Physicochemistry or physiology: cadmium uptake and effects of salinity and osmolality in three crabs of different ecologies (original) (raw)
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Marine Ecology Progress Series, 1992
Effects of salinity on the accumulation of Zn and Cd in the haemolymph (relative indices of Zn and Cd uptake rates) of 2 populations of shore crab Carcinus maenas (L.) were investigated. Zn accumulation rates in the haemolymph of the Scottish (high salinity) crabs were higher than those of the Danish (low salinity) crabs. Decreases in salinity significantly decreased the Zn accumulation rate in the Scottish crabs but increases in salinity did not change the Zn accumulation rates in the Danish crabs significantly. Scottish crabs also showed a higher Cd accumulation rate, as well as elimination rate, than those of the Danish crabs. The highest Cd accumulation rate in Scottish crabs was found at 33 ppt salinity. In contrast the Cd accumulation rate of Danish crabs was highest at 15 ppt. It is proposed that exposure of the crabs to low salinity probably involves changes to crab permeability (e.g. apparent water permeability), thereby off-setting physico-chemical changes promoting the availabilities of free zinc and cadmium ions in solution which would otherwise increase metal uptake rates.
Marine Ecology Progress Series, 2002
The effects of salinity and osmolality differences on the uptake rates of dissolved zinc were investigated in 3 crabs of different ecologies-the euryhaline common shore crab Carcinus maenas, the extremely euryhaline Chinese mitten crab Eriocheir sinensis, and a more stenohaline marine crab, the velvet swimming crab Necora puber. Reduced salinities caused increases in the zinc uptake rate of E. sinensis as expected from the free metal ion model, with increased free zinc ion availabilities in conditions of reduced chloride complexation. In the cases of C. maenas and N. puber, however, reduced salinity was associated with reduced zinc uptake, a result interpreted in terms of a physiological response by these crabs to low salinity offsetting the physicochemical effect of increased free zinc ion availability. Results can be partly explained by reported changes in apparent water permeability (AWP) made by the crabs to low salinity, although experiments manipulating solution osmotic pressures independently of salinity (and therefore chloride concentrations) indicate that other physiological responses may also be coming into effect. The interaction of physiology and physicochemistry in controlling trace metal uptake from solution clearly varies between species.
Trace metal uptake by the Chinese mitten crab Eriocheir sinensis: the role of osmoregulation
Marine Environmental Research, 2002
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%. Crabs were exposed to radio-labelled cadmium and zinc at 23, 33 and 43% 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 Marine Environmental Research 53 (2002) 453-464 www.elsevier.com/locate/marenvrev 0141-1136/02/$ -see front matter # 2002 Elsevier Science Ltd. All rights reserved. P I I : S 0 1 4 1 -1 1 3 6 ( 0 2 ) 0 0 0 9 0 -9 (S.D. Roast).
Cadmium, zinc and the uptake of calcium by two crabs, Carcinus maenas and Eriocheir sinensis
Aquatic Toxicology, 2005
The uptake of dissolved cadmium and zinc by crustaceans can usually be explained by the passive process of facilitated diffusion involving a transport protein in the membranes of permeable surfaces. Cadmium ions will also enter via uptake routes for calcium, given the similar size of the two free ions. This study has investigated the interaction of cadmium (and comparatively zinc) and calcium uptake in two crabs that show different permeability responses to changes in salinity, with consequently different effects on the uptake of cadmium and zinc with salinity change. Ca uptake rates in Carcinus maenas decreased in reduced salinity (33-15) with the decreased Ca concentration of the medium and increased if the Ca concentration was increased at salinity 20. It is concluded that Ca uptake over the salinity range 33-15 is via apical Ca channels in gill ionocytes, passively down an electrochemical gradient. The Ca uptake rate of Eriocheir sinensis showed no significant decrease over the salinity range 33-10 (probably because of the small differences in an already low Ca uptake rate in this crab against a background of inter-individual variability), but decreased significantly at salinity 5. Added calcium increased the Ca uptake rate of E. sinensis at salinities 15 and 5, supporting the interpretation that Ca uptake in gills is typically passive via apical Ca channels. Cadmium (but not zinc) inhibited calcium uptake in both crabs at 15 salinity, indicating sharing of Ca channels by Cd, but not at salinity 5 (E. sinensis only) when Ca may be taken up into gill ionocytes by another (active?) physiological process.
Marine Biology, 1979
The crab Carcinus maenas (L.) was exposed to radioactively labelled cadmium dissolved in seawater at concentrations of 0.1, I and 10 ppm, the latter concentration being toxic to the crabs (50% mortality after 12.3 days). Net accumulation of cadmium from solution was proportional to the level and time period of cadmium exposure. Total absorbed cadmium levels reached 0.0043 and O.O412 mg Cd g-1 dry weight after 40 days exposure to O.1 and I ppm Cd, respectively, and O.1115 mg Cd g-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The highest tissue concentration was found in the midgut gland, reaching 0.786 mg Cd g-1 dry weight after 12.3 days average exposure to 10 ppm Cd. The midgut gland only contained about 10% of the total cadmium absorbed from solution, while the exoskeleton contained the bulk of absorbed cadmium (59 to 80%) probably passively adsorbed onto the surface. When cadmium was absorbed by the crabs from a food source, the midgut gland contained 16.9% of the total absorbed cadmium whereas the exoskeleton now contained only 22.2%. Ten percent of the cadmium available in the food source (Artemia salina) was accumulated by the crabs. When placed in cadmium-free seawater, crabs that had accumulated cadmium from solution lost 69% of the absorbed cadmium in 10 days, mostly from the exoskeleton which lost 78% of its original absorbed cadmium concentration.
Aquatic Toxicology, 2000
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 mg l − 1 of one metal (1.53 mM l − 1 Zn, 0.89 mM 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 mg l − 1 of either zinc (0.76 mM l − 1 ) or cadmium (0.45 mM 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.
Ecophysiology and trace metal uptake in crabs and other crustaceans
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2000
The uptake of dissolved trace metals by crustaceans is potentially affected both by the physicochemistry of the metal in solution, and by any physiological change by the crustacean, such as with stage of the moult cycle or in response to change in salinity.
Marine Environmental Research, 1995
Juvenile blue crabs, Callinectes sapidus, from the Barataria estuary (Louisiana, USA) were exposed to a range of dissolved cadmium concentrations at 2.5 and 25Y6 to determine their response to cadmium. Zl-Day LCsos were an order of magnitude lower at 2.5X (19pg liter-') than at 25%a (186ug liter-'). Crabs were exposed to Cd levels of 0,50 and 1OOug liter-' for measurements of feeding, respiration and excretion rates. Respiration was the primary component (X = 86.2%) of the energy expenditure budget in all cases, relative to excretion. Rates of energy expenditure did not vary with cadmium concentration at either salinity, and were much lower than those of energy consumption and absorption. Scope for growth paralleled energy consumption and absorption. Scope for growth did not vary as a function of cadmium concentration at 25%0; scope for growth at 2.5%0 was significantly lower in crabs exposed to 50 and 1OOug liter-' Cd relative to control crabs. Cadmium levels of up to 1OOpg liter-' do not stress juvenile blue crabs at 25%; but at 2.5%0, these same levels of Cd result in mortality and sub-lethal stress. This jinding is important since nursery grounds for juveniles of this species often lie in low salinity, estuarine waters, and high dissolved cadmium levels have been reported in Louisiana estuaries.
Aquatic Toxicology, 1993
An artificial medium of NaC1 in distilled water, of predictable dissolved metal speciation equilibria, has been used to define the effects of physicochemical changes on the uptake of zinc (Zn) and cadmium (Cd) by the euryhaline littoral amphipod crustacean Orchestia gammarellus (Pallas). At salinities between 36.5 and 25%0, changes in uptake rate of either metal correlated with predicted changes in free metal ion concentrations upon change in salinity, indicating the dominant role of medium physicochemistry in defining metal uptake rates. At 15%0 salinity, however, the change in uptake rate of each metal was no longer proportional to the change in free metal ion concentration, indicating a physiological response on the part of the amphipod to low salinity. It is proposed that such a response might be a reduction in apparent water permeability, characteristic of some euryhaline crustaceans. It is concluded that the use of a simple medium of defined physicochemistry has permitted the resolution of physicochemical and physiological effects on trace metal uptake rates, and that physiological adaptations of euryhaline organisms are significant in determining rates of trace metal uptake.