Living systems exert exquisite control on all aspects of biomineral production and organic components, including proteins, are essential to this biological control. The protein-rich extrapallial (EP) fluid of bivalve molluscs is a strong candidate for the source of such proteins. Differences in calcium carbonate polymorphs between Modiolus modiolus and Mytilus edulis are concurrent with differences in EP fluid protein profiles. In conjunction with this biological control is the environmental influence which is interpreted using proxies such as δ18O to determine the history of ambient seawater temperature. In the horse mussel, Modiolus modiolus, the difference in oxygen isotope fractionation in the nacreous aragonite and the prismatic aragonite layer results in respective δ18O values of 2.1±0.2% and 2.5±0.2%. These δ18O values result in estimates of ambient seawater of 12.1±0.6°C and 10.2±0.6°C for nacreous and prismatic aragonite, respectively. Electron backscatter diffraction is used here to determine the crystallographic orientation at high spatial resolution, allowing the measurements of stable isotopes to be accurately mapped in terms of shell architecture. These preliminary data suggest that it is essential to account for both polymorph and crystal habit when deciphering ambient seawater temperature using δ18O as a proxy.

We report the isolation, development and multiplex optimisation of 12 new microsatelliteloci for the great scallop, Pecten maximus. Diversity was moderate tohigh, with number of alleles ranging from 4 to 20 and observed heterozygosity between 0.28and 0.88. Progeny produced in a commercial hatchery was used to test locus power forparentage assignment. The percentage of offspring that was unambiguously assigned to aunique pair of parents was 97% (software package CERVUS-COLONY). Parentage assignmentrevealed that 22% of the studied progeny resulted from unplanned crosses. Effectivepopulation size of the study progeny was also estimated. Our study illustrates the powerof microsatellites for the genetic monitoring of hatchery-produced great scallops.

The mussel (Mytilus edulis) is successfully grown in aquaculture inEurope. Mussels are usually sold live and wet storage is becoming more common. In thisstudy, oxygen demand and ammonia excretion were assessed at increasing water temperaturesand different post-harvest situations. This information was used to calculate minimal flowrates per unit biomass of live mussels sufficient to keep oxygen above 5 mg L-1or 50% saturation, and avoid accumulation of ammonia in commercial wet storage. In thisstudy, rope-grown mussels were kept out of water for 8 h to simulate harvesting conditionsand then re-immersed in holding tanks at 5, 10 and 15 °C. Oxygen and ammoniaconcentrations were measured immediately after mussels were re-immersed (0 h), after 6 hand then every day for 3 days. After this period, the mussels were again kept out of waterfor 48 h to simulate long-distance transport and once again re-immersed for the sameperiod as before. In the first 6 h after re-immersion, the oxygen consumption was between7.5 and 12.2 μmol g-1 h-1 (dry flesh) and afterthis period it decreased to a standard level of around 4.0 ± 0.9 μmolg-1 h-1 and was independent of temperature. There were no majordifferences in oxygen consumption between mussels having spent 8 and 48 h out of water atany of the subsequent water temperatures used for re-immersion. In contrast, the ammoniaexcretion showed greater differences according to temperature and time out of water.Ammonia excretion was lowest at 5 °C (<0.01 μmol g-1h-1). The implications of these results for the industry and authorities arediscussed considering the water flow rate, depuration specifications and energy costs.

Among the potential biotic factors affecting population dynamics, parasitism has received relatively little attention. The purpose of this study was to inventory marine bivalve parasites and to investigate relations between different parasite communities. Five intertidal stations along the French Atlantic shore were studied between Brittany and Arcachon Bay. Two bivalves (the edible cockle, Cerastoderma edule, and the Manila clam, Ruditapes philippinarum) were sampled and examined. The parasites included a bacterium (Vibrio tapetis), a protozoan (Perkinsus sp.), and digenetic trematode metacercariae (10 species). Perkinsus sp. prevalence and density in clams were higher than those measured in cockles (30 250 vs. 36 cells g−1 of gill wet weight, respectively) while digeneans were more common in cockles (46 metacercariae per cockle host vs. 1 per clam host). Distributions of digeneans and Perkinsus sp. were similar along the Atlantic shore. However, at each sampling station and at the individual scale, no correlation between Perkinsus sp. and digenean abundance was detected. These results suggest different ecological niches used by these two parasites within a community of bivalves but a similar response to environmental factors such as temperature and salinity. Vibrio tapetis was found at relatively high prevalence in all stations for both bivalve species (from 17% to 43% in cockles and from 23% to 50% in clams), but was associated with a low prevalence of Brown Ring Disease (BRD), a shell disease caused by this pathogen. No statistically significant relationship of these parasitic bacteria with trematodes and Perkinsus sp. was evidenced in the present study.

Brown ring disease (BRD) in Ruditapes philippinarum and Ruditapes decussatus is a shell disease caused by Vibrio tapetis. This disease has begun in 1987 in clams beds in Brittany (France) and then has spread along the European Atlantic coast. Since about fifteen years, research on BRD has progress a lot and the purpose of this review is to give a short description of BRD in clams in retrospect and in addition of recent and pertinent results. Diagnosis including isolation, biochemical, serological and molecular characterization has been developed to identify and detect the pathogen. Therefore, Vibrio tapetis-like strains has been detected in other host specie, in cultured fishes during mortalities, such as the wrasse, Symphodus melops in Norway and the halibut, Hippoglossus hippoglossus in Scotland. Mechanisms of host-pathogen interactions modulated by environmental factors were studied using in vivo bacterial challenge and in vitro bio-assays. According to these studies, adherence and cytotoxic factors have been yet identified as virulence factors; identification and characterization of virulence genes are in progress. Field and experimental studies confirmed the significant effect of temperature on the development of BRD and on clam defense related activities. A significant increase in temperature over 21 °C may have a preventive effect on the development of the disease.

The main microbial diseases affecting marine cultured bivalves have been revised on the basis of the etiologic agents, pathogenesis and pathogenicity. Several recent bivalve-interaction models have been studied, including Pecten larvae-Vibrio pectinicida, brown ring disease, juvenile oyster disease, Pacific oyster nocardiosis and summer mortalities of oysters. In addition, the taxonomy and phylogeny of new potential bivalve pathogens and their virulence factors have been established. Facing the difficulty of identifying bacterial strains associated with molluscan diseases (mainly vibriosis), polyphasic approaches have been developed to correlate the phenotype and genotype of potential pathogens. By evaluating likely virulence mechanisms, developing biotests to screen virulent strains and characterising the genes implicated in pathogenesis, a new generation of diagnostic tools, based on potential virulence, will be developed. Acquisition of pertinent diagnostic tools will be of major benefit in disease management, health surveillance and monitoring will contribute to maintaining sustainable aquaculture industries.

The Antarctic bivalve Yoldia eightsi (Couthouy) has been assessed as a monitor species in the vicinity of a research station at Signy Island. For animals of comparable age n-alkane loading was highest at the site closest to the station. The character of the n-alkane pool of Yoldia varied with distance from the station and also differed from that of the sediment. The polycyclic aromatic hydrocarbon (PAH) loading was highest 250 m from the station. Loading of n-alkanes and PAH varied through the year; the lowest levels of n-alkanes were in October and the highest in April. The maximum for PAH was in October. Hydrocarbons increased with age for animals from five to 50 years old; 100–2000 ng animal−1 for n-alkanes and 1–21 ng animal−1 for PAH. Tissue concentrations decreased with age; 6000–500 μg kg1 for n-alkanes and 25–5 μg kg−1 for PAH. Several biogenic branched chain alkenes were also present; one C25.3 isomer was predominant at concentrations up to 290 μg kg−1 in mature animals (40% of the aliphatic fraction). Accumulation was not constant with age and concentrations reflected both anthropogenic and biogenic hydrocarbons in the marine environment. Seasonal variation in PAH load suggested the major proportion of accumulation over the year was only temporary. Yoldia eightsi were not suitable to monitor low level contamination such as that at Signy Island and past incidents were not resolved from the background input.

The Foulden Site of Special Scientific Interest is one of the few Cementstone Group localities that yields significant fauna and flora. Excavations in 1980 and 1981 removed a 1·3 m2 slab of the Fish Bed for laboratory study of the vertical and spatial distribution of the biota. Layer by layer analysis revealed an almost mutually exclusive relationship between the vertical distribution of the palaeoniscoid fishes and malacostracan crustaceans, as well as a horizon crowded with juvenile acanthodians. Elongate elements of this biota showed slight preferred orientations at that prolific horizon. Some 27 m of strata including the Fish Bed, Plant Bed and Shell Bed are recorded in detail, and their biota noted. Interim results of work on the main groups collected are summarised in associated papers in this part of Transactions. Brief reports are given here on the euryhaline marine bivalve mollusc Modiolus latus (Portlock), a rare durophagous bradyodont shark tooth and an Eogyrinus-like amphibian scute.