Abnormal bone composition in female juvenile American alligators from a pesticide-polluted lake (Lake Apopka, Florida)

Reproductive disorders have been found in pesticide-exposed alligators living in Lake Apopka, Florida (USA). These disorders have been hypothesized to be caused by exposure to endocrine- disruptive estrogen-like contaminants. The aim of this study was to expand our analysis beyond previous studies by investigating whether bone tissue, known to be affected by sex steroid hormones, is a potential target of endocrine disruptors. Long bones from 16 juvenile female alligators from Lake Apopka (pesticide-contaminated lake) and Lake Woodruff (control lake) were evaluated by peripheral quantitative computed tomography. We observed significant differences in bone composition, with female alligators from the contaminated lake having greater trabecular bone mineral density (BMD), total BMD, and trabecular mineral content compared with females from the control lake (p < 0.05). Increased trabecular and total BMD measurements suggest that juvenile female alligators from Lake Apopka were exposed to contaminants that created an internal environment more estrogenic than that normally observed. This estrogenic environment could be caused by both natural and anthropogenic compounds. Effects on BMD indicate interference with bone homeostasis. We hypothesize that contaminants present in the lake inhibit the natural and continuous resorption of bone tissue, resulting in increased bone mass. Although this is the only study performed to date examining effects of environmental estrogenic compounds on alligator bones, it supports previous laboratory-based studies in rodents. Further, this study is important in demonstrating that the alterations in morphology and physiology induced in free-ranging individuals living in environments contaminated with endocrine-active compounds are not limited to a few systems or tissues; rather, effects can be observed in many tissues affected by these hormones.     

Developmental abnormalities of the gonad and abnormal sex hormone concentrations in juvenile alligators from contaminated and control lakes in Florida.

The reproductive development of alligators from a contaminated and a control lake in central Florida was examined. Lake Apopka is adjacent to an EPA Superfund site, listed due to an extensive spill of dicofol and DDT or its metabolites. These compounds can act as estrogens. Contaminants in the lake also have been derived from extensive agricultural activities around the lake that continue today and a sewage treatment facility associated with the city of Winter Garden, Florida. We examined the hypothesis that an estrogenic contaminant has caused the current failure in recruitment of alligators on Lake Apopka. Supporting data include the following: At 6 months of age, female alligators from Lake Apopka had plasma estradiol-17 beta concentrations almost two times greater than normal females from the control lake, Lake Woodruff. The Apopka females exhibited abnormal ovarian morphology with large numbers of polyovular follicles and polynuclear oocytes. Male juvenile alligators had significantly depressed plasma testosterone concentrations comparable to levels observed in normal Lake Woodruff females but more than three times lower than normal Lake Woodruff males. Additionally, males from Lake Apopka had poorly organized testes and abnormally small phalli. The differences between lakes and sexes in plasma hormone concentrations of juvenile alligators remain even after stimulation with luteinizing hormone. Our data suggest that the gonads of juveniles from Lake Apopka have been permanently modified in ovo, so that normal steroidogenesis is not possible, and thus normal sexual maturation is unlikely.     

Gender and spatial patterns in metal concentrations in brown anoles (Anolis sagrei) in southern Florida, USA

Comparatively little is known about heavy metal levels in reptiles, particularly for lizards. Yet lizards often are common predators that could serve as bioindicators of contamination on a small spatial scale. This study examined the differences in metal concentrations of adult brown anoles (Anolis sagrei) for arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in six locations in southern Florida, USA, from Lake Okeechobee (Pahokee) south to Key West. We predicted that levels of contaminants would be higher in the industrialized ports (Port Everglades, Port of Miami) and at a landfill (in Key West) compared to a campground, tropical garden, and marine laboratory. Males were significantly larger than females, as expected. Although there were significant locational differences in metal concentrations, they did not fit a consistent pattern, either among sites or between reference and study sites. However, the lowest levels were generally found at Everglades Marina and Campground (except for selenium) and at Fairchild Tropical Garden (except for manganese). For females, size was significantly correlated with cadmium, lead, and mercury levels, while for males, there were significant correlations between length and arsenic, chromium, and manganese concentrations. Where there were gender differences in metal levels, females had significantly higher levels than males even though they were smaller. We attribute these gender differences to differences in diet due to microhabitat differences in foraging locations. Females spend more time feeding near the ground and males spend more time feeding on tree trunks and branches where they consume more flying insects. This is the first study that examines concentrations of metals in lizards in the United States, and suggests that nonnative lizards may be useful in toxicological studies.     

Triiodothyronine (T3) and thyroxine (T4) levels in iron-deficient,hypertriglyceridemic rats

Two experiments were conducted to examine the role and status of thyroid hormone in iron-deficient hypertriglyceridemic rats. In Experiment I, male weanling rats were fed 6 diets containing 2 levels of dietary iron [6 ppm(?Fe) and 240 ppm(+Fe)] and 3 combinations of fats [14% beef tallow +1% safflower oil(B), 7.5% beef tallow +7.5% safflower oil(BS) and 15% safflower(S)]. After 3 weeks, rats receiving ?Fe diets had elevated triglyceride (TG) and depressed triiodothyronine(T3) and thyroxine (T4) levels in serum, regardless of the fat source. No difference in the post-heparin lipolytic activity could be detected after 6 weeks of dietary treatment between rats fed +Fe and ?Fe diets. Feeding the BS+Fe diet to the BS?Fe rats for 1 week brought their serum TG, T3, and T4 to levels similar to those of rats fed the BS+Fe diet for 7 weeks. In Experiment II, male weanling rats were fed B diets containing 6 levels of dietary iron (3, 6, 10, 15, 30, and 60 ppm) for 4 weeks. Weekly determinations of packed cell volume(PCV), serum T3, T4, and TG were made. PCV, serum T3 and T4 levels increased as dietary iron content increased. The relationship between serum TG level with dietary iron level or PCV was quadratic, curvilinear. Data also suggest that part of the iron effect on serum TG level is thyroid hormone related.     

Mercury in eggs and feathers of great egrets (Ardea albus) from the Florida Everglades

Great egret (Ardea albus) eggs and nestling feathers were collected for total mercury (THg) and methylmercury (MeHg) analysis from two colonies in the Florida Everglades in 1999 and 2000. THg was present in all eggs at a mean concentration of 0.39 ± 0.19 μg/g fresh weight (n = 33, range = 0.08–0.86 μg/g). Egg-THg levels did not differ significantly between colonies or years. MeHg concentration in eggs was 0.35 ± 0.18 μg/g fresh weight (n = 20, range = 0.05–0.82 μg/g,), and on average represented 85% of the THg found in the egg. Concentration of THg in feathers from egret nestlings, age 11–31 days, ranged from 1.4 to 8.6 μg/g dry weight. Feather-THg levels also did not differ significantly between colonies or years. THg concentrations in feathers, normalized based on bill length, were positively correlated to THg concentrations in eggs from the same clutch. Levels of THg in both eggs and feathers were lower in 1999 and 2000 than values reported for similar samples collected in 1993–95, indicating that MeHg exposure has decreased in the southern Everglades since the mid-1990s. THg levels in eggs and nestling feathers for the period of this study were below levels associated with toxic reproductive effects. Clutch size, fledging success, and brood size observed in this study were consistent for this species in the Everglades. Collectively, these results suggest that MeHg was not adversely affecting the reproductive performance of this population during the study. Received: 20 December 2000/Accepted: 30 August 2001     

Temporal and spatial variations of selected biomarker activities in flounder (Platichthys flesus) collected in the Baltic proper

The aim of the study was to examine temporal (monthly) and spatial changes in the activities of a battery of biomarkers and evaluate the influence of gender and environmental factors on those activities. Abiotic factors not correlated with chemical pollution—water temperature, salinity, and oxygen concentration—were evaluated.The activities of the following biomarkers—muscular ChEs (acetylcholinesterase (AChE) and butyrylcholinesterase (BChE)), hepatic ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST) and catalase (CAT), and gross indices—condition factor (CF), hepatosomatic index (HSI), and gonadosomatic index (GSI)—were measured in individual flounder Platichthys flesus. Female flounder were collected once a month from April 2003 to April 2004 at Sobieszewo (Gulf of Gdańsk). In December 2003 flounder of both sexes from nine stations in the Baltic Proper were caught and tested.Strong monthly (attributed mainly to spawning, and less—to pollution) and geographical (attributed to pollution) variations in biomarker activities, as well as gender differences, were demonstrated. Correlations between the enzymes with the abiotic properties of the environment were less important.     

Temporal and spatial variation in solar radiation and photoenhanced toxicity risks of spilled oil in Prince William Sound, Alaska, USA

Solar irradiance (W/m2) and downwelling diffuse attenuation coefficients (Kd; 1/m) were determined in several locations in Prince William Sound (AK, USA) between April 2003 and December 2005 to assess temporal and spatial variation in solar radiation and the risks of photo-enhanced toxicity from spilled oil. Weekly irradiance measurements of surface visible light, ultraviolet B (UVB), and ultraviolet A (UVA) radiation in Valdez (AK, USA) followed expected trends of maximum solar irradiance at each summer solstice and minimum values at each winter solstice. Variation from weekly maximum expected surface irradiances was attributed to large variations in environmental conditions over the 142-week monitoring period. Season and proximity to glacial meltwater were significant determinants of Kd, with 1% attenuation depths ranging from 0.4 to 15 m (UVB and UVA) and from 0.5 to 28 m (visible light). The probability of photo-enhanced toxicity risks estimated from UVA dosimetry decreased with increasing water depth, with higher risks during spring and summer and lower risks during fall and winter. These results demonstrate substantial temporal and spatial variation in solar radiation in Prince William Sound and the potential for significant season- and location-specific photo-enhanced toxicity risks from spilled oil.     

Selenium and mercury concentrations in California gulls breeding on the Great Salt Lake, Utah, USA

We examined selenium (Se) and mercury (Hg) concentrations in adult California gulls (Larus californicus) nesting on the Great Salt Lake, Utah, USA, during 2006 and 2007. During 2006, the mean Se concentration (+/- standard error) was 18.1 +/- 1.5 microg/g in blood on a dry-weight basis and 8.1 +/- 0.4 microg/g in liver. During 2007, Se concentrations were 15.7 +/- 1.5 microg/g in blood and 8.3 +/- 0.4 microg/g in liver; Hg concentrations were 2.4 +/- 0.3 microg/g in blood and 4.1 +/- 0.5 microg/g in liver. Gulls collected from a freshwater colony located within the watershed of the Great Salt Lake had similar levels of Se in the blood and liver as gulls collected on the Great Salt Lake but lower Hg concentrations. Body mass of adult gulls was not correlated with Se or Hg concentrations in their blood or liver. Selenium concentration in California gull eggs collected during 2006 was 3.0 +/- 0.10 microg/g. Of 72 eggs randomly collected from Great Salt Lake colonies, only one was infertile, and none of the embryos exhibited signs of malposition or deformities. We examined 100 newly hatched California gull chicks from Great Salt Lake colonies for teratogenesis; all chicks appeared normal. Hence, the elevated Se and Hg concentrations in adult gulls nesting on the Great Salt Lake did not appear to impair gulls' health or reproductive ability.     

Temporal and spatial variation in the amount of cadmium in the phantom midge larvae (Chaoborus spp.)

Several factors, including body size, age, and temporal and spatial variation, which may influence the amount of cadmium (Cd) in the phantom midge larvae, Chaoborus spp., were examined in eight lakes, four from south-central Ontario (Dorset Region) and four from northwestern Ontario (Experimental Lakes Area). All three species of Chaoborus (C. punctipennis, C. trivittatus, C. flavicans) found in Chub Lake (south-central Ontario), were analyzed seasonally. One species, C. punctipennis, was collected and analyzed from all lakes.Smaller Chaoborus tended to have higher Cd concentrations (g Cd/g dry weight), and lower Cd burdens (ng Cd/Animal) than larger Chaoborus. The Cd concentrations of Chaoborus in Chub Lake were lowest during the summer, which coincided with the fastest growth of the organisms. The Cd burdens differed between species, which was attributed to differences in their asynchronous life histories.Cadmium burdens and concentrations were significantly lower in the organisms from northwestern Ontario than those from south-central Ontario. Lower atmospheric deposition rates, lower Cd concentrations in the lake water, as well as life history differences, may explain these results.     

The influence of human growth hormone (GH) and thyroxine (T4) on the differentiation of adipose tissue in the fetus

Late term fetuses from genetically obese dams have slightly larger fat cells, greater adipose tissue lipoprotein lipase (LPL) activities, elevated levels of thyroid hormones, and depressed growth hormone (GH) levels when compared to fetuses from lean dams. We have investigated the influence of thyroid hormone and GH status per se on these and other adipose tissue traits by chronically treating hypophysectomized (hypox) fetuses (day 70) between day 90 and 105 of gestation with either thyroxine (T4) or human GH. Treatment with T4 decreased body weights (P<.05), increased serum T4 levels (P<.05), and enhanced skin and hair development (P<.05). Quantitative analysis of sections of perirenal and subcutaneous adipose tissue indicated that T4 increased LPL activity (P<.05), slightly increased fat cell size, and more than doubled (P<.05) lipid accretion. A hypox induced deficit in fat cell cluster number in the outer layer of subcutaneous tissue was normalized by T4 (P<.05). Conversely, human GH (hGH) treatment had no influence on body weight, increased serum hGH levels, decreased fat cell size (P<.05) and LPL activity (P<.05) but had no influence on lipid accretion. Quantitative analysis of adipose tissue sections provided direct and indirect evidence of a "critical" or "sensitive" period between 90 and 105 days, since fetal hypox at day 70 severely impeded preadipocyte recruitment/replication during this period. Furthermore, T4 but not GH effectively normalized this hypox-induced deficiency in preadipocyte development. Therefore, T4 may have a major role in preadipocyte recruitment/replication during late fetal life.     

The serum triiodothyronine to thyroxine (T3/T4) ratio in various thyroid disorders and after Levothyroxine replacement therapy

In order to examine the significance of differences in the triiodothyronine/thyroxine (T3/T4) ratio in the achievement of euthyroidism and in different thyroidal diseases, we studied 1050 subjects: 233 were euthyroid (Eu), 239 hypothyroid (Hypo) with initial TSH levels >15 mU/L, 273 hypothyroid on substitution therapy with L-thyroxine alone and TSH values of 0.35-3.5 mU/L, (hypoRx), 236 hyperthyroid (hyper) and 69 in the acute phase of subacute thyroiditis De Quervain's (DQ). The ratio of T3/T4 was calculated using the conventional values. Results: The values of T3/T4 ratio in the various categories were: Eu= 15.89, Hypo= 24.12, hyper= 19.57, hypoRx= 13.42, DQ= 15.16. The T3/T4 ratio was lower in the hypoRx group than in the EU group (P <0.001), although neither TSH values nor T3 values showed any differences between these two groups, whereas T4 levels were significantly higher in the hypoRx group (Eu= 7.99+/-1.46, hypoRx = 9.11+/-1.58, P< 0.001). The T3/T4 ratio in the DQ group was comparable to that of the Eu group, but significantly lower than the hyper group (P=0.95 between Eu and DQ, P<0.001 between DQ and hyper). Conclusions: These findings indicate that in hypothyroid patients, L-T4-replacement that is sufficient to maintain a normal serum TSH is accompanied by a serum T4 that is higher than in normal individuals and may not result in an appropriately normal serum T3 concentration. In Thyrotoxicosis, a ratio of total T3/T4 >18.9 suggests Graves' disease or toxic multinodular goiter whereas T3/T4 <16 suggests thyroiditis (subacute or silent).     

Mercury concentrations in fish from Lake Mead,USA, related to fish size,condition, trophic level,location, and consumption risk

Total mercury (Hg) concentrations were determined in the skeletal muscle of 339 fish collected during the fall of 1998 and spring of 1999 from Lake Mead, USA, the nation's largest human-made reservoir. Five species of fish representing a range of trophic levels and the lake's principal game fishes were studied. Hg generally increased with trophic level and fish size. Median Hg concentrations (ng/g wet mass) were 277 in striped bass, 168 in channel catfish, 160 in largemouth bass, 75 in bluegill, and 8 in blue tilapia. Overall, fish from Las Vegas Bay and Boulder Basin had the lowest Hg concentrations, possibly a result of biodilution in this biologically productive area. In general, fish-mercury advisories might include a warning about consuming fillet from emaciated fish, based on the finding that Hg concentrations in 59 striped bass (captured during a scarce-food season) correlated inversely (r = −0.89, p < 0.001) with a fish nutritional-status factor. This is consistent with starvation-concentration, whereby Hg in fish muscle is lost at a slower rate than the muscle mass. The median concentration found for 139 striped bass corresponds to a recommended risk-based consumption limit of three 8-oz. (227-g) meals per month for a 70-kg adult. Finally, this paper serves as a useful archive for future research and long-term studies of Hg in Lake Mead fish. Received: 13 September 2001/Accepted: 10 March 2002     

Geographic, seasonal and ontogenetic variation in cadmium and mercury concentrations in squid (Cephalopoda: Teuthoidea) from UK waters

Cadmium (Cd) and mercury (Hg) levels were measured in the tissue samples of two loliginid (Alloteuthis sp. and Loligo forbesi) and two ommastrephid (Todarodes sagittatus and Todaropsis eblanae) squid species collected from research cruise and fishery (market) samples in UK waters during 2004–05. Concentrations of Cd were generally higher in the ommastrephids, in all tissues except muscle. Hg concentrations were higher in T. sagittatus than in the loliginids. In L. forbesi, metal concentrations differed between tissues and also varied in relation to body size, geographic origin, and season. Cd levels decreased with increasing body size. This may be related to a shift in the diet with growth, since small L. forbesi feed on benthic invertebrates that have relatively high Cd concentrations, whereas larger individuals prey mainly on fish that have low Cd concentrations. Hg levels increased with body size, indicating its retention, and they were highest at the end of the spawning season and in squid from the English Channel and the Scottish West Coast. It is likely that the ambient concentration of Hg in seawater plays an important part in its accumulation in squid tissues. As it is a short-lived species, L. forbesi may therefore function as a bioindicator species for Hg contamination of the marine environment. Our results indicate that there is no significant danger to humans from consuming squid from UK waters.     

A comparison of the reproductive physiology of largemouth bass, Micropterus salmoides, collected from the Escambia and Blackwater Rivers in Florida

Largemouth bass (LMB), Micropterus salmoides, were taken from the Escambia River (contaminated site) and the Blackwater River (reference site) near Pensacola, Florida. The Escambia River collection occurred downstream of the effluent from two identified point sources of pollution. These point sources included a coal-fired electric power plant and a chemical company. Conversely, the Blackwater River's headwaters and most of its length flow within a state park. Although there is some development on the lower part of the Blackwater River, fish were collected in the more pristine upper regions. Fish were captured by electroshocking and were maintained in aerated coolers. Physical measurements were obtained, blood was taken, and liver and gonads were removed. LMB plasma was assayed for the concentration of 17ss-estradiol (E2) and testosterone using validated radioimmunoassays. The presence of vitellogenin was determined by gel electrophoresis (SDS-PAGE) and Western blotting using a monoclonal antibody validated for largemouth bass vitellogenin. No differences in plasma concentrations of E2 or testosterone were observed in females from the two sites. Similarly, males exhibited no difference in plasma E2. However, plasma testosterone was lower in the males from the contaminated site, as compared to the reference site. Vitellogenic males occurred only at the contaminated site. Additionally, liver mass was proportionately higher in males from the contaminated site, as compared to males from the reference site. These data suggest that reproductive steroid levels may have been altered by increased hepatic enzyme activity, and the presence of vitellogenic males indicates that an exogenous source of estrogen was present in the Escambia River.     

Organochlorine concentrations in the Saimaa ringed seal (Phoca hispida saimensis) from Lake Haukivesi,Finland, 1981 to 2000, and in its diet today

Organochlorine and mercury (Hg) pollution has been one possible reason for a decline in the size of the population of the Saimaa ringed seal (Phoca hispida saimensis) in Lake Haukivesi, Finland. In this study, we analyzed changes in the concentrations of organochlorine compounds (OCls) and extractable organic halogen (EOX) in the blubber of Saimaa ringed seals that died from 1981 to 2000. In addition, the present concentrations and biomagnification factors of OCls and Hg from the main prey fish of ringed seal and pike (Esox lucius) were determined. Concentrations of pollutants in bream (Abramis brama) also were analyzed. The decline in the OCl concentrations in blubber was, on average, 25% during the two decades since polychlorinated biphenyls and DDT compounds were banned. Today, concentrations in blubber of Saimaa ringed seals are similar of those in ringed seals from the Arctic. Correspondingly in fish, the OCl and Hg concentrations were, on average, similar to those found in other studies on Finnish and Arctic areas. The low diet concentrations and metabolism of OCls also reflect the lower age correlation of OCls in the male ringed seals in the 1990s than in the 1980s. Biomagnification was considerably higher from fish to the ringed seal than from prey fish to pike because of higher feeding rate of ringed seals and differences in the metabolisms of these animals.     

Variation in the number and position of siphonal setae in Culex quinquefasciatus from Key West and Vero Beach, Florida, USA

Variations in diagnostic siphonal characters of Culex quinquefasciatus larvae collected in Key West and Vero Beach, FL, are described. We observed specimens with 3, 4, and 5 sets of siphonal setae and also observed frequent variation in the insertion point of the proximal and subapical setae.