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At least 19 recordsLinked to original sources
USGS2008

Prominent pancreatic endocrinopathy and altered control of food intake disrupt energy homeostasis in prion diseases

Prion diseases are fatal neurodegenerative diseases that can induce endocrinopathies. The basis of altered endocrine function in prion diseases is not well understood, and the purpose of this study was to investigate the spatiotemporal relationship between energy homeostasis and prion infection in hamsters inoculated with either the 139H strain of scrapie agent, which induces preclinical weight gain, or the HY strain of transmissible mink encephalopathy (TME), which induces clinical weight loss. Temporal changes in body weight, feed, and water intake were measured as well as both non-fasted and fasted concentrations of serum glucose, insulin, glucagon, ??-ketones, and leptin. In 139H scrapie-infected hamsters, polydipsia, hyperphagia, non-fasted hyperinsulinemia with hyperglycemia, and fasted hyperleptinemia were found at preclinical stages and are consistent with an anabolic syndrome that has similarities to type II diabetes mellitus and/or metabolic syndrome X. In HY TME-infected hamsters, hypodipsia, hypersecretion of glucagon (in both non-fasted and fasted states), increased fasted ??-ketones, fasted hypoglycemia, and suppressed non-fasted leptin concentrations were found while feed intake was normal. These findings suggest a severe catabolic syndrome in HY TME infection mediated by chronic increases in glucagon secretion. In both models, alterations of pancreatic endocrine function were not associated with PrPSc deposition in the pancreas. The results indicate that prominent endocrinopathy underlies alterations in body weight, pancreatic endocrine function, and intake of food. The prion-induced alterations of energy homeostasis in 139H scrapie- or HY TME-infected hamsters could occur within areas of the hypothalamus that control food satiety and/or within autonomic centers that provide neural outflow to the pancreas. ?? 2008 Society for Endocrinology.

Journal of Endocrinology↗
USGS2020

Food web controls on mercury fluxes and fate in the Colorado River, Grand Canyon

Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator resistant and a trophic dead end for Hg in food webs we studied. Fishes preferred blackflies, which accounted for 56 to 80% of Hg flux to fishes, even where blackflies were rare. Food web properties, i.e., match/mismatch between insect production and fish consumption, governed amounts of Hg retained in the river versus exported to land. An experimental flood redistributed Hg fluxes in the simplified tailwater food web, but not in complex downstream food webs. Recognizing that species traits, species interactions, and disturbance mediate contaminant exposure can improve risk management of linked aquatic-terrestrial ecosystems.

Arizona, Nevada↗
USGS1988

Food availability controls seasonal cycle of growth in Macoma balthica (L.) in San Francisco Bay, California

A 2-yr field study of growth in the bivalve Macoma balthica (L.) at four locations in San Francisco Bay, California, U.S., showed that the timing and rate of growth (increase in shell length) were related to food supply. This clam feeds on both planktonic and benthic microalgae, depending on availability. Growth was apparently food-limited during some months, during one year more than the other, and at some locations more than others. Tissue-weight changes were also related to food availability. The heaviest animals were found in that year and at those locations with the highest chl a concentrations. Tissue-weight gains usually coincided with increased shell-growth rate or with reproductive development, although some large animals showed weight gain independent of both of these factors during periods with mid-range chl a levels. Weight losses coincided with spawning or periods of low growth rate, except at one station where, during a period when most animals were reproductively ripe, food concentrations were high, and shell growth was rapid, animals lost weight. This study failed to show a relation between salinity and the timing or rate of change of either shell length or tissue weight. The mild temperatures (10-23 ??C water temperature) of the area studied resulted in no growth inhibition due to low temperature, but there was some indication that the high air temperatures found in these intertidal areas limited growth rates. ?? 1988.

Journal of Experimental Marine Biology and Ecology↗
USGS2019

Surface water connectivity controls fish food web structure and complexity across local- and meta-food webs in Arctic Coastal Plain lakes

The need for theories that address food web assembly and complexity over multiple spatial scales are critical to understanding their stability and persistence. In a meta-food web – an integrated network of local food webs – spatial heterogeneity in physical processes may have profound effects on food web function and energy flow. In the Arctic, surface water connectivity plays a vital role in determining fish assemblage composition, and potentially, food web structure. We examined lentic food web complexity associated with heterogeneity in surface water connectivity among Arctic lakes at the at the local scale, by contrasting lakes over a stream-lake connectivity gradient, and at the regional scale, by contrasting two locations with different surface water conditions (i.e., wet and dry) on the Arctic Coastal Plain of Alaska. Among lakes and across locations, increased hydrologic connectivity between streams and lakes increased the number of fish species and increased the complexity of the food web. The interaction of the region’s hydrologic connectivity, local stream-lake connections, and the trophic niches of relevant fish species produced integrated, complex meta-food webs. Fully understanding mechanisms that support meta-food web stability are crucial when assessing future changes to Arctic stream-lake networks and the function and persistence of aquatic food webs.

Food Webs↗
USGS1980

Sex-specific differences in winter distribution patterns of canvasbacks

Winter band recovery distributions of North American Canvasbacks (Aythya valisineria) suggested that males and females exhibit comparable degrees of fidelity to general wintering areas. Of birds banded during the winter, the proportion of males was found to be higher in northern than in southern areas. Winter band recovery distributions of birds banded in particular areas during the summer were found to differ significantly between sexes, with females being recovered farther south. Factors that may have affected the evolution of sex-specific wintering distributions include: (1) possible reproductive benefits derived by males who winter in the north and thus reach northerly breeding areas early; (2) sexual dimorphism in body size, which may render the smaller females especially susceptible to periods of inclement weather and food shortages; and (3) interactions between sexes in which males may control food supply when food is scarce. Two lines of evidence from field data on Canvasbacks in the Chesapeake Bay suggest the existence of competition between males and females. First, Canvasbacks trapped during winter in smaller bodies of water tended to have higher proportions of females and weigh less than birds trapped in large open bodies of water. Second, analysis of aerial photographs of wintering rafts of Canvasbacks showed patterns of intersexual segregation, with females being found more frequently on peripheral areas of rafts.

Condor↗
USGS2010

When parasites become prey: ecological and epidemiological significance of eating parasites

Recent efforts to include parasites in food webs have drawn attention to a previously ignored facet of foraging ecology: parasites commonly function as prey within ecosystems. Because of the high productivity of parasites, their unique nutritional composition and their pathogenicity in hosts, their consumption affects both food-web topology and disease risk in humans and wildlife. Here, we evaluate the ecological, evolutionary and epidemiological significance of feeding on parasites, including concomitant predation, grooming, predation on free-living stages and intraguild predation. Combining empirical data and theoretical models, we show that consumption of parasites is neither rare nor accidental, and that it can sharply affect parasite transmission and food web properties. Broader consideration of predation on parasites will enhance our understanding of disease control, food web structure and energy transfer, and the evolution of complex life cycles.

Trends in Ecology and Evolution↗
USGS2006

Effects of dietary PCB exposure on reproduction in the white-footed mouse (Peromyscus leucopus)

Studies of the impact of environmental contaminants on reproduction have typically focused on effects on fertility and subsequent reproductive failure. Contaminants may also impact reproductive output or other aspects of life history through effects on resource acquisition or allocation. We fed successfully breeding female white-footed mice (Peromyscus leucopus) diets containing polychlorinated biphenyls (2:1 Aroclor 1242:1254) at levels of 0 (n = 10), 10 (n = 12), and 25 (n = 10) ppm (mg polychlorinated biphenyls [PCBs]/kg food). After 4 months on the diets, female mice were bred with male mice maintained on control food. There was no effect of PCB exposure on litter size at birth or weaning, although fewer female mice on the 25-ppm diet gave birth. There was no effect of PCB dose on maternal metabolic rate at peak lactation or on total food (dry matter) intake during lactation. Female mice on the 10-ppm diet, however, consumed more food per pup during lactation and weaned larger pups, although these differences disappeared after 4 weeks of age. We conclude that although moderate-term exposure to PCBs did decrease the number of litters produced for high-dose female mice, it did not change litter size, pup growth rate, or energetic measures for those female mice that did successfully reproduce.

Archives of Environmental Contamination and Toxico↗
USGS1982

Oviposition and the plasma concentrations of LH, progesterone, and corticosterone in bobwhite quail (Colinus virginianus) fed parathion

Bobwhite quail were fed concentrations of parathion (0,50, 100, 200 or 400 p.p.m.) for 10 days. Food intake, body weight change, brain acetylcholinesterase activity, egg production, and ovary weight were reduced in a dose-dependent manner. In a second experiment, birds were fed 0, 25 or 100 p.p.m. parathion or pair-fed control food to equate consumption in the 100 p.p.m. group. Egg production was not affected in birds fed 25 p.p.m. or in the pair-fed group, but the daily time of oviposition was more variable than in the control group. Cessation of egg production, inhibition of follicular development, and reduced plasma LH concentration were observed in birds fed 100 p.p.m. parathion. These findings indicate that exposure to parathion can impair reproduction, possibly by altering gonadotrophin secretion.

Journal of Reproduction and Fertility↗
USGS2007

Determining metal assimilation efficiency in aquatic invertebrates using enriched stable metal isotope tracers

We employ a novel approach that combines pulse-chase feeding and multi-labelled stable isotopes to determine gut passage time (GPT), gut retention time (GRT), food ingestion rate (IR) and assimilation efficiency (AE) of three trace elements for a freshwater gastropod. Lettuce isotopically enriched in 53 Cr, 65 Cu and 106 Cd was fed for 2 h to Lymnaea stagnalis . The release of tracers in feces and water was monitored for 48 h, during which unlabelled lettuce was provided ad libidum . The first defecation of 53 Cr occurred after 5 h of depuration (GPT), whereas 90% of the ingested 53 Cr was recovered in the feces after 22.5 h of depuration (GRT). 53 Chromium was not significantly accumulated in the soft tissues upon exposure. In contrast, 65 Cu and 106 Cd assimilation was detectable for most experimental snails, i.e., 65/63 Cu and 106/114 Cd ratios in exposed snails were higher than those for controls. Food IR during the labelled feeding phase was 0.16 ± 0.07 g g −1 d −1 . IR was inferred from the amount of 53 Cr egested in the feces during depuration and the concentration of 53 Cr in the labelled lettuce. Assimilation efficiencies (±95% CI) determined using mass balance calculations were 84 ± 4% for Cu and 85 ± 3% for Cd. The ratio method yields similar AE estimates. Expanding the application of this novel stable isotope tracer technique to other metals in a wide variety of species will provide unique opportunities to evaluate the interplay between digestive processes and dietary influx of metals. Understanding the biological processes that modulate dietborne metal uptake is crucial to assess the toxicity of dietborne metals.

Aquatic Toxicology↗
USGS2007

Development and certification of the new SRM 695 trace elements in multi-nutrient fertilizer

During the past seven years, several states within the US have enacted regulations that limit the amounts of selected non-nutritive elements in fertilizers. Internationally, several countries, including Japan, China, and Australia, and the European Union also limit the amount of selected elements in fertilizers. The elements of interest include As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, and Zn. Fertilizer manufacturers and state regulatory authorities, faced with meeting and verifying these limits, need to develop analytical methods for determination of the elements of concern and to validate results obtained using these methods. Until now, there were no certified reference materials available with certified mass fraction values for all elements of interest in a blended, multi-nutrient fertilizer matrix. A new standard reference material (SRM) 695 trace elements in multi-nutrient fertilizer, has been developed to help meet these needs. SRM 695 has recently been issued with certified mass fraction values for seventeen elements, reference values for an additional five elements, and information values for two elements. The certificate of analysis includes an addendum listing percentage recovery for eight of these elements, determined using an acid-extraction inductively-coupled plasma optical-emission spectrometry (ICP-OES) method recently developed and tested by members of the Association of American Plant Food Control Officials. ?? Springer-Verlag 2007.

Conference Paper↗
USGS2012

County-level estimates of nitrogen and phosphorus from commercial fertilizer for the Conterminous United States, 1987-2006

The U.S. Geological Survey’s National Water-Quality Assessment program requires nutrient input for analysis of the national and regional assessment of water quality. Detailed information on nutrient inputs to the environment are needed to understand and address the many serious problems that arise from excess nutrients in the streams and groundwater of the Nation. This report updates estimated county-level farm and nonfarm nitrogen and phosphorus input from commercial fertilizer sales for the conterminous United States for 1987 through 2006. Estimates were calculated from the Association of American Plant Food Control Officials fertilizer sales data, Census of Agriculture fertilizer expenditures, and U.S. Census Bureau county population. A previous national approach for deriving farm and nonfarm fertilizer nutrient estimates was evaluated, and a revised method for selecting representative states to calculate national farm and nonfarm proportions was developed. A national approach was used to estimate farm and nonfarm fertilizer inputs because not all states distinguish between farm and nonfarm use, and the quality of fertilizer reporting varies from year to year. For states that distinguish between farm and nonfarm use, the spatial distribution of the ratios of nonfarm-to-total fertilizer estimates for nitrogen and phosphorus calculated using the national-based farm and nonfarm proportions were similar to the spatial distribution of the ratios generated using state-based farm and nonfarm proportions. In addition, the relative highs and lows in the temporal distribution of farm and nonfarm nitrogen and phosphorus input at the state level were maintained—the periods of high and low usage coincide between national- and state-based values. With a few exceptions, nonfarm nitrogen estimates were found to be reasonable when compared to the amounts that would result if the lawn application rates recommended by state and university agricultural agencies were used. Also, states with higher nonfarm-to-total fertilizer ratios for nitrogen and phosphorus tended to have higher urban land-use percentages.

Scientific Investigations Report↗
USGS2019

Catchment-level estimates of nitrogen and phosphorus agricultural use from commercial fertilizer sales for the conterminous United States, 2012

Nutrient inputs from commercial agricultural fertilizer, particularly nitrogen and phosphorus, are important factors contributing to the degradation of surface-water quality and the alteration of aquatic ecosystems. Despite this importance, information about the application of fertilizer to agricultural land is not available in a consistent manner across the United States at a scale useful for regional water-quality assessment. To address this need, an approach is developed to relate commercial fertilizer sales to a set of explanatory variables using spatially referenced modeling methods. Spatially referenced modeling in this study refers to statistically relating fertilizer use, estimated from commercial fertilizer sales data, to spatially referenced data on watershed attributes. Separate models for nitrogen and phosphorus are developed to estimate elemental fertilizer use on agricultural lands for the conterminous United States at the National Hydrography Dataset Plus (NHDPlus) catchment scale for the year 2012. The approach builds on earlier efforts that use Association of American Plant Food Control Officials data on fertilizer sales to provide county-level estimates of nitrogen and phosphorus fertilizer use. The spatially referenced method improves on these efforts by allowing for varying nitrogen to phosphorus ratios at the catchment scale and expanding the set of variables used to allocate county-level sales data to the catchment scale. The models include catchment-level factors that are either primary determinants of fertilizer use, such as the acreage of different crop types, or measures reflecting the intensity of use, such as climate. Explanatory variables available only at the county scale, such as U.S. Department of Agriculture Census of Agriculture estimates of fertilizer expenditures, are included to improve the model predictions of elemental use. The nitrogen and phosphorus models explain more than 90 percent of the variation in elemental use at the state level, and the statistical approach allows for the estimation of uncertainty of predicted use in each catchment. The spatial patterns of model predictions reflect known agricultural cropping practices across the United States that transcend political boundaries, despite the county/state orientation of the fertilizer sales information. The results are expected to be useful for a variety of water-quality assessments that are intended to estimate nitrogen and phosphorus loads to streams.

Scientific Investigations Report↗
USGS2011

Ecosystem ecology meets adaptive management: food web response to a controlled flood on the Colorado River, Glen Canyon

Large dams have been constructed on rivers to meet human demands for water, electricity, navigation, and recreation. As a consequence, flow and temperature regimes have been altered, strongly affecting river food webs and ecosystem processes. Experimental high‐flow dam releases, i.e., controlled floods, have been implemented on the Colorado River, USA, in an effort to reestablish pulsed flood events, redistribute sediments, improve conditions for native fishes, and increase understanding of how dam operations affect physical and biological processes. We quantified secondary production and organic matter flows in the food web below Glen Canyon dam for two years prior and one year after an experimental controlled flood in March 2008. Invertebrate biomass and secondary production declined significantly following the flood (total biomass, 55% decline; total production, 56% decline), with most of the decline driven by reductions in two nonnative invertebrate taxa, Potamopyrgus antipodarum and Gammarus lacustris . Diatoms dominated the trophic basis of invertebrate production before and after the controlled flood, and the largest organic matter flows were from diatoms to the three most productive invertebrate taxa ( P. antipodarum , G. lacustris , and Tubificida). In contrast to invertebrates, production of rainbow trout ( Oncorhynchus mykiss ) increased substantially (194%) following the flood, despite the large decline in total secondary production of the invertebrate assemblage. This counterintuitive result is reconciled by a post‐flood increase in production and drift concentrations of select invertebrate prey (i.e., Chironomidae and Simuliidae) that supported a large proportion of trout production but had relatively low secondary production. In addition, interaction strengths, measured as species impact values, were strongest between rainbow trout and these two taxa before and after the flood, demonstrating that the dominant consumer–resource interactions were not necessarily congruent with the dominant organic matter flows. Our study illustrates the value of detailed food web analysis for elucidating pathways by which dam management may alter production and strengths of species interactions in river food webs. We suggest that controlled floods may increase production of nonnative rainbow trout, and this information can be used to help guide future dam management decisions.

Arizona↗
USGS2021

Foraging behavior in a generalist snake (brown treesnake, Boiga irregularis) with implications for avian reintroduction and recovery

Broad foraging classifications, such as generalist or specialist forager, are generally beneficial for population management in defining expectations of typical behavior. However, better understanding as to how individual variance in behavior interfaces with management actions, such as control of an invasive predator (such as brown treesnakes; Boiga irregularis ) responsible for ecological collapse of a taxonomic group (birds), may affect conservation goals. In the context of predator control, better understanding of foraging ecology and prey specificity helps to ensure that food-based control programs are removing the target individuals. We sought to quantify whether differences in a dietary generalist snake species was measurable during captive trials using mice or birds as the prey choice. We presented snakes with prey choices that could be or are integrated with tools deployed by managers for control to directly relate choice or preference to management action. We collected wild brown treesnakes and classified them as bird eaters or of unknown diet based on food items present in their digestive tract at the time of capture. In experimental tests, we used live birds and live mice in traps, as well as bird and mouse carrion presented on platforms, to measure interest, take rates, and repeatability (preference) by snakes. We found that all individuals spent more time investigating live birds than they did mice, independent of dietary history, which resulted in twice as many snakes being captured in traps with live birds compared to live mice. There was, however, roughly equal interest in mouse and bird carrion. Within individuals, there was evidence for decreased interest in mouse carrion, if individuals ate birds in the wild. Choice of carrion type was repeatable across trials, suggesting preference may exist. Overall, interest in both live mice and mouse carrion was greatest for medium-bodied snakes, while interest in bird carrion was independent of snake size. Our results indicate that management of invasive predators, including reptiles, may more rapidly achieve conservation targets when managers consider individual heterogeneity in behavior. For brown treesnakes more interested in birds, managers may remove more snakes if they use avian food lures; increased removal of avian specialists may facilitate avian recovery.

Applied Animal Behavior Science↗
USGS1989

Effects of Kelthane® on reproduction of captive eastern screech-owls

Eastern screech-owls ( Otus asio ) were fed diets containing 10 ppm Kelthane® with 3.4% DDT-related contaminants (old technical formulation), 10 ppm Kelthane with no detectable DDT contaminants (new technical formulation) or a control diet. Food consumption, adult weight and date of initiation of egg laying were similar for birds in control and dosed treatment groups. Most measures of reproductive success were similar for control and dosed treatment groups. Shell weight and thickness index were significantly lower for both dosed groups than for controls. Shell thickness was significantly lower for the new Kelthane treatment than for controls. Concentrations of p,p' -DDE were significantly higher in eggs laid by pairs receiving old Kelthane than in those of birds receiving new Kelthane or in controls. Concentrations of dichlorobenzophenone, dicofol and dechlorodicofols were significantly higher in carcasses of dosed owls than in controls, whereas concentrations of DDE were significantly higher in carcasses of owls fed old Kelthane than in controls or owls fed new Kelthane.

Environmental Toxicology and Chemistry↗
USGS2002

Fasting modifies Aroclor 1254 impact on plasma cortisol, glucose and lactate responses to a handling disturbance in Arctic charr

Integrated effects of polychlorinated biphenyl (PCB) and nutritional status on responses to handling disturbance were investigated in the Arctic charr ( Salvelinus alpinus ). The fish were orally contaminated with Aroclor 1254 and held either with or without food for 5 months before they were subjected to a 10-min handling disturbance. Food-deprived fish were given 0, 1, 10 or 100 mg PCB kg −1 and the fed fish 0 or 100 mg PCB kg −1 . Plasma cortisol, glucose and lactate levels were measured at 0 (pre-handling), 1, 3, 6 and 23 h after the handling disturbance. Food-deprived control fish had elevated plasma cortisol levels compared with fed fish before handling. These basal cortisol levels were suppressed by PCB in food-deprived fish, and elevated by PCB in fed fish. The immediate cortisol and glucose responses to handling disturbance were suppressed by PCB in a dose-dependent way in food-deprived fish. Although these responses were also lowered by PCB in the fed fish, the effect was much less pronounced than in food-deprived fish. There were only minor effects on plasma lactate responses. Our findings suggest that the stress responses of the Arctic charr are compromised by PCB and that the long-term fasting, typical of high-latitude fish, makes these species particularly sensitive to organochlorines such as PCB.

Comparative Biochemistry and Physiology, Part C: T↗
USGS1999

Summer water clarity responses to phosphorus, Daphnia grazing, and internal mixing in Lake Mendota

Linear models were developed for predicting mean Secchi disk depth readings as a measure of water clarity for the summer months in Lake Mendota, Wisconsin. The 20-yr (1976-1995) data set also included external phosphorus (P) loadings and in-lake April P concentrations as indices of lake nutrient status, and monthly (28 d) water column stabilities and Daphnia biomasses as indices of lake mixing and algal grazing potentials, respectively. June Secchi depths were mostly controlled by food web dynamics, which dictated whether the larger-bodied Daphnia pulicaria or the smaller-bodied D. galeata mendotae dominated during the spring clear-water phase. May Daphnia biomasses were significantly greater in D. pulicaria-dominated years than in D. galeata-dominated years; D. pulicaria-year biomasses were also greater during the summer months. The model for the midsummer (July-August) months indicated that Secchi depths were inversely related to April P concentrations and positively related to midsummer Daphnia biomasses and lake stabilities. Scenarios for midsummer Secchi depths were tested using the observed minimum and maximum values for each predictor variate. While holding two variates constant, April P, Daphnia biomass, and lake stability each resulted in relatively similar Secchi ranges (0.81, 0.81, and 1.17 m, respectively). Our results suggest that summer water clarity in eutrophic Lake Mendota is controlled by interacting ecosystem processes linked to land use activities, lake food web dynamics, and climate.

Limnology and Oceanography↗