Baseline measurements of indicators for sublethal effects of metals in lake whitefish (Coregonus clupeaformis).

Histological and metallothionein (MT) analyses of liver and kidney and measurements of serum electrolytes and hematocrit from lake whitefish (Coregonus clupeaformis), 3.5 years of age, were conducted over a 90-day period that included maximal gonadal maturation in females. Condition factors were higher in females at day 1 and when all data were combined over the 90-day sampling period. Significant differences between females and males of 1.8-fold in hepatic MT concentrations were observed at day 20 when ovaries appeared to be in the most advanced state of maturation, although this parameter was not quantified. Hematocrits were slightly but significantly lower at day 90. No sex differences were observed in the quantitative assessments of epithelium cell height, lumen diameter (LD), tubule diameter (TD), and ratio of LD:TD in the second segment of the proximal tubule (P2); and of hepatocyte area, hepatocyte nuclear diameters, and nucleus area:cytoplasmic area (N:C) ratio. Positive correlations were observed between N:C ratios and fish weight, fork length, and liver weight. No significant correlations between these histological morphometrics and MT concentrations were observed in liver or kidney. The results of this study provide baseline information for investigations designed to determine sublethal effects of metals in lake whitefish.

Toxicology of dietary nickel in lake whitefish (Coregonus clupeaformis).

The sublethal toxicity associated with exposure of adult lake whitefish (Coregonus clupeaformis) to diets containing 0, 10, 100, and 1000 microg Ni per g for 10, 31, and 104 days was assessed through the measurement of responses, through a range of levels of biological organization. The accumulation and distribution of Ni in these fish are described in the previous manuscript (Ptashynski and Klaverkamp, 2001. Aquat. Toxicol. in press). Hematological parameters, including concentrations of glucose and hemoglobin and hematocrit, were not different between control and treated fish. Organ and whole organism parameters, including LSI, growth, and condition factor, were also unaffected. Histopathological lesions in kidney and liver proved to be the most sensitive and reliable indicators of Ni exposure. In livers of treated fish, areas of focal necrosis and altered bile ducts were observed. Histological alterations were observed throughout the posterior kidneys, in glomeruli, tubules, collecting ducts, and hematopoietic tissue, in fish fed medium and high dose diets. In whitefish kidneys, the frequency (%) of altered distal tubules and fields of views with alterations increased with the dose and duration of exposure. Significant increases in metallothionein concentrations were observed in intestine of whitefish fed the high dose diet on day 10, but these increases were not sustained. Significant increases in lipid peroxide concentrations were also observed in plasma of whitefish fed the high dose diet on day 31, but were not observed on day 104. These biochemical responses to dietary Ni require further evaluation. To evaluate exposure of natural populations of fish to Ni, analysis of Ni in kidney and liver and assessment of renal and hepatic histopathology are recommended for use in field bio-monitoring programs.

Accumulation and distribution of dietary nickel in lake whitefish (Coregonus clupeaformis).

Benthic-feeding fish residing in Ni-contaminated systems are exposed to Ni through ingestion of contaminated food items and sediments. Lake whitefish (Coregonus clupeaformis) were fed diets at a ration of 0.5% of body weight three times a week containing 0, 10, 100, and 1000 microg Ni/g (as NiSO(4)) for 10, 31, and 104 days. Stomach, pyloric caeca, intestine, kidney, liver, gall bladder, gonad, gill, bone, muscle, skin, and scales were analyzed to evaluate the accumulation and distribution of Ni. Fish fed the medium and high dose diets accumulated significant amounts of Ni in a majority of the tissues sampled, even after only 10 days of exposure. Ni concentrations were highest in intestine and pyloric caeca of whitefish fed 1000 microg Ni/g on day 10, but decreased on subsequent sampling days, possibly due to protective mechanisms. Ni accumulation in stomach, kidney, liver, gill, skin, and scales was dose and duration-dependent. Ni concentrations measured in bone, gall bladder, gonad, and muscle of fish fed the control diet for 10 days and fish fed the high dose diet for all durations appeared to increase in a duration-dependent manner. Exposure to Ni altered the concentrations of Cu and Zn in tissues of lake whitefish. However, Cu and Zn concentrations in the tissues analyzed were variable and did not follow a common pattern or trend. The tissues that best assess dietary Ni bioavailability are kidney and scales. The toxicology of Ni in these fish is described in the next manuscript (Aquat. Toxicol., in press (b)).

Accumulation and distribution of dietary arsenic in lake whitefish (Coregonus clupeaformis).

Adult lake whitefish (Coregonus clupeaformis) were fed As contaminated diets at nominal concentrations of 0, 1, 10 and 100 microg As/g food (d.w.) for 10, 30 and 64 days. Liver, kidney, stomach, intestine, pyloric caeca, gallbladder, skin and scales were analyzed for As content. The pattern of As accumulation in fish tissues was influenced by reduced feed consumption beginning on day 45 by fish fed the 100 microg As/g food. Significant As accumulation occurred in all tissues examined from fish exposed to the 100 microg As/g food for 30 days, with the exception of gallbladder. After 30 days of exposure, the highest concentration of As was observed in pyloric caeca of fish fed the 100 microg As/g food. Significant accumulation of As occurred in livers and scales of fish fed concentrations of As as low as 10 microg/g for 30 and 64 days. Muscle, gonad, spleen, gills and bone of lake whitefish fed a control diet for 10 days and 100 microg As/g food for 10, 30 and 64 days were also analyzed for As content. As concentrations increased in gonads, spleen and gills of fish fed the 100 microg As/g food for 30 days. Increased concentrations of As were observed in bone of fish fed the high dose food after each duration of exposure. As concentrations did not increase in muscle of fish after 10, 30 or 64 days of exposure. The following manuscript (Pedlar et al., 2001) documents toxicological effects observed in these fish. Analyses of As in pyloric caeca, intestine, liver and scales are recommended to evaluate the bioavailability of As to freshwater fish in environmental monitoring programs.

Toxicological effects of dietary arsenic exposure in lake whitefish (Coregonus clupeaformis).

Adult lake whitefish were fed As contaminated diets at nominal concentrations of 0, 1, 10, and 100 microg As/g food (dry weight) for 10, 30, and 64 days. Reduced feed consumption was observed in lake whitefish fed the 100 microg As/g food, beginning on day 45 of exposure. The accumulation and distribution of As in these fish are described in the previous manuscript [Pedlar, R.M., Klaverkamp, J.F., 2001. The accumulation and distribution of dietary arsenic in lake whitefish (Coregonus clupeaformis). Aquat. Toxicol., in press]. At the molecular level of organization, metallothionein (MT) induction occurred in lake whitefish fed the 100 microg As/g food after 10 and 30 days, and in fish fed the 1 and 10 microg As/g diets for 64 days. Dietary As exposure did not have a significant effect on plasma lipid peroxide (LPO) concentrations. At the tissue and organ level, mean liver somatic index decreased significantly in lake whitefish fed the 100 microg As/g food for 64 days. Blood parameters (hematocrit, hemoglobin concentration, red blood cell count, mean cell volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration) were not affected by exposure to As contaminated diets. Liver and gallbladder histopathologies were observed in lake whitefish fed all As contaminated diets after each duration of exposure. Histopathology observed in liver included nuclear, architectural and structural alterations, areas of inflammation, and focal necrosis. Sloughing of the epithelium, dilation of vascular elements, inflammation, edema, fibrosis, and increased width of the submucosa were some of the alterations observed in gallbladders of lake whitefish fed As contaminated diets. Both organs were sensitive to As exposure, as damage occurred with exposure to dietary concentrations of As as low as 1 microg/g. Whole organism parameters were unaltered by dietary As exposure. Based on the results of this study, histopathological alterations in liver and gallbladder, and hepatic MT induction may be useful indicators of As toxicity in environmental monitoring programs that also measure As concentrations in those tissues.

The accumulation, distribution, and toxicological effects of dietary arsenic exposure in lake whitefish (Coregonus clupeaformis) and lake trout (Salvelinus namaycush).

A 20-day experiment was conducted to compare the accumulation, distribution, and toxicological effects of dietary As, as arsenate, in lake whitefish (LWF, Coregonus clupeaformis) and lake trout (LT, Salvelinus namaycush). Results of this experiment were used to design an experiment of longer duration in which one of the fish species was selected and exposed three times per week to lower dietary As doses. In the present study each treatment group was exposed to a combination of one of three doses of As (0, 100, or 1000 microg As/g) and one of two types of diet, no brine shrimp (NS) or with brine shrimp (WS) for a total of eight dosing events. Brine shrimp were added to determine whether their presence enhanced consumption of As-contaminated food. Modified feeding behavior occurred in both fish species fed As contaminated diets, with the exception of the 100 microg As/g NS food. Brine shrimp addition did not affect feed consumption of the As contaminated diets. Significant As accumulation occurred in stomach, pyloric caeca, intestine, liver, kidney, and gallbladder, but not in bile or muscle. As exposure did not have a significant effect on hepatic and renal metallothionein concentrations. Concentrations of lipid peroxides were only significantly elevated in the plasma of LT fed the 1000 microg As/g WS food. Liver somatic indices decreased significantly in both species, whereas hematological parameters were not affected in either species. Histological lesions occurred in gallbladder, liver, kidney, pyloric caeca and intestine from LWF. These lesions were not observed in LT; however, gallbladders were not examined in this species. Weight gain was lower in both species fed As contaminated diets, however, condition factors were not affected.

Altered distribution of lipid-soluble antioxidant vitamins in juvenile sturgeon exposed to waterborne ethynylestradiol.

Studies in mammals have shown that exposure to estrogenic compounds can affect lipid metabolism and plasma concentrations of lipid-soluble vitamins. However, the potential for estrogenic contaminants to induce these effects in fish has not yet been examined. The ability of the estrogen analog ethynylestradiol (EE2) to alter concentrations of the lipid-soluble vitamins A and E in plasma, liver, and kidney was investigated in juvenile lake sturgeon (430 +/- 20 g). The EE2 was delivered to the sturgeon in the tank water at nominal concentrations of 0 (control), 15, 60, or 125 ng EE2/L for a period of 25 d. Concentrations of the egg yolk precursor, vitellogenin, increased dose dependently in plasma. Plasma vitamin E (tocopherol), A1 (retinol), and A2 (dehydroretinol) were elevated by the two highest EE2 treatments compared with the controls. Esterified storage forms of vitamin A were marginally lower in the livers of fish from the highest EE2 dose group, but vitamin E levels in the liver were not significantly affected. Concentrations of vitamin E and vitamin A were significantly depleted in the kidney of fish from the two highest EE2 dose groups. Total lipid content was elevated in the gonad of fish treated with the highest dose of EE2 compared with the controls. Altered lipid and vitamin distribution may be induced by estrogen to facilitate gonadal maturation in sturgeon. Results from these studies indicate that an examination of the implications for vitamin depletion by estrogenic contaminants in juvenile fish is warranted.

Vitamin and thyroid status in arctic grayling (Thymallus arcticus) exposed to doses of 3,3',4,4'-tetrachlorobiphenyl that induce the phase I enzyme system.

Induction of phase I biotransformation enzymes is recognized as a hallmark response in fish exposed to coplanar PCBs. Depletions of vitamins A and E and disrupted thyroid hormone and glandular structure secondary to this induction have not yet been examined in an arctic fish species. Arctic grayling were exposed to a single oral dose of 0 (control), 10, 100 or 1000 ng 3,3',4,4'-tetrachlorobiphenyl (TCB) g(-1) bodyweight, a contaminant found in most arctic fish. After 30 and 90 days of exposure, TCB concentrations in tissues, hepatic phase I activity (as ethoxyresorufin-O-deethylase (EROD)), plasma and tissue vitamin A and E concentrations, plasma thyroid hormone levels and thyroid glandular structure were examined. Total plasma osmolality, as an indicator of overall fish health was also monitored. TCB recovery in tissues was low and extremely variable, making comparisons between intended dose groups inappropriate. Therefore, correlation analysis between actual recovered TCB concentrations and biochemical responses was employed. Hepatic EROD activity correlated strongly with liver TCB concentrations. Liver concentrations of vitamin A were altered as a function of TCB concentrations and EROD activity, but plasma vitamin A status was not affected. Vitamin E was depleted by TCB accumulation in blood and EROD induction in liver of males only at 90 days postexposure. Thyroid hormones status and glandular structure were not affected by the short duration TCB exposures used in this experiment. TCB concentrations were correlated with an elevation in plasma osmolality. Results from this experiment indicate that the vitamin status and osmoregulation of arctic grayling exposed to TCB can be compromised. Further studies of field populations exposed to this type of contaminant are warranted.

Accumulation, distribution and toxicology of dietary nickel in lake whitefish (Coregonus clupeaformis) and lake trout (Salvelinus namaycush).

An 18-day experiment was conducted to investigate the uptake and sublethal toxicity of dietary Ni in adult lake whitefish (LWF, Coregonus clupeaformis) and lake trout (LT, Salvelinus namaycush) fed diets containing 0, 1000 and 10000 microg Ni/g, prepared with and without brine shrimp. The results of this experiment were used to design an experiment of longer duration in which one of the fish species was selected and exposed to lower dietary Ni doses. In the present study feed refusal was observed in LT and LWF fed 10000 microg Ni/g, after three and 4-5 feedings, respectively. LT fed Ni-contaminated diets exhibited different patterns of Ni accumulation than LWF. Increased Ni concentrations in all LWF tissues, except the intestine, were associated with increased doses of Ni. Copper and Zn concentrations in kidney and liver of LWF were altered. Metallothionein concentrations in kidneys of LT fed 1000 microg Ni/g and 10000 microg Ni/g and LWF fed 10000 microg Ni/g and in livers of LWF fed 10000 microg Ni/g (diet without shrimp only) increased significantly. Increased lipid peroxide production in the plasma of LT fed 10000 microg Ni/g was observed. Blood glucose and electrolytes were affected by Ni exposure. Histopathological alterations were observed in kidneys of LWF fed low and high dose diets, livers of whitefish fed high dose diets, and intestines of LWF fed high dose diets and LT fed low and high dose diets. LT fed high dose diets exhibited significant decreases in weight.

Subcellular distribution of heavy metals in liver and kidney of a narwhal whale (Monodon monoceros): an evaluation for the presence of metallothionein.

The subcellular distribution of Zn, Cd, Cu and Hg in liver and kidney from a narwhal was determined by ultracentrifugation and gel filtration. Most of the total mercury in the liver and kidney was bound by the cellular pellet (88 and 73%, respectively). Of the total mercury, 7 and 11% was in the form of methylmercury in the liver and kidney, respectively. More than half (74%) of the total Zn and Cu in the kidney was in the cytosol and somewhat less than this was in the cytosol of the liver. Almost all of the cadmium in liver and kidney (88 and 92%, respectively) was in cytosol. Cytosolic fractions from liver and kidney were evaluated for the presence of metallothionein by analysing for Zn, Cd, Hg, Cu, Fe and--SH groups, by molecular weight estimation and by u.v. absorption spectra. Metallothionein was found in these organs in estimated concentrations similar to those present in terrestrial and other marine mammals.

Fates of metal radiotracers added to a whole lake: accumulation in slimy sculpin (Cottus cognatus) and white sucker (Catostomus commersoni).

Six gamma-emitting isotopes, iron-59, cobalt-60, zinc-65, selenium-75, cesium-134 and mercury-203, were added in mid-summer to Lake 224 of the Experimental Lakes Area in northwestern Ontario, Canada. Isotope activities in whole bodies of slimy sculpins and in blood, gills, gut contents, kidney, liver and spleen of white suckers were determined for periods up to 247 days after isotope addition. Results demonstrate delay between contamination of a lake and transfer of contaminant to these fish species. General relationships between movement and distribution of isotopes in water and their accumulation in these fish indicate that direct accumulation from water is not a major route of uptake.