum anseris served as models. Irregular growth and development of the parasite in a given host species cannot be used as a sure criterion to determine the quality of the host-parasite system, because this irregularity occurs sometimes in a specific host, too. It is proposed that a host can only be regarded as specific for a particular species of parasite if its life cycle can be completed and development of successive generations can be assured. Not only the main host but an auxiliary, incidental or side one can play the role of a specific host.Keywords:
Obligate parasite
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Journal Article Evolution of Resistance in a Host Population to Attacking Parasite Get access Daniel Olson, Daniel Olson Cornell University, Ithaca, New York Search for other works by this author on: Oxford Academic PubMed Google Scholar David Pimentel David Pimentel Cornell University, Ithaca, New York Search for other works by this author on: Oxford Academic PubMed Google Scholar Environmental Entomology, Volume 3, Issue 4, 1 August 1974, Pages 621–624, https://doi.org/10.1093/ee/3.4.621 Published: 01 August 1974 Article history Received: 07 December 1973 Published: 01 August 1974
Entomology
Host resistance
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Density-dependent effects on Anguillicola crassus (Nematoda) within its European eel definitive host
Density-dependent effects on adult and larval stages of the introduced nematode parasite Anguillicola crassus in the European eel definitive host were examined in the laboratory in naturally infected fish, and in field samples. The effect of adult nematode subpopulations on larval development over time and the effect of increasing adult intensity on the gravid female subpopulations were investigated. At high adult subpopulations the movement of larvae from the swimbladder wall into the swimbladder lumen appears to be inhibited, and A. crassus larvae to be arrested in development in a density-dependent manner. The number of gravid females per host reaches a constant level, and so the proportion of gravid female nematodes per adult subpopulation decreases relative to further increasing total adult nematode numbers. Both these mechanisms have the potential to regulate infrapopulations of A. crassus within the eel definitive host and thus the parasite suprapopulation.
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Abstract Surprisingly little is known about what determines a parasite's host range, which is essential in enabling us to predict the fate of novel infections. In this study, we evaluate the importance of both host and parasite phylogeny in determining the ability of parasites to infect novel host species. Using experimental lab assays, we infected 24 taxonomically diverse species of Drosophila flies (Diptera: Drosophilidae) with five different nematode species (Tylenchida: Allantonematidae: Howardula, Parasitylenchus), and measured parasite infection success, growth, and effects on female host fecundity (i.e., virulence). These nematodes are obligate parasites of mushroom-feeding Drosophila, particularly quinaria and testacea group species, often with severe fitness consequences on their hosts. We show that the potential host ranges of the nematodes are much larger than their actual ranges, even for parasites with only one known host species in nature. Novel hosts that are distantly related from the native host are much less likely to be infected, but among more closely related hosts, there is much variation in susceptibility. Potential host ranges differ greatly between the related parasite species. All nematode species that successfully infected novel hosts produced infective juveniles in these hosts. Most novel infections did not result in significant reductions in the fecundity of female hosts, with one exception: the host specialist Parasitylenchus nearcticus sterilized all quinaria group hosts, only one of which is a host in nature. The large potential host ranges of these parasites, in combination with the high potential for host colonization due to shared mushroom breeding sites, explain the widespread host switching observed in comparisons of nematode and Drosophila phylogenies.
Obligate parasite
Obligate
Tylenchida
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Ovipositor
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In many natural populations, hosts are found to be infected by more than one parasite species. When these parasites have different host exploitation strategies and transmission modes, a conflict among them may arise. Such a conflict may reduce the success of both parasites, but could work to the benefit of the host. For example, the less-virulent parasite may protect the host against the more-virulent competitor. We examine this conflict using the waterflea Daphnia magna and two of its sympatric parasites: the blood-infecting bacterium Pasteuria ramosa that transmits horizontally and the intracellular microsporidium Octosporea bayeri that can concurrently transmit horizontally and vertically after infecting ovaries and fat tissues of the host. We quantified host and parasite fitness after exposing Daphnia to one or both parasites, both simultaneously and sequentially. Under conditions of strict horizontal transmission, Pasteuria competitively excluded Octosporea in both simultaneous and sequential double infections, regardless of the order of exposure. Host lifespan, host reproduction and parasite spore production in double infections resembled those of single infection by Pasteuria. When hosts became first vertically (transovarilly) infected with O. bayeri, Octosporea was able to withstand competition with P. ramosa to some degree, but both parasites produced less transmission stages than they did in single infections. At the same time, the host suffered from reduced fecundity and longevity. Our study demonstrates that even when competing parasite species utilize different host tissues to proliferate, double infections lead to the expression of higher virulence and ultimately may select for higher virulence. Furthermore, we found no evidence that the less-virulent and vertically transmitting O. bayeri protects its host against the highly virulent P. ramosa.
Obligate parasite
Susceptible individual
Horizontal transmission
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An investigation of (1) host infection and respiration, and (2) parasite development and crowding, between two Tribolium hosts and Hymenolepis diminuta has been carried out.The results show that infection of the host was influenced by temperature but not by the host's species or sex or the number of eggs ingested. The respiration of the host was observed to increase with infection and to occur at a higher rate in Tribolium castaneum and the female sex of each host. The results also indicate that parasite development was more rapid in the female host. The effects of parasitic crowding on the parasite could not be demonstrated. The results of this study are discussed in relation to current knowledge and suggestions about the mechanisms of the aforementioned effects are proposed.
Hymenolepis diminuta
Obligate parasite
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Parasite-induced changes in host's thermal preferences not only can be interpreted as a physiological defense response of the host but also can represent a pathological manifestation of the parasite. Both may become established in host-parasite relationships if they are beneficial for at least one of the counterparts. This study investigates parasite-induced changes in the thermoregulatory behavior of first intermediate hosts of Digenea (i.e. Lymnaea stagnalis and Planorbarius corneus), infected with Notocotylidae or Echinostomatidae larvae. The investigated parasite species developed different transmission strategies outside the body of a snail, which may imply a different effect on the behavior of their hosts. Notocotylus attenuatus in L. stagnalis and Notocotylus ephemera in P. corneus produce symptoms of anapyrexia, prolonging the lifespan of their hosts. By contrast, Echinoparyphium aconiatum in L. stagnalis and Echinostoma spiniferum in P. corneus interfere with defensive thermoregulatory behavior of host snails, causing their accelerated death. The results of laboratory research indicate that thermal preferences of the snails infected with all investigated trematodes facilitate the transmission of the parasites in environment.
Lymnaea stagnalis
Digenea
Freshwater snail
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Journal Article Demonstration of Host Discrimination in the Parasite Orgilus lepidus (Hymenoptera: Braconidae) Get access Patrick D. Greany, Patrick D. Greany 2 Department of Biological Control, University of California Citrus Research Center and Agricultural Experiment Station, Riverside. 2Present address: Department of Entomology, Pennsylvania State Univ., University Park 16802. Search for other works by this author on: Oxford Academic Google Scholar Earl R. Oatman Earl R. Oatman Department of Biological Control, University of California Citrus Research Center and Agricultural Experiment Station, Riverside. Search for other works by this author on: Oxford Academic Google Scholar Annals of the Entomological Society of America, Volume 65, Issue 2, 15 March 1972, Pages 375–376, https://doi.org/10.1093/aesa/65.2.375 Published: 15 March 1972 Article history Received: 11 August 1971 Published: 15 March 1972
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Entomology
Agricultural experiment station
Research center
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SUMMARY Host–parasite interactions were studied for the microsporidium Pleistophora intestinalis and its host, Daphnia magna . Two host clones were established from the same population from which the parasites were taken (home-1 and 2), and two clones from two other ponds (neighbour and Munich clone). With increasing clutch number infected females from home-1 clone produced relatively smaller clutches than uninfected females. Age and body length at maturity were not affected by the infection, but body length of the sixth adult instar was reduced. In an experiment including all four host clones, the parasite reproduced well in the two home clones and in the neighbour clone, but poorly in the Munich clone. Juvenile growth and age at maturity was not affected in the two home clones, but for the neighbour and the Munich clone age was delayed by 2·2 days and 4·1 days, and juvenile growth reduced by 16 and 23%, respectively. Significant host-clone x parasite-treatment interactions were also found for size at maturity and clutch size. This pattern of host-parasite interactions suggests that there is no general positive relation between disease severity and parasite multiplication rate.
clone (Java method)
Parthenogenesis
Avian clutch size
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