Taxonomy needs evolution, not revolution.
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Animals↗
Biomedical subjects
P S Rainbow
Publications and source records attributed to P S Rainbow.
Trace metal uptake by the Chinese mitten crab Eriocheir sinensis: the role of osmoregulation.
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.
Animals↗
Partitioning of accumulated trace metals in the talitrid amphipod crustacean Orchestia gammarellus: a cautionary tale on the use of metallothionein-like proteins as biomarkers.
The induction of metallothionein-like proteins (MTLP) as biomarkers of trace metal pollution has been investigated in the talitrid amphipod Orchestia gammarellus, an established biomonitor of trace metal availabilities in coastal areas. Sensitivity to metal exposure, MTLP and copper and zinc concentrations have been examined in amphipods from a metal-contaminated site (Dulas Bay, Wales) and two clean sites (Millport, Scotland and Bradwell, England). Groups of 10 amphipods from Dulas Bay and Millport were exposed separately to one of a concentration series (1, 3.16, 10, 31.6, 100 microM) of Cu or Zn for 17 days at 10 degrees C. Specimens from Bradwell were exposed under similar conditions but the experiment was extended to 25 days with intermediate samplings at 5, 10 and 17 days and additional groups were exposed to a mixture of Cu+Zn (7:10 molar ratio). In addition, specimens from Millport were exposed to 1 or 31.6 microM Cd for 17 days. Amphipods from Dulas Bay, which had been chronically exposed to metals in their natural environment had not acquired any tolerance to Cu and Zn since the lowest LC 50s were registered in these samples. Whatever the origin of the amphipods experimentally exposed to metals and whatever the dose of exposure, both Cu and Zn remained approximately equally distributed between cytosolic and insoluble fractions in the amphipods, suggesting that mechanisms of metal storage were identical over the whole range of conditions. Concentrations of MTLP were higher in O. gammarellus from Dulas Bay than in those from Millport analysed directly after collection, although laboratory exposures to dissolved Cd, Cu or Zn have failed to demonstrate differences in the induction of MTLP between amphipods from the clean or contaminated sites. A potential role for metallothionein-like proteins as biomarkers is thus unlikely although it remains plausible that turnover of these proteins does increase in response to increased metal challenges, enabling MTLP to play a role in metal detoxification.
Animals↗
Biomonitoring of trace metal contamination in the Potengi estuary, Natal (Brazil), using the oyster Crassostrea rhizophorae, a local food source.
The oyster Crassostrea rhizophorae was collected in September 1997 from 10 stations along the Potengi estuary, Natal, Brazil, a mangrove-lined estuary receiving anthropogenic inputs of trace metals. C. rhizophorae is a net accumulator of trace metals and can be used as a biomonitor, the accumulated soft tissue concentrations representing integrated records of bioavailable metal fractions over the life of the oyster. Significant differences in oyster accumulated concentrations (and hence bioavailabilities) of Fe, Zn, Cu, Cr, Pb, Cd, Ni and Ag (but not Mn) were found between stations, and attributed to anthropogenic inputs including discharges of sewage and industrial effluent. The oysters are also a local food source, and concentrations of zinc, copper and lead in some of the oysters are above typical public health recommended limits.
Animals↗
Availability of cadmium and zinc from sewage sludge to the flounder, Platichthys flesus, via a marine food chain.
This paper examines the potential availability to a demersal fish of cadmium and zinc associated with digested sewage sludge, via a food chain as well as directly from the sludge, and the tissue distribution and possible excretion of any accumulated cadmium and zinc. Radioactive tracer techniques were used in order to follow the food chain transfer of the metals. Flounder (Platichthys flesus) accumulated cadmium both directly from sludge (delivered in newly ingested unassimilated gutfuls in the amphipods) and in assimilated form from the tissues of the amphipod crustacean Corophium volutator that had been feeding on a sludge-sediment mixture. Cadmium from both sources could be excreted by the fish. The concentration of cadmium within the whole fish increased as the input of cadmium in the diet increased. Zinc, similarly, is available to the flounder both directly from sludge and from zinc accumulated in C. volutator. Only a limited increase in net accumulation of zinc by the flounder was observed upon increased inputs of zinc through the diet, perhaps indicating some regulation of body zinc concentration by the flounder.
Animals↗
Barnacles as biomonitors of trace metal availabilities in Hong Kong coastal waters: changes in space and time.
The use of selected organisms as biomonitors of trace metal bioavailabilities allows comparisons to be made over space and time. The concentrations of 11 trace metals (arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel, silver, zinc) were measured in the bodies of two barnacle species, Balanus amphitrite and Tetraclita squamosa, from up to 18 littoral sites from Hong Kong coastal waters in April 1998. These data provide evidence on the geographical variation in metal bioavailabilities at this time, and are compared selectively against historical data sets for 1986 and 1989. Geographical variation in bioavailabilities is clear for several metals, with hotspots for arsenic, copper, nickel and silver at Chai Wan Kok, and for lead in Junk Bay. Victoria Harbour sites head the rankings for silver and arsenic, and Tolo Harbour sites exhibit relatively elevated cobalt, manganese and zinc. Many bioavailabilities of trace metals to barnacles are lower in Hong Kong coastal waters in 1998 than in 1986. The two barnacle species are widespread and the extensive data set presented is a benchmark which can be compared to the results of similar biomonitoring programmes elsewhere in the Indo-Pacific and beyond.
Animals↗
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.
Animals↗
Haemocyanin and the binding of cadmium and zinc in the haemolymph of the shore crab Carcinus maenas (L.).
The trace metals cadmium and zinc are taken up from solution into haemolymph of the shore crab, Carcinus maenas, where they bind to the respiratory pigment haemocyanin. Investigations using FPLC and PAGE to separate the constituent dodecamer and hexamer aggregations of haemocyanin showed a difference between the distribution of cadmium and zinc between the two aggregate states. In the haemolymph, labelled cadmium binds not only to haemocyanin but, at least initially, it is also associated with low molecular size material or exists as free cadmium ions. The binding of cadmium to haemocyanin is not an immediate process. Initially the binding of cadmium favours the hexamer; only later is a more even distribution between the two aggregate states apparent. Newly taken up labelled zinc is rapidly bound to haemocyanin. The majority of both total and labelled zinc in the haemolymph is bound to haemocyanin, with the hexamer having a greater binding affinity for zinc than the dodecamer. This suggests that formation of the dodecamer leads to a blocking of zinc-binding sites and/or that the hexamer consists of subunits which possess a relatively high affinity for zinc.
Animals↗
Accumulation of cadmium associated with sewage sludge by a marine amphipod crustacean.
Cadmium bound to sewage sludge (5% mixture with littoral mud) is available to the deposit-feeding marine amphipod crustacean Corophium volutator (Pallas). The amphipod accumulates labelled cadmium from sludge in proportion to both duration of exposure and cadmium concentration of the sludge. Newly accumulated cadmium is added onto the existing cadmium body load without significant excretion. Thus, cadmium in association with sewage sludge dumped at sea may be absorbed and accumulated by deposit-feeding invertebrates, with the potential of being transferred along marine food chains.
Animals↗
A preliminary study of Cu-, Cd- and Zn-binding components in the hepatopancreas of Palaemon elegans (Crustacea: Decapoda).
Three low molecular weight, metal-binding components have been isolated from the hepatopancreas of the shrimp Palaemon elegans. The two larger components P-I (11-15,000) and P-II (4-6000) were associated with large amounts of copper in field-collected and copper-exposed shrimps and with cadmium in shrimps exposed to elevated Cd concentrations. A smaller component, P-III was associated with zinc. The recovery of these components was dependent upon the use of a protease inhibitor and the reducing agent mercaptoethanol (2-M) during the separation procedure. Copper, zinc and cadmium are not evenly distributed between individual tissues of P. elegans, the highest concentrations occurring in the hepatopancreas, gills and eyes.
Animals↗
A modified Lowry assay to measure levels of proteins lacking aromatic amino acid residues (e.g. metallothioneins).
A combination of two modifications to the Lowry protein assay is recommended for estimation of metallothionein (lacking aromatic amino acid residues and requiring reducing conditions for isolation). Serum thymic factor (STF), a decapeptide lacking aromatic amino acids, is recommended for use as a standard after allowance for the effects of short chain length on colour intensity development.
Metallothionein↗