Second-generation rodenticides and polecats (Mustela putorius) in Britain

In Britain, polecats Mustela putorius hunt around farm buildings, especially in winter, and, as a result, may be secondarily exposed to rodenticides by eating contaminated prey. This paper reports the first survey of second-generation rodenticides in polecats. Twenty-nine adult polecats which had been killed either accidentally on roads (24) and in traps (4), or had died of an unknown cause (1) were collected during 1992-1994. The livers of 24 animals and the stomach walls of the remaining five, for which the livers were not available, were analysed for difenacoum, bromadiolone, brodifacoum and flocoumafen. In total, rodenticide residues were detected in 31% of the polecats analysed. Residues were found in seven of the 24 livers (29%) and in two of the five stomachs analysed (40%). Difenacoum was detected most frequently (28% of animals), and was the only rodenticide in the stomach, while bromadiolone and brodifacoum were detected in only 10% and 3% of polecats, respectively. Flocoumafen was not detected in any animals. More than one rodenticide occurred in the livers of two animals; one contained difenacoum and bromadiolone, the other also contained brodifacoum. There was no sex bias in the proportion of animals containing rodenticides. Animals with detectable residues came from more than one county and were collected only during January-April in each year.     

Spatial and temporal analysis of second-generation anticoagulant rodenticide residues in polecats (Mustela putorius) from throughout their range in Britain, 1992-1999

Polecats (Mustela putorius) in Britain are currently expanding their range eastwards from Wales to reoccupy central and eastern areas of England. Second-generation anticoagulant rodenticides (SGARs), to which polecats are exposed by eating contaminated prey, are used more extensively in these central and eastern regions, leading to fears of increased exposure, and possible resultant mortality. We measured bromadiolone, difenacoum, flocoumafen and brodifacoum concentrations in the livers of 50 polecats from areas that included newly recolonised habitats and found that at least one SGAR was detected in the livers of 13 out of 37 (35.1%) male and 5 out of 13 (38.5%) female polecats. Difenacoum and bromadiolone were detected most frequently. We then combined these data with measurements on another 50 individuals from earlier studies to create a dataset for 100 polecats collected throughout the 1990s from across the whole of their current range. Using this dataset, we determined if there was any evidence that contamination in polecats had increased during the 1990s and whether animals from England were more contaminated than those from Wales, as might be expected given regional differences in the patterns of SGAR use. Overall, 31 of the 100 polecats analysed to date contained SGAR residues. The incidence was a little higher (40%) in animals that died between January and June and this probably better reflects the overall proportion of animals that are sub-lethally exposed. There was no statistically significant change during the 1990s in the proportion of polecats exposed to SGARs nor any evidence that greater use of SGARs in England resulted in more contamination of polecats. Contrary to expectation, the proportion of animals that contained difenacoum was marginally higher in Wales than elsewhere.     

Effects of mercury exposure on ionic regulation in the crayfish Orconectes propinquus

Hemolymph sodium, potassium and calcium concentrations were determined in crayfish (Orconectes propinquus) exposed to (203)HgCl(2) mixed with food to a concentration of 1 microg Hg g(-1). Dummy-fed animals were exposed to Hg-dosed food wrapped in dialysis tubing to control for mercury reaching the animals via leaching from food to water. Hemolymph analyses were made following 14-day Hg exposures and again after a further 21-day 'depuration' period during which all animals were fed Hg-free food. After 14 days, the mercury reached a concentration of 0.175 microg g(-1) in the hepatopancreas and approximately half this level in the gills of Hg-fed animals. No depuration occurred from the hepatopancreas although the gills lost approximately two-thirds of their labelled mercury during the depuration period. Hemolymph sodium concentrations in Hg-exposed crayfish, both fed and dummy-fed, after 14 days were significantly lower than in Hg-free controls and remained low following the 21-day depuration period. Hemolymph calcium concentrations were lower in Hg-fed animals than in dummy-fed and control animals after 14 days although calcium levels rose in all treatments after 35 days. This may have been due to the incidence of pre-molt animals in all experimental groups, although the relationship between this and mercury exposure was not established unequivocally. Hemolymph potassium levels showed no differences between treatments.     

Accumulation of anticoagulant rodenticides in a non-target insectivore, the European hedgehog (Erinaceus europaeus)

Studies on exposure of non-targets to anticoagulant rodenticides have largely focussed on predatory birds and mammals; insectivores have rarely been studied. We investigated the exposure of 120 European hedgehogs (Erinaceus europaeus) from throughout Britain to first- and second-generation anticoagulant rodenticides (FGARs and SGARs) using high performance liquid chromatography coupled with fluorescence detection (HPLC) and liquid-chromatography mass spectrometry (LCMS). The proportion of hedgehogs with liver SGAR concentrations detected by HPLC was 3-13% per compound, 23% overall. LCMS identified much higher prevalence for difenacoum and bromadiolone, mainly because of greater ability to detect low-level contamination. The overall proportion of hedgehogs with LCMS-detected residues was 57.5% (SGARs alone) and 66.7% (FGARs and SGARs combined); 27 (22.5%) hedgehogs contained >1 rodenticide. Exposure of insectivores and predators to anticoagulant rodenticides appears to be similar. The greater sensitivity of LCMS suggests that hitherto exposure of non-targets is likely to have been under-estimated using HPLC techniques.     

Depuration of copper and zinc by green oysters and blue mussels of Taiwan

This paper describes depuration processes of copper and zinc in green oysters (Crassostrea gigas) and in blue mussels (Mytilus smarangdium) collected from an environment with heavy copper contamination, and then transferred to natural clean seawater. Results show that the total loss of copper content per oyster is an exponential function of exposure time for the first 6 days with a depuration rate of 351 microg g(-1) day(-1) and then levels off. During this exponential decrease period approximately 67% of the copper accumulated in green oysters was depurated. However, when the copper contents in the oysters decreased from 2225 +/- 111 microg g(-1) to 344 +/- 18.7 microg g(-1) the depuration rates decreased from 245 microg g(-1) day(-1) to 0.08 microg g(-1) day(-1). This means that green oysters had a 16-fold higher copper depuration rate (351 microg g(-1) day(-1)) than normal oysters (21.5 microg g(-1) day(-1)) for the first 6 days. However, the depuration of accumulated copper and zinc by the mussels was a fast process in natural clean seawater. About 91% of the accumulated copper was lost during the first 6-day period; copper contents declined from 20.2 +/- 3.41 microg g(-1) to 1.80 +/- 0.21 microg g(-1). Only 36% of the accumulated zinc was lost during a depuration period of 6 days. Calculations show that the biological half-lives of copper in green and normal oysters were 11.6 and 25.1 days, respectively. The biological half-lives of zinc in green and normal oysters were 16.7 and 30.1 days, respectively. In spite of the relatively low initial copper content in blue mussels being 20.2 +/- 3.41 microg g(-1), the biological half-life is only 6.40 days. From these results it is important to emphasise that the fastest turnover rate is for copper in blue mussels. However, zinc is more retentive in blue mussels than copper.     

Trace metals in primary feathers of the Barn Owl (Tyto alba guttatus) in The Netherlands

The number of Barn Owls in The Netherlands has been reduced substantially over the last few decades. Death as a result of poisoning seems unlikely, but the pathology of all bird species found dead in The Netherlands between 1975 and 1988 (n = 15 422) shows that 21% of all the birds were contaminated. However, the most important factor responsible for the decline in Barn Owl numbers in The Netherlands has not yet been established. As a part of a new national protection plan for the Barn Owl, the role of heavy metals has been investigated. Concentrations of heavy metals in the primary feathers of the Barn Owl varied according to their position in the wing; especially As, Sb, Fe and Zn whose concentrations depended on the place of the primary feather in the wing and the part of the vane which is used for the monitoring. The HS7 feather vane appears to provide a good estimate, even though the metal concentrations of this feather are always slightly lower than the concentrations in mixed samples of all ten primaries. It is recommended that they are used as a standard. Many factors affect metal concentrations. Increasing levels with age are found, presumably because metals are stored during growth at the end of the feathers as a method of reducing possible harmful effects. No significant correlations were found between the metal concentrations in the organs and those in the feather. Kidney and liver concentrations are always lower than the generally accepted levels for pathological damage of these organs. Even though metal concentrations in Barn Owl feathers are high compared with those reported for other birds in the Netherlands, it is concluded that Barn Owls are not adversely affected by current levels of heavy metal contamination in The Netherlands.     

Simultaneous determination of seven anticoagulant rodenticides in agricultural products by gel permeation chromatography and liquid chromatography–tandem mass spectrometry

A sensitive and reliable method for the simultaneous determination of hydroxycoumarin-type (brodifacoum, bromadiolone, coumatetralyl, and warfarin) and indandione-type (chlorophacinone, diphacinone, and pindone) rodenticides in agricultural products by gel permeation chromatography (GPC) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. The procedure involved extraction of the rodenticides from samples with acetone, followed by liquid–liquid partitioning with hexane/ethyl acetate (1:1, v/v) and 10% sodium chloride aqueous solution, then cleanup using GPC, and finally, analysis using LC–MS/MS. High recoveries from the GPC column were obtained for all rodenticides tested using a mobile phase of acetone/cyclohexane/triethylamine (400:1600:1, v/v/v). An ODS column, which contains low levels of metal impurities, gave satisfactory peak shapes for both hydroxycoumarin- and indandione-type rodenticides in the LC–MS/MS separation. The average recoveries of rodenticides from eight agricultural foods (apple, eggplant, cabbage, orange, potato, tomato, brown rice, and soybean) fortified at 0.0005–0.001 mg/kg ranged from 76 to 116%, except for bromadiolone in orange (53%) and diphacinone in soybean (54%), and the relative standard deviations ranged from 1 to 16%. The proposed method effectively removed interfering components, such as pigments and lipids, and showed high selectivity. In addition, the matrix effects were negligible for most of the rodenticide/food combinations. The results suggest that the proposed method is reliable and suitable for determining hydroxycoumarin- and indandione-type rodenticides in agricultural products.     

Chronic effects of Cd on reproduction of Polypedilum nubifer (Chironomidae) through water and food

Chronic effects of Cd on reproduction of Polypedilum nubifer (Chironomidae) were investigated by Cd-exposure from the egg stage using a flow-through aquarium. No significant effect of Cd on reproduction was observed in the midge larvae which had been exposed to 10 or 20 microg Cd litre(-1). Emergence of the Cd-exposed larvae peaked several days before that of the control, although growth was impaired in 1st and/or 2nd instars. The percentage emergence success decreased to about 46% of the control at 40 microg Cd litre(-1). However, other reproductive processes (adult sex ratio, oviposition success and egg hatchability) were not impaired. The emergence success decreased to less than 3% of the control at 80 microg Cd litre(-1). The emergence success of midge larvae which had been fed Cd-contaminated food with 220 or 1800 microg Cd g(-1) decreased to nearly 60% of the control. However, other reproductive processes were not impaired. Emergence success of larvae exposed to food containing 22 microg Cd g(-1) was unaffected.     

Bioaccumulation studies of organochlorinated pesticides in tissues of Cyprinus carpio

Freshwater fish Cyprinus carpio was selected for the study of bioaccumulation of organochlorinated pesticides in tissues like gills, muscle, intestine, kidney, and liver in a continuous fed system. The pesticides used were Aldrin, Dieldrin, BHC, and DDT. The bioaccumulation of Dieldrin was maximum of 85.0 microg g(-1) wet weight in liver tissue while minimum of 7.30 microg g(-1) wet weight for DDT at 30 days exposure time. Bioconcentration factor (BCF) has followed the same trend in liver tissue for Dieldrin and DDT. The rate of bioaccumulation was found to be maximum of 4.3879 microg g(-1) wet weight in liver tissue and minimum of 0.0021 microg g(-1) wet weight in gill tissue for 30 days exposure. As evidenced by the increasing values of BCF, pesticide uptake also showed increased trend with the increase in exposure time. A high correlation coefficient ranging between 0.7247 and 0.9616 between the pesticide concentration and exposure time was observed. Based on actual BCF values, log Kow were calculated and the values are well within the reported values of 6.5 indicating efficient relationship between BCF and log Kow because beyond the 6.5 the bioconcentration levels off.     

The influence of time on lead toxicity and bioaccumulation determined by the OECD earthworm toxicity test

Internationally agreed standard protocols for assessing chemical toxicity of contaminants in soil to worms assume that the test soil does not need to equilibrate with the chemical to be tested prior to the addition of the test organisms and that the chemical will exert any toxic effect upon the test organism within 28 days. Three experiments were carried out to investigate these assumptions. The first experiment was a standard toxicity test where lead nitrate was added to a soil in solution to give a range of concentrations. The mortality of the worms and the concentration of lead in the survivors were determined. The LC50s for 14 and 28 days were 5311 and 5395 microgPb g(-1)soil respectively. The second experiment was a timed lead accumulation study with worms cultivated in soil containing either 3000 or 5000 microgPb g(-1)soil. The concentration of lead in the worms was determined at various sampling times. Uptake at both concentrations was linear with time. Worms in the 5000 microg g(-1) soil accumulated lead at a faster rate (3.16 microg Pb g(-1)tissue day(-1)) than those in the 3000 microg g(-1) soil (2.21 microg Pb g(-1)tissue day(-1)). The third experiment was a timed experiment with worms cultivated in soil containing 7000 microgPb g(-1)soil. Soil and lead nitrate solution were mixed and stored at 20 degrees C. Worms were added at various times over a 35-day period. The time to death increased from 23 h, when worms were added directly after the lead was added to the soil, to 67 h when worms were added after the soil had equilibrated with the lead for 35 days. In artificially Pb-amended soils the worms accumulate Pb over the duration of their exposure to the Pb. Thus time limited toxicity tests may be terminated before worm body load has reached a toxic level. This could result in under-estimates of the toxicity of Pb to worms. As the equilibration time of artificially amended Pb-bearing soils increases the bioavailability of Pb decreases. Thus addition of worms shortly after addition of Pb to soils may result in the over-estimate of Pb toxicity to worms. The current OECD acute worm toxicity test fails to take these two phenomena into account thereby reducing the environmental relevance of the contaminant toxicities it is used to calculate.     

Exposure of Chironomus riparius larvae to uranium: effects on survival, development time, growth, and mouthpart deformities

Among non-biologically essential metals, data concerning uranium effects on freshwater benthic macroinvertebrates are scarce. The effects of uranium on survival, development time, growth and mouthpart deformities of midge Chironomus riparius were investigated. A 10-day static laboratory bioassay was performed exposing first instar larvae to artificial sediment spiked with four concentrations of uranium (2.97; 6.07; 11.44; 23.84 microg U g(-1) dry wt). As uranium was released from the sediment to the overlying water during this bioassay, both the sediment and the water column act as contamination pathways in giving rise to the observed effects. Significant negative effects on survival, development time, and growth were detected at 6.07, 6.07 and 2.97 microg U g(-1) dry wt, respectively. An LC20 of 2.49 microg U g(-1) dry wt (95% CI=1.48-4.27), and an LC50 of 5.30 microg U g(-1) dry wt (95% CI=3.94-7.25) were estimated. With respect to effects of uranium on larvae mouthpart deformities, we found that the lower the concentrations, the higher the deformity rates. These results highlight the potential impact of uranium at population level in environmentally realistic concentrations.     

Uptake of gamma-HCH (Lindane) by pipistrelle bats and its effect on survival

Adult pipistrelle bats were caught at two roosts in Eastern England and kept in captivity on an ad lib diet of mealworms. In Experiment 1, two groups of eight bats were each kept in identical outdoor enclosures where the bats could fly freely and where they had a choice of five roost boxes, one of which was heated. One of these groups was exposed to gamma-HCH applied to planed pine blocks which had been immersed in a hexane solution of gamma-HCH. An initial concentration, estimated from surface wood scrapings, of 9.94 +/- 1.15 mg m(-2) was used for the first 44 days, while 866 +/- 51 mg g(-2) was used for a further 44 days. Blocks were placed in the roost boxes to simulate the type of exposure experienced by wild bats. Blocks dosed with solvent alone were given to the other group of bats (controls). Six of the eight bats in the group exposed to gamma-HCH died, while all bats in the control group survived (P < 0.007). In Experiment 2, three groups of five bats were kept in identical cages. Two groups were exposed to identical wood blocks dosed with gamma-HCH, which gave a concentration of 211 mg m(-2) in surface scrapings taken 1-2 h after dosing, while the other group received a wood block treated with solvent alone (control). All bats in the groups exposed to gamma-HCH died within 17 days, while all bats in the control group survived (P < 0.001). Tissues of bats were analysed for gamma-HCH by gas chromatography. There was a critical concentration of 622 +/- 102 microg gamma-HCH g(-1) extractable lipid at which bats died. The total weight of gamma-HCH in bat carcasses was directly related to the weight of extractable lipid. On average, bats died when the gamma-HCH concentration in the whole body reached 27.9 +/- 4.8 microg g(-1), but this value increased as body weight increased. This study confirmed the results of a previous study that gamma-HCH is toxic to bats in conditions simulating exposure in the wild.     

Age- and sex-based comparative distribution of selected metals in the scalp hair of an urban population from two cities in Pakistan

Concentrations of Cu, Zn, Pb and Ni in the scalp hair of male and female donors, with an age range of 6-60 years, were determined by ICP atomic emission spectroscopy. The donors were drawn from the densely populated city of Lahore and the relatively less-populated capital city of Islamabad for comparative evaluation of the metal levels in relation to age, sex and location. Linear regression analyses and correlation between paired metals indicated a positive correlation between Cu and Zn for both sexes ( [Formula: see text] ) and between Pb and Ni ( [Formula: see text] ) for males and females of Lahore. Metal concentrations varied between the two cities and the two sexes. The highest mean concentration was found for Zn at 180.5 microg g(-1) for males and 202.4 microg g(-1) for females from Lahore, while for counterparts from Islamabad the values were 105.2 microg g(-1) and 206.6 microg g(-1). Copper showed an identical mean concentration (20.8 microg g(-1)) in the hair of both males and females from Lahore; however, relatively lower mean concentrations (7.7 and 10.8 microg g(-1)) were observed for donors from Islamabad. Mean Pb concentrations in hair of male donors from Lahore and Islamabad were 9.4 and 7.0 microg g(-1), respectively; in female groups the concentrations were 14.3 and 5.7 microg g(-1), respectively. Ni showed the lowest concentration range (4.3-4.5 microg g(-1)) of all the four metals for subjects from Lahore, and this was higher than the corresponding range (2.0-3.2 microg g(-1)) for subjects from Islamabad. The findings are discussed in relation to the available data from the literature.     

Residues of phosphamidon in rice fields

Thirty-day-old seedlings of rice plants (IR-20 variety) from the nursery were transplanted into experimental plots and after 52 days were sprayed with phosphamidon (Dimecron 85% EC) at two dose-rates (0.38 kg a.i. ha(-1) and 0.76 kg a.i. ha(-1)). Residues of phosphamidon in the plant, soil and water were analysed by GLC, at various time intervals, and were found to decrease steadily up to 15 days. A second application of the pesticide was made on day 113 and grains harvested on day 138. The residue level in the plants was 0.12 microg g(-1) and in the grains 0.04 microg g(-1) with the high dose. This is slightly below the EPA prescribed tolerance level of 0.05 microg g(-1). The residues in both soil and water were very low, 24 h after spraying.     

Trace phthalate and adipate esters contaminated in packaged food

A method for trace analysis of two plasticizers, di-2-ethylhexyl phthalate (DEHP) and di-2-ethylhexyl adipate (DEHA), contaminated in packaged curry paste were investigated by gas chromatography with flame ionization detector (GC-FID). Curry paste samples were extracted by ultrasonic and solid phase extraction using Florisil(R) cartridge. Analysis by the GC-FID system provided limits of detection for DEHA and DEHP at 12 and 25 microg L(- 1) and a linear dynamic range between 25 microg L(- 1) to 60 mg L(- 1) with a coefficient of determination (R(2)) greater than 0.99. High recoveries were obtained, ranged from 91 to 99% and 88 to 98% for DEHP and DEHA with RSD lower than 7 and 10% respectively. The method detection limit and limits of quantitation were ranged from 27 to 30 and 90 to 100 microg L(- 1). The analysis of curry paste samples showed concentrations of DEHP and DEHA in the range of 4.0 ng g(- 1) to 0.61 microg g(- 1).     

Toxicity of crude oil to the mayfly, Hexagenia bilineata (Ephemeroptera: Ephemeridae)

Effects of crude oil on survival and behavior of the mayfly Hexagenia bilineata were evaluated in laboratory studies. Mayfly nymphs were exposed to the water soluble and oil residue fractions of crude oil. Mayfly survival was not reduced by a 96-h exposure to either the water soluble fraction or the oil residue mixed with sediment. However, significant mortality did result from a 21-day exposure to oil residue mixed with sediment at concentrations as low as 500 microg g(-1). Survival was also reduced after a 21-day exposure to oil-contaminated sediments (1905 microg g(-1)) collected 6 weeks after a crude oil spill in the Chariton River, Missouri. In a behavioral test measuring habitat exclusion, organisms did not avoid contact with sediment containing oil residue (50-800 microg g(-1)). Collectively, results from these studies indicate that exposure to oil residue in sediment will reduce survival of H. bilineata in the laboratory and may reduce survival in the environment for 6 weeks or more after an oil spill.     

Uptake and accumulation of mercury from dental amalgam in the common goldfish,Carassius auratus

In this study, the bioavailability and accumulation of mercury from external environmental exposure to mixed, cured, milled, sieved and proportioned dental amalgam was examined in the common goldfish, Carassius auratus. Fish were exposed to dental amalgam (particle size range from < 0.10 to 3.15 mm) in order to represent the particle size and distribution of that found within the typical dental office wastewater discharge stream. Experimental amalgam water loadings were 0 g/l, 0.5 g/l and 1 g/l in glass aquaria at 15 degrees C for 28 days. Fish tissues were sampled at 5 min and 28 days of exposure, and the liver, brain, muscle and whole body analyzed for total mercury using cold vapor atomic fluorescence spectroscopy. Mercury was found in several tissues examined and generally increased with exposure to higher amounts of dental amalgam. The highest levels were found in the whole body (17.68 +/- 5.73 microg/g) followed by the liver (0.80 +/- 0.16 microg/g) and muscle (0.47 +/- 0.16 microg/g). The lowest concentrations were seen in the brain (0.28 +/- 0.19 microg/g). Compared to controls, concentrations in the whole body, muscle and liver in fish exposed for 28 days to the highest concentration of amalgam were 200-, 233-, and 40-fold higher, respectively. This study shows that mercury from an environmental exposure to representative samples of dental amalgam typically found within the dental wastewater discharge stream is bioavailable to fish and may accumulate in internal tissues.     

Comparative toxicity of polychlorinated biphenyls to earthworms Eisenia foetida and Lumbricus terrestris

Effects of polychlorinated biphenyls (PCB; Aroclor 1254) in the manure worm, Eisenia foetida, on survival (LC50/LD50), and ability of coelomic leukocytes (also called coelomocytes) to form secretory rosettes (SR) and erythrocyte rosettes (ER) with, and to phagocytose antigenic rabbit red blood cells were determined and compared with those published for the earthworm, Lumbricus terrestris. Using a 5-day filter paper contact exposure protocol, LC50 and LD50 were 30.4 microg cm(-2) and 4500 microg g(-1) dry mass, respectively. Nominal PCB exposure concentrations of 5.0 and 10.0 microg cm(-2) resulted in tissue levels of 1400 and 2900 microg g(-1) dry mass. These body burdens resulted in significant reduction in SR formation by 18 and 52%, respectively. ER formation and phagocytosis were reduced 52 and 61%, respectively, only at the higher tissue concentration. Compared to L. terrestris, E. foetida: (1) accumulated considerably more PCB at each exposure concentration; (2) showed lower LC50, but higher LD50; and (3) exhibited effects on coelmocytes only at tissue PCB concentrations that caused some mortality. In terms of lethality and immunomodulation of SR, ER and phagocytosis, E. foetida appears to be more resistant to PCB than L. terrestris.     

Copper regulation and homeostasis of Daphnia magna and Pseudokirchneriella subcapitata: influence of acclimation

This study aimed to evaluate (1) the capacity of the green alga Pseudokirchneriella subcapitata and the waterflea Daphnia magna to regulate copper when exposed to environmentally realistic copper concentrations and (2) the influence of multi-generation acclimation to these copper concentrations on copper bioaccumulation and homeostasis. Based on bioconcentration factors, active copper regulation was observed in algae up to 5 microg Cu L(-1) and in daphnids up to 35 mug Cu L(-1). Constant body copper concentrations (13+/-4 microg Cu g DW(-1)) were observed in algae exposed to 1 through 5 microg Cu L(-1) and in daphnids exposed to 1 through 12 microg Cu L(-1). At higher exposure concentrations, there was an increase in internal body copper concentration, while no increase was observed in bioconcentration factors, suggesting the presence of a storage mechanism. At copper concentrations of 100 microg Cu L(-1) (P. subcapitata) and 150 microg Cu L(-1) (D. magna), the significant increases observed in body copper concentrations and in bioconcentration factors may be related to a failure of this regulation mechanism. For both organisms, internal body copper concentrations lower than 13 microg Cu g DW(-1) may result in copper deficiency. For P. subcapitata acclimated to 0.5 and 100 microg Cu L(-1), body copper concentrations ranged (mean+/-standard deviation) between 5+/-2 microg Cu g DW(-1) and 1300+/-197 microg Cu g DW(-1), respectively. For D. magna, this value ranged between 9+/-2 microg Cu g DW(-1) and 175+/-17 microg Cu g DW(-1) for daphnids acclimated to 0.5 and 150 microg Cu L(-1). Multi-generation acclimation to copper concentrations >or =12 microg Cu L(-1) resulted in a decrease (up to 40%) in body copper concentrations for both organisms compared to the body copper concentration of the first generation. It can be concluded that there is an indication that P. subcapitata and D. magna can regulate their whole body copper concentration to maintain copper homeostasis within their optimal copper range and acclimation enhances these mechanisms.     

Transfer of selenium from prey to predators in a simulated terrestrial food chain

Little is known about the accumulation and effects of selenium in reptiles. We developed a simplified laboratory food chain where we fed commercial feed laden with seleno-D,L-methionine (30 microg/g dry mass) to crickets (Acheta domestica) for 5-7 d. Se-enriched crickets (approximately 15 microg/g Se [dry mass]) were fed to juvenile male and female lizards (Sceloporus occidentalis) for 98 d while conspecifics were fed uncontaminated crickets. Lizards fed contaminated prey accumulated Se concentrations ranging from 9.3 (in female carcass) to 14.1 (in female gonad) microg/g compared to <1.5 microg/g in tissues of controls. Female gonad concentrations approached the highest of thresholds for reproductive toxicity in oviparous vertebrates. However, we observed no consistent effect of dietary treatment on sublethal parameters or survival. Our simplified food chain proved to be an ecologically relevant method of exposing lizards to Se, and forms the foundation for future studies on maternal transfer and teratogenicity of Se.