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PubMed2002

Investigating patterns may reveal processes: evolutionary ecology of ectoparasitic monogeneans.

We reviewed several published and ongoing studies concerning monogenean communities. Patterns of species richness, host specificity, community structure and host--parasite coevolutionary interaction were carefully analysed, and hypotheses of evolutionary processes are proposed. The structuring of monogenean communities seems to be related to both ecological and historical constraints. The database supports an absence of intra- and interspecific competition in monogeneans. Species richness seems to be more due to host characteristics than to parasite interactions. Monogeneans seem to specialise on large hosts, leading to greater species richness on those hosts. The morphometric evolution of attachment and copulatory organs support the hypothesis of a reproductive segregation among conspecifics parasitising the same host(s). It also suggests the existence of concurrent adaptive and non-adaptive processes. The general absence of a coevolutionary pattern between host and parasites also suggests the constraints of history without dismissing the influences of ecological factors in the structuring of the communities. More generally, we strengthen the need to study the structure of communities in a phylogenetic context.

Animals↗
PubMed2002

Diplostomum spathaceum cercariae respond to a unique profile of cues during recognition of their fish host.

During its normal life cycle, Diplostomum spathaceum cercariae attach to and invade fish intermediate hosts. They are also known to attach to various other aquatic animals in response to water currents, touch and carbon dioxide. The purpose of this study was to identify the specific stimuli used by D. spathaceum cercariae to recognise the appropriate fish host. We characterised the host cues which stimulate them to remain on the host (enduring contact) and to penetrate the skin. Cercariae were exposed to animal skin tissues and fish skin surface mucus, their extracts and chemical modifications integrated into agar or offered via membrane filters. Enduring contact was stimulated by hydrophilic extracts Mr<3kDa, which were sensitive to oxidation of carbohydrates. The stimulating cues are probably small molecular carbohydrates, as monosaccharides stimulated enduring contacts, but amino acids, urea, electrolytes and peptides did not. Penetration was stimulated by hydrophilic macromolecules, Mr>30kDa, and by lipids. The hydrophilic stimuli were protease resistant and precipitable with Alcian blue and they were sensitive to alkaline cleavage, to digestion with lysozyme and neuraminidase as well as to oxidation of sialic acids. They were considered to be glycoproteins with O-glycosidically linked carbohydrate chains and bound sialic acids as signal structures. The lipophilic penetration stimuli were contained exclusively in the fatty acid fractions, and the stimulating characteristics of these fatty acids resembled the stimulating penetrations in other cercarial species. Diplostomum spathaceum cercariae respond to a unique profile of cues in their sequence of host-recognition phases. These cues differ from those used in other fish parasites studied to date and underline the diversity of fish recognition strategies.

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PubMed1997

Accumulation of Diplostomum spp. (Digenea: Diplostomatidae) metacercariae in the eyes of 0+ and 1+ roach (Rutilus rutilus).

Unlike other long-term studies of Diplostomum spp. metacercariae in fish eyes, this study investigated accumulation of the parasites in the eyes of very young roach for 3 consecutive years. Fish were caught by electro-fishing in the summers of 1990, 1991 and 1992 and the numbers of parasites located in the hosts eyes were recorded. Two distinct peaks of parasite abundance were observed, 1 in late June and the other in mid-September each year. Significantly, parasite abundance decreased after each of the peaks. Results obtained in a parallel investigation of the accumulation of the same parasites in rainbow trout in an adjacent fish farm showed the same 2 periods of accumulation each year. However, in the fish farm, no decrease in parasite abundance was observed at any time. The decreases in parasite abundance in the wild population can be attributed to mortality of the most heavily parasitized fish. As this did not occur in the farmed fish, in which similar levels of parasitism existed, it is likely that mortality in the wild population was an indirect result of the parasites.

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PubMed1998

South American Monogenea--list of species, hosts and geographical distribution.

Five-hundred and twenty-three species of monogeneans have been recorded in South America: 43 from Argentina, one from Bolivia, 252 from Brazil, 29 from Chile, 15 from Colombia, eight from Ecuador, 26 from Falkland and Patagonian regions, four from French Guyana, 11 from Galapagos, two from Guiana, four from Paraguay, 92 from Peru, 16 from Uruguay and 20 from Venezuela. A list of these species with hosts and geographical distribution is presented.

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PubMed2000

Phylogenetic analysis of the suborder plagiorchiata (Platyhelminthes, Digenea) based on partial lsrDNA sequences.

The phylogenetic relationships and systematic position of the members of the suborder Plagiorchiata, one of the derived and most diverse groups of Digenea, have always been controversial. Here, we present a phylogeny of this group based on the analysis of partial sequences of the lsrDNA in 28 species representing 13 families of Plagiorchiata, as well as four outgroups. Our results show that the Plagiorchiata, as considered by most authors, is not monophyletic, and that the superfamilies Opecoeloidea, and most probably Dicrocoelioidea and Gorgoderoidea, may have to be removed from this suborder. According to our results, the Plagiorchiata includes only parasites of terrestrial vertebrates. We find the Plagiorchiata to be composed of two well-supported clades which can be ranked as superfamilies: (1) Plagiorchioidea, including the Plagiorchiidae, Haematoloechidae, Telorchiidae, Brachycoeliidae and Leptophallidae; and (2) Microphalloidea containing the Microphallidae, Prosthogonimidae, Lecithodendriidae and Pleurogenidae. The genetic analysis also allowed revision of the position of several taxa of Plagiorchiata, including: (1) a confirmation of the position of the Brachycoeliidae within the Plagiorchiata; (2) a close phylogenetic relationships of Macrodera with Paralepoderma, Leptophallus and Metaleptophallus; (3) the grouping of Opisthioglyphe and Telorchis within a distinct and strongly supported clade; and (4) the placement of Allassogonoporus amphoraeformis within the Pleurogenidae, and not close to Lecithodendriidae. Some systematic changes, corresponding to these results, are proposed.

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PubMed2000

Survival of bird schistosomes in mammalian lungs.

Bird schistosome cercariae have a low specificity to vertebrate skin and, thus, they are also able to penetrate into mammals. As a consequence, a hypersensitive skin response-cercarial dermatitis-develops. It was thought that the parasites die in the skin soon after penetration. Our results on Trichobilharzia szidati and Bilharziella polonica in the non-specific murine host confirm that some of the penetrating bird schistosomes may fully transform to schistosomula and migrate to the lungs. They persist there for up to 10days post exposure. In a duck, the worms grow and feed rapidly, but in a mouse the lung schistosomula seem to be inhibited in their development. However, TEM results show that there is no damage to the tegument of these larvae and no immune effector cells attack the parasites. These results suggest that the parasite's failure in the murine host might be caused by some immunologically unrelated factors.

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PubMed2004

Case report: unusual presentation of Fasciolopsis buski in a Vietnamese child.

A Vietnamese child presented with a history of abdominal pain. Shortly afterwards, he vomited eight live trematode flukes that were collected and morphologically identified as Fasciolopsis buski. The identification was confirmed by DNA analysis. Adult worms of F. buski from humans are very rarely seen except at autopsy, and this is the first such report from Vietnam.

Abdominal Pain↗
PubMed2001

Biology of echinostomes except Echinostoma.

This review examines the significant literature on the biology of echinostomes, except Echinostoma, for the following species rich genera: Echinoparyphium, Echinochasmus, Himasthla, and Hypoderaeum. Coverage of these genera includes descriptive studies, life cycle studies, experimental and manipulative studies, and biochemical and molecular studies. Coverage of other echinostome genera, i.e., Petasiger, Euparyphium, Stephanoprora, Isthmiophora, Acanthoparyphium, and Patagifer was mainly concerned with descriptive and life cycle studies. Some groups that are considered echinostome-like were covered because species in these genera have medical, economic, or biological significance (particularly Parorchis, Philophthalmus, and Ribeiroia). A dominant theme of the review is the availability of key species of echinostomes for use in biological research; coverage also includes methods for obtaining and maintaining these organisms in the laboratory. Some species with significant medical, veterinary, and biological importance that have been covered extensively include the Echinoparyphium recurvatum species complex, Echinochasmus liliputanus, Himasthla quissetensis, Himasthla rhigadana, and Hypoderaeum conoideum.

Animals↗
PubMed1996

Faecal examination of Fasciola eggs fixed with formalin solution using the beads technique.

Faecal examination for Fasciola eggs which were preserved in 5% and 10% formalin and TAF solutions for 6 years was carried out using the Beads technique. The morphological characters and the distinctive yellowish color of Fasciola eggs were retained and appeared similar to those of fresh eggs. The mean egg recovery rate of eggs in TAF solution was significantly lower than the others (P < 0.01). The egg recovery rates from 5% and 10% formalin samples were 57.2% and 60.8%, respectively, and these values were similar to the value of 58.8% for fresh Fasciola eggs in cattle faeces. For Paramphistomum eggs, preserved with 5% formalin, the mean egg recovery rate was 64.7%. Fasciola eggs and Paramphistomum eggs were easily identified by their morphological characters in this experiment. The present data demonstrated that preservation with 5% formalin solution is an acceptable means of storing faecal samples for later examination of Fasciola and Paramphistomum eggs using the Beads technique and presumably by other fluke sedimentation methods.

Animals↗
PubMed2002

Pseudodactylogyrus kamegaii sp. n. (Monogenea: Pseudodactylogyridae) from wild Japanese eel, Anguilla japonica.

The monogenean Pseudodactylogyrus kamegaii sp. n. is described, based on specimens collected from the gills of wild Japanese eel Anguilla japonica caught in Chiba Prefecture, Japan. This species is the most similar to P. anguillae (Yin and Sproston, 1948), but different in the shape and measurements of the male copulatory organ, vagina and marginal hook. This new species was collected from the eel in brackish waters, while P. anguillae and P. bini, the other known pseudodactylogyrids of Japanese eel, have been recorded only in fresh waters.

Anguilla↗
PubMed2001

European Lymnaeidae (Mollusca: Gastropoda), intermediate hosts of trematodiases, based on nuclear ribosomal DNA ITS-2 sequences.

Freshwater snails of the family Lymnaeidae are of a great parasitological importance because of the very numerous helminth species they transmit, mainly trematodiases of large medical and veterinary impact. The present knowledge on the genetics of lymnaeids and on their parasite-host inter-relationships is far from being sufficient. The family is immersed in a systematic-taxonomic confusion. The necessity for a tool which enables species distinction and population characterization is evident. This paper aims to review the European Lymnaeidae basing on the second internal transcribed spacer ITS-2 of the nuclear ribosomal DNA. The ITS-2 sequences of 66 populations of 13 European and 1 North American lymnaeid species, including the five generic (or subgeneric) taxa Lymnaea sensu stricto, Stagnicola, Omphiscola, Radix and Galba, have been obtained. The ITS-2 proves to be a useful marker for resolving supraspecific, specific and population relationships in Lymnaeidae. Three different groupings according to their ITS-2 length could be distinguished: Radix and Galba may be considered the oldest taxa (370-406 bp lengths), and Lymnaea s. str., European Stagnicola and Omphiscola (468-491 bp lengths) the most recent, American Stagnicola and Hinkleyia being intermediate (434-450 bp lengths). This hypothesis agrees with the phylogeny of lymnaeids based on palaeontological data, chromosome numbers and radular dentition. ITS-2 sequences present a conserved central region flanked by two variable lateral regions corresponding to the 5' and 3' ends. The number of repeats of two microsatellites found in this conserved central region allows to differentiate Radix from all other lymnaeids. Phylogenetic trees showed four clades: (A) Lymnaea s. str., European Stagnicola and Omphiscola; (B) Radix species; (C) Galba truncatula; and (D) North American stagnicolines. ITS-2 results suggest that retaining Stagnicola as a subgenus of Lymnaea may be the most appropriate and that genus status for Omphiscola is justified. Radix shows a complexity suggesting different evolutionary lines, whereas G. truncatula appears to be very homogeneous. North American and European stagnicolines do not belong to the same supraspecific taxon; the genus Hinkleyia may be used for the American stagnicolines. Genetic distances and sequence differences allowed us to distinguish the upper limit to be expected within a single species and to how different sister species may be. S. palustris, S. fuscus and S. corvus proved to be valid species, but S. turricula may not be considered a species independent from S. palustris. Marked nucleotide divergences and genetic distances detected between different S. fuscus populations may be interpreted as a process of geographic differentiation developping in the present. Among Radix, six valid species could be distinguished: R. auricularia, R. ampla, R. peregra (=R. ovata;=R. balthica), R. labiata, R. lagotis and Radix sp. The information which the ITS-2 marker furnishes is of applied interest concerning the molluscan host specificity of the different trematode species. The phylogenetic trees inferred from the ITS-2 sequences are able to differentiate between lymnaeids transmitting and those non-transmitting fasciolids, as well as between those transmitting F. hepatica and those transmitting F. gigantica. The Fasciola specificity is linked to the two oldest genera which moreover cluster together in the phylogenetic trees, suggesting an origin of the Fasciola ancestors related to the origin of this branch. European Trichobilharzia species causing human dermatitis are transmitted only by lymnaeids of the Radix and Lymnaea s. str.-Stagnicola groups. Results suggest the convenience of reinvestigating compatibility differences after accurate lymnaeid species classification by ITS-2 sequencing. Similarly, ITS-2 sequencing would allow a step forward in the appropriate rearrangement of the actual systematic confusion among echinostomatids.

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