Adaptation to soil pollution by cadmium excretion in natural populations of Orchesella cincta (L.) (Collembola)

Population differentiation in Orchesella cincta (L.) (Collembola) populations, from various heavy metal contaminated sites, was studied by comparing cadmium excretion efficiency in first generation (F₁) laboratory individuals. Animals from sites with high metal concentrations in the litter and with a long history of contamination showed significantly higher excretion efficiencies than animals from low pollution, or reference sites. Differences found in the F₁ laboratory animals suggest evidence for genetic differences between the populations.Beneficial and detrimental effects of cadmium excretion were studied in relation to body growth and cadmium concentrations. In chronically exposed animals from an unpolluted site, no physiological acclimation was observed. Excretion efficiency was negatively correlated with body concentrations of cadmium. No detrimental effects were found.Whole-body equilibrium concentrations of cadmium and lead were similar in F₁ animals from the reference site and polluted sites. Significant differences in excretion efficiencies imply that the distribution of toxic metals over body compartments differs, tolerant populations having a higher proportion deposited in the gut. Body concentrations of zinc were consistently higher in animals from the polluted site, during both cadmium and zinc exposure. No detrimental effects of increased cadmium excretion on body concentrations of zinc were observed. Population comparisons of cadmium excretion efficiency data and growth reduction in F₁ laboratory animals showed that both parameters were inversely related. Cadmium and lead contamination were not the sole factors determining tolerance differentiation.     

Tolerance to Zinc in Populations of the Earthworm Lumbricus rubellus from Uncontaminated and Metal-Contaminated Ecosystems

Zinc tolerance in Lumbricus rubellus populations from two metal-polluted (smelter and mine) sites was studied by comparing the effects of zinc with responses in a reference site strain. For the study, adult worms were collected directly from the field. Thus, no attempt was made to differentiate between tolerance resulting from population-level genetic adaptation or phenotypic plasticity in metal physiology. To compare relative sensitivity for zinc, worms from the three populations were exposed in laboratory tests. Effects on survival, weight change, cocoon production, and internal zinc levels were measured. Prior to exposure, it was anticipated that worms from the metal-contaminated sites would show substantially increased tolerance to zinc. This was not the case for all measured parameters. Thus, although differences in the shape of the dose-response relationships for survival and cocoon production were found, substantial variations in measured responses, effect concentrations, or zinc accumulation rates were not apparent. Overall, therefore, zinc tolerance is unlikely to be a major factor influencing the distribution of L. rubellus in contaminated regions. Received: 8 September 1998/Accepted: 21 March 1999     

Susceptibility of a Carabid Beetle, <Emphasis Type="Italic">Pterostichus oblongopunctatus</Emphasis> Fab., from a Gradient of Heavy Metal Pollution to Additional Stressors

Insects inhabiting contaminated areas show increased susceptibility to other stressors, the purpose of this study was to investigate whether this phenomenon had a genetic basis. We investigated changes in susceptibility to food deprivation and insecticide (dimethoate) treatment of the ground beetle Pterostichus oblongopunctatus originating from four populations situated along a metal pollution gradient. To determine whether the increased susceptibility to additional stressors found in field-exposed animals from chronically metal-polluted sites had a genetic basis, our research was conducted on the second generation of laboratory-reared animals. There was no difference in susceptibility to the additional stressors indicating that the differences between populations observed in earlier studies do not have a genetic basis.     

Dietary zinc reduces uptake but not metallothionein binding and elimination of cadmium in the springtail,Orchesella cincta

In metal-polluted environments, high concentrations of metals such as zinc, cadmium, copper, and lead are present. Many studies have been conducted to determine uptake and binding of the nonessential, toxic metal cadmium. Effects of essential metals on this uptake and binding remain unclear. The aim of the present study was to determine the effect of zinc on cadmium kinetics and metallothionein induction in the springtail Orchesella cincta. Exposure experiments were conducted with cadmium only, zinc only, and cadmium + zinc. Metallothionein was isolated to determine zinc binding to or induction of this cadmium-binding protein. In animals exposed to cadmium only and to cadmium + zinc, metallothionein was induced. In animals exposed to zinc only, no metallothionein was induced, and zinc did not bind to the metallothionein induced by cadmium. Cadmium uptake rate was significantly lower in animals exposed to cadmium + zinc than in animals exposed to cadmium only. No significant pattern of uptake and elimination of zinc was observed. Zinc concentrations in the animals were not significantly different for the different exposures, demonstrating that this element is regulated by O. cincta. These results suggest a protective role of zinc in the uptake of cadmium but no interference of zinc with the internal cadmium distribution and elimination.     

Comparison of cadmium kinetics in four soil arthropod species

Soil organisms may play an important role in the transfer of metals through the ecosystem in metal-polluted environments. To evaluate this role, four representative species were compared through modelling their toxico-kinetics when exposed to cadmium in chronic laboratory experiments. Considerable differences in consumption and assimilation of food and cadmium were found between the species. Cadmium assimilation correlated with food assimilation. Cadmium excretion and equilibrium concentrations also differed considerably between the species. The differences in equilibrium concentrations were comparable to the differences between these species in the field. Cadmium assimilation efficiencies were high in the predatorsNotiophilus biguttatus andNeobisium muscorum, and were lower in the saprotrophsOrchesella cincta andPlatynothrus peltifer. Excretion constants were high in the insectsN. biguttatus andO. cincta and low in the arachnidsN. muscorum andP. peltifer. There was no direct relationship between assimilation efficiency and excretion ability. The differences in cadmium assimilation efficiencies reflect differences in trophic level and most probably differences in nutrient demand, which may be determined taxonomically. The influence of excretion ability on the equilibrium concentration is larger than that of assimilation efficiency. Species with a high equilibrium concentration combine low excretion ability with either low or high assimilation. Together with compartment modelling, the study of uptake and excretion of cadmium by individual species provides a suitable tool for predicting the amount in the different soil invertebrates and for calculating pollutant fluxes.     

Genetic Variation in Bank Vole Populations in Natural and Metal-Contaminated Areas

The effects of isolation and heavy-metal pollution on genetic diversity in Myodes (=Clethrionomys) glareolus populations were studied. Isolation and pollution are considered to have important effects on biodiversity. Animals were collected from ten populations in isolated (island), mainland, and metal-polluted areas. Three populations were in areas near zinc and lead smelters; four were on islands in the relatively unpolluted Mazurian Lake District and in the Bieszczady Mountains; and three were in clean-mainland areas in the Mazurian Lake District, the Niepo?omice Forest, and the Bieszczady Mountains. Cadmium and lead concentrations in liver and kidney were measured to assess the animals’ exposure to metals. The metal concentrations were greater in animals from areas classed as polluted than in animals from the clean-mainland areas and islands. The genetic diversity of each population was analyzed using eight microsatellite markers. The results confirmed that isolation adversely affects genetic diversity in M. glareolus populations (giving low heterozygosity and poor allelic richness), but the effect of metal exposure on genetic diversity was not strong. Of the samples from polluted areas, only the Katowice population, which is exposed to high levels of metal pollution and is also isolated because of human activity, showed genetic variation parameters that were similar to those for the island populations. Nei’s genetic distances indicated that the island populations were genetically distant from each other and from the other populations, and there were noticeable inbreeding effects that would have been caused by the isolation of these populations.     

Dietary assimilation and elimination of Cd, Se, and Zn by Daphnia magna at different metal concentrations

This study examines the influences of Cd, Se, and Zn concentrations in ambient water on the assimilation, elimination, and release budget of metals, and the clearance rate of Daphnia magna through ingestion of phytoplankton diets. With increasing ambient metal concentration over two to three orders of magnitude, the assimilation efficiencies (AEs) of Cd and Se from two green algal species, Scenedesmus obliquus and Chlamydomonas reinhardtii, decreased significantly. In contrast, the Zn AE from ingested food, which typically was low (<7%), was not impacted by the difference in Zn or Cd concentrations in ingested cells. The Cd AE also was reduced significantly by a high Zn concentration in ingested algae, perhaps due to the competitive assimilation between the two metals. Metal elimination was determined after the daphnids were exposed to the radiolabeled diets for 3 d. The elimination rate constant was not dependent on the metal concentration in ingested food. Similarly, the routes of metal elimination (excretion, egestion, molting, and neonate production) were less influenced by the metal concentration. The rapid elimination of Se and Zn may be attributed to the transfer of these metals from mother to offspring. Except at the highest Cd (917 nM) and Se (1,333 nM) concentrations, there was no significant effect of metal concentration on the clearance rate of the animals. Consequently, the metal assimilation in D. magna may play an important role in the regulation of Cd and Se influx into the animals, whereas the regulation of the metal tissue burden in the animals is unlikely to be achieved through the metal elimination. The trophic transfer factors (TTF) of Cd and Se were related inversely to the metal concentration in the water, whereas the TTF of Zn was less variable at different Zn concentrations. The change of TTF with metal concentration will have important implication for ecotoxicity testing using D. magna, especially when the dietary exposure is incorporated.     

Bioavailability of Metals in Stream Food Webs and Hazards to Brook Trout (Salvelinus fontinalis) in the Upper Animas River Watershed, Colorado

The water quality, habitats, and biota of streams in the upper Animas River watershed of Colorado, USA, are affected by metal contamination associated with acid drainage. We determined metal concentrations in components of the food web of the Animas River and its tributaries—periphyton (aufwuchs), benthic invertebrates, and livers of brook trout (Salvelinus fontinalis)—and evaluated pathways of metal exposure and hazards of metal toxicity to stream biota. Concentrations of the toxic metals cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) in periphyton, benthic invertebrates, and trout livers from one or more sites in the upper Animas River were significantly greater than those from reference sites. Periphyton from sites downstream from mixing zones of acid and neutral waters had elevated concentrations of aluminum (Al) and iron (Fe) reflecting deposition of colloidal Fe and Al oxides, and reduced algal biomass. Metal concentrations in benthic invertebrates reflected differences in feeding habits and body size among taxa, with greatest concentrations of Zn, Cu, and Cd in the small mayfly Rhithrogena, which feeds on periphyton, and greatest concentrations of Pb in the small stonefly Zapada, a detritivore. Concentrations of Zn and Pb decreased across each trophic linkage, whereas concentrations of Cu and Cd were similar across several trophic levels, suggesting that Cu and Cd were more efficiently transferred via dietary exposure. Concentrations of Cu in invertebrates and trout livers were more closely associated with impacts on trout populations and invertebrate communities than were concentrations of Zn, Cd, or Pb. Copper concentrations in livers of brook trout from the upper Animas River were substantially greater than background concentrations and approached levels associated with reduced brook trout populations in field studies and with toxic effects on other salmonids in laboratory studies. These results indicate that bioaccumulation and transfer of metals in stream food webs are significant components of metal exposure for stream biota of the upper Animas River watershed and suggest that chronic toxicity of Cu is an important factor limiting the distribution and abundance of brook trout populations in the watershed. Received: 4 April 2000/Accepted: 31 July 2000     

Two-Phase Uptake of Nickel in the Ground Beetle <Emphasis Type="Italic">Pterostichus oblongopunctatus</Emphasis> (Coleoptera: Carabidae): Implications for Invertebrate Metal Kinetics

We studied nickel (Ni) kinetics in the ground beetle Pterostichus oblongopunctatus exposed to different, potentially stressful, temperatures. We found unexpected Ni kinetics in metal-exposed adult and larval beetles. Instead of the pattern observed commonly for other metals, i.e., an increase in metal concentration followed by stabilisation in the uptake phase and a decrease after transfer to uncontaminated food, the Ni-fed beetles apparently switched to decontamination soon after the start of Ni exposure while they were still being fed Ni-spiked food. In addition, internal body Ni concentrations showed high variance. The traditional first-order, one-compartment model with the switch to decontamination set to the last day of the uptake phase appeared inadequate and in most cases was nonsignificant. Instead, the model with a regression-estimated point of switching to decontamination fit the data better, explaining 57.2–91.5% of the temporal variability of mean Ni body concentrations (weighted regression) in adult beetles and 44.1–62.3% in larvae. Temperature did not affect Ni toxicokinetics in adults, but in larvae there were some temperature-dependent differences in kinetic parameters.     

Feeding and Growth Responses of the Snail <Emphasis Type="Italic">Theba pisana</Emphasis> to Dietary Metal Exposure

The effects of dietary exposure to copper (Cu), lead (Pb), and zinc (Zn) on feeding activities, growth response, and mortality of Theba pisana snails were studied in 5-week feeding tests. Snails were fed on an artificial diet containing the following Cu, Pb, or Zn concentrations: 0, 50, 100, 500, 1000, 5000, 10,000, and 15,000 μg/g dry food. At the end of 5 weeks, the food consumption rate was decreased with increasinges in both metal concentrations and time of exposure. The estimated concentrations of metals that reduces food consumption to 50% (EC₅₀) after 5 weeks were 56, 118, and 18 μg/g dry food for Cu, Pb, and Zn, respectively. All tested metals in the diet were found to inhibit growth of the snails in a dose-dependent manner. The toxic effect on growth of the tested metals could be arranged in the order Cu > Zn > Pb. The cumulative percentage mortality among snails fed a Cu- or Zn-contaminated diet was 73.3% and the respective value for a Pb-contaminated diet was 13.3%. There was a positive correlation between growth coefficient and food consumption for all tested metals.     

Cadmium turnover and changes of zinc and copper body status of rats continuously exposed to cadmium and ethanol

The effects of continuous exposure to cadmium (Cd) and ethanol on Cd turnover and zinc (Zn) and copper (Cu) body status of male Wistar rats were studied. The animals received an aqueous solution of 10% (w/v) ethanol and/or 50 mg Cd/l as the only drinking fluid for 12 weeks. The concentrations of Zn, Cu and Cd in the serum (or blood), liver, kidneys, spleen, brain, heart, femoral muscle and femur as well as in 24-h urine and faeces specimens were assessed by atomic absorption spectrometry (AAS). Ethanol alone had no effect on Cd accumulation or excretion. By contrast, co-administration of ethanol with Cd influenced the turnover of this toxic metal. Long-term consumption of ethanol alone caused a decrease in femur Zn and liver Cu concentrations. Moreover, the urinary loss of both bioelements decreased, whereas their faecal excretion was increased. Exposure to Cd resulted in an increase in liver and kidney and in a decrease in femur and 24-h urine Zn concentrations. An increase in Cu concentration in the kidney and a decrease in the brain were also noted. Moreover, Cd increased the total pool of Zn in organs (kidneys, liver, spleen, heart and brain), but did not influence that of Cu. Zn concentration in the liver, kidney and spleen of rats co-exposed to Cd and ethanol were increased, but were decreased in the brain and femur, compared to controls. The concentrations of Cu in livers and brains of these rats were decreased, whereas those in kidney, spleen and heart were increased. The urinary excretion of the elements was decreased, whereas their faecal excretion was increased. Moreover, the total amount of Cu in organs decreased below the control value and that of Zn was in the normal range. These changes in Zn and Cu levels could be explained by different effects of both toxic substances, differences in bioelement intakes (due to reduced consumption of drinking solutions and food), and the modifying effect of ethanol on Cd turnover. Our results suggest that alcoholics may be more susceptible to Cd accumulation and its effects on body Zn and Cu.     

Acute toxicity of aqueous and substrate-bound copper to the midge,Chironomus decorus

Fourth instar larvae of the midge,Chironomus decorus, were exposed to copper in water and copper in food and substrate (bound forms). Copper present in aqueous forms was more toxic than when it was present in bound forms. The relationship between copper in water and copper in midges could be described by an exponential equation while the relationship between copper in substrate and midges was best described by a simple linear regression equation. Midge larvae accumulated copper from water and possessed some mechanisms to regulate copper uptake and excretion when exposed to copper concentrations of 0.05–1.0 mg/L (aqueous forms) and lost that ability when the concentration exceeded 1.0 mg/L. On the contrary, the midge larvae were unable to accumulate copper from food, since the estimated bioconcentration factor was between 0.10 and 0.16. When the midge larvae were exposed to copper in water, the uptake rate increased rapidly from 0–10 hr and then the rate increased very slowly or in some cases it reached a steady state after 10 hr. The steady state was attained within 1 to 3 hr when the midges were exposed to copper in food and substrate.     

Characteristics of immune-competent amoebocytes non-invasively retrieved from populations of the sentinel earthworm Lumbricus rubellus (Annelida; Oligochaeta; Lumbricidae) inhabiting metal polluted field soils

Lumbricus rubellus is a cosmopolitan earthworm devoid of riboflavin-storing eleocytes; its immune competent coelomocytes are predominantly amoebocytes. Our aim was to determine whether amoebocyte cytometrics in L. rubellus are robust biomarkers for innate immunological responses to environmental pollutants. Investigations were conducted on populations inhabiting three unpolluted and five metalliferous (mainly Pb+Zn+Cd) habitats in the UK and Poland. Inter-population differences in worm mass and amoebocyte numbers did not consistently reflect soil or tissue metal concentrations. Flow cytometry indicated that autofluorescence of the amoebocytes differs between cells from the unpolluted and metal-polluted worms, and pinocytosis of neutral red by amoebocytes was lower (especially at 15 versus 60 min incubation) in worms from the polluted Poland site compared with the reference population. To conclude, amoebocyte cytometrics and functionality are potentially useful for environmental diagnostics; deployment is contingent on better understanding potential confounders.     

Enhanced Inhibitory Effects of TBT Chloride on the Development of F1 Rats

Neurotoxicity is one of the major effects of tributyltin (TBT). The effects on the next generation of F₁ rats exposed to TBT via the placenta and their dams’ milk may be stronger than those on adults. Pregnant Wister rats were exposed to TBT at 0 and 125 ppm in their food. Half of the female F₁ rats in both groups were exposed to TBT at 125 ppm in their food from 9 to 15 weeks of age. Female F₁ rats were divided into the following groups: the control-control (CC) group, with no exposure; the TBT-control (TC) group, exposed to TBT via the placenta and their dams’ milk; the control-TBT (CT) group, exposed to TBT via their food from 9 to 15 weeks of age; and the TBT-TBT (TT) group, exposed to TBT via the placenta, their dams’ milk, and their food (n = 10/group). After administration, an open-field test and prepulse inhibition (PPI) test were performed at 15 weeks of age. The mean body weights of the TC and TT groups were significantly lower than that of the CC group from 9 to 15 weeks of age. The mean relative thymus weight of the TC and TT groups was significantly lower than that of the CC group. In the open-field test, a marked decrease in the total locomotion distance was observed in the TT group. The mean values in the TT and TC groups were significantly lower than that in the CC group. For the locomotion distance between 15 and 20 min, the mean values in the CT, TC, and TT groups were significantly lower than that in the CC group. The mean locomotor distance between 25 and 30 min in the TT group was significantly lower than that in the CC and TC groups. The mean values of instances of wall rearing in the TC, CT, and TT groups were significantly lower than that in the CC group. The mean value of face washing or body washing in the TT group was significantly lower than that in the CT group. There were no significant differences in indexes of the PPI test. Exposure to TBT via the placenta and their dams’ milk inhibited the development of F₁ rats, which continued after weaning. Inhibition of the rats’ activity induced by exposure to TBT via the placenta and their dams’ milk and/or via their food was suggested. The effects were most evident in the TT group.     

Heavy metal concentrations in ground beetles, leaf litter, and soil of a forest ecosystem

The objective of this study was to quantify the relationships between heavy metal concentrations in soil, leaf litter, and ground beetles at four sampling sites of a forest ecosystem in Medvednica Nature Park, Croatia. Ground beetles were sampled by pitfall trapping. Specimens were dry-ashed and soil and beetle samples digested with nitric acid. Lead, cadmium, copper, zinc, manganese, and iron were analyzed using atomic absorption spectrometry. Statistically significant differences between plots were found for lead, cadmium, and iron in ground beetles. Correlations between ground beetles and soil or leaf litter were positive for lead and cadmium concentrations and negative for iron concentration. Differences in species metal concentrations were recorded. Higher concentrations of all studied metals were found in female beetles. However, a significant difference between sexes was found only for manganese. Significant differences in species metal concentrations were found for species that differ in feeding strategies and age based on breeding season and emergence of young adults.     

Histological changes in the liver of Oreochromis mossambicus (Cichlidae) after exposure to cadmium and zinc

The toxic effects, of two heavy metals, cadmium (Cd) and zinc (Zn), on the histology of the liver of the southern African freshwater fish Oreochromis mossambicus, were investigated. The goal was to identify whether metal concentrations and exposure period influence the degree and nature of histological changes in the liver of exposed fish. Selected fish were exposed to a mixture of 5% concentrations of the LC₅₀ of cadmium and zinc and to a mixture of 10% concentrations of the LC₅₀ of cadmium and zinc, over both short- and long-term exposure periods. Similar histological changes occurred in the livers of specimens exposed to both 5% and 10% concentrations, indicating a definite toxic response to both the metal concentrations. These histological changes included hyalinization, hepatocyte vacuolation, cellular swelling, and congestion of blood vessels. The intensity of these histological changes was, however, influenced by the extent of the exposure period.     

A comparison between fecal cadmium and urinary beta2-microglobulin, total protein, and cadmium among Japanese farmers. An epidemiological study of cooperation between Japan and Sweden.

A study was made of 156 farmers living in a cadmium-exposed area and 93 farmers in a reference area. All were between 50 and 69 years of age. Cadmium intake from food was estimated from daily fecal cadmium content, body burden from urinary cadmium concentration, and cadmium-induced renal effects from urinary β₂-microglobulin (β₂-m) and total protein concentration. Average cadmium intake in the reference area was about 40 μg/day and in the exposed area about 150 μg/day. Average urinary cadmium excretion in the reference group was 2 μg/liter and in the exposed group 7.5 μg/liter. Average urinary β₂-m concentration in the reference group was 86 μg/liter and we defined tubular proteinuria as a β₂-m concentration higher than the average plus two standard deviations. With this definition the prevalence rate of tubular proteinuria was 3% in the reference group and 14% in the exposed group. Tubular proteinuria increased with age and with exposure duration. Increased total proteinuria was also more common in the exposed group but the prevalence rate ratio was 2.4 as compared to 4.4 for tubular proteinuria.     

Effects of Pentachlorophenol and Biotic Interactions on Soil Fauna and Decomposition in Humus Soil

In a laboratory experiment, effects of chemical stress (pentachlorophenol, PCP, at concentrations of 0, 50, and 500 mg/kg) and biotic interactions (nematodes in the presence or absence of collembolas and enchytraeids) on the community structure of soil animals and decomposition processes were studied. PCP was strongly adsorbed to humus that contained 65% organic matter. Numbers of fungal-feeding nematodes decreased significantly at the highest PCP concentration, while no effects were found in bacterial feeders. There were differences in the numbers of nematodes between different animal combinations, but at the highest PCP concentration, collembolas and enchytraeids had no effect on them. Numbers of collembola Willemia anophtalma were lowered at the highest PCP concentration, although PCP was not acutely toxic at this concentration. The highest PCP concentration was acutely toxic to enchytraeids, and for an unknown reason all of them died in the main experiment. Both ATP content of the soil and soil respiration were reduced at the highest PCP concentration, while no differences were found between animal treatments. Amounts of NH₄---N and PO₄---P in the soil increased with increasing PCP concentration. It was concluded that in the presence of simple animal communities, harmful chemicals like PCP regulate the community structure of soil animals as web as decomposition and nutrient mobilization.     

Effects of heavy metals on riverine benthic macroinvertebrate assemblages with reference to potential food availability for drift-feeding fishes

We examined the influence of heavy metal pollution from an abandoned mine on benthic macroinvertebrates, at population and community levels, and the potential amount of food available for drift-feeding fish in northern Japanese streams. We studied multiple polluted and unpolluted sites with similar longitudinal positions to avoid problems caused by upstream-downstream comparisons. The ranges of zinc, copper, cadmium, and lead concentrations among the study sites were 5 to 812 microg/L, less than 0.12 to 5.2 microg/L, less than 0.0026 to 4.9 microg/L, and 0.1 to 18.6 microg/L, respectively. The abundance of several populations and community metrics showed a significant negative response to heavy metal pollution. Mayfly diversity and abundance was relatively sensitive to heavy metal pollution. In addition, the biomass of groups of macroinvertebrate taxa that are highly available for salmonids were significantly reduced at metal-polluted sites; this decrease in the most highly available group was noticeable (99% at the heavily polluted upper sites and 69% at the moderately polluted lower sites in spring). These results suggest that we should consider the indirect effect of pollution on food availability for the conservation of fish populations that depend on drifting macroinvertebrates.     

Heavy Metal Toxicity and Differential Effects on the Hyperglycemic Stress Response in the Shrimp Palaemon elegans

Agricultural and industrial activities cause heavy metal pollution of the aquatic environment. The sensitivity of crustaceans to heavy metals is well documented. However, the hormonal and metabolic target of physiological functions affected by sublethal toxicity and stress responses have been scarcely investigated. Exposure of Palaemon elegans to increasing concentrations of heavy metals dissolved in artificial sea water resulted in an order of toxicity tested by LC₅₀ for 96 h in intact and eyestalkless animals in which Hg is the most toxic, followed by Cd, Cu, Zn, and Pb. Eyestalkless animals were found to be more sensitive than intact individuals. Heavy metals affect the blood glucose levels, yet manipulative stress does not. The intermediate sublethal concentrations of Hg, Cd, and Pb produced significant hyperglycemic responses within 3 h, while the highest concentrations elicited no hyperglycemia in 24 h. In contrast, animals exposed to Cu and Zn showed hyperglycemia even at high concentrations. This difference in response between Cu or Zn and the nonessential heavy metals Cd, Hg, or Pb can probably be explained by the physiological roles of the former in crustaceans and by tolerance adaptations. Involvement of the crustacean hyperglycemic hormone (cHH) was tested by routine bioassay on eyestalkless individuals; each group was injected with a two-eyestalk-equivalent extract from control animals or from shrimp exposed to high concentrations of Cd, Hg, Pb, or low concentrations of Cu or Zn. All showed a hyperglycemic response within 2 h. In contrast, extracts of eyestalk removed from animals that had developed a full hyperglycemic reaction after exposure to low concentrations of Hg, Cd, Pb, or high concentrations of Cu and Zn were depleted of cHH as shown by the attenuation of the response after injection of the extracts into eyestalkless animals. This generalized and predictable sublethal response can be used as a quantitative physiological biomarker for water quality monitoring assessment. Received: 22 September 1999/Accepted: 9 March 2000