Search results for "Polymorphus"
showing 10 items of 12 documents
Patterns of intermediate host use and levels of association between two conflicting manipulative parasites.
2002
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 negative association between these manipulators. Both Polymorphus minutus and Pomphorhynchus laevis exploit the amphipod Gammarus pulex as intermediate host but differ markedly in their final host, a f…
A manipulative parasite increasing an antipredator response decreases its vulnerability to a nonhost predator.
2009
8 pages; International audience; Trophically transmitted parasites have to deal with the antipredator adaptations of their intermediate hosts. Some of these parasites induce behavioural changes in their intermediate hosts that make them more vulnerable to predation by definitive hosts. However, the adaptiveness of behavioural manipulation also depends on the probability of being eaten by a nonhost predator. Parasites might therefore try to use specific antipredator responses of intermediate hosts to avoid this dead end. We tested this hypothesis using the acanthocephalan Polymorphus minutus and its intermediate amphipod host, Gammarus roeseli. In their natural habitat, uninfected G. roeseli…
Data from: Phylogenomics of Lophotrochozoa with consideration of systematic error
2021
Phylogenomic studies have improved understanding of deep metazoan phylogeny and show promise for resolving incongruences among analyses based on limited numbers of loci. One region of the animal tree that has been especially difficult to resolve, even with phylogenomic approaches, is relationships within Lophotrochozoa (the animal clade that includes molluscs, annelids, and flatworms among others). Lack of resolution in phylogenomic analyses could be due to insufficient phylogenetic signal, limitations in taxon and/or gene sampling, or systematic error. Here, we investigated why lophotrochozoan phylogeny has been such a difficult question to answer by identifying and reducing sources of sys…
Data from: Phylogenomics of Lophotrochozoa with consideration of systematic error
2016
Phylogenomic studies have improved understanding of deep metazoan phylogeny and show promise for resolving incongruences among analyses based on limited numbers of loci. One region of the animal tree that has been especially difficult to resolve, even with phylogenomic approaches, is relationships within Lophotrochozoa (the animal clade that includes molluscs, annelids, and flatworms among others). Lack of resolution in phylogenomic analyses could be due to insufficient phylogenetic signal, limitations in taxon and/or gene sampling, or systematic error. Here, we investigated why lophotrochozoan phylogeny has been such a difficult question to answer by identifying and reducing sources of sys…
Status of Corynosoma (Acanthocephala: Polymorphidae) based on anatomical, ecological, and phylogenetic evidence, with the erection of Pseudocorynosom…
2006
The possession of genital spines has been considered as a key taxonomic trait to differentiate Corynosoma from other genera of the Polymorphidae. However, Corynosoma currently consists of 2 groups of species with clear ecological and morphological divergences: the "marine" group (with ca. 30 species) infects mammals and piscivorous birds in the marine realm, whereas the "freshwater" group (with ca. 7 species) infects waterfowl in continental waters. Species from these groups differ in shape of body and neck, trunk spination, lemnisci length and shape, testes arrangement, and number and shape of cement glands. We tested whether species from these 2 groups formed a monophyletic assemblage bas…
Studies on bucephalid digeneans parasitising molluscs and fishes in Finland I. Ecological data and experimental studies
1991
Two types of bucephalid cercariae are reported from the bivalve Anodonta anatina in two Finnish lakes. One, Type A, resembles in gross morphology the cercaria of Bucephalus polymorphus, and the other, Type B, resembles the cercaria of Rhipidocotyle campanula. Type A daughter-sporocysts develop more slowly, have a greater cercarial productivity and exhibit a differential diurnal rhythm to that of Type B. Cercariae of Type A have a shorter longevity than Type B and tend to encyst in the fins rather than the gill-arches of fish intermediate hosts. The main definitive host of Type A is pike Esox lucius and, in the case of Type B, perch Perca fluviatilis. Adults of Types A and B are morphologica…
Interspecific differences in carotenoid content and sensitivity to UVB radiation in three acanthocephalan parasites exploiting a common intermediate …
2011
9 pages; International audience; 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 translucent cuticle of their crustacean hosts. Indeed, acanthocephalans often bring about behavioural changes in their aquatic intermediate hosts that can increase their expos…
Differential influence of two acanthocephalan parasites on the antipredator behaviour of their common intermediate host
2007
7 pages; International audience; Fish acanthocephalans can modify the antipredator behaviour of their intermediate hosts in response to cues from fish predators. However, it is still unclear whether such behavioural changes are adaptive, or are just the consequence of infection. We addressed this question through studying two acanthocephalans, Pomphorhynchus laevis and Polymorphus minutus, and their intermediate host, the amphipod Gammarus pulex. Pomphorhynchus laevis completes its cycle in a freshwater fish, whereas P. minutus exploits waterbirds as final hosts.We first assessed vulnerability of infected and uninfected gammarids to predation by bullheads, Cottus gobio. Pomphorhynchus laevi…
Infection with acanthocephalans increases the vulnerability of Gammarus pulex (Crustacea, Amphipoda) to non-host invertebrate predators.
2008
SUMMARYPhenotypic 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 to predation by 2 non-host predators in microcosms. Only infection with P. laevis increased the vulnerability of amphipods to predation by crayfish, Orconectes limosus. In contrast, in the ab…
Host manipulation of a freshwater crustacean (Gammarus roeseli) by an acanthocephalan parasite (Polymorphus minutus) in a biological invasion context.
2006
8 pages; International audience; Several gammarid species serve as intermediate hosts for the acanthocephalan parasite Polymorphus minutus. This parasite influences gammarid behaviour in order to favour transmission to its ultimate host, generally a bird. We investigated this host manipulation in Gammarus roeseli, a gammarid species introduced in France 150 years ago which now coexists with several exotic species from different origins. In the field, vertical distribution of G. roeseli revealed a higher proportion of infected individuals close to the water's surface and the size distribution of infected gammarids revealed predation pressure on infected individuals. However, under laboratory…