Research Interests: Endocrinology, Biology, Medicine, Biological Sciences, Environmental Sciences, and 15 moreInternal Medicine, Lizards, Animals, Male, CHEMICAL SCIENCES, Time Factors, The Endocrine System Function, Biological markers, Toxicity Tests, Environmental Toxicology and Chemistry, Enzyme Linked Immunosorbent Assay, Estradiol, Time Course, Vitellogenin, and Endocrine System
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Research Interests: Biology, Ecology, Medicine, Biological Sciences, Growth, and 15 moreEnvironmental Sciences, Lizards, Female, Animals, Laboratory Animals, Male, Animal Model, Iguanidae, Lizard, CHEMICAL SCIENCES, Environmental Pollutants, Environmental Toxicology and Chemistry, Environmental, Estradiol, and Endocrine System
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MARSH NESTING BY MALLARDS GARY L. KRAPU, US Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, ND 58401 LARRY G ... We thank HF Duebbert, RLJessen, and AB Sar-geant for critically reviewing the manu-script,... more
MARSH NESTING BY MALLARDS GARY L. KRAPU, US Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, ND 58401 LARRY G ... We thank HF Duebbert, RLJessen, and AB Sar-geant for critically reviewing the manu-script, SD Becker, DM Janke ...
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There is growing interest in improving ecological risk assessment exposure estimation, specifically by incorporating dermal exposure. At the same time, there is a growing interest in amphibians and reptiles as receptors in ecological risk... more
There is growing interest in improving ecological risk assessment exposure estimation, specifically by incorporating dermal exposure. At the same time, there is a growing interest in amphibians and reptiles as receptors in ecological risk assessment, despite generally receiving less research than more traditional receptors. Previous research has suggested that dermal exposure may be more important than previously considered for reptiles. We measured reptile skin permeability to four pesticides (thiamethoxam, malathion, tebuthiuron, trifluralin) using ventral skin samples. All four pesticides penetrated the skin but generally had low permeability. There was no apparent relationship between physicochemical properties and permeability coefficients. Malathion had a significantly greater permeability rate at all time points compared to the other pesticides. Tebuthiuron had a greater permeability than thiamethoxam. Reptiles and mammals appear to have similar skin permeability suggesting t...
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Reptiles have been understudied in ecotoxicology which limits consideration in ecological risk assessments. The goal of this research was threefold: to improve oral and dermal dosing methodologies for reptiles, to generate reptile... more
Reptiles have been understudied in ecotoxicology which limits consideration in ecological risk assessments. The goal of this research was threefold: to improve oral and dermal dosing methodologies for reptiles, to generate reptile toxicity data for pesticides, and to correlate reptile and avian toxicity. We first assessed the toxicity of different dosing vehicles: 100 µL of water, propylene glycol, or acetone were not toxic. We assessed the oral and dermal toxicity of 4 pesticides following the up-and-down procedure. Neither brodifacoum nor chlorothalonil caused mortality at doses < 1750 µg/g. Under the "neat pesticide" oral exposure endosulfan (LD50 = 9.8 µg/g) was more toxic than λ-cyhalothrin (LD50 = 916.5 µg/g). Neither chemical was toxic via dermal exposure. An acetone dosing vehicle increased λ-cyhalothrin toxicity (oral LD50 = 9.8 µg/g, dermal LD50 = 17.5 µg/g), but not endosulfan. Finally, changes in dosing method and husbandry significantly increased dermal λ-c...
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... LARRY G. TALENT,2 Cooperative Wildlife Research Unit, Oregon State University, Corvallis, OR 97331 GARY L. KRAPU, US Fish and Wildlife Service, Northern Prairie ... On the Me-dina Study Area, about 60% of the wet-land basins held... more
... LARRY G. TALENT,2 Cooperative Wildlife Research Unit, Oregon State University, Corvallis, OR 97331 GARY L. KRAPU, US Fish and Wildlife Service, Northern Prairie ... On the Me-dina Study Area, about 60% of the wet-land basins held water on 1 May 1976, but only 10% did ...
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... TERRENCE G. BIDWELL,&#x27; Oklahoma Cooperative Fish and Wildlife Research Unit, and Department of Zoology, Oklahoma State University, Stillwater, OK ... regenerated stands (66%), 1-13-year-old pine (Pinus spp.) plantations (31%),... more
... TERRENCE G. BIDWELL,&#x27; Oklahoma Cooperative Fish and Wildlife Research Unit, and Department of Zoology, Oklahoma State University, Stillwater, OK ... regenerated stands (66%), 1-13-year-old pine (Pinus spp.) plantations (31%), pastures and hay meadows (2%), and ...
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Metabolic rates of reptiles vary with body temperature; therefore, the sensitivity of reptiles to a particular dose level of a pesticide might be expected to vary as well. The purpose of the present study was twofold: To evaluate the... more
Metabolic rates of reptiles vary with body temperature; therefore, the sensitivity of reptiles to a particular dose level of a pesticide might be expected to vary as well. The purpose of the present study was twofold: To evaluate the effects of temperature on the toxicity to green anole lizards (Anolis carolinensis) of a single concentration of a natural pyrethrin pesticide via percutaneous exposure, and to compare the effects of temperature (20 vs 35 degrees C) on the toxicity of different concentrations of pyrethrins to green anoles. When lizards were exposed to a solution that contained 300 mg/L of pyrethrins, the mortality of lizards maintained at 15 and 20 degrees C was significantly higher (p &amp;amp;amp;amp;amp;amp;lt; 0.01) than the mortality of lizards maintained at 35 and 38 degrees C. In addition, the median lethal concentrations of pyrethrins for lizards maintained at 20 and 35 degrees C were 77.6 and greater than 300 mg/L, respectively. Therefore, temperature clearly influenced the sensitivity of lizards to pyrethrin pesticides.
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The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas. Because much of the dunes sagebrush lizard's habitat occurs in areas of... more
The dunes sagebrush lizard (Sceloporus arenicolus) is a habitat specialist of conservation concern limited to shin oak sand dune systems of New Mexico and Texas. Because much of the dunes sagebrush lizard's habitat occurs in areas of high oil and gas production, there may be direct and indirect effects of these activities. We used the congeneric Western fence lizard (Sceloporus occidentalis) as a surrogate species to determine direct effects of 2 contaminants associated with oil and gas drilling activities in the Permian Basin: herbicide formulations (Krovar and Quest) and hydrogen sulfide gas (H2 S). We exposed lizards to 2 concentrations of H2 S (30 or 90 ppm) and herbicide formulations (1x or 2x label application rate) representing high-end exposure scenarios. We evaluated sublethal behavioral endpoints including sprint speed and time to prey detection and capture. Neither H2 S nor herbicide formulations caused significant behavioral effects compared to controls. In order to ...
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... Rates of gas exchange were calculated and adjusted for standard temperature and pressure ... describing relationships between body mass and whole body metabolism is preferred over reporting ... strongly influenced by body mass, and... more
... Rates of gas exchange were calculated and adjusted for standard temperature and pressure ... describing relationships between body mass and whole body metabolism is preferred over reporting ... strongly influenced by body mass, and metabolism scaled with body mass similarly ...
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Female Redheads (Aythya americana) are known to deposit eggs in nests of Mallards (Anas platyrhynchos). Joyner (J. Wildl. Manage. 40:33-38, 1976) attributed a high rate of Redhead parasitism on Mallard nests at Farmington Bay, Davis Co.,... more
Female Redheads (Aythya americana) are known to deposit eggs in nests of Mallards (Anas platyrhynchos). Joyner (J. Wildl. Manage. 40:33-38, 1976) attributed a high rate of Redhead parasitism on Mallard nests at Farmington Bay, Davis Co., Utah, to crowding of host and parasite into the same habitat. Weller (Ecol. Monogr. 29:333365, 1959) stated that at Knudson Marsh, Utah, only a few deep channels and patches of water were suitable for feeding and courtship by Redheads, and nests of other ducks located near those areas were heavily parasitized; nests farther from the shore were parasitized less often. Redhead nest parasitism resulted in reduced host clutch-size (Weller 1959), displaced and broken host eggs (Joyner 1976) and increased nest abandonment (Ryder, Trans. N. Am. Wildl. Nat. Resour. Conf. 26:134-146, l6l).
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Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been widely used as an explosive in munition formulations, resulting in contamination of wildlife habitat on military installations. To estimate health effects for reptilian species,... more
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been widely used as an explosive in munition formulations, resulting in contamination of wildlife habitat on military installations. To estimate health effects for reptilian species, acute, subacute, and subchronic oral toxicity studies were conducted using the Western fence lizard (Sceloporus occidentalis). Estimated oral median lethal doses were 72 (95% confidence interval [CI], 49-106) mg/kg body weight (slope, 3.754) for males and 88 (95% CI, 65-119) mg/kg (slope, 4.525) for females. Toxicity from RDX suggested the neurological system as the critical target tissue. A 14-d subacute study followed with males dosed orally with RDX (corn oil) at 0, 10, 20, 25, 30, 45, and 60 mg/kg/d. Signs of toxicity frequently included a characteristic body posture. A significant dose-survival relationship was seen over the range of doses, with a significant decrease in survival at 20 mg/kg/d. Males in the 60-d subchronic study were dosed at 0, 1, 2.5, 5, 8, and 11 mg/kg/d, and signs of toxicity included lethargy, cachexia, and anorexia. Survival was decreased at 8 and 11 mg/kg/d. Reduced growth rate and food consumption occurred at 5 mg/kg/d. Brain tissue was assayed for RDX when seizures were observed at a residue concentration of at least 18 microg/g. No abnormalities were observed in the hematologic indices, whereas plasma proteins were reduced. Hepatic enlargement and decreased testes mass occurred at 8 and 11 mg/kg/d. Plasma testosterone concentrations, sperm counts, and motility measures were variable for all treatment levels. Based on survival, growth rate, food intake, and testes to brain weight ratios, these data suggest a lowest-observed-adverse effect level of 5 mg/kg/d and a no-observed-adverse effect level of 2.5 mg/kg/d.
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A need is recognized for one or more laboratory reptile models for use in ecotoxicological studies and risk assessments. Maintenance of breeding populations of most reptile species under laboratory conditions is not practical because of... more
A need is recognized for one or more laboratory reptile models for use in ecotoxicological studies and risk assessments. Maintenance of breeding populations of most reptile species under laboratory conditions is not practical because of their size and slow maturation rate. However, a number of species of spiny lizards (Sceloporus sp.) are small, mature quickly, and reproduce under laboratory conditions. We evaluated three populations of western fence lizards (S. occidentalis) and four populations of eastern fence lizards (S. undulatus) for their performance under laboratory conditions. We reared an F1 generation of each population and compared their performance relative to survival, growth, maturation rate, and reproductive output. A population from the San Joaquin Valley (CA. USA) performed especially well under laboratory conditions and is a good candidate for a laboratory model. We also examined the sensitivity of developing fence lizard embryos to an estrogenic chemical to determine if male secondary sex characteristics were affected. Microinjecting eggs with an estrogenic chemical (17alpha-ethinylestradiol) feminized males and prevented development of embryonic secondary sex characteristics. Therefore, embryonic fence lizards may be useful for studying the effects of endocrine-disrupting chemicals.
Research Interests: Risk assessment, Biological Sciences, Environmental Sciences, Lizards, Female, and 12 moreAnimals, Laboratory Animals, Male, CHEMICAL SCIENCES, The Endocrine System Function, Sex Differentiation, Risk Assessment, Toxicity Tests, Environmental Pollutants, Environmental Toxicology and Chemistry, Environmental, and Estradiol
Some species of reptiles regularly ingest soil in the wild. Therefore, we evaluated the importance of soil ingestion as a route for the uptake of contaminants in lizards. We used sand as a substitute for soil during the present study.... more
Some species of reptiles regularly ingest soil in the wild. Therefore, we evaluated the importance of soil ingestion as a route for the uptake of contaminants in lizards. We used sand as a substitute for soil during the present study. Different groups of leopard geckos (Eublepharis macularius) were provided with a control and five sodium selenite-spiked sand mixtures during a 28-d study. Twenty lizards were assigned to a control group and to each of five selenium-spiked sand mixtures that consisted of nominal selenium (Se) concentrations of 0.05, 0.46, 4.57, 11.41, and 22.83 mg Se/kg dry sand. Leopard geckos readily ingested the Se-spiked sand. We observed concentration-related effects in several endpoints. Overall growth in body mass was the most sensitive endpoint and was significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) lower in lizards that ingested the 4.57, 11.41, and 22.83 mg Se/kg sand mixtures compared to controls. Growth in snout-vent length, mean daily food ingestion, and food conversion efficiency were less sensitive and were significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) lower in lizards that ingested the 11.41 and 22.83 mg Se/kg sand mixtures compared to controls. Although our results are based on nominal amounts of Se ingested, leopard geckos appear to be as sensitive to sodium selenite as birds and mammals. The present study suggests that ingestion of soil could be an important potential route for the uptake of soil contaminants in some reptiles and should be evaluated in ecotoxicological studies and risk analyses of reptiles.
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Contamination of the soil with the explosive 2,4,6-trinitrotoluene (TNT) has been found at military sites, many of which are habitats used by reptiles. To provide data useful in assessing ecological risk for reptilian species, acute,... more
Contamination of the soil with the explosive 2,4,6-trinitrotoluene (TNT) has been found at military sites, many of which are habitats used by reptiles. To provide data useful in assessing ecological risk for reptilian species, acute, subacute, and subchronic oral toxicity studies were conducted with the western fence lizard (Sceloporus occidentalis). Oral median lethal dose (LD50) values for TNT in corn oil were 1,038 and 1,579 mg/kg of body weight for male and female lizards, respectively. Overt signs of toxicity included chromaturia, abdominal enlargement, and tremors. A 14-d subacute study followed in which male lizards were orally dosed with TNT (corn oil) at 0, 33, 66, 132, 263, 525, and 1,050 mg/kg of body weight each day. Clinical signs of toxicity, while similar to the LD50 study, were more subtle and noted in lizards receiving TNT amounts of at least 66 mg/kg/d. Chromaturia was an early consistent sign, often preceding the onset of adverse effects. Male lizards in the 60-d subchronic study were dosed at 0, 3, 15, 25, 35, and 45 mg/kg/d with nearly complete survival (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;90%) for lizards in all treatments. Changes in food consumption and body weight were observed at 35 and 45 mg/kg/d. Alterations in hematological end points; blood chemistries (albumin, total protein, alkaline phosphatase, calcium); kidney, spleen, and liver weights; and adverse histopathology were observed in lizards exposed at 25 to 45 mg/kg/d. Testosterone concentration, sperm count, and motility were variable between treatments. Although not significant, incidences of hypospermia and testicular atrophy were observed in some individuals. Together, these data suggest a lowest-observed-adverse effect level of 25 mg/kg/d and a no-observed-adverse effect level of 15 mg/kg/d in S. occidentalis.
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2,4-dintitrotoluene (2,4-DNT) is an explosive frequently found in the soil of military installations. Because reptiles can be common on these sites, ecological risk assessments for compounds such as 2,4-DNT could be improved with toxicity... more
2,4-dintitrotoluene (2,4-DNT) is an explosive frequently found in the soil of military installations. Because reptiles can be common on these sites, ecological risk assessments for compounds such as 2,4-DNT could be improved with toxicity data specific to reptiles. Western fence lizards, Sceloporus occidentalis, were used to develop a laboratory toxicity model for reptiles. A hierarchical approach was used; acute to subchronic studies were conducted to provide toxicity data relevant to short- and long-term exposures. First, a modified median lethal dose (LD50) study was conducted on male and female lizards using a stage-wise probit model. The LD50 was 577 mg/kg for female and 380 mg/kg for male lizards. Subsequently, a subacute experiment was conducted to further assess 2,4-DNT toxicity to male lizards and to define exposure levels for a longer term, subchronic study. The subchronic study was conducted for 60 consecutive days; male lizards were exposed to 0, 9, 15, 25, 42, 70 mg/kg/d. Dose-dependent mortality was observed in the three highest dose groups (25, 42, and 70 mg/kg/d); all other animals survived the study duration. Benchmark dose model calculations based on mortality indicated a 5% effect level of 15.8 mg/kg/d. At study termination, a gross necropsy was performed, organ weights were taken, and blood was collected for clinical and hematological analysis. Body weight, kidney weight, food consumption, postdose observations, and blood chemistries all were found to be significantly different from controls at doses above 9 mg/kg/d. Also, preliminary results suggest behavioral observations, and reduced food consumption may be a sensitive indicator of toxicity. The present study indicates Sceloporus occidentalis is suitable for evaluating toxicity of compounds to reptilian species.
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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... more
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 &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;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.
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We examined the effects of a commonly used AChE-inhibiting pesticide on terrestrial and arboreal sprint performance, important traits for predator avoidance and prey capture, in the western fence lizard (Sceloporus occidentalis). Lizards... more
We examined the effects of a commonly used AChE-inhibiting pesticide on terrestrial and arboreal sprint performance, important traits for predator avoidance and prey capture, in the western fence lizard (Sceloporus occidentalis). Lizards were exposed to carbaryl (2.5, 25, and 250 microg/g) and were raced before and 4, 24, and 96 h after dosing. In the terrestrial setting, exposure to low concentrations of carbaryl had stimulatory effects on performance, but exposure to the highest concentration was inhibitory. No stimulatory effects of carbaryl were noted in the arboreal environment and performance in lizards was reduced after exposure to both the medium and highest dose of carbaryl. Our findings suggest that acute exposure to high concentrations of carbaryl can have important sublethal consequences on fitness-related traits in reptiles and that arboreal locomotor performance is a more sensitive indicator of AChE-inhibiting pesticide poisoning than terrestrial locomotor performance.
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Although anthropogenic pollutants are thought to threaten reptilian species, there are few toxicity studies on reptiles. We evaluated the toxicity of Pb as lead acetate to the Western fence lizard (Sceloporus occidentalis). The acute... more
Although anthropogenic pollutants are thought to threaten reptilian species, there are few toxicity studies on reptiles. We evaluated the toxicity of Pb as lead acetate to the Western fence lizard (Sceloporus occidentalis). The acute lethal dose and sub-acute (14-day) toxicity studies were used to narrow exposure concentrations for a sub-chronic (60-day) study. In the sub-chronic study, adult and juvenile male lizards were dosed via gavage with 0, 1, 10 and 20 mg Pb/kg-bw/day. Mortality was limited and occurred only at the highest dose (20 mg Pb/kg-bw/d). There were statistically significant sub-lethal effects of 10 and 20 mg Pb/kg-bw/d on body weight, cricket consumption, organ weight, hematological parameters and post-dose behaviors. Of these, Pb-induced changes in body weight are most useful for ecological risk assessment because it is linked to fitness in wild lizard populations. The Western fence lizard is a useful model for reptilian toxicity studies.
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Effects of repeated pollutant exposure on growth, locomotor performance, and behavior have rarely been evaluated in reptiles. We administered three doses of malathion (2.0, 20, or 100mg/kg body weight) to western fence lizards (Sceloporus... more
Effects of repeated pollutant exposure on growth, locomotor performance, and behavior have rarely been evaluated in reptiles. We administered three doses of malathion (2.0, 20, or 100mg/kg body weight) to western fence lizards (Sceloporus occidentalis) over an 81day period. Eight and 23% mortality occurred at 20 and 100mg/kg (p=0.079) and 85% of lizards in the 100mg/kg group exhibited clinical symptoms of poisoning. Growth, food consumption, body condition index, and terrestrial locomotor performance were not significantly influenced by malathion. However, arboreal sprint velocity was significantly reduced in lizards receiving 100mg/kg. Fifty percent of lizards in the 100mg/kg group also refused to sprint in the arboreal setting (p=0.085). Based on these results, arboreal locomotor performance was the most sensitive metric of exposure we evaluated. Further study of compounds such as malathion is warranted due to highly variable application rates and exposure scenarios.
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As part of an investigation determining the trophically available fraction of metals in a model terrestrial food web, i.e., invertebrate prey to Western fence lizards (Sceloporus occidentalis), we evaluated the ability of several... more
As part of an investigation determining the trophically available fraction of metals in a model terrestrial food web, i.e., invertebrate prey to Western fence lizards (Sceloporus occidentalis), we evaluated the ability of several invertebrate prey to bioaccumulate lead and to form metals-rich granules, which are hypothesized to be non-available to predators. Crickets (Acheta domestica), tenebroid beetle larvae (Tenebrio molitor), and isopods (Porcellio scaber) were selected as model prey organisms. Lack of standard exposure methodologies for these species has presented a barrier to trophic transfer evaluations, as each species has particular requirements that create challenges for designing exposure conditions. We were able to devise exposure conditions for all three species that allow long-term exposure studies. All prey organisms accumulated lead from contaminated food, and for all species the majority of the accumulated Pb was associated with the exoskeleton (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;50%), with metals-rich granules accounting for most of the remaining accumulated lead.