The disposition of cadmium and zinc in Pandalus montagui

Influence of ploidy and metal-metal interactions on the accumulation of Ag, Cd, and Cu in oysters Crassostrea gigas thunberg

The present study was designed to compare the response to contaminants in diploid with triploid specimens of the oyster Crassostrea gigas. The reproduction investment in bivalve molluscs has priority on somatic growth. Thus, genetic sterilization by triploidy induction enables the energy flux to be directed toward somatic growth and glucide storage. Bioaccumulation was examined for Ag (10 microg/L), Cd (10 microg/L), and Cu (30 microg/L) to determine if the response to metals follows similar patterns in diploid (2n) and triploid (3n) groups. The effect of ploidy was also evaluated as a function of dry weight of soft tissue and condition index. Moreover, the reciprocal influence of these metals on their incorporation was studied. The results showed that the major factor governing the degree of metal bioaccumulation by oysters is the nature of the metal introduced in the experimental medium. Thus, the uptake of Cd is proportionally more important than in the case of Ag and even more in Cu. For Cu-treated samples, the influence of ploidy on weight and metal body burden (and Cu concentration) was not significant, whereas for Ag and Cd, significant differences according to genetic type were evidenced by higher tissue weight and lower concentrations in triploid than diploid specimens. Metal-metal interactions study especially showed a reciprocal antagonism between Ag and Cu.

Induction of a putative metallothionein gene in the blood cockle, Anadara granosa, exposed to cadmium

The relationship between a putative metallothionein gene (MT) and exposure to cadmium (Cd) in blood cockles (Anadara granosa) is reported. In a 96-h dose-response experiment, mortality of cockles was found to proportionately increase in the range of 0.2-5.0 mg/l Cd with a calculated LC(50) of 2.94 mg/l. Exposure to 0.25 mg/l Cd for 16 days caused significant increases (P<0.05) in Cd concentrations in whole tissues, gills and hepatopancreas, and the accumulation of Cd in these tissues increased with the duration of exposure. Two cDNA libraries constructed using the hepatopancreas from control and Cd-treated cockles gave titres of 5.62 x 10(5) and 1.94 x 10(5) pfu/microg vector, respectively. A putative MT gene, AnaMT, of 510 nucleotides in length, was isolated from the treated cDNA library using a heterologous probe MT20 from the blue mussel, Mytilus edulis. Northern analyses using AnaMT as a probe indicated low expression of the MT mRNA in control animals. In cockles treated with 0.25 mg/l Cd for 4 days, MT mRNA level increased to approximately 168%, but declined to 108% at day 8. After 12 and 16 days of Cd treatment, expression of the MT gene was 138% and 187%, respectively, compared to the controls. These observations suggest that induction of the MT gene by a sublethal dose of Cd is rapid, occurring within 4 days of treatment.

Comparison of metallothionein concentrations and tissue distribution of trace metals in crabs (Pachygrapsus marmoratus) from a metal-rich estuary, in and out of the reproductive season

Crabs, Pachygrapsus marmoratus, were sampled in June 1997 and February 1998 from two sites (at the mouth and 25 km upstream) in the metal-rich Gironde estuary, France. Gills and hepatopancreas were analysed for metal (Cd, Cu, Zn) and metallothionein (MT) contents, in order to examine the influence of both biological and environmental factors on the physico-chemical forms of detoxified metal storage in the crabs. The concentrations of MT and both cytosolic and insoluble metals were not greatly different between males and females, and the influence of organ weights was also minimal. Intersite differences were observed, probably resulting from the gradient of salinity in the estuary, which interacts with both the chemical speciation and bioavailability of metals, and the general protein metabolism of the crabs. Seasonal changes were also important, probably in interaction with the moult and reproductive cycles. In February, concentrations of insoluble metals were generally higher than in June, in both organs, suggesting that essential metals, particularly Zn, are stored during winter then remobilised during the breeding season. The natural variability in the concentrations of MT often concealed any relationship with accumulated metal concentrations. Thus MT in crabs cannot be considered as a useful biomarker of metal pollution.

Observations on the interaction of zinc and cadmium uptake rates in crustaceans (amphipods and crabs) from coastal sites in UK and France differentially enriched with trace metals

This paper presents results on the possible interaction of zinc and cadmium uptake rates in crustaceans. Zn and Cd uptake rates were measured in amphipods (Orchestia gammarellus) and crabs (Carcinus maenas and Pachygrapsus marmoratus) from five coastal sites in Britain and France subjected to different degrees of trace metal enrichment. The presence or absence of 100 µg l(-1) of one metal (1.53 µM l(-1) Zn, 0.89 µM l(-1) Cd) had an inconsistent effect on the rate of uptake of the other metal by O. gammarellus. The presence or absence of 50 µg l(-1) of either zinc (0.76 µM l(-1)) or cadmium (0.45 µM l(-1)) had no effect on the rate of uptake of the other metal by C. maenas (from Millport, Scotland). Zinc and cadmium uptake rates were correlated in individual amphipods and crabs of both species from the five sites. These correlations indicate that zinc and cadmium might share common routes of uptake from solution by crustaceans, but the metals do not consistently interact competitively or synergistically at the exposure concentrations investigated. Regression coefficients of the relationship between zinc and cadmium uptake rates in amphipods and crabs showed occasional, but inconsistent, differences between sites and over time. All three crustaceans take up zinc from solution at a higher rate than cadmium for the same total dissolved metal molar concentration, but at a lower rate than cadmium per free metal ion molar concentration.

Changes in metallothionein concentrations in response to variation in natural factors (salinity, sex, weight) and metal contamination in crabs from a metal-rich estuary

Intermoult male and female crabs Pachygrapsus marmoratus and Carcinus maenas were sampled from three sites between the mouth and 25 km upstream in the Gironde, the most Cd-contaminated estuary in France, in order to study the relative importance of natural factors (salinity, sex, weight) and accumulated metal concentrations on metallothionein (MT) concentrations. In the two species studied, higher metal, total protein and MT concentrations were observed in the hepatopancreas than in the gills. In P. marmoratus, MT concentrations were mainly related to changes in the natural factors even if MT and Zn concentrations were positively correlated in the hepatopancreas whereas in C. maenas, the main relationships were with accumulated metal levels. In the case of the natural factors, the most important ones were weight in gills of both crab species, and salinity changes in both hepatopancreas and gills of P. marmoratus. Cd and Cu concentrations in both organs of the two species were inversely related to salinity. The same observation was found for Zn concentrations in C. maenas but not in P. marmoratus. In the hepatopancreas of both species, the highest total protein concentrations were found in crabs from the site with the highest salinity, whereas there were no such differences in the gills. It seems that changes in MT concentrations are linked more to changes in general protein metabolism than to changes in metal accumulation. Thus it was important to examine the storage of metals in other tissue compartments, particularly the insoluble fraction which includes mineral granules which is known to also contribute to trace metal detoxification in invertebrates. In the gills of the crabs, Zn was present mainly in the insoluble fraction, whereas Cd was nearly equally distributed between soluble and insoluble fractions. In contrast, Cu in the gills and all three metals in the hepatopancreas of both species were mainly cytosolic, but this does not necessarily imply a predominant role for MT since the cytosolic fraction also includes other macromolecules which may be the target binding site for accumulated trace metals.

The chronic toxicity of aluminium, cadmium, mercury, and lead in birds: a review

The toxicity of chronic dietary metal exposure in birds is reviewed. It is concluded that significant physiological and biochemical responses to such exposure conditions occur at dietary metal concentrations insufficient to cause signs of overt toxicity. Particularly important are reproductive effects which include decreased egg production, decreased hatchability, and increased hatchling mortality. Young, growing birds are typically more sensitive to the toxic effects of chronic metal exposure than adults, and altricial species are often more sensitive than precocial species. Factors which modify the absorption and toxicity of heavy metals, such as Se for the case of Hg, and Ca for the case of Pb and Cd, are discussed. Monitoring strategies for assessing environmental metal exposure in birds are evaluated.

Bioaccumulation of cadmium in marine organisms

It has been established that, although Cd occurs in the marine environment in only trace concentrations, most marine organisms, especially molluscs and crustaceans, can accumulate it rapidly. Cadmium is not uniformly distributed in the body and selectively accumulates in specific organs like liver, kidney, gills, and exoskeleton. The concentrations in muscle tissues are several orders of magnitude lower. The disposition of Cd in the organisms in the laboratory studies generally parallels those in nature. A number of biotic factors like body size, maturity, sex, etc. influence bioaccumulation but extensive studies are still lacking. The chemical form of Cd in the environment is of prime importance in bioaccumulation by marine organisms. Salinity can affect the speciation of Cd, and bioaccumulation is affected by both temperature and salinity. The ultimate level of Cd in the organisms will depend not only on the biotic and abiotic factors but also on metabolism of the metal by the organisms. A few studies indicate depuration of Cd by some bivalves but other organisms show very effective retention of Cd. Metallothionein formation for detoxification and storage has been observed in a large variety of marine organisms. Recent reports indicate an alternate storage and excretion mechanism in the formation of membrane-limited vesicles or granules. There seems to be a common link between intracellular localisation of Cd in metal-binding proteins and Cd containing vesicles as detoxifying mechanisms in the marine organisms. Much of what is known about Cd bioaccumulation by marine organisms has come from laboratory studies and there are inherent dangers in trying to extrapolate the results to field situations. In spite of tremendous progress made over the years, the basic understanding of the bioaccumulation process is still very nebulous and will remain so until the uptake, storage, and elimination processes are fully understood.

Persistence of four pyrethroid insecticides in a mineral and an organic soil

Permethrin, cypermethrin, fenpropanate and fenvalerate (emulsifiable concentrates) were applied at 280 g AI/ha and incorporated into mineral and organic soil contained in small field plots. Radishes and carrots were grown to serve as indicators of insecticide uptake. Similar plots were treated with the same insecticides at 140 g AI/ha and the soil surface was left undisturbed following application. Soil cores were removed at appropriate intervals and the crops were harvested when mature. The insecticide concentration in all samples was determined by gas-liquid chromatography. The amount of insecticide in the soil declined rapidly to less than 50% of the initial value in 1 month or less for most material-soil-treatment combinations and within 2 months for all cases. Concentrations remained in excess of 0.01 ppm in the organic soil for at least six months for all material-treatment combinations but fell below this level over 2-5 months in the mineral soils. Organic soil incorporated fenvalerate was the most persistent combination overall with 25, 17 and 7% remaining at 6, 18 and 28 months respectively. The trans-isomers of permethrin and cypermethrin disappeared more quickly than the cis-isomers but the insecticidally active IR isomers were not preferentially degraded relative to the inactive 1S. No residues (less than 0.01 ppm) were found in the radish or carrot crops. First order disappearance rates were not constant for any of the combinations. A comparison of partial rate constants showed: 1) 0-1 mo rates were generally greater in mineral than organic soil, 2) 1-6 mo rates in organic soil were lower than 0-1 mo rates, 3) 1-6 mo rates for surface applications to organic soil were generally less than for incorporated applications. In laboratory experiments, 0-1 mo rates for fenvalerate disappearance in a mineral soil were 2-3x greater for 0.5 ppm than for 10 ppm while 1-6 mo rates were independent of insecticide concentration but were 1.5x greater for 0.5% moisture than for 5%.