Cerastoderma edule is a widely distributed bivalve mollusc, commercially exploited throughout Europe and is also an important food source for birds and crustaceans. Recently, mass surfacing and mortalities of cockles have been observed and reported at sites in Ireland and elsewhere, particularly in the summer months. One such site is Flaxfort Strand, Courtmacsherry Bay, County Cork, Ireland, an important feeding area used by many seabirds during the summer months. For the past few years large numbers of surfaced cockles have been observed at the site in a moribund condition. Samples of cockles from this area were collected over the summer months and their health status assessed. Cockles that had surfaced (moribund) and those still buried in the sediment were quantified and screened: sex, gonadal maturity and size class of cockles were also determined. Disseminated neoplasia and trematodes were observed in screened cockles. The most significant finding during the study was that mortalities and surfacing of cockles was related to a greater incidence of disseminated neoplasia. No neoplasia was observed in the smallest and largest size classes. There was a significantly higher prevalence of neoplasia in moribund cockles than in buried cockles, whereas in both groups a similar concentration of trematode metacercariae was observed in the screened tissues. Also, most of the cockles that had surfaced were either in the process of spawning or were spent. Overall a much larger percentage of moribund cockles exhibited both trematode infections plus neoplasia compared with buried cockles. A combination of the presence of neoplasia and trematodes, along with stress related to spawning, may immunocompromise the cockless, causing the animals to surface and become moribund. KEY WORDS: Cerastoderma edule · Disseminated neoplasia · Trematodes · Surfacing · Gametogenesis Resale or republication not permitted without written consent of the publisherDis Aquat Org 98: [73][74][75][76][77][78][79][80][81][82][83][84] 2012 cockles peaked in 1987 when 106 494 tonnes of cockles were harvested, but decreased to 11 809 tonnes in 2009, the last year for which statistics are available (www.fao.org/fishery/species/3535/en; accessed 6 Sep 2011). Declines in yields can be attributed, in part, to the ban of mechanical cockle fishing in the Wadden Sea (The Netherlands) since 1 January 2005, and to further restrictions on other sand flats such as the Oosterschelde (www.seaonscreen.org/ vleet/content/eng/cockle-fisheries.htm). Yields for cultured C. edule have been variable in the past (www. fao.org/fishery/species/3535/en; accessed 6 Sep 2011).Sexual maturity is usually reached when cockles are 18 mo old or when shell length reaches 15 to 20 mm (Seed & Brown 1977). Seed & Brown (1977) reported that cockles overwinter in a spent condition, but gametogenesis from late autumn/early winter has also been described (Twomey 1987). Gonadal development occurs rapidly once initiated in the spring and spawning begins in late spring/early summe...

Climate variability and the rapid warming of seas undoubtedly have huge ramifications for biological processes such as reproduction. As such, gametogenesis and spawning were investigated at two sites over 200 km apart on the south coast of Ireland in an ecosystem engineer, the common cockle, Cerastoderma edule. Both sites are classed as Special Areas of Conservation (SACs), but are of different water quality. Cerastoderma edule plays a significant biological role by recycling nutrients and affecting sediment structure, with impacts upon assemblage biomass and functional diversity. It plays a key role in food webs, being a common foodstuff for a number of marine birds including the oystercatcher. Both before and during the study (early 2010–mid 2011), Ireland experienced its two coldest winters for 50 years. As the research demonstrated only slight variation in the spawning period between sites, despite site differences in water and environmental quality, temperature and variable climatic conditions were the dominant factor controlling gametogenesis. The most significant finding was that the spawning period in the cockle extended over a greater number of months compared with previous studies and that gametogenesis commenced over winter rather than in spring. Extremely cold winters may impact on the cockle by accelerating and extending the onset and development of gametogenesis. Whether this impact is positive or negative would depend on the associated events occurring on which the cockle depends, that is, presence of primary producers and spring blooms, which would facilitate conversion of this extended gametogenesis into successful recruitment.

The Irish Sea and surrounding regions are a rich source of shellfish production as a result of captive fishing and aquaculture. Key species produced include lobsters (Homarus gammarus), edible crabs (Cancer pagurus), langoustines (Nephrops norvegicus), flat oysters (Ostrea edulis), cockles (Cerestoderma edule) and blue mussels (Mytilus edulis). The role played by infectious disease in limiting the sustainability of the production of these species is largely neglected. This review summarizes our knowledge of the key diseases of commercially important crustaceans and bivalve molluscs and attempts to determine their role in limiting the population of animals available for food production both at present and in the future. It shows that the key diseases threatening the sustainability of shellfish production are bitter crab disease in langoustines and edible crabs, and a wide range of diseases caused by micro- and macro-parasites in some bivalve molluscs including oysters and cockles. Oceanographic models are also employed to predict how changes in climate over the next half century may affect these key diseases and their hosts as found in the Irish Sea. It is concluded that the paucity of information on the potential transfer of some disease agents in pelagic larval stages of hosts and vectors is a major hurdle in predicting how some changes in environmental conditions may influence the prevalence and severity of shellfish diseases in coming years.

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Haplosporidian protist parasites are a major concern for aquatic animal health, as they have been responsible for some of the most significant marine epizootics on record. Despite their impact on food security, aquaculture and ecosystem health, characterizing haplosporidian diversity, distributions and host range remains challenging. In this study, water filtering bivalve species, cockles Cerastoderma edule, mussels Mytilus spp. and Pacific oysters Crassostrea gigas, were screened using molecular genetic assays using deoxyribonucleic acid (DNA) markers for the Haplosporidia small subunit ribosomal deoxyribonucleic acid region. Two Haplosporidia species, both belonging to the Minchinia clade, were detected in C. edule and in the blue mussel Mytilus edulis in a new geographic range for the first time. No haplosporidians were detected in the C. gigas, Mediterranean mussel Mytilus galloprovincialis or Mytilus hybrids. These findings indicate that host selection and partitioning are occurring amongst cohabiting bivalve species. The detection of these Haplosporidia spp. raises questions as to whether they were always present, were introduced unintentionally via aquaculture and or shipping or were naturally introduced via water currents. These findings support an increase in the known diversity of a significant parasite group and highlight that parasite species may be present in marine environments but remain undetected, even in well-studied host species.