Parvatrema spp. (Digenea, Gymnophallidae) with parthenogenetic metacercariae: diversity, distribution and host specificity in the palaearctic.

There are several species of gymnophallid digeneans in the genus Parvatrema that are unique in developing metacercariae that reproduce by parthenogenesis in the second intermediate host. Transmission of these digeneans takes place in coastal ecosystems of the North Pacific and North Atlantic seas. The first intermediate hosts are bivalves, the second ones are gastropods, and the definitive hosts are migratory birds.

No time to relax: Age-dependent infectivity of cercariae in marine coastal ecosystems.

Age dynamics of the ability of cercariae of two digenean species, (Himasthlidae) and (Renicolidae), to infect the second intermediate host (SIH), mussels (), was investigated experimentally. This is the first study of this kind made on cercariae transmitted in the intertidal of the northern seas. The larvae of all tested ages (from 0.

Overview of renicolid digeneans (Digenea, Renicolidae) from marine gulls of northern Holarctic with remarks on their species statuses, phylogeny and phylogeography.

Renicolid digeneans parasitize aquatic birds. Their intramolluscan stages develop in marine and brackish-water gastropods, while metacercariae develop in molluscs and fishes. The systematics of renicolids is poorly developed, their life cycles are mostly unknown, and the statuses of many species require revision.

The Pacific Notocotylus atlanticus (Digenea: Notocotylidae).

Recently two unidentified Notocotylus species have been recovered from a mallard in Hokkaido, Japan. Preliminary data indicated that one of them may belong to N. atlanticus-a species found in Europe and on the Atlantic coast of North America.

Germinal development in embryonic rediae of the hemiuroid digenean Bunocotyle progenetica: an ultrastructural study.

Embryonic development of reproductive organs in rediae of the digenean Bunocotyle progenetica was studied using transmission electron microscopy. The germinal primordium becomes morphologically distinct in early embryos as a weakly separated cell mass with a forming cavity. It consists of undifferentiated, differentiating, and supporting cells.

A month for the mission: using a sentinel approach to determine the transmission window of digenean cercariae in the subarctic White Sea.

In the digenean life cycle the cercaria ensures an important transmission stage, from the first intermediate host to the second or the definitive host. In regions with pronounced seasonality, this process occurs within a certain interval, the transmission window. In high latitudes, the size of transmission window has previously been determined only by comparing data on seasonal dynamics of infection level in various categories of hosts or extrapolating the results of laboratory experiments on cercarial biology to natural conditions.

Elucidation of Himasthla leptosoma (Creplin, 1829) Dietz, 1909 (Digenea, Himasthlidae) life cycle with insights into species composition of the north Atlantic Himasthla associated with periwinkles Littorina spp.

Trematodes of the genus Himasthla are usual parasites of coastal birds in nearshore ecosystems of northern European seas and the Atlantic coast of North America. Their first intermediate hosts are marine and brackish-water gastropods, while second intermediate hosts are various invertebrates. We analysed sequences of partial 28S rRNA and nad1 genes and the morphology of intramolluscan stages, particularly cercariae of Himasthla spp.

It is marine: distinguishing a new species of (Digenea: Notocotylidae) from its freshwater twin.

The morphology of sexual adults is the cornerstone of digenean systematics. In addition, life cycle data have always been significant. The integration of these approaches, supplemented with molecular data, has allowed us to detect a new species that many researchers may have previously seen, but not recognized.

The fine structure of the germinal mass, brood cavity and birth canal of the rediae of the monoxenous hemiuroid digenean Chabaud & Buttner, 1959.

Bunocotyle progenetica is a hemiuroid digenean whose sexual adults become fully developed and lay their eggs inside the rediae in the molluscan host. In this study, the fine structure of the germinal mass, brood cavity and birth canal in the B. progenetica rediae was examined using transmission electron and confocal microscopy.

Short communication: New data support phylogeographic patterns in a marine parasite (Digenea: Notocotylidae).

Intraspecific diversity in parasites with heteroxenous life cycles is guided by reproduction mode, host vagility and dispersal, transmission features and many other factors. Studies of these factors in Digenea have highlighted several important patterns. However, little is known about intraspecific variation for digeneans in the marine Arctic ecosystems.

Transatlantic discovery of Notocotylus atlanticus (Digenea: Notocotylidae) based on life cycle data.

Digenean parasites feature a series of stages with a distinct appearance, reproduction mode, and lifestyle that together constitute their well-known, complex life cycle. Species descriptions of Digenea have always been based on one of these stages-the marita, or sexually reproducing adult in the final host. However, in some cases, data on the life cycle are essential for the differential diagnosis of closely related species.

Reproduction of trematodes in the molluscan host: an ultrastructural study of the germinal mass and brood cavity in daughter rediae of Tristriata anatis Belopolskaia, 1953 (Digenea: Notocotylidae).

This study describes the fine structure of the germinal mass in daughter rediae of Tristriata anatis. The germinal mass consists of undifferentiated cells, germinal cells and supporting cells and contains numerous cercarial embryos up to tail bud stage. Supporting cells and their outgrowths form a tight meshwork of the germinal mass.

Microphallus ochotensis sp. nov. (Digenea, Microphallidae) and relative merits of two-host microphallid life cycles.

A new digenean species, Microphallus ochotensis sp. nov., was described from the intestine of Pacific eiders (Somateria mollissima v-nigrum) from the north of the Sea of Okhotsk.

Patterns and processes influencing helminth parasites of Arctic coastal communities during climate change.

This review analyses the scarce available data on biodiversity and transmission of helminths in Arctic coastal ecosystems and the potential impact of climate changes on them. The focus is on the helminths of seabirds, dominant parasites in coastal ecosystems. Their fauna in the Arctic is depauperate because of the lack of suitable intermediate hosts and unfavourable conditions for species with free-living larvae.

Life cycle and biology of Tristriata anatis (Digenea: Notocotylidae): morphological and molecular approaches.

Notocotylids are common digeneans parasitising birds and mammals. They have a two-host life cycle with cercariae encysting in the open. Particular life cycles remain unknown for majority of notocotylid species, including a common parasite of sea ducks Tristriata anatis.

Genomic diversity of cercarial clones of Himasthla elongata (Trematoda, Echinostomatidae) determined with AFLP technique.

The aim of this study was to reveal genomic diversity formed during parthenogenetic reproduction of rediae of the trematode Himasthla elongata in its molluskan host Littorina littorea. We applied amplification fragment length polymorphism (AFLP) to determine the genomic diversity of individual cercariae within the clone, that is, the infrapopulation of parthenogenetic progeny in a single molluskan host. The level of genomic diversity of particular cercariae isolates from a single clone, detected with EcoR1/Mse1 AFLP reaction, was significantly lower than the variability of cercariae from different clones.

[PATTERNS IN CIRCULATION AND TRANSMISSION OF MARINE BIRD PARASITES IN HIGH ARCTIC: A CASE OF ACANTHOCEPHALAN POLYMORPHUS PHIPPSI (PALAEACANTHOCEPHALA, POLYMORPHIDAE)].

This study, based on the materials on parasitic infection of marine birds and invertebrates in Frantz Josef Land (FJL) collected in 1991-1993, focussed on the acanthocephalan Polymorphus phippsi. We identified this parasite, confirmed its species status and analysed its circulation and transmission patterns in high Arctic. The causes of its erroneous identification as P.

Trematode reproduction in the molluscan host: an ultrastructural study of the germinal mass in the rediae of Himasthla elongata (Mehlis, 1831) (Digenea: Echinostomatidae).

The germinal mass in Himasthla elongata rediae was studied in detail using transmission electron microscopy. It was shown to be a specialized reproductive organ consisting of germinal cells at various maturation stages, supporting cells and stem cells. The germinal mass also contains early cercarial embryos emerging as a result of cleavage division of mature germinal cells.

[Clonal variability in longevity of the cercariae of Himasthla elongata (Trematoda: Echinostomatidae)].

The study was carried out on Himasthla elongata cercariae shed by infected Littorina littorea snails. The infected periwinkles were collected from the settlement with the low prevalence of H. elongata.

[A case study of singular spectrum analysis application in parasitology: dynamics of prevalence of Cryptocotyle concavum and Bunocotyle progenetica trematode parthenitae in Hydrobia ventrosa snails at the White Sea].

In this study parasitological data were analyzed by different methods of revealing the structure of time series, namely auto-correlation analysis (ACA), Fourier spectrum analysis (SA) and singular spectrum analysis (SSA), and the results of these analysis were compared (SSA makes it possible to present non-stationary time series as a sum of independent components and to determine the contribution of each component into the dispersion of the initial series--Golyandina et al., 2001). This case study was based on the result of 10-year-long monitoring of changes in the prevalence of Cryptocotyle concavum and Bunocotyle progenetica trematode parthenitae in intertidal snails Hydrobia ventrosa at the White Sea (in total, 45 observations).

Life cycles, molecular phylogeny and historical biogeography of the 'pygmaeus' microphallids (Digenea: Microphallidae): widespread parasites of marine and coastal birds in the Holarctic.

The 'pygmaeus' microphallids (MPG) are a closely related group of 6 digenean (Platyhelminthes: Trematoda) Microphallus species that share a derived 2-host life cycle in which metacercariae develop inside daughter sporocysts in the intermediate host (intertidal and subtidal gastropods, mostly of the genus Littorina) and are infective to marine birds (ducks, gulls and waders). Here we investigate MPG transmission patterns in coastal ecosystems and their diversification with respect to historical events, host switching and host-parasite co-evolution. Species phylogenies and phylogeographical reconstructions are estimated on the basis of 28S, ITS1 and ITS2 rDNA data and we use a combination of analyses to test the robustness and stability of the results, and the likelihood of alternative biogeographical scenarios.

In vitro encystment of Himasthla elongata cercariae (Digenea, Echinostomatidae) in the haemolymph of blue mussels Mytilus edulis as a tool for assessing cercarial infectivity and molluscan susceptibility.

Infectivity of Himasthla elongata cercariae to mussels, their second intermediate hosts, and resistance by these hosts to infection were assessed on the basis of the cercariae's ability to encyst in mussel haemolymph in vitro. A series of experimental in vivo infections of mussels with batches of cercariae, each batch released from a different single infected mollusc and referred to as a clone (due to their shared genotype), demonstrated that the results of the in vitro tests corresponded to the actual indices of infectivity/susceptibility of the parasites and their hosts. Most cercarial clones had high infectivity, with a few clones having very high or, at the other extreme, very low infectivity.

[Clonal variability in expression of geo- and photoorientation in cercariae of Himasthla elongata (Trematoda: Echinostomatidae)].

The study was carried out on Himasthla elongata, a digenean common in the coastal ecosystems of the northern European seas. This species utilises intertidal prosobranchs Littorina spp. as the first intermediate host, bivalves (in the White Sea, Mytilus edulis) as the second intermediate host and gulls as the final host.

Morpho-functional specialization of the branching sporocyst of Prosorhynchoides borealis Bartoli, Gibson & Bray, 2006 (Digenea, Bucephalidae).

Sporocysts of Prosorhynchoides borealis were obtained from the marine bivalves Abra prismatica and studied using transmission electron microscopy. The sporocyst body consists of a mass of branching and intertwining hollow tubules that ramify through the host's digestive gland and gonads. This study investigated the ultrastructure of the sporocyst branches which comprise alternate distended areas (brood chambers) with a relatively thin body wall, narrower portions with a thicker body wall (constricted areas) and terminal regions.