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Although increasing evidence links planar chlorinated hydrocarbons, such as polychlorinated biphenyls (PCBs), to decreases in survival and reproduction of fish, mammals, and birds near Green Bay, Wisconsin,and the Great Lakes, USA, relatively little is known of their bioaccumulation or of their possible effects in amphibians. We exposed embryos and larvae of two ranid species commonly occurring in the Green Bay ecosystem, the green frog (Rana clamitans) and the leopard frog (Rana pipiens), to PCB 126, a model coplanar PCB compound. Nominal concentrations ranged from 0.005 to 50 mu g/L, and exposure lasted through metamorphosis. Tissue concentrations of PCB 126 in tadpoles that did not metamorphose by the end of the experiment ranged from 1.2 to 9,600 ng/g wet mass. No significant mortality of embryos occurred before hatching; however, survival of larvae was significantly reduced at the highest concentration for both species. Few deformities were observed, but the incidence of edema was significantly higher in tadpolesexposed to 50 mug/L. Swimming speed and growth of tadpoles was also significantly reduced in this treatment. The percent of tadpoles thatreached metamorphosis was significantly lower in green frogs at the highest concentration, and no leopard frogs survived past day 47 of the experiment in this treatment. At high concentrations, PCB 126 affected both ranid species; however, sublethal effects were not apparentfor the parameters we measured at concentrations that occur in waterin the Green Bay ecosystem. [ABSTRACT FROM AUTHOR]

We measured concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) in northern leopard frogs collected from the Green Bay ecosystem and explored the catalytic activity of hepatic cytochrome P450-associated monooxygenase (P450 enzyme) as a biomarker for exposure to aryl hydrocarbon receptor (AhR) agonists. The two hypotheses tested were PCH concentrations in northern leopard frogs would be positively correlated with sediment polychlorinated hydrocarbon (PCH) levels in wetland habitats along a contamination gradient and hepatic ethoxyresorufin-O-deethylase (EROD) activity of northern leopard frogs, which is presumably mediated by aryl hydrocarbon receptor (AhR), would be positively correlated with PCH concentrations in frog carcasses (whole body minus liver) from different collection sites. In 1994 to 1995, frogs from seven sites along the lower Fox River and Green Bay, USA, were assayed for hepatic EROD activities and whole carcass concentrations of PCBs, PCDDs, and PCDFs. Tissue total PCB concentrations ranging from 3 to 154 ng/g were significantly correlated with sediment PCB levels. Only one PCDD and two PCDFs at concentrations of 6 to 8 pg/g were found in the frogs collected from one of the sites. The ERODactivity in frogs ranging from 186 to 270 pmol/min/mg protein was not significantly correlated with frog body weight and was similar among sites except for Peter's Marsh. No significant correlation was found between EROD activity and carcass PCB concentration. This result was consistent with the fact that the frogs collected from the Green Bay ecosystem had relatively low PCB concentrations compared with what was required for induction in the laboratory (ED50 for EROD is between 700 and 2,300 ng/g). [ABSTRACT FROM AUTHOR]

Leopard frog (Rana pipiens), green frog (Rana clamitans), and American toad (Bufo americanus) embryos were exposed to different un-ionized ammonia (NH3) levels over an ecologically relevant range(0-2 mg NH3/L H2O). Hatching success and prevalence of deformities were recorded after acute exposures (3-5 d duration) at 23 deg. C and pH 8.7. Green frog tadpoles were exposed to different NH3 levels in a subchronic experiment (114 d), and growth, survival, and metamorphosis were monitored. Survival declined, the prevalence of deformities increased, and growth and development were slow in anuran embryos and tadpoles exposed to NH3 concentrations in excess of 0.6 mg/L (green frogs) or 1.5 mg/L (leopard frogs). No effects were observed in American toads up to a concentration of 0.9 mg/L NH3. It appears from the few data available that anurans may not be particularly sensitive to NH3 when compared with many fish species and that water quality criteria determined using data collected on fish species will be protective for many anuran amphibians. The NH3 concentrations that caused negativeeffects in these experiments are higher than measured values for water in the Fox River-Green Bay ecosystem (WI, USA) but lower than for pore sediment water. In this ecosystem, anuran amphibians are potentially exposed to hazardous levels of NH3 when they hibernate on the bottom or buried in sediments or during episodic releases ofNH3 from sediments. [ABSTRACT FROM AUTHOR]

Northern leopard frogs (Rana pipiens) were injected intraperitoneally either with a solution of polychlorinated biphenyl (PCB) 126 in corn oil at a concentration of 0.2, 0.7, 2.3, or 7.8 mg/kg body weight or with corn oil alone. Appropriate assay conditions with hepatic microsomes were determined for four cytochrome P450-associated monooxygenases: ethoxyresorufin-0-dealkylase (EROD), methoxy-ROD (MROD), benzyloxy-ROD (BROD), and pentoxy-ROD (PROD). One week after PCB administration, the specific activities of EROD, MROD, BROD, and PROD were not elevated at doses 0.05) but were significantly increased at doses >/=2.3 mg/kg compared to the control groups (p < 0.05). The increased activities of these four enzymes were 3 to 6.4 times those in the control groups. The increased activities were maintainedfor at least 4 weeks. Because of a lack of induction at low doses ofPCB 126, which were still relatively high compared to currently known environmental concentrations, we suspect that EROD, MROD, BROD, andPROD activities are not sensitive biomarkers for coplanar PCB exposure in leopard frogs. [ABSTRACT FROM AUTHOR]