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Leopard Frogs (leopard + frog)

Distribution by Scientific Domains

Life Sciences	91%

Kinds of Leopard Frogs

northern leopard frog

Selected Abstracts

EFFECTIVE POPULATION SIZES AND TEMPORAL STABILITY OF GENETIC STRUCTURE IN RANA PIPIENS, THE NORTHERN LEOPARD FROG

EVOLUTION, Issue 11 2004
Eric A. Hoffman
Abstract Although studies of population genetic structure are very common, whether genetic structure is stable over time has been assessed for very few taxa. The question of stability over time is particularly interesting for frogs because it is not clear to what extent frogs exist in dynamic metapopulations with frequent extinction and recolonization, or in stable patches at equilibrium between drift and gene flow. In this study we collected tissue samples from the same five populations of leopard frogs, Rana pipens, over a 22,30 year time interval (11,15 generations). Genetic structure among the populations was very stable, suggesting that these population were not undergoing frequent extinction and colonization. We also estimated the effective size of each population from the change in allele frequencies over time. There exist few estimates of effective size for frog populations, but the data available suggest that ranid frogs may have much larger ratios of effective size (Ne) to census size (Nc) that toads (bufonidae). Our results indicate that R. pipiens populations have effective sizes on the order of hundreds to at most a few thousand frogs, and Nee/Nc ratios in the range of 0.1,1.0. These estimates of Ne/Nc are consistent with those estimated for other Rana species. Finally, we compared the results of three temporal methods for estimating Ne. Moment and pseudolikelihood methods that assume a closed population gave the most similar point estimates, although the moment estimates were consistently two to four times larger. Wang and Whitlock's new method that jointly estimates Ne and the rate of immigration into a population (m) gave much smaller estimates of Ne and implausibly large estimates of m. This method requires knowing allele frequencies in the source of immigrants, but was thought to be insensitive to inexact estimates. In our case the method may have failed because we did not know the true source of immigrants for each population. The method may be more sensitive to choice of source frequencies than was previously appreciated, and so should be used with caution if the most likely source of immigrants cannot be identified clearly. [source]

Remarkable Amphibian Biomass and Abundance in an Isolated Wetland: Implications for Wetland Conservation

CONSERVATION BIOLOGY, Issue 5 2006
J. WHITFIELD GIBBONS
biodiversidad; declinación de anfibios; recuperación de humedales sequía; uso de suelo Abstract:,Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts for the past 54 years. We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.), to sample all amphibians for 1 year following a prolonged drought. Despite intensive agricultural use of the land surrounding Ellenton Bay prior to 1951, we documented 24 species and remarkably high numbers and biomass of juvenile amphibians (>360,000 individuals; >1,400 kg) produced during one breeding season. Anurans (17 species) were more abundant than salamanders (7 species), comprising 96.4% of individual captures. Most (95.9%) of the amphibian biomass came from 232095 individuals of a single species of anuran (southern leopard frog[Rana sphenocephala]). Our results revealed the resilience of an amphibian community to natural stressors and historical habitat alteration and the potential magnitude of biomass and energy transfer from isolated wetlands to surrounding terrestrial habitat. We attributed the postdrought success of amphibians to a combination of adult longevity (often >5 years), a reduction in predator abundance, and an abundance of larval food resources. Likewise, the increase of forest cover around Ellenton Bay from <20% in 1951 to >60% in 2001 probably contributed to the long-term persistence of amphibians at this site. Our findings provide an optimistic counterpoint to the issue of the global decline of biological diversity by demonstrating that conservation efforts can mitigate historical habitat degradation. Resumen:,A pesar de la pérdida de hábitats de humedales y las declinaciones asociadas de poblaciones de anfibios, se han realizado pocos intentos para traducir las pérdidas de humedales en pérdidas mensurables en los ecosistemas. Estimamos la productividad potencial de la comunidad de anfibios que se afectaría por la pérdida de un humedal aislado que ha estado protegido de los impactos industriales, agrícolas y urbanos durante los últimos 54 años. Utilizamos un cerco de desvío en la Bahía Ellentonn, un humedal dulceacuícola de 10 ha en el Río Savannah, cerca de Aiken, Carolina del Sur (E.U.A.), para muestrear todos los anfibios durante 1 año después de una sequía prolongada. A pesar del intensivo uso agrícola del suelo alrededor de la Bahía Ellenton antes de 1951, documentamos 24 especies y números y biomasa de anfibios juveniles notablemente altos (>360,000 individuos; >1,400 kg) en una temporada reproductiva. Los anuros (17 especies) fueron más abundantes que las salamandras (7 especies), y comprendieron 96.4% de las capturas individuales. La mayor parte (95.9%) de la biomasa provino de 232095 individuos de una sola especie de anuro (Rana sphenocephala). Nuestros resultados revelaron que la resiliencia de la comunidad de anfibios a los estresantes naturales y a la alteración histórica del hábitat y la magnitud potencial de la transferencia de biomasa y energía desde los humedales aislados hacia el hábitat terrestre circundante. Atribuimos el éxito post-sequía de los anfibios a una combinación de longevidad de adultos (a menudo > 5 años), la reducción de la abundancia de depredadores y la abundancia de recursos alimenticios para las larvas. Asimismo, el incremento de la cobertura forestal alrededor de la Bahía Ellerton de < 20% en 1951 a > 60% en 2001 probablemente contribuyó a la persistencia de los anfibios a largo plazo en este sitio. Nuestros hallazgos proporcionan un contrapunto optimista al tema de la declinación global de la diversidad biológica al demostrar que los esfuerzos de conservación pueden mitigar a la degradación histórica del hábitat. [source]

Seasonal changes in frequency tuning and temporal processing in single neurons in the frog auditory midbrain

DEVELOPMENTAL NEUROBIOLOGY, Issue 1 2005
Jozien BM Goense
Abstract Frogs rely on acoustic signaling to detect, discriminate, and localize mates. In the temperate zone, reproduction occurs in the spring, when frogs emerge from hibernation and engage in acoustically guided behaviors. In response to the species mating call, males typically show evoked vocal responses or other territorial behaviors, and females show phonotactic responses. Because of their strong seasonal behavior, it is possible that the frog auditory system also displays seasonal variation, as evidenced in their vocal control system. This hypothesis was tested in male Northern leopard frogs by evaluating the response characteristics of single neurons in the torus semicircularis (TS; a homolog of the inferior colliculus) to a synthetic mating call at different times of the year. We found that TS neurons displayed a seasonal change in frequency tuning and temporal properties. Frequency tuning shifted from a predominance of TS units sensitive to intermediate frequencies (700,1200 Hz) in the winter, to low frequencies (100,600 Hz) in the summer. In winter and early spring, most TS neurons showed poor, or weak, time locking to the envelope of the amplitude-modulated synthetic call, whereas in late spring and early summer the majority of TS neurons showed robust time-locked responses. These seasonal differences indicate that neural coding by auditory midbrain neurons in the Northern leopard frog is subject to seasonal fluctuation. © 2005 Wiley Periodicals, Inc. J. Neurobiol, 2005 [source]

Dietary exposure to low pesticide doses causes long-term immunosuppression in the leopard frog (Rana pipiens)

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2007
Anathea Albert
Abstract This study examines the relationship between dietary exposure of pesticides, DDT, and dieldrin and immunosuppression in the northern leopard frog (Rana pipiens). Immune function was measured before, during, and after a 10-week exposure period with the use of both adaptive and innate immunity responses. Exposure to low doses (75 ng/g body wt DDT or 2.1 ng/g dieldrin total dose over the 10 weeks) resulted in significant suppressive effects on antibody production and secondary delayed-type hypersensitivity (DTH). The high doses (750 ng/g DDT and 21 ng/g dieldrin), however, did not affect antibody production, DTH, or oxidative burst in a predictable dose,response manner. The differences in magnitude and direction of the effects of the two dosing regimes were likely due to differences in chemical exposure on the basis of feeding and effectiveness of chemical uptake. The low dose results demonstrated that moderate concentrations of pesticides, frequently observed in the environment, are able to weaken the immune response of R. pipiens. [source]

Immunosuppression in the northern leopard frog (Rana pipiens) induced by pesticide exposure

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2003
Mary-Kate Gilbertson
Abstract An injection study and a field study were used to investigate the hypothesis that environmental xenobiotics have the potential to alter the immune function of northern leopard frogs (Rana pipiens). Three assays, IgM-specific antibody response to keyhole limpet hemocyanin linked to dinitrophenyl (KLH-DNP), zymozan induced chemiluminescence (CL) of whole blood and the delayed-type hypersensitivity (DTH), were used to assay humoral, innate and cell-mediated immune endpoints. Sublethal doses of DDT (923 ng/g wet wt), malathion (990 ng/g wet wt), and dieldrin (50 ng/g wet wt) were used in the injection study. In all pesticide-injected groups, antibody response was dramatically suppressed, DTH reactions were enhanced, and respiratory burst was lower. When the order of administration of pesticides and antigens was reversed, no differences in immune function between the control and dosed groups were apparent, indicating that frogs exposed to pathogens prior to pesticide exposure can still respond. A field study found significant differences in immune function between frog populations in pesticide-exposed and pesticide-free locations. The antibody response and CL were suppressed and the DTH enhanced in frogs from Essex County (ON, Canada). Overall, the results suggest that exposure to these pesticides can cause both stimulatory and suppressive immune changes in adult frogs and is doing so in wild populations. [source]

Pond canopy cover: a resource gradient for anuran larvae

FRESHWATER BIOLOGY, Issue 3 2006
LUIS SCHIESARI
Summary 1.,The gradient in pond canopy cover strongly influences freshwater species distributions. This study tested the effects of canopy cover on the performance of two species of larval anurans, a canopy cover generalist (Rana sylvatica, the wood frog) and an open-canopy specialist (R. pipiens, the leopard frog), and tested which factors co-varying with canopy cover mediate these effects. 2.,A field transplant experiment demonstrated that canopy cover had negative performance effects on both species. However, leopard frogs, which grow faster than wood frogs in open-canopy ponds, were more strongly affected by closed-canopy pond conditions. 3.,Closed-canopy ponds had lower temperature, dissolved oxygen (DO), and food nutritional quality as indicated by carbon-to-nitrogen ratio (C : N) analysis of field-sampled food types, and of gut contents of transplanted larvae. 4.,Laboratory experiments demonstrated that higher temperature and food quality but not DO substantially increased larval growth. However, only food quality increased growth rates of leopard frogs more than wood frogs. 5.,The strong correlation of growth rates to gut content C : N in the field, and the similarity of growth curves as a function of resource quality in the field and laboratory, strongly suggest that resources are of primary importance in mediating intraspecific, and especially interspecific differences in performance across the canopy cover gradient. [source]

Metabolic rate models and the substitutability of predator populations

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2004
David R. Chalcraft
Summary 1Much of the debate surrounding the consequences of biodiversity loss centres around the issue of whether different species are functionally similar in their effects on ecological processes. In this study, we examined whether populations consisting of smaller, more abundant individuals are functionally similar to populations of the same species with larger, fewer individuals. 2We manipulated the biomass and density of banded sunfish (Enneacanthus obesus) and measured their impact on populations of Southern leopard frog (Rana sphenocephala) larvae. We also evaluated the ability of models relating metabolic rate to body size to predict the relative impacts of populations that differ in average body size and population density. 3Our results indicate that population biomass, density and their interaction each play a large role in determining the effect of a predator population on its food resource. Populations with smaller but more abundant individuals had effects as large or larger than those populations with larger but fewer individuals. 4Although we found qualitative agreement between the observed relative effects of populations with that predicted by allometric models, we also found that density-dependence can cause effects of a population to differ from that expected based on allometry. 5The substitutability of populations differing in average body size appears to depend on complex relationships between metabolic rate, population density and the strength of density-dependence. The restrictive conditions necessary to establish functional equivalence among different populations of the same species suggests that functional equivalence should be rare in most communities. [source]

Distribution and regulation of substance P-related peptide in the frog visual system

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2001
Elizabeth A. DebskiArticle first published online: 10 AUG 200
Abstract Modulation of visual signal activity has consequences for both signal processing and for activity-dependent structuring mechanisms. Among the neuromodulatory agents found in visual areas are substance P (SP)-related peptides. This article reviews what is known about these substances in the amphibian retina and optic tectum with special emphasis on the leopard frog, Rana pipiens. It is found that the distribution of these SP-related peptides is remarkably similar to that seen in mammals. This suggests that study of model amphibian systems may significantly enhance our understanding of how neuropeptides contribute to visual system function and organization. Microsc. Res. Tech. 54:220,228, 2001. © 2001 Wiley-Liss, Inc. [source]

Immunohistochemical distribution of enkephalin, substance P, and somatostatin in the brainstem of the leopard frog, Rana pipiens

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2001
Sherry L. Stuesse
Abstract The brainstems of frogs contain many of the neurochemicals that are found in mammals. However, the clustering of nuclei near the ventricles makes it difficult to distinguish individual cell groups. We addressed this problem by combining immunohistochemistry with tract tracing and an analysis of cell morphology to localize neuropeptides within the brainstem of Rana pipiens. We injected a retrograde tracer, Fluoro-Gold, into the spinal cord, and, in the same frog, processed adjacent sections for immunohistochemical location of antibodies to the neuropeptides enkephalin (ENK), substance P (SP), and somatostatin (SOM). SOM+ cells were more widespread than cells containing immunoreactivity (ir) to the other substances. Most reticular nuclei in frog brainstem contained ir to at least one of these chemicals. Cells with SOM ir were found in nucleus (n.) reticularis pontis oralis, n. reticularis magnocellularis, n. reticularis paragigantocellularis, n. reticularis dorsalis, the optic tectum, n. interpeduncularis, and n. solitarius. ENK-containing cell bodies were found in n. reticularis pontis oralis, n. reticularis dorsalis, the nucleus of the solitary tract, and the tectum. The midbrain contained most of the SP+ cells. Six nonreticular nuclei (griseum centrale rhombencephali, n. isthmi, n. profundus mesencephali, n. interpeduncularis, torus semicircularis laminaris, and the tectum) contained ir to one or more of the substances but did not project to the spinal cord. The descending tract of V, and the rubrospinal, reticulospinal, and solitary tracts contained all three peptides as did the n. profundus mesencephali, n. isthmi, and specific tectal layers. Because the distribution of neurochemicals within the frog brainstem is similar to that of amniotes, our results emphasize the large amount of conservation of structure, biochemistry, and possibly function that has occurred in the brainstem, and especially in the phylogenetically old reticular formation. Microsc. Res. Tech. 54:229,245, 2001. © 2001 Wiley-Liss, Inc. [source]

Suitability of Golf Course Ponds for Amphibian Metamorphosis When Bullfrogs Are Removed

CONSERVATION BIOLOGY, Issue 1 2008
MICHELLE D. BOONE
charcas en campos de golf; competencia; depredación; metamorfosis de anfibios; Rana catesbeiana Abstract:,Managing areas designed for human recreation so that they are compatible with natural amphibian populations can reduce the negative impacts of habitat destruction. We examined the potential for amphibians to complete larval development in golf course ponds in the presence or absence of overwintered bullfrog tadpoles (Rana catesbeiana), which are frequently found in permanent, human-made ponds. We reared larval American toads (Bufo americanus), southern leopard frogs (R. sphenocephala), and spotted salamanders (Ambystoma maculatum) with 0 or 5 overwintered bullfrog tadpoles in field enclosures located in ponds on golf courses or in experimental wetlands at a reference site. Survival to metamorphosis of American toads, southern leopard frogs, and spotted salamanders was greater in ponds on golf courses than at reference sites. We attributed this increased survival to low abundance of insect predators in golf course ponds. The presence of overwintered bullfrogs, however, reduced the survival of American toads, southern leopard frogs, and spotted salamanders reared in golf course ponds, indicating that the suitability of the aquatic habitats for these species partly depended on the biotic community present. Our results suggest that ponds in human recreational areas should be managed by maintaining intermediate hydroperiods, which will reduce the presence of bullfrog tadpoles and predators, such as fish, and which may allow native amphibian assemblages to flourish. Resumen:,El manejo de áreas diseñadas para la recreación humana de manera que sean compatibles con las poblaciones naturales de anfibios puede reducir los impactos negativos de la destrucción del hábitat. Examinamos el potencial de anfibios para completar el desarrollo larvario en lagos en campos de golf en presencia o ausencia de renacuajos de Rana catesbeiana, que frecuentemente son encontrados en charcas artificiales permanentes. Criamos sapos (Bufo americanus), ranas (R. sphenocephala) y salamandras manchadas (Ambystoma maculatum) con cero o cinco renacuajos de R. catesbeiana en encierros localizados en charcas en campos de golf o en humedales experimentales en un sitio de referencia. La supervivencia hasta la metamorfosis de B. americanus, R. sphenocephala y A. maculatum fue mayor en los campos de golf que en los sitios de referencia. Atribuimos este incremento en la supervivencia a la baja abundancia de insectos depredadores en las charcas de los campos de golf. Sin embargo, la presencia de renacuajos de R. catesbeiana redujo la supervivencia de B. americanus, R. sphenocephala y A. maculatum en los campos de golf, indicando que el beneficio de los hábitats acuáticos para estas especies dependía parcialmente de la comunidad biótica presente. Nuestros resultados sugieren que las charcas en áreas recreativas deberían ser manejadas manteniendo hidroperíodos intermedios, que reducirían la presencia de renacuajos de R. catesbeiana y de depredadores, como peces, y que permitirían que florezcan ensambles de anfibios nativos. [source]

Seasonal changes in frequency tuning and temporal processing in single neurons in the frog auditory midbrain

Determination of polychlorinated biphenyl and polycyclic aromatic hydrocarbon elimination rates in adult green and leopard frogs

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2006
Jocelyn L. Leney
Abstract The purpose of the present study was to quantify elimination kinetics of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in adult green frogs (Rana clamitans) and leopard frogs (Rana pipiens). Three experiments were conducted: PCB elimination rate constants were determined for both frog species, and PAH elimination rate constants were determined for leopard frogs only. In green frogs, significant PCB elimination rate constants ranged from 0.013 to 0.04 d,1 (time for frogs to achieve 90% steady state with water [t90] = 57.8-178.2 d). In leopard frogs, significant PCB elimination rate constants ranged from 0.004 to 0.047 d,1 (t90 = 48.8-657.9 d). Polycyclic aromatic hydrocarbon elimination in leopard frogs was faster than PCB elimination in either frog species: Significant PAH rate constants ranged from 0.069 to 0.188 d,1 (t90 = 12.2-33.5 d). In both species, and for both PCBs and PAHs, a significant inverse relationship was found between the chemical elimination rate constant and Kow. These results show that adult anurans have relatively low elimination rates of PCBs but exhibit a small capacity for metabolic biotransformation of PAHs that is comparable to that of invertebrates but lower than that of fish. These findings suggest that adult amphibians have the potential to be used as biomonitors for persistent organic chemicals. [source]

Synergistic impacts of malathion and predatory stress on six species of North American tadpoles

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2004
Rick A. Relyea
Abstract The decline of many amphibian populations is associated with pesticides, but for most pesticides we know little about their toxicity to amphibians. Malathion is a classic example; it is sprayed over aquatic habitats to control mosquitoes that carry malaria and the West Nile virus, yet we know little about its effect on amphibians. I examined the survival of six species of tadpoles (wood frogs, Rana sylvatica; leopard frogs, R. pipiens; green frogs, R. clamitans; bullfrogs, R. catesbeiana; American toads, Bufo americanus; and gray tree frogs, Hyla versicolor) for 16 d in the presence or absence of predatory stress and six concentrations of malathion. Malathion was moderately toxic to all species of tadpoles (median lethal concentration [LC50] values, the concentration estimated to kill 50% of a test population, ranged from 1.25,5.9 mg/L). These values are within the range of values reported for the few amphibians that have been tested (0.2,42 mg/L). In one of the six species, malathion became twice as lethal when combined with predatory stress. Similar synergistic interactions have been found with the insecticide carbaryl, suggesting that the synergy may occur in many carbamate and organophosphate insecticides. While malathion has the potential to kill amphibians and its presence is correlated with habitats containing declining populations, its actual role in amphibian declines is uncertain given the relatively low concentration in aquatic habitats. [source]

Gonadal differentiation in frogs exposed to estrogenic and antiestrogenic compounds

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003
Constanze A. Mackenzie
Abstract Exposure of amphibians to endocrine disrupting compounds (EDCs) may alter differentiationof gonads, especially when exposures begin during early life stages. Gonadal differentiation was observed in leopard frogs (Rana pipiens) and wood frogs (Rana sylvatica) exposed as tadpoles to estrogenic (estradiol, ethinylestradiol, nonylphenol) and antiestrogenic compounds (an aromatase inhibitor, flavone, and an antiestrogen, ICI 182780). Exposure to all compounds at ,g/L concentrations altered gonadal differentiation in some animals by inducing either complete feminization or an intersex condition, and altered testicular tubule morphology, increased germ cell maturation (vitellogenesis), and oocyte atresia. Comparisons between the two species indicate that R. pipiens are more susceptible to sex reversal and development of intersex gonads. However, R. sylvatica also showed alterations to testicular morphology, germ cell maturation, and ooctye atresia. These laboratory results indicate that amphibians could be susceptible to altered gonadal differentiation and development when exposed to estrogenic and antiestrogenic compounds in aquatic environments, such as those impacted by agricultural, industrial, and municipal runoff. [source]

Immunosuppression in the northern leopard frog (Rana pipiens) induced by pesticide exposure

Immunohistochemical localization of cytochrome P4501A induced by 3,3,,4,4,,5-pentachlorobiphenyl (PCB 126) in multiple organs of northern leopard frogs, Rana pipiens

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2001
Yue-Wern Huang
Abstract Monoclonal antibody 1 12,3(MA1 12,3)recognizesanepitopeexclusivetocytochromeP450sinsubfamily1A (CYP1A) from all vertebrates tested so far, including one amphibian species. In this study, we first tested the utility of MAb 1,12-3 for detection of presumed CYP1A proteins in hepatic microsomes of northern leopard frogs treated without or with 3,3,,4,4,,5-pentachlorobiphenyl (PCB 126). Statistical analysis showed that ethoxyresorufin- O -deethylase (EROD) activities and CYP1A equivalents in treated groups were significantly increased at doses >2.3 mg/kg compared with the control groups (p < 0.05), and the increases were maintained for at least four weeks. This result confirmed that MAb 1,12-3 can be used for detection of CYP1A in northern leopard frogs and indicated that CYP1A is the primary catalyst for EROD in this species. In a subsequent experiment, sections of organs of PCB 126-treated frogs were immunohistochemically stained with MAb 1,12-3 to identify localization of the CYP1A in different cell types. The CYP1A staining was seen prominently in hepatocytes and epithelium of nephronic duct, while capillaries close to gastric epithelium and submucosal vascular epithelium in both stomach and intestine exhibited moderate to strong staining. The CYP1A was immunodetected in coronary endothelium and the vascular endothelium of lung and gonad. In skin, mild staining was seen in epithelial cells of mucous glands and serous glands and in vascular endothelium, demonstrating induction of CYP1A in the dermal layer. [source]

Oral bioavailability and toxicokinetics of 3,3,,4,4,,5-pentachlorobiphenyl in northern leopard frogs, Rana pipiens

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2000
Yue-wern Huang
Abstract This study is the first report on oral bioavailability, whole-body elimination, and distribution of a specific polychlorinated biphenyl (PCB) congener on an amphibian species, northern leopard frogs. Each frog was orally dosed once with either 0.35 or 5.0 mg/kg PCB 126 (based on frog wet wt), including tracer 14C-PCB 126 (3,,4,,5,-phenyl-ring- 14C) by force feeding it a cricket injected with the PCB. We found no statistical difference (t = 0.917, df = 5, p = 0.401) in the average 48-h oral bioavailabilities of 0.35- and 5.0-mg/kg dosage groups, which were 84.6 ± 5.8% (mean ± SE, n = 4) and 90.9 ± 1.5% (n = 3), respectively. Statistical analysis indicated that time was the only independent variable affecting the retention of whole-body 14C content. Kinetics were apparently first order because elimination rate was independent of dose. Assuming a single pool and one elimination rate, the t1/2 value for whole-body elimination of PCB-derived 14C was 763 d. Liver, fat bodies (corpora adiposa), carcass (head, bone, cartilage materials, and residues of other tissues), skin, and muscle were the major organs for PCB 126 retention in both dosage groups. The concentrations of 14C residue in fat bodies were relatively constant throughout the experiment. However, total residues in fat bodies declined throughout the experiment in both dosage groups in correlation with declining masses of fat bodies. Gonad, kidney, stomach, intestine, and a tissue pool including esophagus, lung, spleen, heart, and cloacal materials each accumulated <1% of the initial total 14C residue. The egg follicles in 19 females contained 1 to 23% of the initial total 14C residue, with an average of 10.0 ± 9.2% (mean ± SE, n = 19). [source]