Anfipodoek, mundu osoko krustazeo-talde ugarienetako eta anitzenetako bat osatzen dute. Duten garrantzi ekologikoa, nonahikotasuna, tamaina txikia eta hainbat substantzia toxikorekiko sentikortasuna dela eta, kutsaduraren efektuen zentinela gisa erabili ohi dira. Anfipodoak ere, izaki gehienak bezala, birusez, bakterioz eta protistoz parasitatuta egon daitezke. Protistoen artean baditugu mikrosporideoak eta aszetosporak. Horiek, ostalariaren gonadak infekta ditzakete disrupzio endokrino “naturala” eraginez, itsas baliabide biologikoen osasunean eta kutsaduraren efektuen monitorizazio programen gain eragina eduki dezakeena. Hemen, Bizkaiko Golkoko anfipodoak infektatzen dituzten bi protisto leinu hauek ezaugarritu eta berezko agente feminizatzaile gisa duten papera ikertzen dugu.

The velvet swimming crab Necora puber has been fished in Ireland since the early 1980s and contributes significant income to smaller fishing vessels. From 2016 onwards, reduced landings have been reported. We undertook a full pathological investigation of crabs from fishing grounds at 3 sites on the west (Galway), southwest (Castletownbere) and east (Howth) coasts of Ireland. Histopathology, transmission electron microscopy and molecular taxonomic and phylogenetic analyses showed high prevalence and infection level of Paramarteilia canceri, previously only reported from the edible crab Cancer pagurus. This study provides the first molecular data for P. canceri, and shows its phylogenetic position in the order Paramyxida (Rhizaria). Other parasites and symbionts detected in the crabs were also noted, including widespread but low co-infection with Hematodinium sp. and a microsporidian consistent with the Ameson and Nadelspora genera. This is the first histological record of Hematodinium sp. in velvet crabs from Ireland. Four N. puber individuals across 2 sites were co-infected by P. canceri and Hematodinium sp. At one site, 3 velvet crabs infected with P. canceri were co-infected with the first microsporidian recorded from this host; the microsporidian 18S sequence was almost identical to Ameson pulvis, known to infect European shore crabs Carcinus maenas. The study provides a comprehensive phylogenetic analysis of this and all other available Ameson and Nadelspora 18S sequences. Together, these findings provide a baseline for further investigations of N. puber populations along the coast of Ireland.

ABSTRACTThis study provides a morphological, ultrastructural, and phylogenetic characterization of a novel micro-eukaryotic parasite (2.3-2.6 µm) infecting generaEchinogammarusandOrchestia. Longitudinal studies across two years revealed that infection prevalence peaked in late April and May, reaching 64% inEchinogammarussp. and 15% inOrchestiasp., but was seldom detected during the rest of the year. The parasite infected predominantly haemolymph, connective tissue, tegument, and gonad, although hepatopancreas and nervous tissue were affected in heavier infections, eliciting melanization and granuloma formation. Cell division occurred inside walled parasitic cysts, often within host haemocytes, resulting in haemolymph congestion. Small subunit (18S) rRNA gene phylogenies including related environmental sequences placed the novel parasite as a highly divergent lineage within Class Filasterea, which together with Choanoflagellatea represent the closest protistan relatives of Metazoa. We describe the new parasite asTxikispora philomaiosn. sp. n. g., the first confirmed parasitic filasterean lineage, which otherwise comprises four free-living flagellates and a rarely observed endosymbiont of snails. Lineage-specific PCR probing of other hosts and surrounding environments only detectedT. philomaiosin the platyhelminthProcerodessp. We expand the known diversity of Filasterea by targeted searches of metagenomic datasets, resulting in 13 previously unknown lineages from environmental samples.

This study provides morphological, ultrastructural and phylogenetic characterization of 2 novel species of the order Haplosporida (Haplosporidium echinogammari n. sp. and H. orchestiae n. sp.) infecting amphipods of the genera Echinogammarus and Orchestra collected in southwestern England. Both parasites infect the connective tissues associated with the digestive gland and the tegument, and eventually infect other organs causing disruption of host tissues with associated motor impairment and fitness reduction. Prevalence of infection varied with host species, provenance and season, being as high as 75% for individuals of E. marinus infected with H. echinogamman in June (n = 50). Although no spores were found in any of the infected amphipods examined (n = 82), the morphology of monokaryotic and dikaryotic unicellular stages of the parasites enabled differentiation between the 2 new species. Phylogenetic analysis of the new species based on the small subunit (SSU) rDNA gene placed H. echinogammari close to H. diporeiae in haplosporidian lineage C, and H. orchestiae in a novel branch within Haplosporidium. An additional 25 new haplosporidian SSU rDNA sequences were generated from crab, isopod, and crayfish samples, significantly increasing the number of crustacean-derived sequences within Haplosporida, which was previously thought to comprise mostly parasites of molluscs. Phylogenetic analysis of these new sequences revealed 3 clades of primarily crustacean-derived sequences within Haplosporida.

The edible mussel Mytilus edulis is a major aquaculture commodity in Europe, with 168000 t produced in 2015. A number of abundant, well characterised parasites of the species are known, though none are considered to cause significant mortality. Haplosporida (Rhizaria, Endomyxa) is an order of protistan parasites of aquatic invertebrates, the best studied of which are the oyster pathogens Haplosporidium nelsoni and Bonamia ostreae. While these species are well characterised within their hosts, the diversity, life-cycle and modes of transmission of haplosporidians are very poorly understood. Haplosporidian parasites have previously been reported from Mytilus spp., however the majority of these remain uncharacterised, and no molecular data exist for any species. In this study, we identified 2 novel haplosporidian parasites of M. edulis present in the UK. The first of these, observed by light microscopy and in situ hybridisation infecting the gills, mantle, gonadal tubules and digestive connective tissues of mussels in the Tamar estuary, England, we describe as Minchinia mytili on the basis of 18S sequence data. The second, observed infecting a single archive specimen collected in Loch Spelve, Mull, Scotland, infects the foot muscle, gills and connective tissue of the digestive gland. Sequence data places this parasite in an uncharacterised clade of sequences amplified from tropical bivalve guts and water samples, sister to H. nelsoni. Screening of water and sediment samples collected at the sample site in the Tamar estuary revealed the presence of both sequence types in the water column, suggesting host-free or planktonic life stages.

Invasive and non-native species can pose risks to vulnerable ecosystems by co-introducing bacterial pathogens. Alternatively, co-introduced bacterial pathogens may regulate invasive population size and invasive traits. We describe a novel candidate genus and species of bacteria ('Candidatus Aquirickettsiella gammari') found to infect Gammarus fossarum, from its native range in Poland. The bacterium develops intracellularly within the haemocytes and cells of the musculature, hepatopancreas, connective tissues, nervous system and gonad of the host. The developmental cycle of 'Candidatus Aquirickettsiella gammari' includes an elementary body (496.73 nm ± 37.56 nm in length, and 176.89 nm ± 36.29 nm in width), an elliptical, condensed spherical stage (737.61 nm ± 44.51 nm in length and 300.07 nm ± 44.02 nm in width), a divisional stage, and a spherical initial body (1397.59 nm ± 21.26 nm in diameter). We provide a partial genome for 'Candidatus Aquirickettsiella gammari', which clades phylogenetically alongside environmental 16S rRNA sequences from aquatic habitats, and bacterial symbionts from aquatic isopods (Asellus aquaticus), grouping separately from the Rickettsiella, a genus that includes bacterial pathogens of terrestrial insects and isopods. Increased understanding of the diversity of symbionts carried by G. fossarum identifies those that might regulate host population size, or those that could pose a risk to native species in the invasive range. Identification of 'Candidatus Aquirickettsiella gammari' and its potential for adaptation as a biological control agent is explored.

Invasive and non-native species can pose risks to vulnerable ecosystems by co-introducing bacterial pathogens. Alternatively, co-introduced bacterial pathogens may regulate invasive population size and invasive traits. We describe a novel candidate genus and species of bacteria ('Candidatus Aquirickettsiella gammari') found to infect Gammarus fossarum, from its native range in Poland. The bacterium develops intracellularly within the haemocytes and cells of the musculature, hepatopancreas, connective tissues, nervous system and gonad of the host. The developmental cycle of 'Candidatus Aquirickettsiella gammari' includes an elementary body (496.73 nm +/- 37.56 nm in length, and 176.89 nm +/- 36.29 nm in width), an elliptical, condensed spherical stage (737.61 nm +/- 44.51 nm in length and 300.07 nm +/- 44.02 nm in width), a divisional stage, and a spherical initial body (1397.59 nm +/- 21.26 nm in diameter). We provide a partial genome for 'Candidata Aquirickettsiella gammari', which clades phylogenetically alongside environmental 16S rRNA sequences from aquatic habitats, and bacterial symbionts from aquatic isopods (Asellus aquaticus), grouping separately from the Rickettsiella, a genus that includes bacterial pathogens of terrestrial insects and isopods. Increased understanding of the diversity of symbionts carried by G. fossarum identifies those that might regulate host population size, or those that could pose a risk to native species in the invasive range. Identification of 'Candidatus Aquirickettsiella gammari' and its potential for adaptation as a biological control agent is explored.

•A novel candidate genus is erected for aquatic bacterial pathogens.•‘Candidatus Aqurickettsiella gammari’ infects the gammarid host, Gammarus fossarum.•Gammarus fossarum has been recently identified as an invasive species.•This novel bacterium may have a role as a control agent of this invasive host.

Invasive and non-native species can pose risks to vulnerable ecosystems by co-introducing bacterial pathogens. Alternatively, co-introduced bacterial pathogens may regulate invasive population size and invasive traits. We describe a novel candidate genus and species of bacteria ('Candidatus Aquirickettsiella gammari') found to infect Gammarus fossarum, from its native range in Poland. The bacterium develops intracellularly within the haemocytes and cells of the musculature, hepatopancreas, connective tissues, nervous system and gonad of the host. The developmental cycle of 'Candidatus Aquirickettsiella gammari' includes an elementary body (496.73 nm ± 37.56 nm in length, and 176.89 nm ± 36.29 nm in width), an elliptical, condensed spherical stage (737.61 nm ± 44.51 nm in length and 300.07 nm ± 44.02 nm in width), a divisional stage, and a spherical initial body (1397.59 nm ± 21.26 nm in diameter). We provide a partial genome for 'Candidatus Aquirickettsiella gammari', which clades phylogenetically alongside environmental 16S rRNA sequences from aquatic habitats, and bacterial symbionts from aquatic isopods (Asellus aquaticus), grouping separately from the Rickettsiella, a genus that includes bacterial pathogens of terrestrial insects and isopods. Increased understanding of the diversity of symbionts carried by G. fossarum identifies those that might regulate host population size, or those that could pose a risk to native species in the invasive range. Identification of 'Candidatus Aquirickettsiella gammari' and its potential for adaptation as a biological control agent is explored.