M9 PM Multiple Stressors in Amphibian and Reptile Ecotoxicology|
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 339-340
169 (FEL-1117-839123) Amphibian Declines in the Sierra Nevada mountains of California: why are we worried about contaminants?
Start time: 1:50 PM
Fellers, Gary1, Kleeman, Patrick1, 1 Western Ecological Research Center, USGS, Point Reyes National Seashore, Point Reyes, CA, USA
Since 1991, we have visited >6,000 field sites throughout California to evaluate the presence and abundance of pond-breeding amphibians. We have found that most, if not all, species of pond-breeding amphibians in the Sierra Nevada mountains of California are declining. Cascades frogs (Rana cascadae) are almost entirely gone from Lassen Volcanic National Park, mountain yellow-legged frogs (Rana muscosa) are gone from large portions of Sequoia NP, and Yosemite toads (Bufo canorus) are now hard to find in many formerly occupied areas of Yosemite NP. The preponderance of data suggest that contaminants are playing a significant role in these, and other declines. Prevailing winds move pesticides from the valley into the Sierra Nevada. An experimental reintroduction of mountain yellow-legged frogs in Sequoia NP failed. Pond-breeding amphibians in watersheds that face the highly agriculturalized Central Valley of California have experienced the most dramatic declines. A series of studies comparing contaminants levels in frog and tadpole tissue, sediment, air, snow, and water in coastal and mountain parts of California strongly support the view that contaminants are playing a role in amphibian declines.
170 (MCC-1117-887315) Investigating Pesticide Exposure Pathways in Amphibian Habitat of the Sierra Nevada Mountains.
Start time: 2:10 PM
McConnell, L1, Drakeford, L1, Fellers, G2, Sparling, D3, Cowman, D4, Kleeman, P2, Harner, T5, Bidleman, T6, 1 USDA-ARS, Beltsville, MD, USA2 Western Ecological Research Center, USGS, Point Reyes, CA, USA3 Southern Illinois University, Carbondale, IL, USA4 Texas A&M University College, College Station, TX, USA5 Environment Canada, Downsview, ONT, Canada6 Environment Canada, Egbert, ONT, Canada
Wildlife biologists have observed severe declines in several amphibian populations in the Sierra Nevada Mountains of California, USA. Disease, habitat loss, UV (ultraviolet) radiation, predation, and pollution are factors that have been hypothesized to be involved with the disappearance of amphibians over the last two decades. A number of recent studies have also illustrated the cold-trap effect occurring in alpine regions with respect to organic pollutants such as pesticides. Samples of water (n=130), sediment (n=104), snow (n=36), air (n=72), and adult Hyla Regilla (n=89) were collected from a number of locations along the Sierra Nevada Mountain range during 2000-2005 as part of a series of related studies to determine the exposure of tree frogs to agricultural pesticides and other legacy organochlorine insecticide contaminants. Initial results suggest that agricultural pesticides are deposited to the alpine amphibian habitat via snow and other atmospheric deposition processes. However, only the more persistent organochlorine pesticides were detected in the sediment, water, and amphibian tissue samples collected during the summer months while sites are accessible. Environmental conditions present in typical alpine amphibian habitat during the summer months (warm temperatures, high UV radiation, shallow ponds with significant animal and plant biomass) likely lead to rapid degradation of most current use pesticides.
171 (COW-1117-773885) Cholinesterase inhibition in metamorphs and tadpoles in the Sierra Nevada Mountains, CA.
Start time: 2:30 PM
Cowman, D.1, Sparling, D.2, Fellers, G.3, McConnell, L.4, Lacher, T.1, 5, 1 Texas A&M University, College Station, Texas, USA2 Southern Illinois University, Carbondale, Illinois, USA3 USGS Western Ecological Research Center, Point Reyes, California, USA4 USDA Agricultural Research Service, Environmental Quality Lab, Beltsville, Maryland, USA5 Conservation International, Washington, D.C., USA
Declines of native ranid frog populations in the Sierra Nevada mountains may be linked to aerial deposition of pesticides originating from the Central Valley of CA. Pseudacris regilla (Pacific chorus frog) hatchings were translocated (with controls in each park) and placed in cages in sites (approximately 7-8000 ft. in elevation) located in Lassen, Yosemite, and Sequoia National Parks. Cholinesterase was measured in tadpoles collected at 28 days and in juvenile frogs collected upon metamorphosis. Animals were staged according to Gosner; then grouped in the following categories: (PL) prelimb (24-26); (LB) limbbud (27-34); (EHL) early hind limb (35-36); (MHL) middle hind limb (37-39); (LHL) late hind limb (40-41); (meta) metamorph (42-46). ANOVA showed overall differences (p<.0001) between ChE values for metas and all other groups; between LHL and all other groups; there were no differences between MHL, EHL, LB. and PL. ChE values for metas and tadpoles raised at Lassen National Park (reference site) were significantly higher (p<.0001) than values for metas and tadpoles raised at Sequoia and Yosemite National Parks regardless of origin. ChE inhibition can be an indicator of organophosphate insecticide exposure. Effects noted in P. regilla may be magnified in long lived ranid species that are positively correlated with the presence of P. regilla.
172 (SPA-1117-745051) Effects of ultra low concentrations of endosulfan on California amphibians.
Start time: 2:50 PM
Hunt, J.1, Sparling, D.1, 1 Southern Illinois University, Carbondale, IL, USA
Several species of amphibians are declining in the Sierra Nevada Mountains of California. To date the most important factors resulting in these declines are pesticides that are aerially deposited from the Central Valley and introduced predators including trout and bullfrogs. The pesticides that are used in the greatest quantities in the Central Valley include chlorpyrifos, endosulfan, diazinon, and malathion. Of these, endosulfan is the most toxic. In a previous laboratory study we showed that concentrations in water as low as 0.8 ppb killed over 80% of foothills yellow-legged frog (Rana boylii) larvae before they could metamorphose. The more abundant Pacific treefrog (Pseudacris regilla) were more tolerant to endosulfan and both species were more tolerant to chlorpyrifos than they were to endosulfan. This study continues the low concentration exposure of endosulfan to R. boylii, and P. regilla. In a laboratory study from early stage larvae through metamorphosis both species were exposed to endosulfan concentrations ranging from 0.005 ppb to 15 ppb. At the time of this abstract, mortality in both R. boylii and P. regilla was similar to the previous study at concentrations > 0.8 ppb. At lower concentrations mortality is reduced but present and tadpoles appear hyperexcitable. Early results suggest a hometic effect evidenced by rapid development and metamorphosis at low endosulfan concentrations compared to controls. However, tadpoles that metamorphose early may be at a disadvantage because they are significantly smaller than those metamorphosing later.
(58145) Afternoon Break.
Start time: 3:10 PM
173 (WID-1117-833498) Effects of exposure to chlorpyrifos on tadpole growth and behavioral measures in four species.
Start time: 3:50 PM
Widder, P1, Bidwell, J1, 1 Oklahoma State University, Stillwater, Oklahoma, USA
Recent studies have reported a correlative connection between agricultural chemicals and reductions in amphibian populations. However, supplementing these studies with ecologically based laboratory investigations will help facilitate a definitive connection between agricultural chemicals and the loss of amphibian populations. In this study, we examined how a commonly used organophosphate pesticide (OP), chlorpyrifos, impacted the response of tadpole cholinesterase (ChE; the biomarker of exposure to OPs), growth, and swim speed in four species of amphibians (Hyla chrysoscelis, Rana sphenocephala, Acris crepitans, and Gastrophryne olivacea) using laboratory tests with an environmentally realistic experimental design. This design included five environmentally relevant concentrations of chlorpyrifos and examined the influence of pond sediment on tadpole responses after four days. In two species, we also examined how a longer exposure (twelve days) influenced these same responses. Chlorpyrifos exposure significantly impacted tadpole mass in H. chrysoscelis (p=0.0131) and ChE in all species. H. chrysoscelis ChE activity was the most sensitive and R. sphenocephala the least. We found that both sediment and longer duration influenced both these responses in an inconsistent pattern among species. Tadpole swim speed was significantly impaired only in H. chrysoscelis tests without the presence of sediment, despite the inhibition level of 75% in sediment treatments and inhibition of ChE up to 90% in the other species. Furthermore, individual ChE activity did not correlate with individual swim speed. These results indicate that exposure to chlorpyrifos in environmentally realistic scenarios may have a significant impact on tadpole ChE activity and growth, however, swim speed, and therefore potential predator escape ability, is likely to remain unaffected in a real exposure situation.
174 (CHE-1117-573757) Effects of chronic exposure of cadmium and lead on amphibian adults.
Start time: 4:10 PM
Karasov, W1, Gross, J1, 2, Chen, T-H1, 1 Department of Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA2 Department of Animal Sciences, University of Wisconsin-Madison, Madison, WI, USA
We evaluated the effects of chronic exposure to cadmium and lead in adult northern leopard frogs (Rana pipiens). Frogs were exposed to 10 or 50 g of cadmium or lead per gram of body mass via consumption of heavy metal injected crickets for 15 weeks, and then allowed to hibernate. Feeding behavior, overall health, and mortality were monitored through the exposure period and hibernation. Gonad mass and oocyte profiles were also examined in females exposed to cadmium. Survival was 100% during the oral exposure period. All frogs in the high cadmium group developed abnormal lingual flipping movements, significantly compromising feeding ability. Mortality was observed during hibernation in two cadmium and low lead groups. Edema was only recorded in two cadmium groups. Compared to the controls, females in the high cadmium group had significantly decreased gonad mass and higher proportion of immature and abnormal oocytes. Our study suggests that sublethal level of oral exposure to cadmium may cause negative effects on feeding behaviors, overall health and survival during hibernation, and oogenesis in northern leopard frogs. The sensitivity to cadmium will be compared in adult northern leopard frogs and western clawed frogs (Xenopus tropicalis). [Supported by Sea Grant R/MW-84]
175 (GRO-1117-837804) Interaction of cadmium and Ribeiroia ondatrae on development and limb malformations in northern leopard frogs.
Start time: 4:30 PM
Gross, J1, Johnson, P1, Prahl, L1, Schowalter-Hay, E1, Chen, T1, Karasov, W1, 1 University of Wisconsin - Madison, Madison, Wisconsin, US
Concerns over global amphibian population declines have prompted research on the interactions of multiple stressors in amphibian development. Pollutants such as cadmium have been shown to alter immune function in vertebrates which may contribute to an increased risk to pathogens. This study examines the effects of cadmium on an amphibian trematode pathogen, Ribeiroia ondatrae, and its interaction with cadmium on northern leopard frog development. Initially the effects of cadmium on survival and development in miracidia and survival and swimming activity in cercariae (both free swimming stages) were assessed. R. ondatrae cercariae were shed from wild-caught snail (Planorbella trivolvis) hosts and adult trematodes were excised from two week old single comb white leghorn chickens Gallus domesticus for ova collection. Leopard frog embryos and tadpoles (n=300) were exposed (control, 1.0, 10.0 g/l, as CdCl2; static renewal system) to sublethal doses of cadmium from embryonic stages to complete tail resorption. Tadpoles (n=109) were individually exposed to R. ondatrae cercariae (n=91) at limb bud stages of development (Gosner stages (GS) 26-29), and tadpole survival, growth (snout vent length), development (GS), and time to metamorphosis was recorded. Tadpole survival was >95% through two weeks of development (prior to parasite infections) for all treatments. Tadpoles exposed to 10.0 g/l Cd demonstrated more rapid growth and development by two weeks (P<0.001 and P<0.01 respectively) relative to all treatments. Parasite infestation, cyst survival, and limb malformations were also recorded in tadpoles. This is the first study examining the effects of cadmium on R. ondatrae′s free swimming life stages and the first study of the interactive effects of the trematode and a heavy metal on parasite infestation, and survival, development, and hind limb malformations in an amphibian. [Supported by Sea Grant R/MW-84, EPASTAR Predoctoral Fellowship]
176 (BOO-1117-827118) Examining the Role of Contaminants in the Sensitivity of Amphibians to a Pathogen.
Start time: 4:50 PM
Boone, M1, 1 Miami University, Oxford, OH, USA
Reports of amphibian declines have not been clearly attributed to any single cause and recently many researchers have suggested that multiple sublethal stressors may contribute to population declines. I have examined the effects of sublethal exposure to a fertilizer, insecticide, or herbicide on susceptibility of tadpoles and embryos to a widespread pathogenic fungus, Saprolegnia ferax, in experimental laboratory and field studies using spotted salamanders, gray treefrogs, and American toads. In the laboratory, eggs were exposed to no, low, or high levels of S. ferax and the presence or absence of an expected environmental concentration of a contaminant. In field studies, tadpoles were exposed to the presence or absence of a contaminant (ammonium nitrate) and five levels of S. ferax to examine if the chemical exposure influenced susceptibility or if the stressors interacted synergistically. Preliminary evidence in the laboratory and field suggest that presence of chemical contamination can increase the susceptibility of eggs and tadpoles to infection, which could contribute to juvenile recruitment into the breeding population and potentially to population declines.
177 (ROW-1117-568038) Temporally- and Spatially-Disparate Influences of Anthropogenic Stressors on Amphibian Populations: Effects of Aquatic Contaminants and Terrestrial Habitat Reduction.
Start time: 5:10 PM
Rowe, C1, Hopkins, W2, Salice, C3, Pechmann, J, 1 University of Maryland Center for Environmental Science, Solomoms, MD2 Virginia Polytechinic University, Blacksburg, VA3 U.S. Environmental Protection Agency, Washington, DC
The complex life cycles exhibited by most extant amphibians results in susceptibility to environmental stressors operating at temporally- and spatially-distinct scales. The relatively brief aquatic life stages of many species limits the duration of exposure to conditions in aquatic habitats, and the spatially-limited nature of such habitats may provide exposures to stressors unique to the breeding site. On the other hand, long-lived adults dispersing into terrestrial habitats may experience landscape-scale disturbances operating over much longer periods of time. Focusing on the eastern narrowmouth toad (Gastrophryne carolinensis), we combined novel and existing data to construct matrix population models to examine potential influences of aquatic habitat contamination and reduced per capita availability of terrestrial habitat on projected population growth rates. Under conditions of low terrestrial habitat availability and contamination of the aquatic habitat, population growth rate was primarily influenced by survival through the first year (embryos, larvae, terrestrial metamorphs), followed by survival through year 2 (terrestrial juveniles). Under conditions of high terrestrial habitat availability and contaminated aquatic conditions, population growth rate was also primarily influenced by survival through the first year, however survival through ensuing years was relatively unimportant. When examined individually, aquatic contamination had a greater influence on population growth rate (33 % reduction) than did terrestrial habitat restrictions (19 % reduction). With respect to contaminants, larval survival had the greatest influence on population growth compared to reductions in hatching success and fecundity of females inhabiting the contaminated site. The combined influences of aquatic contamination and reduction in terrestrial habitat reduced projected population growth rates by 46 % compared to optimal conditions. Our study emphasizes the importance of considering multiple sources of stress operating at distinct temporal and spatial scales when attempting to identify potential correlates with amphibian population declines.