Cestode diversity in shrews from islands in the Sea of Japan and the Sea of Okhotsk.

A comparative analysis of taxonomic diversity on shrew cestodes among four islands in the Sea of Japan and the Sea of Okhotsk (Sakhalin, Kunashir, Hokkaido, and Moneron) was performed. Cestode species shared among the islands were identified and their host specificity was investigated. On Sakhalin Island, 33 species of the families Hymenolepididae, Dilepididae and Mesocestoididae were recorded in four shrew species (Sorex caecutiens, S. gracillimus, S. minutissimus and S. unguiculatus). In S. caecutiens, S. gracillimus, and S. unguiculatus on Kunashir Island, 22 species of the same families were found and, on Hokkaido Island, 23 species of the families Hymenolepididae and Dilepididae were recorded. On Moneron Island, three species of cestodes were registered in S. tundrensis. The Sakhalin-Hokkaido-Kunashir complex of shrew cestodes includes eastern-Palearctic, trans-Palearctic and endemic species. High endemism (~22%) of shrew tapeworms in the Sakhalin-Kunashir-Hokkaido Islands was noted as compared to continental territories. The different numbers of cestode species in S. unguiculatus (31), S. caecutiens (29), S. gracillimus (19) and S. minutissimus (1) were found. It was concluded that the cestodes species diversity of shrews of Sakhalin-Kunashir-Hokkaido depended primarily on the history of island formation, their modern physical and geographical features, the abundance of definitive and intermediate cestodes hosts and, to a lesser extent, on the size and remoteness of the islands from the mainland and the diversity of host species.

New cestode species of the genus Neoskrjabinolepis Spassky, 1947 (Cyclophyllidea: Hymenolepididae) from the Common Shrew (Sorex araneus L.) in Europe.

Neoskrjabinolepis (Neoskrjabinolepis) yanchevi n. sp. is described from common shrews Sorex araneus L. (Eulipotyphla: Soricidae) from Pirin Mts., Bulgaria (type-locality) and Russia (Arkhangelskaya Oblast'). The new species is characterised by ten rostellar hooks 37-40 µm long and possessing claw-like blades with crooked middle parts and well-developed epiphyseal thickenings of handles; a whip-shaped cirrus, 80-100 µm long, consisting of basal region with numerous small, rosethorn-shaped spines, and middle and distal regions armed with fine, needle-shaped spines; vagina provided with sphincter close to its orifice, with copulatory and conductive part not clearly distinct from one another; 40-50 eggs per gravid uterus. The species is differentiated from the remaining 4 species of the nominotypical subgenus of the genus Neoskrjabinolepis, which are parasites of the Palaearctic shrews of the genus Sorex.

Spatial and temporal variation of compositional, functional, and phylogenetic diversity in ectoparasite infracommunities harboured by small mammals.

We studied patterns of compositional, functional, and phylogenetic α- and ß-diversity in flea and gamasid mite infracommunities of small Siberian mammals, taking into account host-associated (species) and environmental (biome or sampling period) factors. We asked: (a) How do these factors and their interactions affect infracommunity diversity? (b) Does infracommunity composition, in terms of species, traits, and phylogenetic lineages, deviate from random? (c) Are species, traits, and phylogenetic lineages in infracommunities clustered or overdispersed?, and (d) Do patterns of diversity differ between the three diversity facets and/or the two ectoparasite taxa? We found that the α-diversity of infracommunities was strongly affected by host species, biome, and sampling period. The highest proportion of infracommunity diversity in both taxa was associated with the interaction between either host species and biome or host species and sampling period. Infracommunities of both taxa within, as well as between, host species, biomes, and sampling periods were characterized by the clustering of species, traits and lineages. The patterns of the effects of host species, biome, and sampling period on infracommunity diversity were congruent among the three diversity facets in both fleas and mites. We conclude that the assembly patterns in ectoparasite infracommunities mirror those characteristics of component and compound communities.

Mastomys natalensis (Smith, 1834) as a natural host for Schistosoma haematobium (Bilharz, 1852) Weinland, 1858 x Schistosoma bovis Sonsino, 1876 introgressive hybrids.

Cercarial emission of schistosomes is a determinant in the transmission to the definitive host and constitutes a good marker to identify which definitive host is responsible for transmission, mainly in introgressive hybridization situations. Our goal was to test the hypothesis that micro-mammals play a role in Schistosoma haematobium, S. bovis, and/or S. haematobium x S. bovis transmission. Small mammal sampling was conducted in seven semi-lacustrine villages of southern Benin. Among the 62 animals trapped, 50 individuals were investigated for Schistosoma adults and eggs: 37 Rattus rattus, 3 Rattus norvegicus, 9 Mastomys natalensis, and 1 Crocidura olivieri. Schistosoma adults were found in four R. rattus and two M. natalensis, with a local prevalence reaching 80% and 50%, respectively. Two cercarial chronotypes were found from Bulinus globosus experimentally infected with miracidia extracted from naturally infected M. natalensis: a late diurnal and nocturnal chronotype, and an early diurnal, late diurnal, and nocturnal chronotype. The cytochrome C oxidase subunit I mtDNA gene of the collected schistosomes (adults, miracidia, and cercariae) belonged to the S. bovis clade. Eleven internal transcribed spacer rDNA profiles were found; four belonged to S. bovis and seven to S. haematobium x S. bovis. These molecular results together with the observed multi-peak chronotypes add M. natalensis as a new host implicated in S. haematobium x S. bovis transmission. We discuss the origin of the new chronotypes which have become more complex with the appearance of several peaks in a 24-h day. We also discuss how the new populations of offspring may optimize intra-host ecological niche, host spectrum, and transmission time period.

Specific and non-specific cestodes of shrews (Eulipotyphla: Soricidae) in Europe with a description of Coronacanthus longicirrosus n. sp (Cestoda: Hymenolepididae).

This paper presents a review of host specificity among cestodes collected from Soricidae mammals in Europe and a revision of cestodes preserved in formalin in the collection of the East-Slovakian Museum in Kosice. The morphological re-examination of cestodes showed that cestodes found in non-specific hosts (Soricidae and Talpidae) were identified incorrectly. The majority of the redescribed species are specific to a particular host genus. Only one species of the Staphylocystis Villot, 1877 genus, which could be Staphylocystis brusatae (Vaucher, 1971) according to the number, shape and length of hooks, as originally described from Crocidura suaveolens (Pallas) from Switzerland, was found in a host of the genus Sorex Linnaeus. The host specificity of the majority of Hymenolepididae cestode species is stenoxenous, but this study of the collection and the critical review of cestodes from non-specific Soricidae hosts disclosed that representatives of the genus Staphylocystis are euryxenous. So, these cestodes are better adapted to spreading into new ecosystems. A new species from Neomys fodiens (Pennant) from Slovakia, Western Carpathian, belonging to the genus Coronacanthus Spassky, 1954, Coronacanthus longicirrosus n. sp., is described. The new species is easily distinguishable by the number of small rostellar hooks (12-18, 4-5 µm), hooks shape, long cirrus (70-86 µm) and the presence of the vaginal sphincter.

Helminth fauna of small mammals from public parks and urban areas in Bangkok Metropolitan with emphasis on community ecology of infection in synanthropic rodents.

In 2018, extensive field studies of diversity and prevalence of helminth infection in synanthropic rodents and non-rodent small mammals from public parks and citified areas in the Bangkok Metropolitan were conducted. Rattus rattus complex was the dominant small mammal in public parks. Of the 197 animals, 147 individuals were infected with one or more species of helminths, yielding an infection prevalence of 74.6%. Twenty-five species of helminths were recovered during necropsy. Pterygodermatites tani was the most prevalent (36.2%); other encountered species included Raillietina celebensis, Hydatigera taeniaformis (metacestode in liver tissue), Gongylonema neoplasticum and Hymenolepis diminuta. Different helminth assemblages infected three different host taxa, i.e. synanthropic Rattus spp., Tupaia belangeri (Northern treeshrew) and Suncus murinus (Asian house shrew). Nine species of possible zoonotic helminths were identified. The focus on synanthropic rats influenced the findings of helminth diversity by either host intrinsic or extrinsic factors. A significant positive correlation was found between host body mass and helminth species richness. Greater helminth species richness was found in rats from public parks compared with animals from citified areas (e.g. inside buildings or offices). Also, helminth species richness was negatively correlated with the proportion of post-flooding/rain-fed land. These results provide essential information for assessing the incidence of potential zoonotic health threats in Bangkok and updating research in parasite ecology.

Circulation of Rickettsia species and rickettsial endosymbionts among small mammals and their ectoparasites in Eastern Slovakia.

Bacteria belonging to the genus Rickettsia are known as causative agents of vector-borne zoonotic diseases, such as spotted fevers, epidemic typhus and endemic typhus. Different species of ticks, mites and fleas could act as reservoirs and arthropod vectors of different pathogenic Rickettsia species. The aim of this work was to establish active surveillance of Rickettsia spp. in mites, ticks and fleas collected from small mammals (rodents and shrews) in Eastern Slovakia. A total of 964 animal ear biopsies, 871 mites, 667 ticks and 743 fleas were collected from small mammals in the Kosice region, Eastern Slovakia. All specimens were identified using specialized taxonomic keys, and were conserved in ethanol until DNA extraction was performed. After DNA extraction, identification of Rickettsia species was performed by PCR-based methods. The total prevalence of rickettsiae from ear biopsies was 4.6% (95% CI, 3.2-5.9), in tested mites 9.3% (95% CI, 7.4-11.2), 17.2% (95% CI, 14.3-20.1) in I. ricinus ticks and 3.5% (95% CI, 2.2-4.8) in fleas. Sequence analysis of the partial gltA gene and Rickettsia helvetica-, Rickettsia slovaca-, Rickettsia raoultii- species specific real-time PCR tests revealed the presence of R. helvetica, R. slovaca, unidentified Rickettsia and rickettsial endosymbionts. These pathogenic and symbiotic species were confirmed in the following ectoparasite species-Laelaps jettmari, Haemogamasus nidi, Laelaps agilis and Eulaelaps stabularis mites, Ixodes ricinus ticks, Ctenophthalmus solutus, C. assimilis and Megabothris turbidus fleas infesting host-Apodemus agrarius, A. flavicollis, Microtus arvalis and Myodes glareolus small mammals. These results confirm the circulation of R. helvetica, R. slovaca, unidentified Rickettsia and rickettsial endosymbionts in mites, ticks and fleas collected on small mammals in the Kosice region, Eastern Slovakia.

Phylogeny of hymenolepidid cestodes (Cestoda: Cyclophyllidea) from mammalian hosts based on partial 28S rDNA, with focus on parasites from shrews.

The aims of the study are to enrich the partial 28S rDNA dataset for hymenolepidids by adding new sequences for species parasitic in the genera Sorex, Neomys and Crocidura (Soricidae) and to propose a new hypothesis for the relationships among mammalian hymenolepidids. New sequences were obtained for Coronacanthus integrus, C. magnihamatus, C. omissus, C. vassilevi, Ditestolepis diaphana, Lineolepis scutigera, Spasskylepis ovaluteri, Staphylocystis tiara, S. furcata, S. uncinata, Vaucherilepis trichophorus and Neoskrjabinolepis sp. The phylogenetic analysis (based on 56 taxa) confirmed the major clades identified by Haukisalmi et al. (Zool Scr 39:631-641, 2010) based on analysis of 31 species: Ditestolepis clade, Hymenolepis clade, Rodentolepis clade and Arostrilepis clade; however, the support was weak for the early divergent lineages of the tree and for the Arostrilepis clade. Novelties revealed include the molecular evidence for the monophyly of Coronacanthus, the non-monophyletic status of Staphylocystis and the polyphyly of Staphylocystoides. The analysis has confirmed the monophyly of Hymenolepis, the monophyly of hymenolepidids from glirids, the position of Pararodentolepis and Nomadolepis as sister taxa, the polyphyly of Rodentolepis, the position of Neoskrjabinolepis and Lineolepis as sister taxa, and the close relationship among the genera with the entire reduction of rostellar apparatus. Resolved monophyletic groups are supported by the structure of the rostellar apparatus. The diversification of the Ditestolepis clade is associated with soricids. The composition of the other major clades suggests multiple evolutionary events of host switching, including between different host orders. The life cycles of Coronacanthus and Vaucherilepis are recognised as secondarily aquatic as these taxa are nested in terrestrial groups.

Molecular investigation of vector-borne parasites in wild micromammals, Barcelona (Spain).

Information about the role of micromammals in the epidemiology of Leishmania infantum and Babesia sp. in southern Europe is scarce. Wild micromammals were captured in natural areas in the Barcelona province (NE Spain) in 2011 and analysed by real-time PCR for the presence of DNA of Piroplasmida (n = 253) and Leishmania infantum (n = 166). The wood mouse (Apodemus sylvaticus) was the most abundant species, but all specimens tested negative for L. infantum, for which two out of 15 (13.3%) white-toothed shrews (Crocidura russula) and one out of 23 (4.3%) Algerian mice (Mus spretus) resulted positive. No individual was positive for Piroplasmida DNA. The role of wild micromammals in the epidemiology of these parasites in the study area seems negligible.

Redescription of Maupasina weissi (Seurat, 1913) (Nematoda: Ascaridida) from sengis, Elephantulus spp. and Macroscelides proboscideus (Shaw) (Macroscelidea), in Africa.

Maupasina weissi (Seurat, 1913), is redescribed from the eastern rock sengi, Elephantulus myurus Thomas & Schwann, from Limpopo Province and compared with material collected from Free State and North West Provinces, South Africa, as well as the description of the type-material from South Tunisia. Distinguishing features of the species include a corona radiata of 12 pointed leaflike elements, a complex bipartite buccal capsule with 3 large bicuspid denticular lobes and 4 smaller club-shaped lobes and 11 (occasionally 10) pairs of cloacal papillae in the male. The complex taxonomic history of the genus Maupasina Seurat, 1917 is discussed. The probable misidentification of Macroscelides proboscideus Shaw, the short eared sengi, from North West Province, South Africa, as a host of M. weissi is explained, indicating that M. weissi occurs only in species of the genus Elephantulus Thomas & Schwann. The widely separated geographical regions, stretching the length of the African continent, in which M. weissi has been found are indicative of a conservative species with a broad geographical distribution. Tenebrionid beetles, up to 50% of stomach contents of E. myurus in Limpopo Province may act as intermediate hosts in the life-cycle of M. weissi.

A new eimerian (Apicomplexa: Eimeriidae) from southern short-tailed shrews, Blarina carolinensis (Bachman) (Soricimorpha: Soricidae: Soricinae) from southeastern Oklahoma, USA.

A new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) is described from faecal samples of two of three southern short-tailed shrews, Blarina carolinensis (Bachman) (Soricidae) from southeastern Oklahoma, USA. Oöcysts of Eimeria tkachi n. sp. are subspheroidal to ovoidal with a rough-pitted, tan colored, bi-layered wall, measure 16.5 × 15.2 µm, and have a length/width (L/W) ratio of 1.1; both micropyle and oöcyst residuum are absent, but polar granule(s) are present. Sporocysts are ovoidal, 9.5 × 6.5 µm, L/W 1.4; a distinct button-like Stieda body is present, but the sub-Stieda and para-Stieda bodies are absent and the sporocyst residuum is composed of large globules distributed throughout the sporocyst. Sporozoites have a spheroidal anterior refractile body, a subspheroidal posterior refractile body, and one centrally-located nucleus. This is the smallest eimerian described thus far from the Soricidae, the initial description of a coccidian from B. carolinensis, and the first from any shrew from Oklahoma.

Identification of Hepatozoon erhardovae Krampitz, 1964 from bank voles (Myodes glareolus) and fleas in Southern Hungary.

In order to investigate the prevalence and life cycle of apicomplexan parasites, small mammals were live-trapped with modified Sherman traps in Southern Hungary between 2010 and 2012. Altogether, 528 rodents (Apodemus flavicollis Melchior, 1834, Apodemus agrarius Pallas, 1771, Myodes glareolus Schreber, 1780, Microtus agrestis Linnaeus, 1761, Mus musculus Linnaeus, 1758 and Micromys minutus Pallas, 1771) were collected and four shrews (Sorex spp.) were by-catched. Captured animals belonging to non-protected species were euthanized, and spleen samples were preserved for histological and molecular analyses. During the examination of spleen smears, Hepatozoon parasites were observed in eight out of 48 bank voles (M. glareolus). DNA was isolated from altogether 221 spleen samples, and 18S rDNA was amplified using two different PCR protocols. The eight bank vole samples were positive with PCR, but none of the other M. glareolus spleen samples or any of the tissue samples from other species were found to be infected. Sequenced amplicons were very similar to Hepatozoon spp. detected in M. glareolus in Spain and Poland. Ectoparasites were collected from the small mammal carcasses and from the vegetation. Hepatozoon DNA was not found in the 181 ticks removed from the small mammals or in the 162 ticks collected with flagging, but was detected in all three flea species (4/43 Megabothris turbidus Rothschild, 1909, 3/10 Ctenophthalmus assimilis Taschenberg, 1880 and 7/78 Ctenophthalmus agyrtes Heller, 1896). Based on gamont morphology, vertebrate and arthropod host species and DNA sequences, the parasites in our study can be identified as Hepatozoon erhardovae.

A synopsis of records of myxozoan parasites (Cnidaria: Myxozoa) from shrews, with additional data on Soricimyxum fegati from common shrew Sorex araneus in Hungary and pygmy shrew Sorex minutus in Slovakia.

Myxozoans (Cnidaria: Myxozoa) are almost exclusively endoparasites of aquatic vertebrates and invertebrates, with the notable exception being two species of Soricimyxum Prunescu, Prunescu, Pucek et Lom, 2007 described from terrestrial shrews (Soricidae) in central Europe. Myxospores of the two parasites are morphologically indistinguishable, but have SSU rDNA sequences that differ by about 4%. Herein, we report additional molecular and histology data from Soricimyxum fegati Prunescu, Prunescu, Pucek et Lom, 2007 from common shrew (Sorex araneus Linnaeus) from Hungary, and add a new geographic record for S. fegati in pygmy shrew (Sorex minutus Linnaeus) from Slovakia. A limited survey of shrews from the northern United States, Blarina brevicauda Say and Sorex sp. from New York, and Sorex spp. from Oregon, did not discover any infections, which is in stark contrast to the relatively high infection rates (up to 66%) in European shrew populations. We also provide a summary and discussion of literature records of species of Soricimyxum and a host survey. Given the lack of distinguishing morphological or morphometric characters between Soricimyxum spp., and the overlap in vertebrate hosts and geographic ranges, unambiguous identification of these closely related shrew parasites can presently only be achieved through sequence comparison of one or more variable SSU rDNA regions.

Revision of the genus Soricinia Spassky & Spasskaja, 1954 (Cestoda: Cyclophyllidea: Hymenolepididae) with redescriptions of three species, an amended generic diagnosis and an identification key to species.

Redescriptions of three species of Soricinia Spassky & Spasskaja, 1954 are provided. The type-species of the genus, Soricinia soricis (Baer, 1925), is redescribed on the basis of the holotype from the Alpine shrew Sorex alpinus Schinz collected in Salève Mountain, France. Since the type-material of Soricinia infirma (Zarnowski, 1955) has apparently been lost, a neotype from the type-host Sorex araneus L. and from a region reasonably close to the type-locality (Poltavska Oblast' in the Ukraine), is designated. The type-material of Soricinia quarta (Karpenko, 1983) Karpenko, 1999 from Sorex isodon Turov in Khabarovsk Kray (Russia) is redescribed. A taxonomic revision and an overview of the geographical distribution of species of the genus Soricinia are presented. An amended generic diagnosis and a key to identification of Soricinia spp. are also presented.

Crocidurobia faini n. sp. (Acariformes: Myobiidae), a new mite species parasitising shrews of the genus Crocidura Wagler (Soricomorpha: Soricidae) in DR Congo.

A new species Crocidurobia faini n. sp. (Acariformes: Myobiidae) recorded on Crocidura denti Dollman (type-host) (Soricomorpha: Soricidae), Crocidura cf. niobe Thomas, Crocidura cf. littoralis Heller, and Crocidura sp. from DR Congo is described. This new species differs in both sexes from all other species of the subgenus Crocidurobia Jameson, 1970 by short setae c2, more than three times shorter than setae se. Females of the new species differ from those of the close species Crocidurobia toroensis Dusbabek, 1983 by setal bases e2 situated slightly anterior to the level of setal bases e1; males of the new species differ by the genital shield bearing five pairs of setae situated anterior to the level of setal bases d1.

Stammerinema hyalinum n. comb. for Filaria hyalina von Linstow, 1890 and its recognition as a senior synonym of Stammerinema rhopalocephalum (Soltys, 1952) (Spirurida: Acuariidae), a parasite of shrews.

Based on a re-examination of type-specimens of Filaria hyalina von Linstow, 1890 from Sorex araneus L. (Mammalia: Soricidae) and morphological studies (light and scanning electron microscopy) of specimens collected from the same host species in Bulgaria and previously identified as Stammerinema rhopalocephalum (Soltys, 1952), both these forms are considered to be conspecific. Accordingly, F. hyalina is transferred to the genus Stammerinema Osche, 1955 as Stammerinema hyalinum n. comb. and the species originally described as Synhimantus rhopalocephalus Soltys, 1952 is considered its junior synonym.

Differentiation of flea communities infesting small mammals across selected habitats of the Baltic coast, central lowlands, and southern mountains of Poland.

Only a few studies comparing flea composition on the coast and in the mountains have been conducted. We investigated differences in flea communities infesting small mammals in selected habitats in northern, central, and southern Poland. We predicted (1) a greater number of flea species in the southeastern Poland and a lower number in the north, (2) a greater number of flea species in fertile and wet habitats than in poor and arid habitats, and (3) a low similarity of flea species between flea communities in western and eastern Poland. We found a negative effect of increasing latitude on flea species richness. We suppose that the mountains providing a variety of environments and the limits of the geographic ranges of several flea subspecies in southeastern Poland result in a higher number of flea species. There was a positive effect of increasing wetness of habitat on flea species richness. We found a high diversity in flea species composition between western and eastern Poland (beta diversity = 11) and between central and eastern Poland (beta diversity = 12). Re-colonization of Poland by small mammals and their ectoparasites from different (western and eastern) refugees can affect on this high diversity of flea species.

Occurrence of helminths in shrews and small rodents on territories transformed by reclamation.

Shrews and small rodents inhabit the drainage channel banks in reclai med areas and have their own helminth complex. The aim of the study is to conduct the 3rd research period during 2015-2019 the helminth fauna of these animals living on the drainage channel banks of model reclamation systems in Brest Polesie (south-western part of Belarus), to establish the species composition of helminths and the animal infection by these, and to compare the data obtained with previous research periods. 4,000 trap-days were worked out. 151 specimens of shrews of 4 species and 510 small rodents of 8 species were caught. Animals were examined by the method of complete helminthological dissections. Their numbers were 3.78 and 12.75 individuals per 100 trap-days, and helminth infection was 94.7% and 65.9%, respectively. 66 helminth species were found in animals. The dominant helminth species in infection have been identified. The trematode Prosolecithus danubica Tkach et Bray, 1995 (definitive host: common shrew), the acanthocephalans Centhrorhynchus aluconis (Müller, 1780) (larval host: lesser shrew) and Moniliformis moniliformis (Bremser, 1811) (definitive host: striped field mouse) are new species of helminths for Belarus. New hosts in Belarus have been found for 6 helminth species. Shrews and small rodents are involved in the life cycles of bird, non-ruminant artiodactyl and carnivorous mammal helminths. Nine helminth species have significance for medicine and 7 species for veterinary science. The results are compared with data from the 1st (1996-1999) and 2nd (2005-2010) research periods.

Ticks (Acari: Ixodidae) on small mammals in Kootenay National Park, British Columbia, Canada.

Two hundred and ninety-one ticks (i.e., 185 larvae, 72 nymphs, and 34 adults) were removed from 153 small mammals comprising six species collected in Verdant Forest, Numa Forest, and Marble Canyon within Kootenay National Park, British Columbia, Canada. Morphological examination and molecular analyses (i.e., polymerase chain reaction-single-strand conformation polymorphism [PCR-SSCP] and DNA sequencing of the mitochondrial 16S rRNA gene) of the ticks revealed that most individuals were Ixodes angustus Neumann. All life cycle stages of I. angustus were found primarily on southern red-backed voles, Clethrionomys gapperi (Vigors). Two Dermacentor andersoni Stiles females were also found on these small mammals. The results of the molecular analyses also revealed that there were three 16S haplotypes of I. angustus and two 16S haplotypes of D. andersoni. A comparison of available sequence data suggests genetic divergence between I. angustus near the western and eastern limits of the species distributional range in North America. Additional studies are needed to determine whether there are genetic differences between I. angustus from North America, Japan, and Russia, and whether there is geographical variation in the ability of ticks to transmit pathogens to their mammalian hosts.

Ultrastructure of the intrauterine eggs of the microphallid trematode Maritrema feliui: evidence of early embryonic development.

Intrauterine embryonic development in the microphallid trematode Maritrema feliui is examined by means of transmission electron microscopy. Both fertilization and eggshell formation take place in the ootype. The eggshell is formed from a shell globule material derived from the vitelline cells combined with secretions of Mehlis' gland. The proximal uterus is packed with unembryonated eggs of the oligolecithal type, each composed of a fertilized oocyte and several vitelline cells, all surrounded by the shell. Intrauterine embryonic development of the egg is followed to the early stage of outer embryonic envelope formation, resulting in an embryo of ~20 blastomeres of three different types: macromeres, mesomeres and micromeres. The first equal cleavage division of the zygote produces two macromeres. The outer envelope is of cellular origin and formed by the cytoplasmic fusion of two macromeres, which become situated at opposite poles in the peripheral layer of the embryo just beneath the eggshell. Simultaneously, other blastomeres multiply and differentiate, whereas several micromeres exhibit clear signs of degeneration or apoptosis. These results show that the embryonic development of M. feliui starts in utero and represents an example of early stage ovoviviparity. A reduction in the number of blastomeres results from a continued degeneration of micromeres, which after autolysis and re-absorption, appear to represent an important source of nutritive reserves for the embryo. The embryonic development of this digenean is discussed in relation to its life cycle.