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Gregarine apicomplexans are ubiquitous endosymbionts of invertebrate hosts. Despite their ecological and evolutionary importance, inferences about the phylogenetic relationships of major gregarine groups, such as the Lecudinidae and Urosporidae, have been hindered by vague taxonomic definitions and limited molecular and morphological data. In this study, we investigated five gregarine species collected from four families of polychaete hosts (Nereididae, Oenonidae, Hesionidae, and Phyllodocidae) using light microscopy (LM) and scanning electron microscopy (SEM). We also generated small subunit ribosomal DNA sequences from these species and conducted molecular phylogenetic analyses to elucidate the evolutionary relationships within the Lecudinoidea. Our results include new molecular and morphological data for two previously described species (Lecudina cf. platynereidis and Lecudina cf. arabellae), the discovery of a new species of Lecudina (L. oxydromus n. sp.), and the discovery of two novel species, namely Amplectina cordis n. gen. et. n. sp. and Sphinctocystis inclina n. sp. These two species exhibited unique shapes and movements, resembling those of urosporids but with a phylogenetic affinity to lecudinids, blurring the border between lecudinids and urosporids. Our study emphasizes the need for further investigations into this highly diverse group, which has achieved great success across multiple animal phyla with diverse shapes and movements., (© 2024 The Author(s). Journal of Eukaryotic Microbiology published by Wiley Periodicals LLC on behalf of International Society of Protistologists.)

A taxonomic study of deep-sea polychaetes collected at a depth of 2,805 m off the northern coast of California revealed a scaleworm of the family Sigalionidae with an attached parasitic copepod. The copepod represents an undescribed genus of the family Herpyllobiidae, comprising mesoparasitic copepods chiefly recorded from polychaetes of the family Polynoidae. Blakerius gen. nov. diverges from the other herpyllobiid genera by its possession of 1) a chalice-shaped ectosoma with several protuberances along the posterior margin and a long cylindrical shaft with a hyaline coating and integumental sculpturing, a short stalk with a small, anteriorly placed sclerotized ring, 2) a relatively large, discoid-shaped endosoma with digitiform process, and 3) attached male copepodids with 3-segmented antennules, containing limbless sac-like males. The new genus is compared with other herpyllobiids. This discovery increases the number of known herpyllobiid genera to six and is the first record of a herpyllobiid parasitizing a sigalionid polychaete.urn: lsid: zoobank.org:pub:5E31FEED-D3EB-460E-AEA4-02A9D3A778D6., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Gregarines are the most biodiverse group of apicomplexan parasites. This group specializes on invertebrate hosts (e.g., ascidians, crustaceans, and polychaetes). Marine gregarines are of particular interest because they are considered to be the earliest evolving apicomplexan lineage, having subsequently speciated (and radiated) through virtually all existing animal groups. Still, mechanisms governing the broad (global) distribution and speciation patterns of apicomplexans are not well understood. The present study examines Pacific lecudinids, one of the most species-rich and diverse groups of marine gregarines. Here, marine polychaetes were collected from intertidal zones. Single trophozoite cells were isolated for light and electron microscopy, as well as molecular phylogenetic analyses using the partial 18S rRNA gene. The cytochrome c oxidase subunit 1 gene was used to confirm morphology-based host identification. This study introduces Undularius glycerae n. gen., n. sp. and Lecudina kitase n. sp. (Hokkaido, Japan), as well as Difficilina fasoliformis n. sp. (California, USA). Occurrences of Lecudina cf. longissima and Lecudina cf. tuzetae (California, USA) are also reported. Phylogenetic analysis revealed a close relationship between L. pellucida, L. tuzetae, and L. kitase n. sp. Additionally, clustering among North Atlantic and Pacific L. tuzetae formed a species complex, likely influenced by biogeography., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

Urosporid eugregarines (Apicomplexa: Urosporidae) are unicellular eukaryotic parasites inhabiting the coelom or the intestine of marine invertebrates such as annelids, molluscs, nemerteans, and echinoderms. Despite the availability of published morphological and phylogenetical analyses of coelomic gregarines, their long-term survival in the host body cavity and dispersal routes into the marine environment remain unclear. Here, we focus on Urospora gametocysts and oocysts with sporozoites, which were found viable inside the so-called brown bodies floating in the body cavity of the polychaete Travisia forbesii. Brown bodies form as a result of host defence where coelomocytes encapsulate dead host cells and foreign objects including potential pathogens. We hypothesise the long-term persistence of Urospora eugregarines in brown bodies through evasion of the host immunity and outline possible pathways for their egress into the marine environment, applicable as dispersal routes for other parasites as well. Unique features revealed by detailed ultrastructural analysis of detected eugregarine stages include asynchronous sporogony, a massive sporozoite secretion apparatus, as well as the presence of free (possibly autoinfective) sporozoites within the gametocyst. The assignment to the genus Urospora and the complete identity with U. ovalis and U. travisiae were confirmed by analysing 18S rDNA sequences obtained from isolated gametocysts. The 18S rDNA phylogeny confirmed the affiliation of Urosporidae to Lecudinoidea and the grouping of all Urospora sequences with Difficilina from nemerteans and environmental sequences from the Artic region. We also enriched the Apicomplexa set by partial 28S rDNA sequences of two Urospora species enabling more complex phylogenetic analyses prospectively., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests that would influence the work presented in this article., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Metchnikovellids are a deep-branching group of microsporidia, parasites of gregarines inhabiting the alimentary tract of polychaetes and some other invertebrates. The diversity and phylogeny of these hyperparasites remain poorly studied. Modern descriptions and molecular data are still lacking for many species. The results of a light microscopy study and molecular data for Metchnikovella spiralis Sokolova et al., 2014, a hyperparasite of the eugregarine Polyrhabdina sp., isolated from the polychaete Pygospio elegans, were obtained. The original description of M. spiralis was based primarily on the analysis of stained preparations and transmission electron microscopy images. Here, the species description was complemented with the results of in vivo observations and phylogenetic analysis based on the SSU rRNA gene. It was shown that in this species, free sporogony precedes sac-bound sporogony, as it occurs in the life cycle of most other metchnikovellids. Spore sacs are entwined with spirally wound cords, and possess only one polar plug. Phylogenetic analyses did not group M. spiralis with M. incurvata, another metchnikovellid from the same gregarine species, but placed it as a sister branch to Amphiacantha. The paraphyletic nature of the genus Metchnikovella was discussed. The taxonomic summary for M. spiralis was emended.

The cyclopoid copepod family Bradophilidae includes a few species of mesoparasitic copepods infecting flabelligerid polychaetes. It contains two species of Bradophila Levinsen, 1878, the type genus: B. pygmaea Levinsen, 1878 and B. minuta Boxshall, O'Reilly, Sikorski & Summerfield, 2019, both known from North Europe. Two other genera (i.e., Trophoniphila M'Intosh, 1885 and Flabellicola Gravier, 1918) have some affinities with this family including their host preference. Mesoparasitic copepods are highly specialized, morphologically reduced forms. Part of their body (endosoma) is partially lodged in the host body and the other part is external (ectosoma); both parts are connected by an intersomital stalk. Infection by these copepods can be readily detected by the presence of the egg-carrying ectosoma on the host external surface. From the analysis of flabelligerid polychaetes collected in 2012 from the Chukchi Sea, two ovigerous female individuals of a bradophilid copepod were recorded. These specimens were recognized as representative of an undescribed species of Bradophila. The new species, B. susanae n. sp., shows the generic diagnostic characters and differs from its two other known congeners in several respects, including the cuticular ectosomal ornamentation, body proportions, size of the intersomital stalk, position of the genital pore, and shape and arrangement of egg sacs. Also, the new species ectosomal size range (0.440 - 0.450 μm) falls between the size range of its two known congeners. Our finding expands the known host range of bradophilid copepods to include a new flabelligerid host, Bradabyssa nuda (Annenkova-Chlopina) from the Russsian Arctic region.

The species Metchnikovella dogieli (Paskerova et al. Protistology 10:148-157, 2016) belongs to one of the early diverging microsporidian groups, the metchnikovellids (Microsporidia: Metchnikovellidae). In relation to typical ('core') microsporidia, this group is considered primitive. The spores of metchnikovellids have no classical polar sac-anchoring disk complex, no coiled polar tube, no posterior vacuole, and no polaroplast. Instead, they possess a short thick manubrium that expands into a manubrial cistern. These organisms are hyperparasites; they infect gregarines that parasitise marine invertebrates. M. dogieli is a parasite of the archigregarine Selenidium pygospionis (Paskerova et al. Protist 169:826-852, 2018), which parasitises the polychaete Pygospio elegans. This species was discovered in samples collected in the silt littoral zone at the coast of the White Sea, North-West Russia, and was described based on light microscopy. No molecular data are available for this species, and the publicly accessible genomic data for metchnikovellids are limited to two species: M. incurvata Caullery & Mesnil, 1914 and Amphiamblys sp. WSBS2006. In the present study, we applied single-cell genomics methods with whole-genome amplification to perform next-generation sequencing of M. dogieli genomic DNA. We performed a phylogenetic analysis based on the SSU rRNA gene and reconstructed a multigene phylogeny using a concatenated alignment that included 46 conserved single-copy protein domains. The analyses recovered a fully supported clade of metchnikovellids as a basal group to the core microsporidia. Two members of the genus Metchnikovella did not form a clade in our tree. This may indicate that this genus is paraphyletic and requires revision.

Some fish blood flukes of the genus Cardicola (Aporocotylidae) are considered important pathogens of farmed/ranched tuna, Thunnus spp. Infections with Cardicola spp. might obstruct the blood flow in the gills via massive accumulations of eggs and often lead to mass mortalities in captive tuna. At present, oral administration of an anthelminthic drug, praziquantel is the most effective treatment, but the tuna farming industries are seeking non-drug control measures. Development of prophylactic and holistic measures have been difficult, owing to a lack of basic knowledge about these parasites. Unlike other trematodes which use molluscs, blood flukes of marine actinopterygian fish use terebellid polychaetes as intermediate hosts. However, information about the development of Cardicola spp. within intermediate hosts is very limited. Recent success in Cardicola opisthorchis sporocyst transplantation into the host polychaete has opened possibilities for the cultivation of Cardicola in the laboratory. Here, we conducted several transplantation trials with another tuna blood fluke, Cardicol orientalis, into its natural and surrogate polychaete hosts. Cardicola orientalis sporocysts were injected into a total of 195 Nicolea gracilibranchis, the natural host, and clear sporocyst development and reproduction was observed in 32 recipients (overall success rate 16.4%). The production of daughter sporocysts in the transplanted polychaete occurred within 14 days post injection, and one sporocystogenous cycle took approximately 4 weeks. Serial passage culture via transplantation of in vivo-cultured sporocysts was also achieved, but with limited sporocyst reproduction. In addition, sporocysts were successfully retrieved from six and one individuals of the surrogate hosts, Thelepus setosus (n = 10) and Thelepus japonicus (n = 5), respectively. These results indicate that the in vivo cultivation of C. orientalis sporocysts is possible, not only in its natural host but also in other terebellids, although the problems of high mortality and inconsistency in successful transplantation need to be resolved., (Copyright © 2020 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

Four epibiotic sessilid peritrichs, i.e., Zoothamnium wilberti n. sp., Baikalonis microdiscus n. sp., Epistylis anastatica (Linnaeus, 1767) Ehrenberg, 1830, and Rhabdostyla commensalisMöbius, 1888, were isolated from one syllid polychaete and three crustacean hosts in Qingdao, China. For each species, specimens were observed both in vivo and following silver staining. Their SSU rDNA was also sequenced for phylogenetic analyses. Zoothamnium wilberti n. sp. is characterized by the appearance of its colony, which is up to 350 μm high, and usually has fewer than 16 zooids, and the dichotomously branched stalk with transverse wrinkles, the conspicuously conical peristomial disc, and infundibular polykinety 3 comprising three isometric ciliary rows. Baikalonis microdiscus n. sp. can be recognized by its barrel-shaped zooid, small peristomial disc, smooth and short stalk, and its unusual infundibular polykinety 3 comprising a long inner row and a short outer row. Two poorly known species, i.e., Epistylis anastatica and Rhabdostyla commensalis, are redescribed and redefined. Phylogenetic analyses reveal that: (i) R. commensalis is closely related to the family Astylozoidae rather than to the morphologically similar Epistylididae; (ii) B. microdiscus n. sp. is sister to the family Scyphidiidae; (iii) E. anastatica groups with vorticellids and ophrydiids, which further supports the polyphyly of the genus Epistylis; and (iv) Z. wilberti n. sp. is nested within the Zoothamniidae, as expected., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

The metacestodes of aploparaksid cestode Wardium cirrosa Krabbe, 1869 parasitic in gulls were found in polychaetes of the family Nereidae collected off the Black Sea coast, Ukraine. Two species of polychaetes, Hediste diversicolor (prevalence 5.3%; intensity 1-3 specimens) and Neanthes succinea (prevalence 9.9%; intensity 1-39 specimens), were infected with cysticercoids that were observed either individually or in accumulations. The preliminary identification of the material based on morphological characteristics was later confirmed by experimental infection of the definitive host, Larus cachinnans (Charadriiformes: Laridae) with metacestodes, and by the identity of the partial 28S rDNA sequences of cysticercoids and experimentally obtained adults. Although previous studies suggested freshwater leeches as the intermediate host for W. cirrosa, our study provides the evidence for marine polychaetes to serve as intermediate hosts. This study is the first to present the morphological characteristics of metacestodes of W. cirrosa in addition to molecular data for this species, as well as reporting the possibility of several cysticercoids developing from a single oncosphere. Morphology of the adult specimens obtained in the experiment was compared with adults of W. cirrosa previously collected from L. cachinnans in Ukraine. The results of our study suggest that further research focused on the elucidation of the life cycles of cestodes within the genus Wardium should consider marine invertebrates as potential intermediate hosts.

In a survey of marine annelids for myxosporean infection in Charleston Harbor, South Carolina, we collected 3,214 polychaetes from 21 families and found infections in 6 spionid individuals. Based on gross morphology and COI sequencing, all infected spionids were identified as Streblospio benedicti. Infection prevalence was 0.8% (6/734) of that species of spionid, and 0.2% of all 3,214 polychaetes examined. Pansporocysts contained 8 actinospores and developed in the tegument of the annelid host. This is the first myxozoan infection recorded from this polychaete species, second in the family, and the first marine myxozoan found in the Americas. It is the first marine species found to develop in the tegument of its annelid host; a site of development observed only once before, in Ceratonova shasta infections of its freshwater sabellid polychaete host. Mature actinospores were morphologically simple, truncated ellipsoids, lacking processes or ornamentation, 9.0 ± 0.5 μm × 6.0 ± 0.4 μm. Their sack-like shape was similar to 9 of the 12 actinospores described previously from polychaetes; 10/12 had been and ascribed originally to the morphological collective group Tetractinomyxon despite 9 of these having few similarities to the original description of this group. We propose to name the simple, spherical to ellipsoidal spore morphotype Saccimyxon to encompass both our novel actinospore and the 9 other sack-like polychaete actinospore types in the literature. In the present study, 18S rDNA sequencing demonstrated that the myxozoans that infected the 6 spionids were genetically the same species (type sample 1,737 nucleotides, GenBank accession number MH791159) and was not >95% similar to any sequence in GenBank. Phylogenetic analysis showed that the myxozoan species we encountered is basal to the kudoids and thus likely to have a morphologically simple myxospore stage with fewer than 4 valves. However, without a genetic match, the presumptive vertebrate host remains unknown.

Life cycles of spirorchiids that infect the vascular system of turtles are poorly understood. Few life cycles of these blood flukes have been elucidated and all intermediate hosts reported are gastropods (Mollusca), regardless of whether the definitive host is a freshwater or a marine turtle. During a recent survey of blood fluke larvae in polychaetes on the coast of South Carolina, USA, spirorchiid-like cercariae were found to infect the polychaetes Amphitrite ornata (Terebellidae) and Enoplobranchus sanguineus (Polycirridae). Cercariae were large, furcate, with a ventral acetabulum, but no eyespots were observed. Partial sequences of D1-D2 domains of the large ribosomal subunit, the internal transcribed spacer 2, and the mitochondrial cytochrome oxidase 1 genes allowed the identification of sporocysts and cercariae as belonging to two unidentified Neospirorchis species reported from the green turtle, Chelonia mydas, in Florida: Neospirorchis sp. (Neogen 13) in A. ornata and Neospirorchis sp. (Neogen 14) in E. sanguineus. Phylogenetic analysis suggests that infection of annelids by blood flukes evolved separately in aporocotylids and spirorchiids. Our results support the contention that the Spirorchiidae is not a valid family and suggest that Neospirorchis is a monophyletic clade within the paraphyletic Spirorchiidae. Since specificity of spirorchiids for their intermediate hosts is broader than it was thus far assumed, surveys of annelids in turtle habitats are necessary to further our understanding of the life history of these pathogenic parasites., (Copyright © 2018 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

Archigregarines are a key group for understanding the early evolution of Apicomplexa. Here we report morphological, ultrastructural, and molecular phylogenetic evidence from two archigregarine species: Selenidium pygospionis sp. n. and S. pherusae sp. n. They exhibited typical features of archigregarines. Additionally, an axial row of vacuoles of a presumably nutrient distribution system was revealed in S. pygospionis. Intracellular stages of S. pygospionis found in the host intestinal epithelium may point to the initial intracellular localization in the course of parasite development. Available archigregarine SSU (18S) rDNA sequences formed four major lineages fitting the taxonomical affiliations of their hosts, but not the morphological or biological features used for the taxonomical revision by Levine (1971). Consequently, the genus Selenidioides Levine, 1971 should be abolished. The branching order of these lineages was unresolved; topology tests rejected neither para- nor monophyly of archigregarines. We provided phylogenies based on LSU (28S) rDNA and near-complete ribosomal operon (concatenated SSU, 5.8S, LSU rDNAs) sequences including S. pygospionis sequences. Although being preliminary, they nevertheless revealed the monophyly of gregarines previously challenged by many molecular phylogenetic studies. Despite their molecular-phylogenetic heterogeneity, archigregarines exhibit an extremely conservative plesiomorphic structure; their ultrastructural key features appear to be symplesiomorphies rather than synapomorphies., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Gregarines are a common group of parasites that infect the intestines of marine invertebrates, and particularly polychaetes. Here, we describe for the first time four gregarine species that inhabit the intestines of three spionid species: Dipolydora cf. flava, Spio quadrisetosa and Boccardia proboscidea from the Patagonian coast, Argentina, using light and scanning electron microscopy and molecular phylogenetic analyses of small subunit (SSU) rDNA sequences. Even though the spionid species thrive in the same environments, our results showed a high host specificity of the gregarine species. Selenidium cf. axiferens and Polyrhabdina aff. polydorae were both identified from the intestine of D. cf. flava. The new species, Polyrhabdina madrynense sp. n. and Selenidium patagonica sp. n., were described from the intestines of S. quadrisetosa and the invasive species B. proboscidea, respectively. All specimens of D. cf. flava and S. quadrisetosa were infected by gregarines (P = 100%), recording the highest mean intensity values of infection (MI = 80; 60 respectively), in contrast to B. proboscidea (P = 60%; MI = 38). We associated this finding with the recent invasion of this host. It is expected that in the future, an increase of its population density might favour a rising intensity of this gregarine infection., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Metchnikovellids are highly specialized hyperparasites, which infect and reproduce inside gregarines (Apicomplexa) inhabiting marine invertebrates. Their phylogenetic affiliation was under constant discussion until recently, when analysis of the first near-complete metchnikovellid genome, that of Amphiamblys sp., placed it in a basal position with respect to most Microsporidia. Microsporidia are a highly diversified lineage of extremely reduced parasites related to Rozellida (Rozellosporidia = Rozellomycota = Cryptomycota) within the Holomycota clade of Opisthokonta. By sequencing DNA from a single-isolated infected gregarine cell we obtained an almost complete genome of a second metchnikovellid species, and the first one of a taxonomically described and well-documented species, Metchnikovella incurvata. Our phylogenomic analyses show that, despite being considerably divergent from each other, M. incurvata forms a monophyletic group with Amphiamplys sp., and confirm that metchnikovellids are one of the deep branches of Microsporidia. Comparative genomic analysis demonstrates that, like most Microsporidia, metchnikovellids lack mitochondrial genes involved in energy transduction and are thus incapable of synthesizing their own ATP via mitochondrial oxidative phosphorylation. They also lack the horizontally acquired ATP transporters widespread in most Microsporidia. We hypothesize that a family of mitochondrial carrier proteins evolved to transport ATP from the host into the metchnikovellid cell. We observe the progressive reduction of genes involved in DNA repair pathways along the evolutionary path of Microsporidia, which might explain, at least partly, the extremely high evolutionary rate of the most derived species. Our data also suggest that genome reduction and acquisition of novel genes co-occurred during the adaptation of Microsporidia to their hosts.

This study describes a novel species of Haplozoon, H. ezoense n. sp., a dinoflagellate parasite isolated from the intestines of Praxillella pacifica (Polychaeta). Trophonts (feeding stages) of H. ezoense n. sp. were isolated and studied with scanning and transmission electron microscopy, and molecular phylogenetic analyses was performed using 18S rDNA and 28S rDNA. Trophonts had an average length of 120μm, and were linear, forming a single longitudinal row comprising a trophocyte with a stylet, an average of 14 gonocytes (width=10μm), and bulbous cells that we concluded were likely sporocytes. The surface of H. ezoense n. sp. was covered with projections of the amphiesma. Sections viewed under TEM revealed multiple triple membrane-bound organelles reminiscent of relic non-photosynthetic plastids within the gonocytes. Haplozoon ezoense n. sp., H. praxillellae, and H. axiothellae formed a well-supported clade in the 18S rDNA datasets. The sequences of H. ezoense n. sp. differed from H. praxillellae, a species of Haplozoon isolated from the same host species in the Northeast Pacific, at 88/1,748 bases; and 155/1,752 bases from H. axiothellae. Concatenated 18S rDNA and 28S rDNA datasets were unable to resolve the deeper relationships of Haplozoon in the context of dinoflagellates., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Marine gregarines are unicellular parasites of invertebrates commonly found infecting the intestine and coelomic spaces of their hosts. Situated at the base of the apicomplexan tree, marine gregarines offer an opportunity to explore the earliest stages of apicomplexan evolution. Classification of marine gregarines is often based on the morphological traits of the conspicuous feeding stages (trophozoites) in combination with host affiliation and molecular phylogenetic data. Morphological characters of other life stages such as the spore are also used to inform taxonomy when such stages can be found. The reconstruction of gregarine evolutionary history is challenging, due to high levels of intraspecific variation of morphological characters combined with relatively few traits that are taxonomically unambiguous. The current study combined morphological data with a phylogenetic analysis of small subunit rDNA sequences to describe and establish a new genus and species (Cuspisella ishikariensis n. gen., n. sp.) of marine gregarine isolated from the intestine of a polynoid host (Lepidonotus helotypus) collected from Hokkaido, Japan. This new species possesses a set of unusual morphological traits including a spiked attachment apparatus and sits on a long branch on the molecular phylogeny. Furthermore, this study establishes a molecular phylogenetic position for Loxomorpha cf. harmothoe, a previously described marine gregarine, and reveals a new group of gregarines that infect polynoid hosts., (© 2018 The Author(s) Journal of Eukaryotic Microbiology © 2018 International Society of Protistologists.)

Aporocotylidae comprises a diverse family of fish blood flukes, with adults found in blood or body cavity of marine, brackish, or freshwater fish. Aporocotylids are unique among the Digenea with many developing in polychaetes. The life cycle has been elucidated for only a few species that develop in polychaetes from marine/brackish environments and none for western Atlantic aporocotylids. The basis for this study was observations of blood fluke larvae in annelids from South Carolina, USA in 1982 prior to possible usage of molecular tools to specifically identify parasite larvae. Recent description of aporocotylid species and genotyping tools prompted revisiting original collection sites to examine polychaetes and fish as potential hosts. Polycirrid Enoplobranchus sanguineus and terebellids Amphitrite ornata, and Terebella lapidaria revealed infections with aporocotylid larvae. Adult blood flukes were also collected from fish commonly encountered in the same habitat: spotted seatrout (Cynoscion nebulosus), red drum (Sciaenops ocellatus), black drum (Pogonias cromis), and Atlantic croaker (Micropogonias undulatus). Sporocysts containing cercariae were found in individuals of each annelid species. Adult Cardicola parvus were found in spotted seatrout and Atlantic croaker, C. laruei in spotted seatrout, C. currani in red drum, and C. palmeri in black drum. Genotype analysis of ITS-2 and lsrDNA of all forms confirmed conspecific infections by C. parvus in E. sanguineus and A. ornata and C. laruei in T. lapidaria. This is the first description of complete life cycles of aporocotylids in the Western Atlantic and first evidence of cryptic infections of Cy. nebulosus with C. parvus., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Gregarine apicomplexans are unicellular parasites commonly found in the intestines and coeloms of invertebrate hosts. Traits associated with the conspicuous feeding stage of gregarines, known as the trophozoite, have been used in combination with molecular phylogenetic data for species delimitation and the reconstruction of evolutionary history. Trophozoite morphology alone is often inadequate for inferring phylogenetic relationships and delimiting species due to frequent cases of high intraspecific variation combined with relatively low interspecific variation. The current study combined morphological data with small subunit (SSU) rDNA sequences to describe and establish two novel marine gregarine species isolated from the intestine of a polychaete host Lumbrineris inflata collected in British Columbia (Canada): Paralecudina anankea n. sp. and Lecudina caspera n. sp. The sister species to the host is Lumbrineris japonica, which can be found on the opposite side of the Pacific Ocean (Japan) and contains two different species of gregarine parasites: Paralecudina polymorpha and Lecudina longissima. Molecular phylogenetic analyses placed P. anankea n. sp. as the sister species to P. polymorpha and L. caspera n. sp. as the sister species to L. longissima. This phylogenetic pattern demonstrates a co-evolutionary history whereby speciation of the host (Lumbrineris) corresponds with simultaneous speciation of the two different lineages of intestinal gregarines (Paralecudina and Lecudina)., (© 2017 The Author(s) Journal of Eukaryotic Microbiology © 2017 International Society of Protistologists.)

Blood flukes (Aporocotylidae) of actinopterygians (bony fishes) have been shown to infect freshwater gastropods and marine polychaetes as intermediate hosts. However, no life cycle is known for any aporocotylid of chondrichthyans (cartilaginous fishes) and no adult aporocotylid has been linked to a cercaria infecting a bivalve. Here we report two novel infections that fill these gaps. Cercariae consistent with the family Aporocotylidae were found developing in sporocysts in the gonad of the surf pipi, Donax deltoides Lamarck, 1818 (Bivalvia: Donacidae), from Stockton Beach, central New South Wales, Australia. Adult aporocotylids were found in the heart of the giant shovelnose ray, Glaucostegus typus (Anonymous [Bennett], 1830), from Moreton Bay, southeastern Queensland, Australia. Phylogenetic analyses of the 28S rDNA region generated from the new specimens resulted in phylograms in which the two parasites form a strongly supported clade with Chimaerohemecus trondheimensis van der Land, 1967, the only aporocotylid known from a holocephalan and the only other chondrichthyan-infecting aporocotylid for which sequence data are available. Most marine aporocotylids of actinopterygians also form a strongly supported clade. These findings lead us to hypothesise that the aporocotylids of chondrichthyans are distinct from all other blood flukes in infecting bivalves as intermediate hosts. Putative cophyly between three major blood fluke clades and both definitive and intermediate host groups is consistent with diversification of the Schistosomatoidea over 400million years ago., (Copyright © 2017 Australian Society for Parasitology. All rights reserved.)

Fish blood flukes of the genus Cardicola (Digenea: Aporocotylidae) are important pathogens in tuna aquaculture. Recent advances in marine blood fluke research have led to the elucidation of the lifecycles of 3 Cardicola spp. infecting tuna; all 3 flukes utilize terebellid polychaetes as the intermediate host. In our survey, we obtained large numbers of Nicolea gracilibranchis infected by larval Cardicola orientalis at our tuna farming site. To determine the spatial and temporal changes in the distribution of N. gracilibranchis surrounding tuna culture cages and their infection by C. orientalis, we conducted monthly sampling for a period of 1 yr. Terebellids were most abundant on the floats and ropes of culture cages, but a significantly higher proportion of infected N. gracilibranchis was detected on ropes, particularly up to 4 m in depth. Cardicola orientalis infection in N. gracilibranchis was clearly seasonal, with a higher infection rate between April and July. Our findings indicate that the infected terebellids inhabit specific microhabitats, and both abiotic and biotic factors likely influence blood fluke infection in the intermediate terebellid host. This information is important to better understand the general biology of marine aporocotylids and may be useful to develop a control strategy for blood fluke infection in tuna aquaculture.

Microscopic and phylogenetic analyses were performed on endocommensal astome ciliates retrieved from the middle intestine of a marine cirratulid polychaete, Cirriformia tentaculata, collected in the bay of Roscoff (English Channel, Northwest French coast) and on the Southwest English coast. Three morphotypes of the astome genus Durchoniella were identified, two corresponding to described species (the type species Durchoniella brasili (Léger and Duboscq, 1904) De Puytorac, 1954 and Durchoniella legeriduboscqui De Puytorac, 1954) while a third morphotype remains undescribed. Their small subunit (SSU) rRNA gene sequences showed at least 97.2% identity and phylogenetic analyses grouped them at the base of the subclass Scuticociliatia (Oligohymenophorea), as a sister lineage to all astomes from terrestrial oligochaete annelids. Ultrastructural examination by transmission electron microscopy and fluorescence in situ hybridization analyses revealed the presence of endocytoplasmic cocci and rod-shaped bacteria surrounded by a very thin membrane. These endocytoplasmic bacteria may play a role in the association between endocommensal astome ciliates and cirratulid polychaetes inhabiting in anoxic coastal sediments., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Cardicola opisthorchis is a blood fluke pathogen significantly affecting cultured Pacific bluefin tuna Thunnus orientalis in Japan. It is known that the intermediate host of C. opisthorchis is a terebellid polychaete Terebella sp. In order to study the intrapolychaete larval development of C. opisthorchis, we transplanted sporocysts, which contained a large number of cercariae, of C. opisthorchis obtained from Terebella sp. into sporocyst-free Terebella sp., which had been maintained at 20°C. The transplanted sporocysts switched from cercarial to sporocystal production by 17days after transplantation (d.a.t.) and daughter sporocysts were released into the polychaete body cavity at 25d.a.t. Subsequently, the released daughter sporocysts produced daughter sporocysts again. Thereafter, daughter sporocysts that contained cercariae appeared at 38d.a.t. and gradually increased. At 51d.a.t., 136 sporocysts that had multiplied from the original two transplanted sporocysts were observed in the body of one polychaete, and cercariae were released from daughter sporocysts inside the polychaete body cavity. Subsequently the cercariae were found to be released outside the polychaete at 57d.a.t. This is the first successful case of in situ observation of the development of a blood fluke within the intermediate host., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Farming of Pacific bluefin tuna (PBT), Thunnus orientalis, is a rapidly growing industry in Japan. Aporocotylid blood flukes of the genus Cardicola comprising C. orientalis, C. opisthorchis and C. forsteri are parasites of economic importance for PBT farming. Recently, terebellid polychaetes have been identified as the intermediate hosts for all these parasites. We collected infected polychaetes, Terebella sp., the intermediate host of C. opisthorchis, from ropes and floats attached to tuna cages in Tsushima, Nagasaki Prefecture, Japan. Also, Neoamphitrite vigintipes (formerly as Amphitrite sp. sensu Shirakashi et al., 2016), the intermediate host of C. forsteri, were collected from culture cages in Kushimoto, Wakayama Prefecture, Japan. The terebellid intermediate hosts harbored the sporocysts and cercariae in their body cavity. Developmental stages of these blood flukes were molecularly identified using species specific PCR primers. In this paper, we describe the cercaria and sporocyst stages of C. opisthorchis and C. forsteri and compare their morphological characteristics among three Cardicola blood flukes infecting PBT. We also discuss phylogenetic relations of the six genera of the terebellid intermediate hosts (Artacama, Lanassa, Longicarpus, Terebella, Nicolea and Neoamphitrite) of blood flukes infecting marine fishes, based on their morphological characters., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

The life cycle of Proctoeces maculatus (Looss, 1901) (Digenea, Fellodistomidae) was studied in Bizerte Lagoon (Tunisia). Three sequential hosts appear to be involved: the Mediterranean mussel Mytilus galloprovincialis Lamarck, 1819 (Mytilidae) as the first intermediate host; the polychaete Sabella pavonina Savigny, 1822 (Sabellidae), as the second intermediate host; and fishes (Lithognathus mormyrus (Linnaeus, 1758) (Sparidae), Trachinotus ovatus (Linnaeus, 1758) (Carangidae) and Sparus aurata Linnaeus, 1758 (Sparidae) as the definitive hosts. It should be noted that S. pavonina was recorded as second intermediate host for P. maculatus for the first time. Molecular confirmation of the morphological identification of the life-cycle stages of this digenean was obtained using partial 28S rDNA sequences. Comparative sequences revealed that the sporocysts and the metacercariae are conspecific but they diverged by 0.3% from the adults. The present results raised the possibility of the existence of cryptic species within the different developmental stages. However, all the present isolates differed from material from Archosargus probatocephalus in the Gulf of Mexico identified as P. maculatus.

The type material of four monotypic genera, Leaniricola, Oestrella, Praxillinicola and Trophoniphila (Copepoda, Cyclopoida), described by M'Intosh (1885) from deep water polychaete hosts collected during the H.M.S. Challenger expedition, is re-examined. Leaniricola rotundata M'Intosh (1885) is removed from its floating status as species inquirenda in the Nereicolidae and fixed as the type of a new family, Leaniricolidae fam. nov., based on the presence of an oral cone and massive, three-dimensionally expanded, mandibular gnathobases which are used to anchor the parasite in the parapodial integument of its host. The ectoparasitic Praxillinicola kroyeri (M'Intosh, 1885), previously treated as a species inquirenda in the Clausiidae, cannot be placed in any of the currently recognized poecilostome families and is here fixed as the type of a new family, Praxillinicolidae fam. nov. Females are characterized by unique bilobate antennules, contained within anterior sockets shared with the reduced antennae, and by paired labral hooks, both of which probably serve as auxiliary attachment organs. Despite its highly transformed body P. kroyeri has retained the plesiomorphic condition of the female genital system, with the gonopores positioned dorsolaterally and the paired copulatory pores lying close together on the midventral surface. The position of the mesoparasitic Trophoniphila bradyi M'Intosh, 1885 in the Bradophilidae is confirmed based on the presence of a median copulatory pore in the female, the disproportionately large egg sacs, the shape of the ectosoma and host utilization. Both sexes of Bradophila pygmaea Levinsen, 1878 are re-examined and the male is redescribed in detail. Flabellicola Gravier, 1918a is treated as a genus incertae sedis in the Bradophilidae. The anal prominence, previously reported in the female of Oestrella (= Melinnacheres) levinseni M'Intosh, 1885 (Saccopsidae), proved upon re-examination to be one of the paired genital apertures. The third and fourth pairs of appendages reported in male saccopsids are here interpreted as the maxillae and maxillipeds, respectively.

Known life cycles of myxosporean parasites have two hosts, but very few life cycles have been disclosed, especially in the marine environment. Sphaerospora dicentrarchi Sitjà-Bobadilla and Álvarez-Pellitero, 1992 is a systemic parasite from the European seabass, Dicentrarchus labrax (Linnaeus, 1758), a highly valuable commercial fish. It affects its health, leading to aquaculture production losses. During 2013 and 2014, an actinospore survey was conducted in a total of 5942 annelids collected from a fish farm in Algarve and from the Aveiro Estuary, in Portugal. A new tetractinomyxon actinospore was found in a capitellid polychaete, belonging to the genera Capitella collected at the fish farm. The tetractinomyxons were pyriform measuring 11·1 ± 0·7 µm in length and 7·2 ± 0·4 µm in width, and presented three rounded polar capsules measuring 2·4 ± 0·3 µm in diameter. The molecular analysis of the 18S rRNA gene sequences from the tetractinomyxons revealed a similarity of 100% with the DNA sequences deposited in the GenBank from S. dicentrarchi myxospores collected from the European seabass and the spotted seabass in the same fish farm and 99·9% similarity with the DNA sequence obtained from the myxospores found infecting the European seabass in the Aveiro Estuary. Therefore, the new tetractinomyxons are inferred to represent the actinospore phase of the S. dicentrarchi life cycle.

Urosporids (Apicomplexa: Urosporidae) are eugregarines that parasitise marine invertebrates, such as annelids, molluscs, nemerteans and echinoderms, inhabiting their coelom and intestine. Urosporids exhibit considerable morphological plasticity, which correlates with their different modes of motility and variations in structure of their cortical zone, according to the localisation within the host. The gregarines Urospora ovalis and U. travisiae from the marine polychaete Travisia forbesii were investigated with an emphasis on their general morphology and phylogenetic position. Solitary ovoid trophozoites and syzygies of U. ovalis were located free in the host coelom and showed metabolic activity, a non-progressive movement with periodic changes of the cell shape. Solitary trophozoites of U. travisiae, attached to the host tissue or free floating in the coelom, were V-shaped. Detached trophozoites demonstrated gliding motility, a progressive movement without observable cell body changes. In both gregarines, the cortex formed numerous epicytic folds, but superfolds appeared exclusively on the surface of U. ovalis during metabolic activity. SSU rDNA sequences obtained from U. ovalis and U. travisiae revealed that they belong to the Lecudinoidea clade; however, they are not affiliated with other coelomic urosporids (Pterospora spp. and Lithocystis spp.), but surprisingly with intestinal lecudinids (Difficilina spp.) parasitising nemerteans., (Copyright © 2016 Elsevier GmbH. All rights reserved.)

We used PCR to screen pooled individuals of Manayunkia speciosa from western Lake Erie, Michigan, USA for myxosporean parasites. Amplicons from positive PCRs were sequenced and showed a Ceratonova species in an estimated 1.1% (95% CI=0.46%, 1.8%) of M. speciosa individuals. We sequenced 18S, ITS1, 5.8S, ITS2 and most of the 28S rDNA regions of this Ceratonova sp., and part of the protein-coding EF2 gene. Phylogenetic analyses of ribosomal and EF2 sequences showed the Lake Erie Ceratonova sp. is most similar to, but genetically distinct from, Ceratonova shasta. Marked interspecific polymorphism in all genes examined, including the ITS barcoding genes, along with geographic location suggests this is an undescribed Ceratonova species. COI sequences showed M. speciosa individuals in Michigan and California are the same species. These findings represent a third parasite in the genus Ceratonova potentially hosted by M. speciosa., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Fish blood flukes (Aporocotylidae) are important pathogens of farmed finfish around the world. Among them, Cardicola spp. infecting farmed tuna are considered to be serious threats to tuna farming and have received tremendous attention. We conducted periodical samplings at a tuna farming site in Japan between January and May, 2015 to determine the life cycle of Cardicola spp. We collected over 4700 terebellid polychaetes from ropes, floats and frames of tuna culture cages and found nearly 400 infected worms. Sporocysts and cercariae found in Nicolea gracilibranchis were genetically identified as Cardicola orientalis by 28S and ITS2 ribosomal DNA sequences. This was the first discovery of the intermediate host for this parasite species. Infection prevalence and the abundance of N. gracilibranchis significantly varied between sampling points and the highest number of infected terebellids were collected from ropes. We also demonstrated morphologically and molecularly that asexual stages found in a single Amphitrite sp. (Terebellidae) and adult worms isolated from farmed juvenile tuna were Cardicola forsteri. This is the first report of C. forsteri in Pacific bluefin tuna (PBT) Thunnus orientalis in Japan. Our results demonstrated that all three species of Cardicola orientalis, C. forsteri and Cardicola opisthorchis exist in Japanese farmed PBTs and that they all use terebellid polychaetes as the intermediate hosts., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Polychaete worms are hosts to a wide range of marine parasites; yet, studies on trematodes using these ecologically important species as intermediate hosts are lacking. During examination of the spionid polychaete Marenzelleria viridis collected on the north shore of Long Island, New York, putative trematode cysts were discovered in the body cavity of these polychaetes. In order to verify these cysts as metacercariae of trematodes, specimens of the eastern mudsnail Ilyanassa obsoleta (a very common first intermediate host of trematodes in the region) were collected for molecular comparison. DNA barcoding using cytochrome C oxidase I regions confirmed the presence of three species of trematodes (Himasthla quissetensis, Lepocreadium setiferoides, and Zoogonus lasius) in both M. viridis and I. obsoleta hosts. Brown bodies were also recovered from polychaetes, and molecular testing confirmed the presence of L. setiferoides and Z. lasius, indicating an immune response of the polychaete leading to encapsulation of the cysts. From the 125 specimens of M. viridis collected in 2014, 95 (76.8 %) were infected with trematodes; of these 95 infected polychaetes, 86 (90.5 %) contained brown bodies. This is the first confirmation that trematodes use M. viridis as a second intermediate host and that this intermediate host demonstrates a clear immune response to metacercarial infection. Future research should explore the role of these polychaetes in trematode life cycles, the effectiveness of the immune response, and transmission pathways to vertebrate definitive hosts.

A new species of the snapping shrimp genus Alpheus Fabricius, 1798, Alpheus ikedosoma, is described and illustrated on the basis of material from Boso Peninsula and Ariake Sea, Japan. All examined specimens were extracted with the help of a bait suction pump from burrows of innkeeper worm (Annelida: Echiura), constructed on easily accessible intertidal sand beaches or sand flats. The host worm from Boso Peninsula was identified as Ikedosoma elegans (Ikeda, 1904) (Echiuridae). The new species is tentatively referred to the A. brevirostris (Olivier, 1811) species group, but it is characteristic in having several unusual features for the group, such as the very short rostrum without dorsal ridge, the absence of adrostral grooves on the carapace, the strongly reduced dorsolateral spines on the telson, the unarmed antennal basicerite, the non-elongate, almost glabrous major chela, and the lack of movable spines or spinules on ventromesial margin of each cheliped merus. The new species represents the sixth species of Alpheus associated with echiuran burrows.

A new genus and species of copepod, Jasmineiricola mackiei n. gen. et n. sp., parasitic on at least three species of the sabellid polychaete genus Jasmineira Langerhans, 1880 is described. The adult female is mesoparasitic, living with part of its body (the endosoma) embedded within the host and part (the ectosoma) protruding through the host's body wall. The endosoma consists of a well defined head region carried anteriorly on the trunk which has paired lateral lobes housing the ovaries. The head bears a rosette-like array of eight slender lobes, which are probably derived from the mouthparts. The only limbs present on the trunk are the subchelate maxillipeds positioned immediately posterior to the head. The ectosoma consists of a posterior genito-abdominal lobe bearing paired genital apertures. The male is unknown. The new genus cannot be placed in any of the five existing families of mesoparasitic copepods on polychaete hosts and is treated as the type of a new monotypic family, the Jasmineiricolidae. The new species occurs over a depth range from 19 to 279 m, and is widely distributed from UK coastal waters to Norwegian waters inside the Arctic Circle.

Previous studies have shown that the bioturbating polychaete Hediste (Nereis) diversicolor can affect the composition of bacterial communities in oil-contaminated sediments, but have not considered diversity specifically within bioturbator burrows or the impact on microbial eukaryotes. We tested the hypothesis that H. diversicolor burrows harbour different eukaryotic and bacterial communities compared with un-bioturbated sediment, and that bioturbation stimulates oil degradation. Oil-contaminated sediment was incubated with or without H. diversicolor for 30 days, after which sediment un-affected by H. diversicolor and burrow DNA/RNA samples were analysed using quantitative reverse transcription PCR (Q-RT-PCR) and high-throughput sequencing. Fungi dominated both burrow and un-bioturbated sediment sequence libraries; however, there was significant enrichment of bacterivorous protists and nematodes in the burrows. There were also significant differences between the bacterial communities in burrows compared with un-bioturbated sediment. Increased activity and relative abundance of aerobic hydrocarbon-degrading bacteria in the burrows coincided with the significant reduction in hydrocarbon concentration in the bioturbated sediment. This study represents the first detailed assessment of the effect of bioturbation on total microbial communities in oil-contaminated sediments. In addition, it further shows that bioturbation is a significant factor in determining microbial diversity within polluted sediments and plays an important role in stimulating bioremediation., (© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Marteilia sydneyi (Phylum Paramyxea, Class Marteiliidea, Order Marteiliida) (the causative agent of QX disease) is recognised as the most severe parasite to infect Saccostrea glomerata, the Sydney rock oyster, on the east coast of Australia. Despite its potential impact on industry (>95% mortality), research towards lessening these effects has been hindered by the lack of an experimental laboratory model of infection as a consequence of our incomplete understanding of the life cycle of this parasite. Here, we explored the presence of this parasite in hosts other than a bivalve mollusc from two study sites on the Hawkesbury River, New South Wales, Australia. We employed PCR-based in situ hybridisation and sequence analysis of a portion of the first internal transcribed spacer of rDNA in an attempt to detect M. sydneyi DNA in 21 species of polychaete worm. Marteilia DNA was detected in 6% of 1247 samples examined by PCR; the analysis of all amplicons defined one distinct sequence type for first internal transcribed spacer, representing M. sydneyi. Of the polychaete operational taxonomic units test-positive in PCR, we examined 116 samples via in situ hybridisation DNA probe staining and identified M. sydneyi DNA in the epithelium of the intestine of two specimens of Nephtys australiensis. Two differing morphological forms were identified: a 'primordial' cell that contained a well-defined nucleus but had little differentiation in the cytoplasm, and a 'plasmodial' cell that showed an apparent syncytial structure. This finding represents the first known record of the identification of M. sydneyi being parasitic in an organism other than an oyster, and only the third record of any species of Marteilia identified from non-molluscan hosts. Future work aims at determining if N. australiensis and S. glomerata are the only hosts in the life cycle of this paramyxean, and the development of experimental models to aid the production of QX disease-resistant oysters., (Copyright © 2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

This study focused on the attachment strategy, cell structure and the host-parasite interactions of the protococcidian Eleutheroschizon duboscqi, parasitising the polychaete Scoloplos armiger. The attached trophozoites and gamonts of E. duboscqi were detected at different development stages. The parasite develops epicellularly, covered by a host cell-derived, two-membrane parasitophorous sac forming a caudal tipped appendage. Staining with Evans blue suggests that this tail is protein-rich, supported by the presence of a fibrous substance in this area. Despite the ultrastructural evidence for long filaments in the tail, it stained only weakly for F-actin, while spectrin seemed to accumulate in this area. The attachment apparatus consists of lobes arranged in one (trophozoites) or two (gamonts) circles, crowned by a ring of filamentous fascicles. During trophozoite maturation, the internal space between the parasitophorous sac and parasite turns translucent, the parasite trilaminar pellicle seems to reorganise and is covered by a dense fibrous glycocalyx. The parasite surface is organised in broad folds with grooves in between. Micropores are situated at the bottom of the grooves. A layer of filaments organised in bands, underlying the folds and ending above the attachment fascicles, was detected just beneath the pellicle. Confocal microscopy, along with the application of cytoskeletal drugs (jasplakinolide, cytochalasin D, oryzalin) confirmed the presence of actin and tubulin polymerised forms in both the parasitophorous sac and the parasite, while myosin labelling was restricted to the sac. Despite positive tubulin labelling, no microtubules were detected in mature stages. The attachment strategy of E. duboscqi shares features with that of cryptosporidia and gregarines, i.e. the parasite itself conspicuously resembles an epicellularly located gregarine, while the parasitophorous sac develops in a similar manner to that in cryptosporidia. This study provides a re-evaluation of epicellular development in other apicomplexans and directly compares their niche with that of E. duboscqi.

Ceratonova shasta is a myxozoan parasite of salmon and trout transmitted by waterborne actinospores. Based on DNA sequence data and host specificity, 4 distinct parasite genotypes are recognized. Genotypes I and II are common in the lower reaches of the Klamath River, Oregon-California, but only infection by genotype I causes mortality in Chinook salmon. We conducted sentinel fish exposures and determined genotype composition in river water during exposure, and in fish gills, intestine, and tank water post-exposure to determine whether: (1) transmission of parasites having different genotypes is host-specific and (2) all transmitted genotypes persist in the host through to release as waterborne stages. Initial parasite transmission to the fish host appears indiscriminant, since we detected both genotypes I and II in 83.6% of the fish gills sampled. However, only genotype I was detected in fish that succumbed to infection, while both genotypes persisted in fish that survived. Persistence was likely dependent on exposure dose, initial infection type (mixed or single) and infection outcome (mortality or survival). The transmission of both genotypes to a majority of Chinook salmon and the persistence of multiple genotypes raises questions about how infection with mixed genotypes could result in within-host interactions that affect disease severity.

A new genus Neocamacolaimus gen. n., with one new species N. parasiticus gen. n., sp. n. is described from the benthic polychaete Sphaerosyllis cf. hystrix collected in the Skagerrak off the west coast of Sweden. Neocamacolaimus gen. n. is placed in the family Camacolaimidae and is particularly characterised by having annulated cuticle with lateral alae; setiform cephalic sensilla located at level with amphids; amphidial fovea ventrally spiral; buccal cavity without armament; pharynx muscular; nerve ring located at base of pharynx; male reproductive system diorchic with outstretched testes; spicules weakly arcuate with straight manubrium; gubernaculum absent; alveolar supplements located in the pharyngeal region; tubular supplements absent; tail conoid; caudal glands and spinneret present. Juveniles of this genus are particularly characterised by their parasitic lifestyle and the following unique morphological features: lips form a dorso-ventrally elongated perioral disc with internal sclerotizations: one midventral and two dorsosublateral (right and left); cephalic sensilla setiform, subventral sensilla are noticeably longer than the subdorsal ones; intestine extends posterior to rectum and anal opening, forming a post-anal pouch.

We found aporocotylid larval stages (sporocysts and cercariae) from five individuals of terebellid polychaete Terebella sp., which were collected from seabed substrate and ropes and floats attached to tuna cages in a tuna farm on the coast of Tsushima Island, Nagasaki, Japan. Nucleotide sequences of the regions of internal transcribed spacer 2 ribosomal DNA and 28S ribosomal DNA from these larval stages were 100% identical to those of Cardicola opisthorchis registered in GenBank. C. opisthorchis is a pathogen causing blood fluke infection of Pacific bluefin tuna Thunnus orientalis, which is considered to have a significant impact on the Japanese Pacific bluefin tuna aquaculture industry. This is the first description of the intermediate host of C. opisthorchis. This indicates that the life cycle of C. opisthorchis is completed within tuna farms in this area., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

We analyzed the tissue carbon, nitrogen, and sulfur stable isotope contents of macrofaunal communities associated with vestimentiferan tubeworms and bathymodiolin mussels from the Gulf of Mexico lower continental slope (970-2800 m). Shrimp in the genus Alvinocaris associated with vestimentiferans from shallow (530 m) and deep (1400-2800 m) sites were used to test the hypothesis that seep animals derive a greater proportion of their nutrition from seeps (i.e. a lower proportion from the surface) at greater depths. To account for spatial variability in the inorganic source pool, we used the differences between the mean tissue δ(13)C and δ(15)N of the shrimp in each collection and the mean δ (13)C and δ(15)N values of the vestimentiferans from the same collection, since vestimentiferans are functionally autotrophic and serve as a baseline for environmental isotopic variation. There was a significant negative relationship between this difference and depth for both δ(13)C and δ(15)N (p=0.02 and 0.007, respectively), which supports the hypothesis of higher dependence on seep nutrition with depth. The small polychaete worm Protomystides sp. was hypothesized to be a blood parasite of the vestimentiferan Escarpialaminata. There was a highly significant linear relationship between the δ(13)C values of Protomystides sp. and the E. laminata individuals to which they were attached across all collections (p < 0.001) and within a single collection (p = 0.01), although this relationship was not significant for δ(15)N and δ(34)S. We made several other qualitative inferences with respect to the feeding biology of the taxa occurring in these lower slope seeps, some of which have not been described prior to this study.

An updated review of the helminth parasites using polychaetes as hosts is provided. Fifteen relevant search terms were entered into the Institute for Scientific Information Web of Science online database in order to locate papers published since the last review, and subsequent supplementary article, given by Margolis (J Fish Res Board Can 28:1385-1392, 1971, J Fish Res Board Can 30:469-470, 1973), entitled "Polychaetes as intermediate hosts of helminth parasites of vertebrates: a review" and "Additional notes on polychaetes as intermediate hosts of helminth parasites of vertebrates," respectively. The World Register of Marine Species was used to provide the most current scientific names for both helminth parasites and their respective polychaete hosts. A total of 35 new reports were found. Across the taxa examined, digenetic trematodes appear to be the most prominent of the helminth parasites utilizing polychaete annelids as hosts. Nematodes are the second most common helminth grouping--followed by cestodes--using polychaetes as hosts. An incidence of possible parasitism by a turbellarian using a polychaete as a host is also reported.

Selenidium is a genus of gregarine parasites that infect the intestines of marine invertebrates and have morphological, ecological, and motility traits inferred to reflect the early evolutionary history of apicomplexans. Because the overall diversity and phylogenetic position(s) of these species remain poorly understood, we performed a species discovery survey of Selenidium from tube-forming polychaetes. This survey uncovered five different morphotypes of trophozoites (feeding stages) living within the intestines of three different polychaete hosts. We acquired small subunit (SSU) rDNA sequences from single-cell (trophozoite) isolates, representing all five morphotypes that were also imaged with light and scanning electron microscopy. The combination of molecular, ecological, and morphological data provided evidence for four novel species of Selenidium, two of which were established in this study: Selenidium neosabellariae n. sp. and Selenidium sensimae n. sp. The trophozoites of these species differed from one another in the overall shape of the cell, the specific shape of the posterior end, the number and form of longitudinal striations, the presence/absence of transverse striations, and the position and shape of the nucleus. A fifth morphotype of Selenidium, isolated from the tube worm Dodecaceria concharum, was inferred to have been previously described as Selenidium cf. echinatum, based on general trophozoite morphology and host association. Phylogenetic analyses of the SSU rDNA sequences resulted in a robust clade of Selenidium species collected from tube-forming polychaetes, consisting of the two new species, the two additional morphotypes, S. cf. echinatum, and four previously described species (Selenidium serpulae, Selenidium boccardiellae, Selenidium idanthyrsae, and Selenidium cf. mesnili). Genetic distances between the SSU rDNA sequences in this clade distinguished closely related and potential cryptic species of Selenidium that were otherwise very similar in trophozoite morphology., (© 2013 The Author(s) Journal of Eukaryotic Microbiology © 2013 International Society of Protistologists.)

Class Rudimicrosporea Sprague 1977, with its single family Metchnikovellidae, comprises hyperparasites of gregarines from the guts of marine invertebrates. Metchnikovellids remain poorly studied in spite of their significance to the evolutionary history of microsporidia; their ultrastructure and life cycles require further investigation. Here we present results of the light- and electron-microscopy study of Metchnikovella incurvata Caulleri and Mesnil 1914, isolated from lecudinid gregarines, parasitizing polychaetes Pygospio elegans in the White Sea littoral zone, and yet described only on the light-microscopic level. The life cycle of this microsporidium includes 2 sporogonies: free (FS) and sac-bound (SBS). In FS, sporonts develop into multinuclear cells (sporogonial plasmodia), which generate sporoblasts and free spores residing in direct contact with the host cytoplasm. Electron microscopy revealed their metchnikovellidean structure: a horseshoe-shaped nucleus, short manubrium perpendicular to the long axis of the spore, and a polar cap in a separate membrane container. Merogony was not observed. The earliest stages of SBS were chains of binucleate cells. They underwent a series of nuclear and cell divisions, produced extracellular envelopes, and split into boomerang-shaped spore sacs, containing up to 16 spores each. Ultrastructure and sizes of sac-bounded spores were similar to those of free-living ones. An amended diagnosis of M. incurvata is provided.

A myxosporean producing actinospores of the tetractinomyxon type in Hydroides norvegicus Gunnerus (Serpulidae) in Denmark was identified as a member of the family Parvicapsulidae based on small-subunit ribosomal DNA (SSU rDNA) sequences. Myxosporean samples from various Danish and Norwegian marine fishes were examined with primers that detect the novel myxosporean. Sprattus sprattus (Linnaeus) and Clupea harengus Linnaeus (Teleostei, Clupeidae) were found to be infected. The sequences of this parvicapsulid from these hosts were consistently slightly different (0.8% divergence), but both these genotypes were found in H. norvegicus. Disporic trophozoites and minute spores of a novel myxosporean type were observed in the renal tubules of some of the hosts found infected through PCR. The spores appear most similar to those of species of Gadimyxa Køie, Karlsbakk et Nylund, 2007, but are much smaller. The actinospores of the tetractinomyxon type from H. norvegicus have been described previously. In GenBank, the SSU rDNA sequences of Parvicapsulidae gen. sp. show highest identity (82%) with Parvicapsula minibicornis Kent, Whitaker et Dawe, 1997 infecting salmonids (Oncorhynchus spp.) in fresh water in the western North America. A phylogenetic analysis places P. minibicornis and Parvicapsulidae gen. sp. in a sister clade to the other parvicapsulids (Parvicapsula spp. and Gadimyxa spp.).

Marine gregarines are poorly understood apicomplexan parasites with large trophozoites that inhabit the body cavities of marine invertebrates. Two novel species of gregarines were discovered in polychaete hosts collected in Canada and Japan. The trophozoites of Trichotokara japonica n. sp. were oval to rhomboidal shaped, and covered with longitudinal epicytic folds with a density of six to eight folds/micron. The nucleus was situated in the middle of the cell, and the mucron was elongated and covered with hair-like projections; antler-like projections also extended from the anterior tip of the mucron. The distinctively large trophozoites of Trichotokara eunicae n. sp. lacked an elongated mucron and had a tadpole-like cell shape consisting of a bulbous anterior region and a tapered tail-like posterior region. The cell surface was covered with longitudinal epicytic folds with a density of three to five folds/micron. Small subunit (SSU) rDNA sequences of both species were very divergent and formed a strongly supported clade with the recently described species Trichotokara nothriae and an environmental sequence (AB275074). This phylogenetic context combined with the morphological features of T. eunicae n. sp. required us to amend the description for Trichotokara. The sister clade to the Trichotokara clade consisted of environmental sequences and Lecudina polymorpha, which also possesses densely packed epicyctic folds (3-5 folds/micron) and a prominently elongated mucron. This improved morphological and molecular phylogenetic context justified the establishment of Paralecudina (ex. Lecudina) polymorpha n. gen. et comb., (© 2012 The Author(s) Journal of Eukaryotic Microbiology © 2012 International Society of Protistologists.)

Descriptions are given of 18 species of copepods that live in symbiotic association with polychaete worms in European Seas. Three new genera and six new species of the family Clausiidae Giesbrecht, 1895 are described: Boreoclausia rectan. gen. et n. sp. is described from Galathowenia fragilis (Nilson & Holthe, 1985), Boreoclausia holmesi n. gen. et n. sp.is described from Myriochele danielsseni Hansen, 1879, Sheaderia bifida n. gen. et n. sp. from Euclymene oerstedii (Claparède, 1863), Vivgottoia garwoodi n. gen. et n. sp., was found inside the tail fragment of a terebellid host (probably Phisidia aurea Southward, 1956), Rhodinicola tenuis n. sp. from an unknown host, and R. similis n. sp., from Rhodine gracilor (Tauber, 1879). In addition, four other clausiid species, Clausia lubbockii Claparède, 1863, Mesnilia cluthae (T. and A.Scott, 1896), Rhodinicola gibbosus Bresciani, 1964 and R. rugosum (Giesbrecht, 1895), are redescribed in detail on the basis of newly collected material. The previously-unknown hosts of C. lubbockii were found to be species of the spionid polychaete genus Dipolydora Verrill, 1881. Clausia uniseta Bocquet & Stock, 1960 were recognized as a junior subjective synonym of C. lubbockii, and Mesnilia martinensis Canu, 1898 was recognized as a junior subjective synonym of M. cluthae. The sole species of the monotypic family Anomoclausiidae Gotto, 1964, Anomoclausia indrehusae Gotto, 1964, is redescribed based on new material. The host of A. indrehusae, reported here for the first time, is the spionid Pseudopolydora paucibranchiata (Okuda, 1937). Four new species of the family Nereicolidae Claus, 1875 are described, three belonging to the genus Anomopsyllus Sars, 1921: Anomopsyllus bifurcus n. sp. from Notomastus latericeus M. Sars, 1851, A. geminus n. sp. from Ampharete lindstroemi Malmgren, 1867, and A. hamiltonae n. sp., from Mugga wahrbergi Eliasson, 1955. The fourth new species is Vectoriella gabesensis n. sp., both sexes of which are described from the paraonid Aricidea catherinae Laubier, 1967 collected in the Mediterranean Sea off the coast of Tunisia. Another nereicolid, Sigecheres brittae Bresciani, 1964 is redescribed based on new material collected from the type host Sige fusigera Malmgren, 1865. It is recognized as a junior subjective synonym of Nereicola concinna T. Scott, 1902 and the valid name of this taxon becomes Sigecheres concinna (T. Scott, 1902) new combination. A new species of the family Spiophanicolidae Ho, 1984, Spiophanicola atlanticus n. sp., is described based on European material. Previously European material of Spiophanicola Ho, 1984 has been reported as S. spinulosus Ho, 1984, but based on consistent differences between the Californian S. spinulosus and material from Norway and the British Isles, there is sufficient justification to establish a new species for the European material. Finally one new genus and species is described which cannot be placed, with confidence, in any existing family. This new parasite, Notomasticola frondosus n. gen. et n. sp., is based on material from two hosts, a spionid (Pseudopolydora paucibranchiata) and a capitellid (Notomastus latericeus). It is highly derived and may represent a terminal branch within an existing family. The cluster of families using polychaetes as hosts is in need of revision based on a comprehensive phylogenetic analysis.

In Mar Chiquita coastal lagoon (Argentina), the reefs of the invasive polychaete Ficopomatus enigmaticus (Serpulidae) serve as concentration areas for invertebrates and vertebrates and as potential foci of parasite transmission (mainly digeneans). To analyse the role of F. enigmaticus as facilitator of parasite transmission, and to evaluate the influence of the habitats selected by 2 species of cochliopid snails (Heleobia conexa and Heleobia australis), on the richness and on the prevalence of the digenean assemblages that parasitize them, 1945 snails were collected from 2 sampling sites. The comparisons between larval digenean communities parasitizing both snail hosts revealed significant differences related to the overall prevalence and the prevalence contributed by birds in the snails collected from reefs. These results support the idea that the reefs may increase the number of links between intermediate and definitive hosts of digeneans, facilitating parasite transmission only when the aggregates of F. enigmaticus become the unique habitat of the snail host. This first report of an exotic species acting as facilitator of parasite transmission in an estuarine area highlights the importance of analysing the effects of the assimilation process of exotic species by recently colonized environments (including the possible effects on parasite transmission).

Abstract: In a study of the benthic polychaete fauna of the southern Gulf of Mexico and the Caribbean Sea, several specimens of the terebellid polychaete Scionides reticulata (Ehlers) were found to host endoparasitic copepods that represent an undescribed species of the rare cyclopoid genus Entobius Dogiel, 1948. The new species, E. scionides sp. n., can be distinguished from its congeners by a combination of characters including a genital region without constrictions, three-segmented antennules, a reduced antenna with a blunt terminal process, reduced ornamentation of endopods of legs 1-4 and its relatively small size (2.3-2.7 mm). It is the smallest species of the genus. Comments on immature females are also provided, but males of this species remain unknown. It has a high prevalence (53%) in populations of the terebellid S. reticulata in the southern Gulf of Mexico, but it is absent from the Caribbean. This is the first occurrence of this copepod genus in the Americas. The finding of the new species of Entobius in S. reticulata confirms the strict specificity of most members of the genus and expands the host range of this copepod genus. A key for the identification of the species of Entobius is provided.

Specimens of a deep-living sabellid polychaete of the genus Perkinsiana Knight-Jones dredged in Antarctic waters were found to be parasitised by an undescribed species of the cyclopoid copepod genus Sabellacheres M. Sars, 1862. Specimens of both sexes were studied using light microscopy and SEM, and compared with its congeners. The new species, Sabellacheres antarcticus n. sp., can be distinguished from its congeners by the shape and proportions of the body and brood-pouch, its 4-segmented antennae, the shape and length of the distal process of the second antennular segment, the position of leg 3, and the structure of the male maxilliped. This is only the second record of a species of this genus from the southern hemisphere. The new species was found on a single host species, as is typical for most species of Sabellacheres. A key for the identification of both sexes of the species of Sabellacheres is included.

The ultrastructure of the spores and developmental stages of Ellipsomyxa mugilis in Nereis diversicolor were studied by transmission electron microscopy. The ultrastructure features and the developmental stages show many similarities with the general pattern described for other actinospores. However, several new features are definitely worth noting. For example, tetranucleated cells precede the formation of the initial pansporocyst, which preserves the 2 original enveloping cells until the end of sporogony. In the initial stages of sporogony, the future sporoplasm cell acquires the first secondary cell by an engulfment process. In the final stage of sporogony, spores are formed by a sporoplasm with 2 secondary cells and 1 somatic nucleus, and the polar capsule has a polar filament with a helicoidal arrangement possessing 7-8 coils.