| infection with an acanthocephalan manipulates an amphipod's reaction to a fish predator's odours. | many parasites with complex life cycles increase the chances of reaching a final host by adapting strategies to manipulate their intermediate host's appearance, condition or behaviour. the acanthocephalan parasite pomphorhynchus laevis uses freshwater amphipods as intermediate hosts before reaching sexual maturity in predatory fish. we performed a series of choice experiments with infected and uninfected gammarus pulex in order to distinguish between the effects of visual and olfactory predator ... | 2007 | 17049528 |
| colonization and establishment of pomphorhynchus laevis (acanthocephala) in an isolated english river. | the successful colonization, establishment and spread of pomphorhynchus laevis in a small, isolated, devon river 128 km from the parasite's nearest focus in dorset was followed over 11 years from 1985. the parasite was first detected in anguilla anguilla and platichthys flesus in 1988: by 1995 it had attained prevalence levels of 22.6% in a. anguilla and 43.6% in p. flesus and also occurred in 100% salmo trutta, 50% cottus gobio and noemacheilus barbatulus. as judged by prevalence, abundance, pr ... | 1996 | 8991914 |
| variation between populations and local adaptation in acanthocephalan-induced parasite manipulation. | many trophically transmitted parasites manipulate their intermediate host phenotype, resulting in higher transmission to the final host. however, it is not known if manipulation is a fixed adaptation of the parasite or a dynamic process upon which selection still acts. in particular, local adaptation has never been tested in manipulating parasites. in this study, using experimental infections between six populations of the acanthocephalan parasite pomphorhynchus laevis and its amphipod host gamm ... | 2010 | 20394670 |
| density-dependent effects on parasite growth and parasite-induced host immunodepression in the larval helminth pomphorhynchus laevis. | larval helminths exploit the physiology of their intermediate hosts: first, as a resource for energy and space and second by altering the immune system activity to ensure their survival. whereas the growth pattern under parasite competition has been investigated, the effect of multiple infections on the level of parasite-induced immunodepression in a trophically transmitted helminth has been neglected. in this study, amphipods gammarus pulex were infected in the laboratory by the acanthocephalan ... | 2011 | 20696096 |
| biological invasion and parasitism: invaders do not suffer from physiological alterations of the acanthocephalan pomphorhynchus laevis. | biological invasions expose parasites to new invasive hosts in addition to their local hosts. however, local parasites are often less successful in infecting and exploiting their new hosts. this may have major consequences for the competitive ability of hosts, and finally on the fate of the parasite-host community. in burgundy (eastern france), the acanthocephalan parasite, pomphorhynchus laevis, infects 2 amphipod species living in sympatry: the native gammarus pulex and the invasive gammarus r ... | 2010 | 19765338 |
| variation and covariation in infectivity, virulence and immunodepression in the host-parasite association gammarus pulex-pomphorhynchus laevis. | parasites often manipulate host immunity for their own benefit, either by exacerbating or suppressing the immune response and this may directly affect the expression of parasite virulence. however, genetic variation in immunodepression, which is a prerequisite to its evolution, and the relationship between immunodepression and virulence, have rarely been studied. here, we investigated the variation among sibships of the acanthocephalan parasite, pomphorhynchus laevis, in infecting and in immunod ... | 2009 | 19726474 |
| carotenoid-based colour of acanthocephalan cystacanths plays no role in host manipulation. | manipulation by parasites is a catchy concept that has been applied to a large range of phenotypic alterations brought about by parasites in their hosts. it has, for instance, been suggested that the carotenoid-based colour of acanthocephalan cystacanths is adaptive through increasing the conspicuousness of infected intermediate hosts and, hence, their vulnerability to appropriate final hosts such as fish predators. we revisited the evidence in favour of adaptive coloration of acanthocephalan pa ... | 2009 | 18796399 |
| immune depression induced by acanthocephalan parasites in their intermediate crustacean host: consequences for the risk of super-infection and links with host behavioural manipulation. | parasite survival in hosts mainly depends on the capacity to circumvent the host immune response. acanthocephalan infections in gammarids are linked with decreased activity of the prophenoloxidase (propo) system, suggesting an active immunosuppression process. nevertheless, experimental evidence for this hypothesis is lacking: whether these parasites affect several immune pathways is unknown and the consequences of such immune change have not been investigated. in particular, the consequences fo ... | 2009 | 18708062 |
| infection with acanthocephalans increases the vulnerability of gammarus pulex (crustacea, amphipoda) to non-host invertebrate predators. | phenotypic alterations induced by parasites in their intermediate hosts often result in enhanced trophic transmission to appropriate final hosts. however, such alterations may also increase the vulnerability of intermediate hosts to predation by non-host species. we studied the influence of both infection with 3 different acanthocephalan parasites (pomphorhynchus laevis, p. tereticollis, and polymorphus minutus) and the availability of refuges on the susceptibility of the amphipod gammarus pulex ... | 2008 | 18371238 |
| modification of hosts' behavior by a parasite: field evidence for adaptive manipulation. | parasites relying on trophic transmission to complete their life cycles often induce modifications of their host's behavior in ways that may increase their susceptibility to predation by final hosts. these modifications have often been interpreted as parasite adaptations, but very few studies have demonstrated that host manipulation has fitness benefits for the parasite. the aim of the present study was to address the adaptive significance of parasite manipulation by coupling observations of beh ... | 2007 | 18051653 |
| the effects of parasite age and intensity on variability in acanthocephalan-induced behavioural manipulation. | numerous parasites with complex life cycles are able to manipulate the behaviour of their intermediate host in a way that increases their trophic transmission to the definitive host. pomphorhynchus laevis, an acanthocephalan parasite, is known to reverse the phototactic behaviour of its amphipod intermediate host, gammarus pulex, leading to an increased predation by fish hosts. however, levels of behavioural manipulation exhibited by naturally-infected gammarids are extremely variable, with some ... | 2008 | 18314127 |
| larval morphology, genetic divergence, and contrasting levels of host manipulation between forms of pomphorhynchus laevis (acanthocephala). | studies on parasite species with a wide geographic and ecological range may be confounded by still equivocal taxonomic identification. here, we investigated genetic polymorphism and behavioural changes induced in a common intermediate host, in two different forms of pomphorhynchus laevis based on the morphology of the larval infective stage (cystacanth). a 'smooth type' (s) and a 'wrinkled type' (w) of cystacanth were distinguished based on their surface and shape. we analysed sequence divergenc ... | 2004 | 14711589 |
| field evidence of host size-dependent parasitism in two manipulative parasites. | the distribution of parasites within host natural populations has often been found to be host age-dependent. host mortality induced by parasites is the commonest hypothesis proposed for explaining this pattern. despite its potential importance in ecology, the parasitism intensity in relation with the host age has rarely been studied in the field. the 2 manipulative acanthocephalans, polymorphus minutus and pomphorhynchus laevis, use the amphipod gammarus pulex as an intermediate host, and their ... | 2007 | 17918352 |
| altered host behaviour and brain serotonergic activity caused by acanthocephalans: evidence for specificity. | manipulative parasites can alter the phenotype of intermediate hosts in various ways. however, it is unclear whether such changes are just by-products of infection or adaptive and enhance transmission to the final host. here, we show that the alteration of serotonergic activity is functionally linked to the alteration of specific behaviour in the amphipod gammarus pulex infected with acanthocephalan parasites. pomphorhynchus laevis and, to a lesser extent, pomphorhynchus tereticollis altered pho ... | 2006 | 17015346 |
| differential influence of pomphorhynchus laevis (acanthocephala) on brain serotonergic activity in two congeneric host species. | the physiological mechanisms by which parasites with complex life cycles manipulate the behaviour of their intermediate hosts are still poorly understood. in burgundy, eastern france, the acanthocephalan parasite pomphorhynchus laevis inverses reaction to light in its amphipod host gammarus pulex, but not in gammarus roeseli, a recent invasive species. here, we show that this difference in manipulation actually reflects a difference in the ability of the parasite to alter brain serotonergic (5-h ... | 2007 | 17443968 |
| differential phenoloxidase activity between native and invasive gammarids infected by local acanthocephalans: differential immunosuppression? | manipulative endoparasites can alter the behaviour and the physiology of their intermediate hosts in ways that increase the probability of successful transmission to the final host. this requires that the parasite is able to circumvent its host's immune defence. successful immune evasion may depend on host-parasite coevolutionary history and the appearance of new hosts invading the local host population may promote local parasite maladaptation. to test this hypothesis, we examined the effect of ... | 2003 | 14700193 |
| effects of two acanthocephalan parasites on the fecundity and pairing status of female gammarus pulex (crustacea: amphipoda). | acanthocephalan parasites are known to alter the reproductive biology and physiology of their hosts in various ways. in this study we investigated the influence of two acanthocephalan parasites, pomphorhynchus laevis and polymorphus minutus, on the fecundity and pairing success of female gammarus pulex. the results show that p. laevis and p. minutus affect female intermediate host reproduction in different ways. females infected with p. minutus were totally castrated, whereas those infected with ... | 2002 | 12095239 |
| differential influence of pomphorhynchus laevis (acanthocephala) on the behaviour of native and invader gammarid species. | although various species of acanthocephalan parasites can increase the vulnerability of their amphipod intermediate hosts to predation, particularly by altering their photophobic behaviour, their influence on the structure of amphipod communities and the success of invader species has so far received little attention. we compared the prevalence and behavioural influence of a fish acanthocephalan parasite, pomphorhynchus laevis, in two species of amphipods, gammarus pulex and gammarus roeseli in ... | 2000 | 11428335 |
| a predator's dilemma: prey choice and parasite susceptibility in three-spined sticklebacks. | the acanthocephalan parasite pomphorhynchus laevis is transmitted by a suitable intermediate host such as the amphipod gammarus pulex to its definitive fish host. parasite-induced alterations in both appearance and behaviour concur to render infected gammarids more vulnerable to predation, thus promoting parasite transmission. experimental infection of laboratory bred full- and half-sib groups of three-spined sticklebacks (gasterosteus aculeatus) provided evidence that the parasite imposes a sur ... | 2003 | 12741513 |
| the effect of the acanthocephalan parasite pomphorhynchus laevis on the lipid and glycogen content of its intermediate host gammarus pulex. | besides conspicuous changes in behaviour, manipulative parasites may also induce subtle physiological effects in the host that may also be favourable to the parasite. in particular, parasites may be able to influence the re-allocation of resources in their own favour. we studied the association between the presence of the acanthocephalan parasite, pomphorhynchus laevis, and inter-individual variation in the lipid and glycogen content of its crustacean host, gammarus pulex (amphipoda). infected g ... | 2001 | 11306112 |
| parasite-altered behavior in a crustacean intermediate host: field and laboratory studies. | the effects of the acanthocephalan parasite pomphorhynchus laevis on the behavior of its crustacean intermediate host, the amphipod echinogammarus stammeri, were studied. a drift study revealed that infected amphipods were disproportionately represented in drift samples taken throughout a 24-hr period; infection with more than 1 parasite enhanced this effect. infection also interacted with the daily timing of drift, with parasitized amphipods beginning to drift earlier in the evening. two distin ... | 1998 | 9920297 |
| parasitic infection and developmental stability: fluctuating asymmetry in gammarus pulex infected with two acanthocephalan species. | several studies have reported a negative association between developmental stability and parasitic infection. however, the host-parasite associations examined so far consist only of a limited number of parasite taxa, and developmental stability was appraised on definitive hosts. the present study examines the association between infection by 2 acanthocephalan parasites. pomphorhynchus laevis and polymorphus minutus, and the developmental stability of their common intermediate host gammarus pulex ... | 2002 | 12053979 |
| patterns of intermediate host use and levels of association between two conflicting manipulative parasites. | for many parasites with complex life cycles, manipulation of intermediate host phenotypes is often regarded as an adaptation to increase the probability of successful transmission. this phenomenon creates opportunities for either synergistic or conflicting interests between different parasite species sharing the same intermediate host. when more than one manipulative parasite infect the same intermediate host, but differ in their definitive host, selection should favour the establishment of a ne ... | 2002 | 11796118 |
| uptake of lead by pomphorhynchus laevis cystacanths in gammarus pulex and immature worms in chub (leuciscus cephalus). | the uptake of lead by cystacanths of the acanthocephalan pomphorhynchus laevis in naturally infected amphipods, gammarus pulex, and by immature parasites in experimentally infected fish, leuciscus cephalus, was examined following 3-week experimental exposures (0.01 and 0.1 mg l(-1) pb2+). both g. pulex and the cystacanths of p. laevis accumulated lead but concentrations in the parasites were lower than in the host tissues at the low lead dose and significantly lower at the high dose. p. laevis f ... | 1998 | 9694375 |
| conflict between co-occurring manipulative parasites? an experimental study of the joint influence of two acanthocephalan parasites on the behaviour of gammarus pulex. | when two parasite species are manipulators and have different definitive hosts, there is a potential for conflict between them. selection may then exist for either avoiding hosts infected with conflicting parasites, or for hijacking, i.e. competitive processes to gain control of the intermediate host. the evidence for both phenomena depends largely on the study of the relative competitive abilities of parasites within their common intermediate host. we studied the effects of simultaneous infecti ... | 2000 | 10874725 |
| the effect of the acanthocephalan pomphorhynchus laevis upon the respiration of its intermediate host, gammarus pulex. | | 1974 | 4826717 |
| interspecific differences in carotenoid content and sensitivity to uvb radiation in three acanthocephalan parasites exploiting a common intermediate host. | few endoparasite species are pigmented. acanthocephalans are an exception however, with several species being characterised by yellow to orange colouration both at the immature (cystacanth) and adult stages. however, the functional and adaptive significance of carotenoid-based colourations in acanthocephalans remains unclear. one possibility is that the carotenoid content of acanthocephalan cystacanths acts as a protective device against ultra-violet radiation (uvr) passing through the transluce ... | 2011 | 20833172 |
| co-variation between the intensity of behavioural manipulation and parasite development time in an acanthocephalan-amphipod system. | pomphorhynchus laevis, a fish acanthocephalan parasite, manipulates the behaviour of its gammarid intermediate host to increase its trophic transmission to the definitive host. however, the intensity of behavioural manipulation is variable between individual gammarids and between parasite populations. to elucidate causes of this variability, we compared the level of phototaxis alteration induced by different parasite sibships from one population, using experimental infections of gammarus pulex b ... | 2010 | 20796137 |
| parasite virulence when the infection reduces the host immune response. | parasite infections often induce a reduction in host immune response either because of a direct manipulation of the immune system by the parasite or because of energy depletion. although infection-induced immunodepression can favour the establishment of the parasite within the host, a too severe immunodepression may increase the risk of infection with opportunistic pathogens, stopping the period over which the parasite can be transmitted to other hosts. here, we explore how the risk of contracti ... | 2010 | 20200031 |
| intraspecific conflict over host manipulation between different larval stages of an acanthocephalan parasite. | competitive interactions between coinfecting parasites are expected to be strong when they affect transmission success. when transmission is enhanced by altering host behaviour, intraspecific conflict can lead to 'coinfection exclusion' by the first-in parasite or to a 'sabotage' of behavioural manipulation by the youngest noninfective parasite. we tested these hypotheses in the acanthocephalan parasite pomphorhynchus laevis, reversing phototaxis in its intermediate host gammarus pulex. no evide ... | 2010 | 20964763 |