Long-term survey discloses a shift in the dynamics pattern of an emerging disease of cockles Cerastoderma edule, marteiliosis, and raises hypotheses to explain it.

Drivers of marine disease outbreaks are poorly understood in spite of their growing impact. We present here results from a unique case study examining how cockles Cerastoderma edule have responded to the introduction of the novel protistan Marteilia cochillia, which led in 2012 to cockle fishery collapse in Galician rias. Based on intensive survey for eight years (2011-2019) of two affected shellfish beds, inner and outer in the Ría de Arousa, involving monthly evaluation of cockle health status and estimation of mortality, detailed information is provided of the declining impact of marteiliosis over a wild cockle population with evidence suggesting its increasing resistance.

Decline of Marteilia cochillia in Ría de Arousa may be due to increased resistance in host Cerastoderma edule.

A huge, unprecedented mortality of cockle Cerastoderma edule caused by the protist Marteilia cochillia, which had never before been detected in Galicia (NW Spain), brought on a cockle fishery collapse in the Ría de Arousa (Galicia) in 2012. Since then, the disease dynamic pattern in the shellfish bed of Lombos do Ulla (at the inner area of that ria) involved an overwhelming annual wave of infections and subsequent cockle mass mortality that caused the near extinction of every cohort recruited to that bed. However, a pattern shift was detected among wild cohorts recruiting since 2016, with progressive declines of marteiliosis prevalence and increments in cockle survival.

Discovery of the parasite Marteilia cocosarum sp. nov. In common cockle (Cerastoderma edule) fisheries in Wales, UK and its comparison with Marteilia cochillia.

Diseases of bivalve molluscs caused by paramyxid parasites of the genus Marteilia have been linked to mass mortalities and the collapse of commercially important shellfish populations. Until recently, no Marteilia spp. have been detected in common cockle (Cerastoderma edule) populations in the British Isles.

Cosmopolitan Distribution of -Like Organisms and Other Intracellular Microcolonies of Bacteria Causing Infection in Marine Mollusks.

Intracellular microcolonies of bacteria (IMC), in some cases developing large extracellular cysts (bacterial aggregates), infecting primarily gill and digestive gland, have been historically reported in a wide diversity of economically important mollusk species worldwide, sometimes associated with severe lesions and mass mortality events. As an effort to characterize those organisms, traditionally named as -like organisms, 1950 specimens comprising 22 mollusk species were collected over 10 countries and after histology examination, a selection of 99 samples involving 20 species were subjected to 16S rRNA gene amplicon sequencing. Phylogenetic analysis showed sequences in all the mollusk species analyzed.

Marteilia cochillia is released into seawater via cockle Cerastoderma edule faeces.

Outbreaks of Marteilia cochillia have caused massive mortalities of common cockle, Cerastoderma edule, in some natural beds in Galicia (NW Spain) since 2012. The life cycle of Marteilia spp. is still unresolved and the most accepted hypothesis suggests that an additional host is involved.

Temporal dynamics of infection of cockles Cerastoderma edule with the protistan parasite Minchinia tapetis (Rhizaria: Haplosporida) in Galicia (NW Spain).

Uninucleate and binucleate cells and multinucleate plasmodia of a haplosporidan-like protist associated with heavy haemocytic infiltration were observed in histological sections of cockles, Cerastoderma edule, from the Ría de Noia (Galicia, NW Spain) in the course of a cockle health surveillance programme. Molecular assays provided identification of this protist as Minchinia tapetis, which we thus record from a new host. Prevalence of M.

Marteilia refringens and Marteilia pararefringens sp. nov. are distinct parasites of bivalves and have different European distributions.

Marteilia refringens causes marteiliosis in oysters, mussels and other bivalve molluscs. This parasite previously comprised two species, M. refringens and Marteilia maurini, which were synonymized in 2007 and subsequently referred to as M.

A Minchinia mercenariae-like parasite infects cockles Cerastoderma edule in Galicia (NW Spain).

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni- and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad.

Parasites, pathological conditions and resistance to Marteilia cochillia in lagoon cockle Cerastoderma glaucum from Galicia (NW Spain).

A histopathological survey revealed parasites and pathological conditions affecting lagoon cockles Cerastoderma glaucum along the Galician coast; serious pathological threats were not detected because the potentially pathogenic conditions (infections with a Marteilia-like parasite and bucephalid sporocysts, disseminated neoplasia and a condition involving large foci of heavy haemocytic reaction) were rare, while more prevalent parasites had negligible or limited pathogeny. Considering that C. edule and C.

Widespread transmission of independent cancer lineages within multiple bivalve species.

Most cancers arise from oncogenic changes in the genomes of somatic cells, and while the cells may migrate by metastasis, they remain within that single individual. Natural transmission of cancer cells from one individual to another has been observed in two distinct cases in mammals (Tasmanian devils and dogs), but these are generally considered to be rare exceptions in nature. The discovery of transmissible cancer in soft-shell clams (Mya arenaria) suggested that this phenomenon might be more widespread.

Long-term epidemiological study of disseminated neoplasia of cockles in Galicia (NW Spain): temporal patterns at individual and population levels, influence of environmental and cockle-based factors and lethality.

The dynamics of disseminated neoplasia (DN) affecting cockles Cerastoderma edule (L.) in Galicia was addressed at individual and population levels. Early stage of DN was characterized by isolated neoplastic cells occurring in branchial vessels or in the connective tissue of gills, mantle, gonad or digestive gland.

Neoplastic diseases of marine bivalves.

Two types of prevalent neoplastic diseases have been described in marine bivalves of commercial interest: disseminated neoplasia (DN) and gonadal neoplasia. The first involves the excessive proliferation of abnormal cells with unknown origin (probably of hemic source in some cases/species), disseminating through the circulatory system and infiltrating the connective tissue of various organs; the second consists of an abnormal proliferation of undifferentiated germinal cells of the gonad. These two types of bivalve neoplasia fit the criteria of malignant tumors: pleomorphic and undifferentiated cells, rapid and invasive growth, abundance of mitotic figures, metastasis and progressive development often resulting in the death of the affected individual.

Oyster parasites Bonamia ostreae and B. exitiosa co-occur in Galicia (NW Spain): spatial distribution and infection dynamics.

Bonamiosis constrains the flat oyster industry worldwide. The protistan species Bonamia ostreae had been considered solely responsible for this disease in Europe, but the report of B. exitiosa infecting Ostrea edulis 5 yr ago in Galicia (NW Spain), and subsequently in other European countries, raised the question of the relevance of each species in bonamiosis.

Cockle Cerastoderma edule fishery collapse in the Ría de Arousa (Galicia, NW Spain) associated with the protistan parasite Marteilia cochillia.

The highest shellfishery catch in Galicia (NW Spain) has traditionally been cockle Cerastoderma edule. The shellfish bed located in Lombos do Ulla (Ría de Arousa) used to be among those with the highest cockle production; however, cockle mortality rate increased sharply in this bed in April 2012, reaching 100% in May 2012. Salinity and temperature were discounted as potential causes of the mortality.

Cloning and characterization of neoplasia-related genes in flat oyster Ostrea edulis.

Bonamiosis and disseminated neoplasia (DN) are the most important diseases affecting cultured flat oysters Ostrea edulis in Galicia (NW Spain). Previous research using suppresive substraction hybridisation that had been performed addressing the molecular basis of DN as well as the induction and development of the disease in oysters, yielded the whole open reading frame of nine genes: XBP-1, RACK, NDPk, C1qTNF, RPA3, SAP18, p23, ubiquitin and ferritin. These nine genes were characterized in this study.

Molecular characterisation of TNF, AIF, dermatopontin and VAMP genes of the flat oyster Ostrea edulis and analysis of their modulation by diseases.

Bonamiosis and disseminated neoplasia (DN) are the most important diseases affecting cultured flat oysters (Ostrea edulis) in Galicia (NW Spain). Previous research of the response of O. edulis against bonamiosis by suppression subtractive hybridisation yielded a partial expressed sequence tag of tumour necrosis factor (TNF) and allograft inflammatory factor (AIF), as well as the whole open reading frame for dermatopontin and vesicle-associated membrane (VAMP).

Biomarkers and transcription levels of cancer-related genes in cockles Cerastoderma edule from Galicia (NW Spain) with disseminated neoplasia.

Disseminated neoplasia (DN) is a pathological condition reported for several species of marine bivalves throughout the world, but its aetiology has not yet been satisfactorily explained. It has been suggested that chemical contamination could be a factor contributing to neoplasia. The aim of the present study was to compare cell and tissue biomarkers and the transcription level of cancer-related genes in cockles (Cerastoderma edule) affected by DN with those of healthy cockles in relation to chemical contaminant burdens.

Disseminated neoplasia causes changes in ploidy and apoptosis frequency in cockles Cerastoderma edule.

A proliferative disease, usually referred as disseminated neoplasia (DN), shows high prevalence in some cockle Cerastoderma edule beds of Galicia (NW Spain). Chromosome counts, examination of chromosome morphology, DNA quantification by flow cytometry and estimation of apoptosis frequency by TUNEL assay and flow cytometry were performed in cockles with different DN severity. Metaphases obtained from gills of DN-affected cockles displayed a chromosome number ranging from 41 to 145, while normal number is 38; changes in chromosome morphology were also evident, with numerous microchromosomes occurring.

Disseminated neoplasia in clams Venerupis aurea from Galicia (NW Spain): histopathology, ultrastructure and ploidy of the neoplastic cells, and comparison of diagnostic procedures.

This study reports evidence of a neoplastic disorder in the clam Venerupis aurea. In the first stage of the disease, masses of neoplastic cells were mainly observed in connective tissue of gills. These masses of neoplastic cells appeared more compact than in cases of disseminated neoplasia of other bivalve molluscs.

Identification of relevant cancer related-genes in the flat oyster Ostrea edulis affected by disseminated neoplasia.

Disseminated neoplasia (DN), an oyster disease resembling leukaemia, has been reported in a number of species of marine bivalve molluscs. The disease is characterised by a proliferation of abnormal circulating cells of unknown origin resulting in the invasion of tissues and organs, frequently with a fatal end of the affected individuals. To obtain a more comprehensive view of bivalve cancer processes, suppressive subtracted hybridisation (SSH) and quantitative RT-PCR (q-PCR) approaches were combined to investigate changes in the transcriptome of Ostrea edulis haemolymph cells associated to DN.

Disseminated neoplasia in cockles Cerastoderma edule: ultrastructural characterisation and effects on haemolymph cell parameters.

Disseminated neoplasia (DN) has been detected in cockles from various beds in Galicia (NW Spain). A study was performed to characterise cockle neoplastic cell ultrastructure and to evaluate the effect of this disease at different severity stages on various haemolymph cell parameters. Examination of cockle neoplastic cells with transmission electron microscopy (TEM) showed round shapes and a lack of pseudopods, a high nucleus:cytoplasm diameter ratio, Golgi complexes, abundant mitochondria, ribosomes, and numerous endoplasmic reticulum tubes and electron-lucent vesicles.

Expression of mutant protein p53 and Hsp70 and Hsp90 chaperones in cockles Cerastoderma edule affected by neoplasia.

High prevalence of disseminated neoplasia has been found in cockles Cerastoderma edule of Galicia (NW Spain). Disseminated neoplasia has been associated with high mortalities of various bivalve species. In vertebrates, proteins such as p53 and heat shock proteins (HSPs) play important roles in carcinogenesis.

Evidence of retroviral etiology for disseminated neoplasia in cockles (Cerastoderma edule).

Epizootiologic outbreaks of disseminated neoplasia have been reported in association with massive mortalities of various bivalve species. In cockles, Cerastoderma edule, this pathological condition was described in Ireland and France. Since 1997, different populations affected by this pathology have been detected in Galicia (NW Spain).