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Biodynamic parameters of the ragworm Nereis diversicolor from southern Spain and south England were experimentally derived to assess the inter-population variability of physiological parameters of the bioaccumulation of Ag, Cd and Zn from water and sediment. Although there were some limited variations, these were not consistent with the local metal bioavailability nor with temperature changes. Incorporating the biodynamic parameters into a defined biodynamic model, confirmed that sediment is the predominant source of Cd and Zn accumulated by the worms, accounting in each case for 99% of the overall accumulated metals, whereas the contribution of dissolved Ag to the total accumulated by the worm increased from about 27 to about 53% with increasing dissolved Ag concentration. Standardised values of metal-specific parameters were chosen to generate a generalised model to be extended to N. diversicolor populations across a wide geographical range from western Europe to North Africa. According to the assumptions of this model, predicted steady state concentrations of Cd and Zn in N. diversicolor were overestimated, those of Ag underestimated, but still comparable to independent field measurements. We conclude that species-specific physiological metal bioaccumulation parameters are relatively constant over large geographical distances, and a single generalised biodynamic model does have potential to predict accumulated Ag, Cd and Zn concentrations in this polychaete from a single sediment metal concentration.

Bioaccumulation of cadmium, copper, and zinc was examined in common ragworms Hediste diversicolor from control (Bay of Somme, Blackwater) and metal-rich (Seine estuary, Boulogne harbor, Restronguet Creek) sites in France and the United Kingdom. The degree of exposure in the field was assessed by considering both total concentrations in superficial sediment and the quantities of metals which may be released in vitro at different pH levels. Among the three contaminated sites, release of the three metals was not detectable in Boulogne harbor, in correlation with limited enhancement of the metal concentrations in the common ragworms from this site. Even at those sites where zinc could be released in vitro from the sediment, zinc concentrations were not enhanced in common ragworms, in agreement with previous findings indicating that the body content of this metal is regulated in H. diversicolor. At all the studied sites, bioaccumulated zinc was mainly in cytosolic form. The distribution of cadmium and copper varied according to the origin of the common rag-worms, the insoluble fraction increasing with the degree of contamination (cadmium in the Restronguet Creek, copper in the Seine estuary, and even more in Restronguet Creek). In the cytosolic fraction, metals were partly linked to cytosolic heat-stable thiolic compounds (CHSTC) with molecular masses (5-6 kDa and about 12 kDa) consistent with metallothionein-like proteins (MTLP). Metal-binding to MTLP varied with the degree of contamination and with the metal studied. In contrast to many invertebrates, the presence of metal-binding CHSTC (MM about 2 kDa) other than MTLP seems to be a peculiar feature of H. diversicolor.

Changes in salinity affect the bioavailability and consequent uptake of trace metals by euryhaline invertebrates. In many cases, salinity-related effects on metal uptake can be explained by changes in chemical speciation but salinity may also influence uptake indirectly through its action on osmoregulatory mechanisms. Specifically, it can be hypothesised that trace metal uptake may be reduced at salinities approaching the isosmotic point of a species because, at this point, there is reduced activity of ionic exchange pumps. The present study tested this hypothesis using the Chinese mitten crab, Eriocheir sinensis, a hyper-hypoosmoregulator with an isosmotic point around 33 per thousand. Crabs were exposed to radio-labelled cadmium and zinc at 23, 33 and 43 per thousand for 4 days. To eradicate speciation effects, crabs were exposed to the same concentration of the radio-labelled free metal ion (estimated using MineQL computer software) at each salinity. Haemolymph samples were taken daily and radio-labelled metal concentrations were estimated from radioactivity counts and used to provide relative measures of metal uptake. Neither cadmium nor zinc uptake was lowest at the isosmotic point. The uptake of cadmium increased significantly with increase in salinity, while the uptake of zinc showed no significant change with increased salinity. Thus changes in trace metal uptake rates in E. sinensis do not appear to be controlled only by changes in free metal ion concentrations. The different effects of salinity change on the uptake of cadmium and zinc (in the absence of free metal ion change) also indicate that physiological responses to osmotic change alone do not control metal uptake rates for this species.

Chronic exposure to cadmium has been linked to bone loss, low bone mass, and increased incidence of fracture. To determine if Cd could directly increase the formation of cells responsible for bone resorption, we cultured normal canine bone marrow cells containing the progenitor cells for osteoclasts. Cultures were evaluated for the number of multinucleate osteoclast-like cells (MNOCs) formed. Exposure to Cd (10-100 nM) increased the number of MNOCs formed over control values when cultured in the presence but not in the absence of a bone wafer. The MNOCs formed were functional, evidenced by pits excavated on the bone wafers included in the cultures. By 12 days, MNOCs formed in the presence of 50 nM Cd excavated significantly more pits and a greater pit area than did untreated MNOCs. By 14 days, the control values were similar to those of the Cd-exposed MNOCs, but pit formation was enhanced by Cd in that the ratio of pit complexes to single pits was increased twofold over that for untreated cultures. Mature osteoclasts, isolated from the long bones of rat neonates and cultured for 1-3 days on bone slices, provided a direct method to assess the effect of Cd on osteoclast activity. Exposure of osteoclast cultures to 100 nM Cd increased the number of osteoclasts present over that for untreated osteoclasts by a factor of 1.7 +/- 0.1, the number of pits excavated by 2.8 +/- 0.6, the area excavated by 3.2 +/- 0.8, and the area excavated per osteoclast by 1.8 +/- 0.4 (mean +/- SE; n = six experiments). These data suggest that Cd accelerates the differentiation of new osteoclasts from their progenitor cells and activates or increases the activity of mature osteoclasts.

The article focuses on a study on the application of biodynamic modelling to compare bioaccumulation and the importance of water and sediment as sources of the trace metals including silver, cadmium and zinc among six populations of the infaunal estuarine polychaete, Nereis diversicolor. In this study, accumulated steady state concentrations in the worms from biodynamic modelling are forecasted. It also compares the predictions with independently measured accumulated concentrations in these worms. It discovers that bioaccumulated metal concentrations predicted from the model demonstrates agreement with concentrations in field-collected worms.