Histopathological survey of putative parasites and pathogens in non-native slipper limpets Crepidula fornicata.

Two populations of the invasive slipper limpet Crepidula fornicata were sampled in Swansea Bay and Milford Haven, Wales, UK, to determine the presence of putative pathogens and parasites known to affect co-located commercially important shellfish (e.g. oysters). A multi-resource screen, including molecular and histological diagnoses, was used to assess 1800 individuals over 12 mo for microparasites, notably haplosporidians, microsporidians and paramyxids. Although initial PCR-based methods suggested the presence of these microparasites, there was no evidence of infection when assessed histologically, or when all PCR amplicons (n = 294) were sequenced. Whole tissue histology of 305 individuals revealed turbellarians in the lumen of the alimentary canal, in addition to unusual cells of unknown origin in the epithelial lining. In total, 6% of C. fornicata screened histologically harboured turbellarians, and approximately 33% contained the abnormal cells-so named due to their altered cytoplasm and condensed chromatin. A small number of limpets (~1%) also had pathologies in the digestive gland including tubule necrosis, haemocytic infiltration and sloughed cells in the tubule lumen. Overall, these data suggest that C. fornicata are not susceptible to substantive infections by microparasites outside of their native range, which may contribute in part to their invasion success.

Invasive slipper limpets Crepidula fornicata are hosts for sterilizing digenean parasites.

Invasion and spread of alien species can drive ecosystem changes, such as, the dynamics of infectious diseases. The non-native, marine gastropod Crepidula fornicata has become established across European coastlines over the last century, but there remains little insight into its disease carrying capacity and potential role as a source/sink of parasites. To address this knowledge gap, we surveyed limpets from two sites in South Wales, UK for signatures of disease/pathology using polymerase chain reaction-based methods (haemolymph) and histology (solid tissue). We encountered trematode-like parasites in ~1% individuals (5 out of 462). Three limpets displayed gross damage in the gonad, i.e. castration, and encysted metacercariae were found in the muscle of two other individuals. On the basis of 28S rDNA and internal transcribed spacer 2 genomic targets, we identified the gonad-infecting trematodes as members of the family Microphallidae ­ putative novel species related to the genus Longiductotrema. Earlier reports suggest that C. fornicata is not a host for trematode parasites in either its native or alien range but may act as a sink due to its filter feeding lifestyle. We provide clear evidence that C. fornicata is parasitized by at least one trematode species at two sites in Wales, UK, and likely act as a spillback or accidental host among native littorinids.

Hematodinium sp. infection does not drive collateral disease contraction in a crustacean host.

Host, pathogen, and environment are determinants of the disease triangle, the latter being a key driver of disease outcomes and persistence within a community. The dinoflagellate genus Hematodinium is detrimental to crustaceans globally - considered to suppress the innate defences of hosts, making them more susceptible to co-infections. Evidence supporting immune suppression is largely anecdotal and sourced from diffuse accounts of compromised decapods. We used a population of shore crabs (Carcinus maenas), where Hematodinium sp. is endemic, to determine the extent of collateral infections across two distinct environments (open-water, semi-closed dock). Using a multi-resource approach (PCR, histology, haematology, population genetics, eDNA), we identified 162 Hematodinium-positive crabs and size/sex-matched these to 162 Hematodinium-free crabs out of 1191 analysed. Crabs were interrogated for known additional disease-causing agents; haplosporidians, microsporidians, mikrocytids, Vibrio spp., fungi, Sacculina, trematodes, and haemolymph bacterial loads. We found no significant differences in occurrence, severity, or composition of collateral infections between Hematodinium-positive and Hematodinium-free crabs at either site, but crucially, we recorded site-restricted blends of pathogens. We found no gross signs of host cell immune reactivity towards Hematodinium in the presence or absence of other pathogens. We contend Hematodinium sp. is not the proximal driver of co-infections in shore crabs, which suggests an evolutionary drive towards latency in this environmentally plastic host.

Mycosis is a Disease State Encountered Rarely in Shore Crabs, Carcinus maenas.

There is a paucity of knowledge regarding the diversity and impact(s) of disease-causing fungi in marine animals, especially shellfish. In efforts to address this knowledge gap for the shore crab Carcinus maenas, a year-long disease screen was carried out across two sites in Swansea Bay (Wales, UK) with a view to characterising putative fungal infections. Crabs were sampled between November 2017 and October 2018, and screened systematically for disease signatures using haemolymph (blood) preparations, targeted PCR and tissue histopathology. Strikingly, mycosis was confirmed in ~0.4% of total crabs tested (n = 1191) and restricted to one location only (Mumbles Pier). Clinical infections were observed in four out of four infected crabs. In these animals, the gills and hepatopancreas were congested with fungal morphotypes. In addition, some evidence indicates haemocyte (immune cell) reactivity toward the fungi. Phylogenetic placement of the partial internal transcribed spacer (ITS1) gene regions amplified from three mycotic crabs revealed the causative agent to be related to hypocrealean fungi, thereby representing a novel species.

Diagnosis and prevalence of two new species of haplosporidians infecting shore crabs Carcinus maenas: Haplosporidium carcini n. sp., and H. cranc n. sp.

This study provides a morphological and phylogenetic characterization of two novel species of the order Haplosporida (Haplosporidium carcini n. sp., and H. cranc n. sp.) infecting the common shore crab Carcinus maenas collected at one location in Swansea Bay, South Wales, UK. Both parasites were observed in the haemolymph, gills and hepatopancreas. The prevalence of clinical infections (i.e. parasites seen directly in fresh haemolymph preparations) was low, at ~1%, whereas subclinical levels, detected by polymerase chain reaction, were slightly higher at ~2%. Although no spores were found in any of the infected crabs examined histologically (n = 334), the morphology of monokaryotic and dikaryotic unicellular stages of the parasites enabled differentiation between the two new species. Phylogenetic analyses of the new species based on the small subunit (SSU) rDNA gene placed H. cranc in a clade of otherwise uncharacterized environmental sequences from marine samples, and H. carcini in a clade with other crustacean-associated lineages.

Prevalence and histopathology of the parasitic barnacle, Sacculina carcini in shore crabs, Carcinus maenas.

Sacculina carcini is a common parasite of the European shore crab, Carcinus maenas. Following successful penetration of the host, numerous rootlets are formed that permeate through the hosts' tissues. Ultimately, these form an externa that houses the developing nauplii larvae of the parasite. Most studies have quantified levels of infection by counting the presence of reproductive externae and their breakdown structures, called scars. However, the diagnosis of the disease based only on external features may lead to underreporting the prevalence of the parasite. In the current study, we examined the presence and severity of S. carcini in C. maenas (n = 221) in the Prince of Wales Dock, South Wales, U.K. using a range of diagnostic approaches to give an accurate representation of temporal dynamics of infection. Parasitized crabs were found with a mean prevalence of 24% as determined by histological examination of the hepatopancreas. However, the prevalence of S. carcini based on the presence of externae and scars was only 6.3% and 1.8%, respectively. Overall, parasitism was associated with smaller crabs, crabs later in the moulting cycle that were orange in colour (as opposed to green or yellow), and those with a higher number of bacteria in the haemolymph. Interestingly, only 7.5% of infected crabs showed evidence of distinct host (cellular) response to the presence of rootlets in the hepatopancreas.

Demographic reconstruction from ancient DNA supports rapid extinction of the great auk.

The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.

Spatial and temporal disease dynamics of the parasite Hematodinium sp. in shore crabs, Carcinus maenas.

BACKGROUND: The parasitic dinoflagellates of the genus Hematodinium represent the causative agent of so-called bitter or pink crab disease in a broad range of shellfish taxa. Outbreaks of Hematodinium-associated disease can devastate local fishing and aquaculture efforts. The goal of our study was to examine the potential role of the common shore (green) crab Carcinus maenas as a reservoir for Hematodinium. Carcinus maenas is native to all shores of the UK and Ireland and the North East Atlantic but has been introduced to, and subsequently invaded waters of, the USA, South Africa and Australia. This species is notable for its capacity to harbour a range of micro- and macro-parasites, and therefore may act as a vector for disease transfer. METHODS: Over a 12-month period, we interrogated 1191 crabs across two distinct locations (intertidal pier, semi-closed dock) in Swansea Bay (Wales, UK) for the presence and severity of Hematodinium in the haemolymph, gills, hepatopancreas and surrounding waters (eDNA) using PCR-based methods, haemolymph preparations and histopathology. RESULTS: Overall, 13.6% were Hematodinium-positive via PCR and confirmed via tissue examination. Only a small difference was observed between locations with 14.4% and 12.8% infected crabs in the Dock and Pier, respectively. Binomial logistic regression models revealed seasonality (P < 0.002) and sex (P < 0.001) to be significant factors in Hematodinium detection with peak infection recorded in spring (March to May). Male crabs overall were more likely to be infected. Phylogenetic analyses of the partial ITS and 18S rRNA gene regions of Hematodinium amplified from crabs determined the causative agent to be the host generalist Hematodinium sp., which blights several valuable crustaceans in the UK alone, including edible crabs (Cancer pagurus) and langoustines (Nephrops norvegicus). CONCLUSIONS: Shore crabs were infected with the host generalist parasite Hematodinium sp. in each location tested, thereby enabling the parasite to persist in an environment shared with commercially important shellfish.

Mitogenomic evidence of close relationships between New Zealand's extinct giant raptors and small-sized Australian sister-taxa.

Prior to human arrival in the 13th century, two large birds of prey were the top predators in New Zealand. In the absence of non-volant mammals, the extinct Haast's eagle (Hieraaetus moorei), the largest eagle in the world, and the extinct Eyles' harrier (Circus teauteensis) the largest harrier in the world, had filled ecological niches that are on other landmasses occupied by animals such as large cats or canines. The evolutionary and biogeographic history of these island giants has long been a mystery. Here we reconstruct the origin and evolution of New Zealand's giant raptors using complete mitochondrial genome data. We show that both Eyles' harrier and Haast's eagle diverged from much smaller, open land adapted Australasian relatives in the late Pliocene to early Pleistocene. These events coincided with the development of open habitat in the previously densely forested islands of New Zealand. Our study provides evidence of rapid evolution of island gigantism in New Zealand's extinct birds of prey. Early Pleistocene climate and environmental changes were likely to have triggered the establishment of Australian raptors into New Zealand. Our results shed light on the evolution of two of the most impressive cases of island gigantism in the world.

An ?Aukward' Tale: A Genetic Approach to Discover the Whereabouts of the Last Great Auks.

One hundred and seventy-three years ago, the last two Great Auks, Pinguinusimpennis, ever reliably seen were killed. Their internal organs can be found in the collections of the Natural History Museum of Denmark, but the location of their skins has remained a mystery. In 1999, Great Auk expert Errol Fuller proposed a list of five potential candidate skins in museums around the world. Here we take a palaeogenomic approach to test which-if any-of Fuller's candidate skins likely belong to either of the two birds. Using mitochondrial genomes from the five candidate birds (housed in museums in Bremen, Brussels, Kiel, Los Angeles, and Oldenburg) and the organs of the last two known individuals, we partially solve the mystery that has been on Great Auk scholars' minds for generations and make new suggestions as to the whereabouts of the still-missing skin from these two birds.

Circulating T follicular helper cell and regulatory T cell frequencies are influenced by B cell depletion in patients with granulomatosis with polyangiitis.

OBJECTIVE: Granulomatosis with polyangiitis (GPA) is a rare and sometimes fatal systemic autoimmune disease. ANCAs specific for PR3 are associated with GPA. Remission in GPA can be achieved through B cell depletion (BCD) therapy. Our aim was to understand whether the frequencies of T cell subsets are influenced by BCD. METHODS: The frequencies of circulating T follicular helper cells (cTFHs) and regulatory T cells (Tregs) from 36 GPA patients including 11 rituximab-treated patients and 10 healthy controls were studied by flow cytometry. The functional capacity of Tregs was assessed by in vitro co-culture assays. RESULTS: We observed an increased frequency of cTFHs and a reduced frequency of antigen-experienced Tregs in peripheral blood from GPA patients on conventional therapies but not in those treated with rituximab compared with healthy controls. Furthermore, the ratio of cTFHs to Tregs was significantly higher in GPA patients on conventional therapies than in GPA patients treated with rituximab who were clinically improved or controls. Whereas Tregs were numerically reduced in GPA patients on conventional therapy, the suppressive capacity of Tregs on a per cell basis was not significantly altered in these individuals. CONCLUSION: Our study illustrated increased cTFHs with decreased antigen-experienced Tregs in GPA patients on conventional therapies, but in B cell-depleted patients the levels of cTFHs and Tregs were similar to healthy controls. The negative correlation between cTFHs and Tregs implies the balance between T cell subsets and its B cell dependence impact on disease activity in GPA.

Residents' perceptions and experiences of social interaction and participation in leisure activities in residential aged care.

Social interaction and participation in leisure activities are positively related to the health and well-being of elderly people. The main focus of this exploratory study was to investigate elderly peoples' perceptions and experiences of social interaction and leisure activities living in a residential aged care (RAC) facility. Six residents were interviewed. Themes emerging from discussions about their social interactions included: importance of family, fostering friendships with fellow residents, placement at dining room tables, multiple communication methods, and minimal social isolation and boredom. Excursions away from the RAC facility were favourite activities. Participants commonly were involved in leisure activities to be socially connected. Poor health, family, the RAC facility, staffing, transportation, and geography influenced their social interaction and participation in leisure activities. The use of new technologies and creative problem solving with staff are ways in which residents could enhance their social lives and remain engaged in leisure activities.