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ABSTRACT: Parasites often face a trade-off between exploitation of host resources and transmission probabilities to the next host. In helminths, larval growth, a major component of adult parasite fitness, is linked to exploitation of intermediate host resources and is influenced by the presence of co-infecting conspecifics. In manipulative parasites, larval growth strategy could also interact with their ability to alter intermediate host phenotype and influence parasite transmission.
We used experimental infections of Gammarus pulex by Pomphorhynchus laevis (Acanthocephala), to investigate larval size effects on host behavioural manipulation among different parasite sibships and various degrees of intra-host competition.
Intra-host competition reduced mean P. laevis cystacanth size, but the largest cystacanth within a host always reached the same size. Therefore, all co-infecting parasites did not equally suffer from intraspecific competition. Under no intra-host competition (1 parasite per host), larval size was positively correlated with host phototaxis. At higher infection intensities, this relationship disappeared, possibly because of strong competition for host resources, and thus larval growth, and limited manipulative abilities of co-infecting larval acanthocephalans.
Our study indicates that behavioural manipulation is a condition-dependant phenomenon that needs the integration of parasite-related variables to be fully understood.
Parasites & Vectors 08/2012; 5:166. · 2.94 Impact Factor
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ABSTRACT: “Drifting” is known to subject aquatic invertebrates to intense predation by drift feeding fish. Consequently, interspecific “Drifting” is known to subject aquatic invertebrates to intense predation by drift feeding fish. Consequently, interspecific
variations in drifting behaviour could lead to differences in predation pressure between coexisting prey species. Predation variations in drifting behaviour could lead to differences in predation pressure between coexisting prey species. Predation
being an important factor determining the success of invaders, differences in drift patterns could advantage either native being an important factor determining the success of invaders, differences in drift patterns could advantage either native
or exotic invertebrates through differential predation by native fish predators. The exotic freshwater amphipod (Gammarus roeseli) has now largely colonized Western Europe where it is often found in sympatry with a native species (Gammarus pulex). Here we documented interspecific differences in drifting behaviour that might have favored the invader’s success through or exotic invertebrates through differential predation by native fish predators. The exotic freshwater amphipod (Gammarus roeseli) has now largely colonized Western Europe where it is often found in sympatry with a native species (Gammarus pulex). Here we documented interspecific differences in drifting behaviour that might have favored the invader’s success through
differential predation. Benthic and drifting amphipods were sampled three times at the same site to compare the proportion differential predation. Benthic and drifting amphipods were sampled three times at the same site to compare the proportion
of each species within and between sample types (benthos or drift) across time. Compared with the benthos, where the invader of each species within and between sample types (benthos or drift) across time. Compared with the benthos, where the invader
(G. roeseli) was significantly less abundant than the native (G. pulex), G. roeseli was proportionally overrepresented in the drift but displayed a very different drifting pattern. While G. pulex drift rates remained roughly constant over a 24h period, G. roeseli showed a marked diel periodicity with low diurnal and high nocturnal drift rates. Such drifting behaviour could procure this (G. roeseli) was significantly less abundant than the native (G. pulex), G. roeseli was proportionally overrepresented in the drift but displayed a very different drifting pattern. While G. pulex drift rates remained roughly constant over a 24h period, G. roeseli showed a marked diel periodicity with low diurnal and high nocturnal drift rates. Such drifting behaviour could procure this
species with a competitive advantage regarding predation as most drift feeding fish are diurnal. As a result, the native appears species with a competitive advantage regarding predation as most drift feeding fish are diurnal. As a result, the native appears
more disadvantaged with respect to drift. This may partly explain the ability of G. roeseli to coexist with G. pulex in a habitat more suitable to the native. more disadvantaged with respect to drift. This may partly explain the ability of G. roeseli to coexist with G. pulex in a habitat more suitable to the native.
KeywordsInvertebrate drift– KeywordsInvertebrate drift–
Gammarus pulex Gammarus pulex
– –
Gammarus roeseli Gammarus roeseli
–Biological invasion –Biological invasion
Biological Invasions 04/2012; 13(6):1409-1421. · 2.90 Impact Factor
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ABSTRACT: Previously undescribed fourth-stage larvae of anisakid nematodes were found in the haemocoel of the amphipod Paracorophium excavatum (Thomson, 1884) (Corophiidae) in New Zealand. Morphological examination by light microscopy showed that the worms belonged
to a species of Hysterothylacium Ward et Magath, 1917, based on several characters including the presence of interlabia, the location of the excretory pore
posterior to the nerve ring, and the characteristics of the intestinal caecum and ventricular appendix. Interestingly, several
male specimens showed precocious sexual development. This is the first record of fourth larval stage and precocious adult
male specimens of Hysterothylacium in an invertebrate host, as well as the first record of anisakid larvae in New Zealand crustaceans. In addition, metacercariae
of two trematode species, Coitocaecum parvum and Microphallus sp., are recorded for the first time from the amphipod P. excavatum.
Acta Parasitologica 04/2012; 52(2):146-150. · 0.79 Impact Factor
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ABSTRACT: The life cycle of Hedruris spinigera Baylis, 1931 (Nematoda: Hedruridae) is determined here with the first formal identification of the parasite's intermediate host: the crustacean amphipod Paracorophium excavatum Thomson. Adult H. spinigera are redescribed from specimens collected from the stomach of fishes, Retropinna retropinna (Richardson) and Aldrichettaforsteri (Valenciennes), from Lake Waihola, New Zealand. Immature adults of the parasite collected from intermediate hosts (P. excavatum) are also described for the first time. The prevalence, abundance and intensity of infection of H. spinigera in several fish species are quantified along with the occurrence of P. excavatum, the parasite's intermediate host, in fish stomach contents. Although H. spinigera's transmission mode (trophic transmission) and fish diet potentially expose all fish species to infection, some level of host specificity must exist as parasite prevalence, abundance and intensity of infection vary greatly between potential definitive host species. We suggest here that the anatomy of the fish digestive tract and especially that of the stomach plays an important role in host suitability for H. spinigera. While P. excavatum is the only intermediate host in Lake Waihola, H. spinigera was found in six different fish species: Aldrichetta forsteri, Galaxias maculatus (Jenyns), Retropinna retropinna, Rhombosolea retiaria Hutton, Perca fluviatilis Linnaeus and Salmo trutta Linnaeus; although typical hedrurid attachment and mating positions were observed only in R. retropinna and A. forsteri. The limited distribution of H. spinigera is most likely due to that of its different host species (intermediate and definitive), all inhabitants of coastal fresh and brackish waters.
Folia parasitologica 09/2010; 57(3):223-31. · 1.81 Impact Factor
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ABSTRACT: One of the most complex and least understood transmission strategies displayed by pathogenic parasites is that of manipulation of host behaviour. A wide variety of parasites alter their host's behaviour, including species of medical and veterinary importance, such as Diplostomum spathaceum, Echinococcus spp. and Toxoplasma gondii. The manipulative ability of these parasites has implications for pathology and transmission dynamics. Domestic animals are hosts for manipulative pathogens, either by being the target host and acquiring the parasite as a result of vector-host manipulation, or by having their behaviour changed by manipulative parasites. This review uses several well-known pathogens to demonstrate how host manipulation by parasites is potentially important in epidemiology.
The Veterinary Journal 03/2009; 184(1):9-13. · 2.24 Impact Factor
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ABSTRACT: Theoretical models predict that genetic relatedness affects the competition within and between parasite clonal groups sharing a common host. Here, we studied natural and experimental multiple infections of the trematode Coitocaecum parvum in its intermediate host. We focused on the effects of clonality on the life-history strategy of parasites competing for resources. Coitocaecum parvum can either delay maturation until its amphipod host is ingested by a definitive host, or adopt a progenetic strategy and reproduce inside the amphipod. Within a common host, clonal parasites were more likely to adopt identical life-history strategies than different genetic clones, both in natural and experimental infections. However, when timing of infection and other factors were controlled experimentally, parasites sharing a host were likely to adopt identical strategies regardless of their clonal identity, although pairs of clones were more likely to adopt progenesis than pairs of nonclones. The asymmetries in relative size and egg production between coinfecting parasites adopting the same life-history strategy were slightly, but not significantly, higher between different clones than identical clones. Our results suggest that the dynamics of competition between coinfecting parasites, although influenced by numerous external factors, is also modulated by genetic relatedness among parasites.
Evolution 02/2009; 63(6):1417-26. · 5.15 Impact Factor
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ABSTRACT: Predation is often considered as one of the most important biotic factor determining the success of exotic species. The freshwater amphipod Gammarus roeseli has widely colonized Western Europe, where it is frequently found in sympatry with the native species (Gammarus pulex). Previous laboratory experiments revealed that G. roeseli may have an advantage over G. pulex through differential predation by native fish (brown trout). Morphological anti-predator defences (spines) were found responsible for lower rates of predation on the invasive G. roeseli. Here, using both field surveys and laboratory experiments, we tested if a differential of predation exists with other fish predators naturally encountered by gammarids. The main predators present in our field site were nocturnal benthic feeders (mainly bullheads, Cottus gobio). Fish diet analysis showed that, compared to its global availability in the river, G. roeseli was less consumed than G. pulex. In the field, however, G. roeseli was found mainly in the aquatic vegetation whereas G. pulex was found in all habitat types. Laboratory experiments in microcosms revealed that G. roeseli was less prone to predation by C. gobio only when vegetation was present. Depending on the type of predator, the differential of predation could therefore be mediated by antipredator behaviour, and a better usage of refuges, rather than by morphological defences.
Naturwissenschaften 09/2008; 95(9):839-44. · 2.28 Impact Factor
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ABSTRACT: Larval helminths often share intermediate hosts with other individuals of the same or different species. Competition for resources and/or conflicts over transmission routes are likely to influence both the association patterns between species and the life history strategies of each individual. Parasites sharing common intermediate hosts may have evolved ways to avoid or associate with other species depending on their definitive host. If not, individual parasites could develop alternative life history strategies in response to association with particular species. Three sympatric species of helminths exploit the amphipod Paracalliope fluviatilis as an intermediate host in New Zealand: the acanthocephalan Acanthocephalus galaxii, the trematode Microphallus sp. and the progenetic trematode Coitocaecum parvum. Adult A. galaxii and C. parvum are both fish parasites whereas Microphallus sp. infects birds. We found no association, either positive or negative, among the three parasite species. The effects of intra- and interspecific interactions were also measured in the trematode C. parvum. Both intra- and interspecific competition seemed to affect both the life history strategy and the size and fecundity of C. parvum. Firstly, the proportion of progenesis was higher in metacercariae sharing their host with Microphallus sp., the bird parasite, than in any other situation. Second, the intensity of intraspecific competition apparently constrained the ability of metacercariae to adopt progenesis and limited both the growth and egg production of progenetic individuals. These results show that the life history strategy adopted by a parasite may be influenced by other parasites sharing the same host.
International journal for parasitology 06/2008; 38(12):1435-44. · 3.39 Impact Factor
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ABSTRACT: We examined the utility of fluorescent fatty acid analog dyes for labeling larval trematodes to use in experimental infections. Our goals were to identify two dyes that label larval trematodes belonging to the species Maritrema novaezealandensis and Coitocaecum parvum, determine if the dyes influence survival and infectivity of larval trematodes and/or host mortality, and if larval trematodes labeled with alternative dyes could be distinguished post-infection. The two dyes tested, BODIPY FL C(12) and BODIPY 558/568 C(12), successfully labeled all treated larval trematodes, did not influence cercariae survival or infectivity, and did not influence host mortality in either host-parasite system. All larval parasites were fluorescent and distinguishable after 5 days in amphipod intermediate hosts. In addition, larval Acanthoparyphium sp. were strongly fluorescent with both dyes after 5 weeks within cockle hosts. This method should be extremely useful for experimental studies using trematode-host systems as models for addressing a range of ecological and evolutionary questions.
Experimental Parasitology 05/2008; 120(1):15-20. · 2.12 Impact Factor
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ABSTRACT: The frequent co-occurrence of two or more genotypes of the same parasite species in the same individual hosts has often been predicted to select for higher levels of virulence. Thus, if parasites can adjust their level of host exploitation in response to competition for resources, mixed-clone infections should have more profound impacts on the host. Trematode parasites are known to induce a wide range of modifications in the morphology (size, shell shape or ornamentation) of their snail intermediate host. Still, whether mixed-clone trematode infections have additive effects on the phenotypic alterations of the host remains to be tested. Here, we used the snail Potamopyrgus antipodarum-infected by the trematode Coitocaecum parvum to test for both the general effect of the parasite on host phenotype and possible increased host exploitation in multi-clone infections. Significant differences in size, shell shape and spinosity were found between infected and uninfected snails, and we determined that one quarter of naturally infected snails supported mixed-clone infections of C. parvum. From the parasite perspective, this meant that almost half of the clones identified in this study shared their snail host with at least one other clone. Intra-host competition may be intense, with each clone in a mixed-clone infection experiencing major reductions in volume and number of sporocysts (and consequently multiplication rate and cercarial production) compared with single-clone infections. However, there was no significant difference in the intensity of host phenotype modifications between single and multiple-clone infections. These results demonstrate that competition between parasite genotypes may be strong, and suggest that the frequency of mixed-clone infections in this system may have selected for an increased level of host exploitation in the parasite population, such that a single-clone is associated with a high degree of host phenotypic alteration.
International Journal for Parasitology 12/2007; 37(13):1459-67. · 3.39 Impact Factor
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ABSTRACT: 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 behavioral manipulation to estimates of trophic transmission to the definitive host in the natural environment. We show that the acanthocephalan parasite Pomphorhynchus laevis manipulates the drifting behavior of one of its intermediate hosts, the amphipod Gammarus pulex, but not of a sympatric host, the introduced amphipod Gammarus roeseli. We found a 26.3-28.3 times higher proportion of infected G. pulex in the stomach content of one of the definitive hosts of P. laevis, the bullhead Cottus gobio, than in the benthos. No such trend was observed for G. roeseli. The bell-shaped curve of mean parasite abundance (MPA) relative to host size observed in G. pulex also supported an increased predation mortality of P. laevis-infected individuals compared to uninfected amphipods. Again, no such pattern was observed in G. roeseli. Furthermore, our results indicate that the modifications induced by P. laevis are specific to the definitive host and do not increase the risk of predation by inappropriate hosts, here the adult edible frog Rana esculenta. Overall, our study is original in that it establishes, under field conditions, a direct link between parasitic manipulation and increased transmission to the definitive host, and more importantly, identifies the specificity of the manipulation both in the intermediate host species and toward the definitive host.
Ecology 12/2007; 88(11):2839-47. · 4.85 Impact Factor
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ABSTRACT: Nine polymorphic microsatellite loci were characterized from the freshwater trematode Coitocaecum parvum. This parasite can either reproduce sexually in the definitive host or produce eggs by selfing inside its second intermediate host. Two to 11 alleles per locus were detected in 24 trematode sporocysts and observed heterozygosities ranged from 0.04 to 0.96. These loci will be useful for identifying parasite genetic clones within hosts and testing for effects of relatedness on parasite life history strategy.
Molecular Ecology Notes 06/2007; 7(4):694 - 696. · 2.38 Impact Factor
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ABSTRACT: We examined the utility of fluorescent fatty acid analog dyes for labeling larval trematodes to use in experimental infections. Our goals were to identify two dyes that label larval trematodes belonging to the species Maritrema novaezealandensis and Coitocaecum parvum, determine if the dyes influence survival and infectivity of larval trematodes and/or host mortality, and if larval trematodes labeled with alternative dyes could be distinguished post-infection. The two dyes tested, BODIPY FL C12 and BODIPY 558/568 C12, successfully labeled all treated larval trematodes, did not influence cercariae survival or infectivity, and did not influence host mortality in either host–parasite system. All larval parasites were fluorescent and distinguishable after 5 days in amphipod intermediate hosts. In addition, larval Acanthoparyphium sp. were strongly fluorescent with both dyes after 5 weeks within cockle hosts. This method should be extremely useful for experimental studies using trematode–host systems as models for addressing a range of ecological and evolutionary questions.
Experimental Parasitology.
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ABSTRACT: Selective predation may be an important proximate cause of the success or failure of invader species. Gammarus roeseli is an invasive amphipod, for which the causes of establishment in rivers where the native species, Gammarus pulex, predominates remain unstudied. Freshwater amphipods are important prey for numerous fish predators, but empirical evidence of lower predation rates on exotic prey is scarce. In laboratory experiments, we compared the susceptibility of G. pulex and G. roeseli to fish predation, determined the mechanisms influencing prey selection, and studied the interaction between behavioural and morphological defences. Fish predators (brown trout, Salmo trutta fario) preyed selectively on G. pulex, but not because of differences in attack or capture probability. The presence of spines in G. roeseli appeared to contribute to its underpredation. Differential prey selection in this case might therefore have resulted from the trout's reaction to an adverse stimulus. We found no significant difference in antipredator behaviour between G. pulex and G. roeseli. General behavioural differences were nevertheless found between species, with G. roeseli spending more time under shelters than G. pulex. However, microcosm experiments suggested that this difference was not important for differential predation. Antipredator behaviour may nevertheless be important for G. roeseli against other predators less sensitive to spines.
Animal Behaviour.
