Accumulation,tissue distribution and elimination of 203HgCl2 and CH3 203HgCl in the tissues of the American oyster Crassostrea virginica

Oysters (Crassostrea virginica) were exposed for 3 days to mercury-203 labeled HgCl₂ or CH₃HgCl added directly to artificial seawater or added preconcentrated on the marine diatom Phaeodactylum tricornutum. The concentration of mercury in 5 tissues was measured for 45 days after mercury was removed from the ambient water. At the beginning of the depuration period, the highest concentrations of mercury in tissues were attained in: gill>digestive system>mantle>gonad>muscle in oysters exposed to water containing mercury; and in digestive system>gill>mantle> gonad>muscle in oysters fed labeled algae. This same distribution pattern is seen for both chemical forms of mercury. Although the initial pattern of accumulation was identical for both mercury compounds within each exposure group, the fate of the accumulated mercury was very different after 45-days depuration. In oysters accumulating mercury directly from seawater, inorganic mercury residues rapidly declined in gill and digestive tissue, but were slowly reduced in mantle, gonadal, and muscle tissue. This pattern was duplicated by oysters exposed to methyl mercuric chloride in seawater except that gonadal and muscle residues greatly increased during depuration. In oysters ingesting labeled P. tricornutum cells, mercuric chloride and methyl mercuric chloride residues rapidly declined in gill and digestive tissue, remained constant in the mantle, but sharply increased in gonadal and muscle tissue during depuration.     

Toxic effects of heavy metals upon cultures of Uronema marinum (Ciliophora: Uronematidae)

The lethal levels of mercuric, lead and zinc chlorides were determined for the marine ciliated protozoan Uronema marinum Dujardin; the 24 h LC₅₀ values were 0.006, 60 and 400 mg l^-1, respectively. A factorial experiment was used to study the inhibition of cell division in U. marinum cultures by mixtures of mercury, lead and zinc. The three metals were found to interact in their effects. A regression model was fitted to the experimental results and the response surface was plotted. The addition of mercury, lead or zinc at concentrations which inhibited cell division did not appear to affect the duration of the lag phase or the yield of cells. A culture of U. marinum was maintained for 18 weeks in a medium containing mercury, lead and zinc in an attempt to acclimatise the ciliates to heavy metals. A subsequent factorial experiment which examined the cell division rate indicated that a prolonged exposure did not induce in the ciliates a measurable tolerance to the metals.     

Histochemical demonstration of mercury in the intestine,nephridia and epidermis of the marine polychaete Nereis virens exposed to inorganic mercury

Marine polychaetes Nereis virens (Sars) were exposed to 9 ppb Hg as mercuric chloride in the aquarium water. Concentrations of mercury in the water and in the worms were monitored using radiolabelled mercury. After 11 d, the average mercury concentration in the nereids was 8.41 ppm Hg and the bioconcentration factor was calculated to be 930. Accumulations of mercury in the tissues were made visible for light and electron microscopy by autometallographic silver enhancement. Mercury was demonstrated in the intestine, nephridia, epidermis and cuticula. In the intestine, mercury was found to be located predominantly in the apical part of the epithelial cells. In the nephridia, mercury deposits were apparent in the peritoneal cells of the nephridial tubules. Silver-enhanced mercury was also observed at the epicuticula, in the collagen fibres of the endocuticula and in the epidermal basal cells. Intracellularly, the observed mercury accumulations were localised predominantly in lysosomes. Extracellularly, mercury was observed in the basal laminae of the intestine and the epidermis, and also in the intestinal peritrophic membrane. How N. virens copes with mercury toxicity is discussed.     

Survival and chloride ion regulation of the porcelain crab Petrolisthes armatus exposed to mercury

Acute toxicity bioassays conducted at various salinities demonstrated that mercury (as mercuric chloride) at low concentrations was lethal to Petrolisthes armatus. Ninety-six hour LC₅₀ values varied from 50 to 64 parts per billion (ppb) of mercury, depending on test salinities. Lower salinities. decreased the time to death of mercuryexposed crabs. Differences in survival after 96 h due to salinity were not statistically significant. Blood chloride concentrations were regulated hyperchloride to the medium at low salinities and hypochloride at high salinities by acclimated crabs. The salinity isochloride to blood was 20 S. Transfer of crabs from 15 S to salinities ranging from 7 to 35 S resulted in new steadystate chloride levels within 12 h. Exposure to 50 ppb mercury did not alter chloride ion regulation of either acclimated crabs or crabs adjusting to new salinities.     

Combined effects of selenium/mercury and selenium/copper on the cell population of the alga Dunaliella minuta

The type of interaction of selenium and mercury, and selenium and copper on the cell growth of the planktonic alga Dunaliella minuta Lerche has been studied. The results for the various selenium/mercury and selenium/copper ratios showed that: (a) although mercury and selenium inhibited the growth of D. minuta when added to its cultures separately at levels greater than their respective threshold concentrations, they had antagonistic effects towards each other when added simulataneously at the beginning of growth; prior exposure of the culture to either metal for 2 d did not alter this antagonistic action; (b) similar antagonism was observed in combinations of selenium and copper for cultures with and without prior exposure to either metal. The reasons for the Se/Hg and Se/Cu antagonism are unknown; several hypotheses concerning possible detoxification mechanisms are proposed.     

Effects of copper and cadmium on osmoregulation and oxygen consumption in two species of estuarine crabs

Green crabs (Carcinus maenas) and rock crabs (Cancer irroratus) were exposed to various concentrations of copper as cupric chloride (CuCl₂ · 2 H₂O), and cadmium as cadmium chloride (CdCl₂ · 21/2 H₂O) for 48 h. The exposures were conducted at 5 different salinities. At the end of each exposure period, tests of blood-serum osmolality and gill-tissue oxygen consumption were performed. Copper-exposed crabs exhibited loss of osmoregulatory function with increasing copper concentration until normally hyperosmotic serum became isosmotic with the surrounding medium. Cadmium elevated greencrab serum above its normal hyperosmotic state. Copper had no effect on gill-tissue oxygen consumption; however, cadmium reduced the rate of oxygen consumption in both species tested.     

Bioavailability of dissolved copper to the American oyster Crassostrea virginica. I. Importance of chemical speciation

The effect of complexation on the accumulation of dissolved copper by the American oyster Crassostrea virginica was determined in chemically defined exposure media. The speciation of copper was varied by varying the concentrations of total copper and model chelator, nitrilotriacetic acid (NTA). Accumulation of copper in 14-d experiments was related to the cupric ion activity and not the concentration of chelated copper. Rapid accumulation of copper occurred at cupric ion activities above 10^-10 M and there was no measurable accumulation at 10^-11 M.Southeast Fisheries Center Contribution No. 81-45B. Reprint request should be addressed to this author     

Protective role of Curcuma longa extract and curcumin on mercuric chloride-induced nephrotoxicity in rats: evidence by histological architecture

Mercury (Hg) is a potent nephrotoxin. The aim of this study was to investigate the protective role of Curcuma longa extract and curcumin against HgCl₂-induced nephrotoxicity. Male Sprague Dawley rats were administered HgCl₂ (12 μmol kg^?1, ip; once only) followed by treatment of Curcuma longa extract (200 mg kg^?1, po) and curcumin (80 mg kg^?1, po) for three days after 24 h of HgCl₂ administration. The present results showed that mercuric chloride administration caused an impairment of renal function system which was evident from significant increase in urea, creatinine, uric acid, and blood urea nitrogen concentration in serum. In addition, the swelling in glomerulus and degenerated renal tubules with obstructed lumen was also observed by acute mercuric chloride administration. Treatment with Curcuma longa extract and curcumin was effective in restoring all variables of kidney functions near to control group, which was consistent with kidney histoarchitecture. In conclusion, these results suggest that Curcuma longa extract and curcumin protect against HgCl₂-induced nephrotoxicity. This study could be important for the further understanding of mercury toxicity in renal tissues and in the development of better treatments for people and/or animals exposed to the metal.     

Differential predation by males on moulted females may explain the competitive displacement of Gammarus duebeni by G. pulex (Amphipoda)

Summary Several studies have reported the ability of Gammarus pulex to successfully compete with and ultimately displace G. duebeni in freshwater. These studies have been unable, however, to provide adequate explanations for this displacement based on mechanisms of exploitative competition and/or differences in the environmental tolerances of the species. The present study investigates the role of predation as an extreme form of interference competition between G. pulex and G. duebeni. The data presented show that: (1) given the opportunity, males of both species prey on females of the other species, but only on females that have recently moulted; (2) mate guarding in both species significantly reduces the incidence of predation on moulted females; (3) mate guarding by male G. pulex is more successful in reducing predation on moulted females than is guarding by male G. duebeni. We propose that differential predation rate on moulted females may constitute the primary mechanism by which G. pulex displaces G. duebeni. Offprint requests to: J.T.A. Dick     

Effects of cupric and zinc ion activities on the survival and reproduction of marine copepods

The toxicity of copper and zinc to the estuarine copepod Acartia tonsa and to the two diatom food species Thalassiosira pseudonana and T. weissflogii was measured in nitrilotriacetate-trace metal ion buffer systems at 25 S. Overall, A. tonsa appeared to be more sensitive to cupric and zinc ion activity than either of the diatoms; however, its sensitivity varied among the different life stages examined. Adult survival was not affected within the zinc ion activity range 10^-11 to 10^-8 M and cupric ion activity range 10^-13 to 10^-11 M over a 96-h period, but a cupric ion activity of 10^-10 M caused total mortality of adults within 72 h. Egg-laying rate was most sensitive to zinc, and was reduced at zinc ion activities 10^-10 M. Naupliar survival after 96 h was reduced by zinc ion activities 10^-8 M and by cupric ion activities 10^-11 M, and was reduced to zero at a zinc ion activity of 10^-7 M and at a cupric ion activity of 10^-10.5 M. In an interspecies comparison of 96-h adult survival, Centropages typicus was more sensitive to copper and zinc than A. tonsa and the survival of Labidocera aestiva was dependent on the ratio of cupric to zinc ion activity. A comparison of our results with estimates of zinc and cupric ion activities in estuaries suggests that ionic activities of these metals are high enough in some polluted estuaries to affect the survival and reproduction of copepods.     

Effects of mercury on the behaviour and oxygen consumption of Monodonta articulata

The trochid snail Monodonta articulata Lamarck was exposed to mercuric sulphate at concentrations of 0.2, 0.5, 0.8 and 1 ppm Hg⁺⁺. At 24 h, retraction into the shell was observed in 0.8 and 1 ppm Hg⁺⁺; this retraction increased in these concentrations at 36 h. Retracted snails died if retained in the solutions, but generally recovered within 24 to 48 h if transferred to uncontaminated sea water. Immersionemersion behaviour and interface activity were studied over 24 h by means of an aktograph; snails in normal sea water spent more time below than above the water surface, and exhibited frequent periods of activity. Exposure to mercuric sulphate at concentration of 0.25, 0.5, 0.8 and 1 ppm Hg⁺⁺ progressively reduced both the length and frequency of activity periods. From 0.5 ppm Hg⁺⁺ upwards, emersion periods increased, and immersion periods decreased. Oxygen consumption of snails was measured in sea water and in mercuric sulphate at concentrations of 0.2, 0.5, 0.8 and 1 ppm Hg⁺⁺. Oxygen consumption decreased significantly with each progressive rise in mercury concentration. It is considered that mercury affects M. articulata by interfering with respiration, initially reducing interface activity, then forcing the snail for longer and longer periods out of the water. Retraction occurs when activity is no longer possible. It is concluded that respiratory and behavioural alterations of this nature would afford a good indicator of the presence of sub-lethal concentrations of pollutants.     

Effects of copper and zinc on two planktonic ciliates

The interactive effects of copper and zinc on two estuarine planktonic ciliates, Favella sp. and Balanion sp., were determined in seawater media in which the free metal ion activities were controlled by nitrilotriacetic acid (NTA) trace metal ion buffer systems. Cupric ion activities of 10^-10 M caused abnormal motility in both ciliates in shortterm (5 h) tests, and cupric ion activities as low as 10^-12.8 M decreased the growth rates of both species in longer-term experiments. In the short-term tests, zinc ion activity by itself did not affect the motility of the ciliates, but there were significant interactions between copper and zinc. In the longer-term experiments, the growth of Favella sp. was optimal at the lowest cupric ion activity (10^-13 M) and the two lowest zinc ion activities (10^-12 and 10^-13 M) and the two lowest zinc ion activities (10^-12 and 10^-11 M), and copper and zinc inhibited growth at activities above these values. By contrast, optimal growth rate of Balanion sp. occurred at the highest zinc ion activity (10^-10 M) and the lowest cupric ion activities (10^-13 to 10^-12 M) and growth rate was reduced at zinc ion activities 10^-11 M. There was an antagonism between copper and zinc which was particularly pronounced in Balanion sp.Contribution No. 5871 from the Woods Hole Oceanographic Institution     

Factors affecting the accumulation and removal of mercury from tissues of the American oyster Crassostrea virginica

Adult oysters, Crassostrea virginica (Gmelin) were held in seawater containing 10 or 100 ppb mercury in the form of mercuric acetate for 45 days. Mercury concentration in tissues was determined by analysis of individually homogenized oyster meats using wet digestion and flameless absorption spectrophotometry. After 45 days, average mercury tissue concentration was 91,600 and 12,100 ppb in the 100 and 10 ppb mercury groups, respectively. A slight decline in mercury residues in the 100 ppb group during the accumulation period was attributed to spawning. Clearance of mercury from tissues was studied in a constant temperature regime (25°C±2C^o) for 25 days and in a declining temperature regime (25° to 5°C) for 80 days by exposing treated adults to estuarine water with no mercury added. The biological half-life of mercuric acetate was 16.8 and 9.3 days in the 25°C temperature regime, and 35.4 and 19.9 days in the declining temperature regime, for the 10 and 100 ppb groups, respectively. Smaller oysters (0 to 7 g) consistently accumulated more mercury per gram wet weight than larger oysters (7 to 20 g) in populations exposed to 10 and 100 ppb mercury.     

Toxicity of cupric lon to eggs of the spot Leiostomus xanthurus and the Atlantic silverside Menidia menidia

Experiments were conducted to determine the toxicity of free cupric ion to the eggs of two marine fish: the spot Leiostomus xanthurus, and the Atlantic silverside Menidia menidia. A cupric ion buffer consisting of 5 mM of the chelator, trishydroxymethylamino methane (Tris), and varied concentrations of CuSO₄ was employed to achieve stable cupric ion activities in experimental seawater media. Egg hatch of the silverside appears to be more sensitive to cupric ion than that of the spot. The silverside had 60% inhibition of hatch at a pCu (negative logarithum of cupric ion activity) of 9.4 with complete supporession of hatching at pCu values below 8.2, while the spot had 50% inhibition at a pCu of 9.0 and complete suppression at a pCu of 8.0. Cupric ion was most toxic to the eggs of silverside at or around the time of hatching, whereas a pronounced sensitivity at hatching was not apparent with the eggs of spot. Calculated estimates of the range of cupric ion activity in seawater indicate that natural activity levels may in some instances inhibit the hatching of silverside and spot eggs.     

Balanus amphitrite (Cirripedia: Thoracica) — A potential indicator of fluoride,copper, lead,chromium and mercury in North Adriatic lagoons

The capacity of the barnacle Balanus amphitrite Darwin to accumulate pollutants above ambient levels was examined in two North Adriatic lagoons with respect to fluoride, copper, lead, chromium and mercury. Levels in soft tissues ranged from 138 to 312 ppm (dry weight) for fluoride, 41 to 109 ppm for copper, 7.1 to 11.7 ppm for lead, 2.10 to 3.89 ppm for chromium, and from 0.96 to 1.35 ppm for mercury. The concentration factor was of the order of 10² for fluoride, 10³ for copper, and possibly higher than 10³ for lead, chromium and mercury. The differences of about 2:1 in the fluoride and copper concentrations in the waters of the two lagoons were clearly reflected by the levels in the barnacles. B. amphitrite that had set on experimental panels had levels similar to those found in specimens collected from long-term natural populations as early as 42 days after immersion of the panels. Compared with literature data, the accumulation levels found in B. amphitrite for fluoride were among the highest known for invertebrates; the values for copper and lead were considerable, but exceeded by others published for B. balanoides; the results for chromium and mercury were one order of magnitude lower than values reported for other suspension-feeders or indicator organisms. B. amphitrite appears to possess most of the properties considered essential for a biological indicator. Eventual determination of the response time of the barnacle to changes in environmental level could profitably be carried out utilizing experimental panels.     

Mercuric chloride effects on adult rat oval cells-induced apoptosis

In the present investigation, the toxicity of mercuric chloride (HgCl₂) was evaluated in adult oval cells isolated from rat utilizing the 2-acetylaminofluorene/partial hepatectomy technique. Isolated oval cells were incubated with 5 μM of HgCl₂ for 8 hr to elucidate in vitro cytotoxic responses. Recently, autophagic cell death was found in rat hepatocytes in vitro within 30 min of incubation with 5 μM of mercury (Hg) which triggered apoptosis and necroptosis in a time-dependent manner. Nuclear degradation occurred within 30 min of incubation and progressed with time until 8 hr. Apoptosis evidenced by activation of caspase-dependent pathway between 30 min to 8 hr of incubation was mediated via interchange of death domain signaling pathways. Receptor-interacting protein played a positive role to modulate the death domain receptors in the scenario of apoptotic death of oval cells until 6 hr. Autophagic marker proteins ATG12 and LC3B exerted a significant role in triggering apoptosis in 5 μM Hg-treated oval cells. No apparent expression of apoptosis-inducing-factor (AIF) and HMGB1 indicated absence of caspase-independent apoptosis and necrosis in the rat oval cells between 30 min and 8 hr. Thus a low concentration of Hg modulates programmed cell death in adult rat oval cells by altering expression of proteins involved in the molecular mechanisms of cellular functions.     

Accumulation and depuration of mercury in the American oyster Crassostrea virginica

To study the kinetics of mercury uptake in oysters, adult Crassostrea virginica (Gmelin) were held in seawater containing 10 g mercury/l (ppb) or 100 g mercury/l (ppb), added in the form of mercuric acetate, for 60 days. Mercury concentration in tissues was determined by analysis of individually homogenized oyster meats, using wet digestion and flameless absorption spectrophotometry. After 45 days, average mercury tissue concentration was 140,000 g mercury/kg tissue (ppb) and 28,000 g mercury/kg tissue (ppb) in the 100 ppb and 10 ppb experimental groups, respectively. After this time, concentrations dropped sharply, probably due to spawning. Clearance of mercury from tissue was studied by exposing treated adults to estuarine water (with no additions) for 30 days (100 ppb group) and 160 days (10 ppb group). Tissue concentrations in the 100 ppb mercury environment group declined from 115,000 to 65,000 ppb, and those of the 10 ppb group declined from 18,000 to 15,000 ppb, in 18 days; there-after, no further decline occurred in either group. Oysters accumulated mercury 1,400 times and 2,800 times above the environmental concentrations of 100 and 10 ppb mercury, respectively. Total self-purification was not achieved over a 6 month cleansing period.     

Acclimation and tolerance of Artemia salina to copper salts

The brine shrimp Artemia salina L. was acclimated in sea water with cupric chloride, acetate, carbonate, and sulphate, each at concentrations of 0.1, 0.05 and 0.025 ppm Cu⁺⁺, together with sea water controls. Growth inhibition was observed in all four compounds, generally in direct relationship to the concentration. It was least in sulphate, and increased progressively in chloride, acetate and carbonate in that order. No inhibition however was observed in carbonate at 0.025 ppm Cu⁺⁺. In toxicity tests, 2-week old larvae from each solution were exposed to concentrations of 10, 7.5, 5, 2.5 and 1 ppm Cu⁺⁺ of the same compounds, together with unacclimated larvae of the same age. Similar tests were held with 6-week old adults acclimated (a) in 0.1 ppm Cu⁺⁺ (chloride, acetate and sulphate) using the same concentrations and (b) in 0.5 ppm Cu⁺⁺ (carbonate), using 150, 125, 100, 75, and 50 ppm Cu⁺⁺. Toxicity to unacclimated larvae and adults differed with the compounds, carbonate being the least toxic, followed by sulphate, chloride and acetate in increasing order. Larvae acclimated in chloride (0.025 ppm Cu⁺⁺) and sulphate (0.1 and 0.5 ppm Cu⁺⁺) showed an increased tolerance to 1 and 2.5 ppm Cu⁺⁺ compared to untreated controls. Tolerance was not enhanced from 5 ppm Cu⁺⁺ upwards. In both compounds, adults acclimated in 0.1 ppm Cu⁺⁺ showed an increased tolerance to concentrations between 1 and 7.5 ppm Cu⁺⁺ compared to controls. Larval mortality in carbonate was below 50% in all test solutions. Adults acclimated at 0.5 ppm Cu⁺⁺ showed an increased tolerance to 50 ppm Cu⁺⁺ compared to controls. Considerable precipitation occurred with the high levels of this compound, thus effecting the final concentrations. No acclimation effect was observed in acetate for either larvae or adults. It is suggested that in A. salina, copper toxicity depends on the particular form of the metal, and that this difference is also evident in growth inhibition and in the potential acquisition of increased tolerance through exposure to low concentrations.     

Hepatoprotective effects of taurine against mercury induced toxicity in rats

An attempt has been made to study the influence of taurine on mercury intoxicated rats. The animals were treated with sublethal dose of mercuric chloride (2 mg/kg body wt.) for 30 days. During the mercury treatment, the level ofAspartate transaminase(AST), Alanine transaminase (ALT) and Alkaline phosphatase(ALP) in serum and lipid peroxidation (LPO) in liver tissue significantly increased whereas Glutathione (GSH), Glutathione peroxidase(GPx), Catalase (CAT) and Superoxide dismutase (SOD) were simultaneously decreased in the liver tissue. Present results indicate that the liver tissue was completely damaged, after mercury treatment. In another group of animals, taurine (5 mg/kg body wt.) was administrated for another 15 days. Taurine administration was observed to improve the liver function in mercury intoxicated animal as indicated by the decline in increased levels of AST, ALT and ALP in serum and LPO content in liver tissue. The decreased level of antioxidant system (GSH, GPx, CATand SOD) has been promoted Results suggested that taurine played a vital role in reducing the mercury toxicity in intoxicated animals.     

Trace Metal Studies on the Starfish Asterias rubens L. From the Western Baltic Sea

In 1984, 115 samples of the starfish Asterias rubens L. collected in the south-eastern part of Cadet Trench (Mecklenburg Bay/Western Baltic Sea) were analyzed for their contents of a few major (calcium, magnesium) and trace elements (cadmium, copper, iron, mercury, manganese, nickel, lead, selenium and zinc). Distinct differences were found between starfish from different stations, and these are attributed to the composition of the sediments acting as a substrate for their prey (mussels, snails). Except for cadmium, the concentrations of the elements studied all correlated negatively with the diameter and weight of the starfish.

Parallel analyses of starfish arms and the central discs of the same animals showed that iron, zinc, copper and mercury levels were 16 to 30% higher, and selenium, manganese, magnesium, calcium and lead were 4 to 9% higher in the arms. Cadmium concentrations were 20% higher in the central discs than in the arms.

Stock estimations (about 52,000 tons fresh weight) show that starfish play a significant role in the benthic ecosystem of the western Baltic Sea. They can consume up to 200,000 tons of mussels and clams (Mytilus edulis, Macoma baltica) a year and may therefore represent a notable factor in the trace metal balance of the region.