The threat of global mercury pollution to bird migration: potential mechanisms and current evidence

Mercury is a global pollutant that has been widely shown to adversely affect reproduction and other endpoints related to fitness and health in birds, but almost nothing is known about its effects on migration relative to other life cycle processes. Here I consider the physiological and histological effects that mercury is known to have on non-migrating birds and non-avian vertebrates to identify potential mechanisms by which mercury might hinder migration performance. I posit that the broad ability of mercury to inactivate enzymes and compromise the function of other proteins is a single mechanism by which mercury has strong potential to disrupt many of the physiological processes that make long-distance migration possible. In just this way alone, there is reason to expect mercury to interfere with navigation, flight endurance, oxidative balance, and stopover refueling. Navigation and flight could be further affected by neurotoxic effects of mercury on the brain regions that process geomagnetic information from the visual system and control biomechanics, respectively. Interference with photochemical reactions in the retina and decreases in scotopic vision sensitivity caused by mercury also have the potential to disrupt visual-based magnetic navigation. Finally, migration performance and possibly survival might be limited by the immunosuppressive effects of mercury on birds at a time when exposure to novel pathogens and parasites is great. I conclude that mercury pollution is likely to be further challenging what is already often the most difficult and perilous phase of a migratory bird's annual cycle, potentially contributing to global declines in migratory bird populations.

New insights into methylmercury induced behavioral and energy-related gene transcriptional responses in European glass eel (Anguilla anguilla)

The effect of methylmercury (MeHg) was investigated in glass eel migration behavior and metabolism. To migrate up estuary, glass eels synchronize their swimming activity to the flood tide and remain on or in the substratum during ebb tide. Following seven days of exposure to MeHg (100 ng L^-1), glass eels migration behavior was expressed by their swimming synchronization to the water current reversal every 6.2 h (mimicking the alternation of flood and ebb tides) and their swimming activity level. In relation to their behavior, we then analyzed the energy-related gene expression levels in individual head, viscera and muscle. Results showed that MeHg decreased the number of glass eels synchronized to the change in water current direction and their swimming activity level. This last effect was more pronounced in non-synchronized fish than in synchronized ones, supporting the idea that non-synchronized glass eels could be more vulnerable to stress. As regard the expression of energy-related genes, no significant difference was observed between control and MeHg-exposed fish. In contrast, when the swimming activity levels were plotted against transcriptional responses, positive correlations were evidenced in viscera and especially in the head of exposed glass eels but not in control. Finally, it is noteworthy that non-synchronized glass eels displayed lower expression level of metabolism genes than their synchronized counterpart, but only in the head. Altogether, these results support the interest of focusing on the head to investigate the facultative migration behavior in glass eels and the effect of environmental stressors on this rhythmic behavior.

Negative impacts of the sea lice prophylactic emamectin benzoate on the survival of hatchery released salmon smolts in rivers

Emamectin benzoate (EB) is a prophylactic pharmaceutical used to protect Atlantic salmon (Salmo salar) smolts migrating out of rivers and into the ocean against sea lice parasites. Randomized control trials comparing the marine survival of smolts treated with EB to a control group is used to calculate the fraction of marine mortality attributable to sea lice parasitism. However, it is assumed that there is no baseline difference in survival induced by the application of EB treatment. We used a combined laboratory and field study approach to investigate the potential impacts of EB treatment on behaviour and survival of hatchery-reared Atlantic salmon in western Norway. In aquaria experiments, EB-treated salmon smolts did not differ significantly in exploratory behaviour. Fish from treated groups responded similarly to simulated predator attack with spontaneous escape and elevated gill beat rate. Three rivers in the Osterfjord system of western Norway were selected for field experiments, Dale, Vosso, and Modalen. Dale River smolts were treated with intraperitoneal EB injections and had lower probability of detection in a wolf trap downstream of the release site than control smolts. Salmon smolts raised in the Vosso River hatchery were treated with EB delivered in their food and were detected on PIT antennas at the rivermouth of Vosso and Modalen at lower rates than control fish, but only when released at downstream sites. Calculation of risk ratios suggested that the bias in mortality caused by treatment with EB decreased the estimated survival of treated fish from an expected 18%to 46%, reducing the observable negative impact of sea lice on Atlantic salmon smolts in randomized control trials. The results suggest that estimates of the fraction of mortality attributable to sea lice may be underestimated due to lower baseline survival of treated fish caused by treatment and bring urgent attention towards a potential systematic underestimation of the impacts of sea lice on wild salmon.

Effects of pH on the incubation and early development of fish species with different reproductive strategies

Fish reproduction in natural environments tends to occur in conditions, including extreme pH values, ideal for the survival of offspring. In this context, the purpose of this study was to assess the influence of pH on both survival and early development of two fish species, Astyanax lacustris (short-distance migrating fish) and Piaractus mesopotamicus (long-distance migrating fish), with different reproductive strategies. Our experiments were divided into two tests (incubation and larviculture) at five pH levels. First was incubation through a water recirculation system using 2 L incubators followed by larviculture using a 2.5 L aquarium. pH had no influence on the hatching rate of A. lacustris eggs, but affected the yolk-sac diameter, while the newly-hatched larvae had some skeletal disorders. For P. mesopotamicus, pH influenced the hatching rate and perivitelline space, while the newly-hatched larvae had several skeletal disorders. The larviculture of A. lacustris revealed no effect on the survival rate, but the analyzed morphometric variables indicated significant differences between the treatments. An acidic pH negatively influenced the survival rate of P. mesopotamicus, and all morphometric variables also varied significantly between the treatments. We concluded that both the survival and development of A. lacustris and P. mesopotamicus revealed different responses at pH levels during incubation and larviculture tests.

Sub-lethal effects of a neonicotinoid, clothianidin, on wild early life stage sockeye salmon (Oncorhynchus nerka)

One of the categories of environmental contaminants possibly contributing to declining sockeye salmon (Oncorhynchus nerka) in the Fraser River, British Columbia, Canada is pesticides. In this 4-month study, the effects of environmentally relevant concentrations of a waterborne neonicotinoid, clothianidin (0.15, 1.5, 15 and 150 μg/L), on embryonic, alevin and early swim-up fry sockeye salmon derived from four unique genetic crosses of the Pitt River, BC stock were investigated. There were no significant effects of clothianidin on survival, hatching, growth or deformities, although genetic variation significantly affected these endpoints. Clothianidin caused a significant 4.7-fold increase in whole body 17β-estradiol levels in swim-up fry after exposure to 0.15 μg/L, but no effects were observed on testosterone levels. In addition, hepatic expression of the gene encoding glucocorticoid receptor 2 was also impacted at the highest concentration of clothianidin tested, and was found to be ∼4-fold lower compared to the sockeye reared in control water. These results indicate additional examination of clothianidin and its effects on salmonid gonad development and the reproductive and stress endocrine axes in general, is warranted.

Mercury contamination in resident and migrant songbirds and potential effects on body condition

Methlymercury is a significant risk to environmental health globally. We examined the ecological drivers of methylmercury bioaccumulation in songbirds and its effect on body condition while experimentally removing the potentially confounding and predominant effects of site and habitat. We measured blood and feather mercury concentrations and body condition in nearly 1200 individuals representing resident or migrant songbirds of 52 species and 5 foraging guilds. Songbird mercury concentrations differed among species, foraging guilds, residency status, dates, and ages, but not sexes. Blood mercury concentrations 1) ranged from 0.003 in house finch to 0.85 μg/g ww in American robin, 2) were 125 times greater in insectivores than granivores and 3.6 times greater in insectivores than omnivores, 3) were 3.3 times greater in summer residents than in migrating songbirds, 4) increased by 25% throughout spring and summer, and 5) were 45% higher in adults than juveniles. Songbird mercury concentrations were negatively correlated with body condition, with blood mercury concentrations decreasing by 44% and 34% over the range of standardized body masses and fat scores, respectively. Our results highlight the importance of foraging and migration ecology in determining methylmercury contamination in birds, and the potential for reduced body condition with methylmercury exposure in songbirds.

Polycyclic aromatic hydrocarbon exposure impairs pre-migratory fuelling in captively-dosed Sanderling (Calidris alba)

Efficient fuelling is essential for migratory birds because fuel loads and fuelling rates affect individual fitness and survival during migration. Many migrant shorebirds are exposed to oil pollution and its toxic constituents, polycyclic aromatic hydrocarbons (PAHs), at migratory staging sites, which has the potential to interfere with avian refuelling physiology. In this study, we orally dosed shorebirds with environmentally-relevant PAH mixtures to simulate dietary exposure during staging. Forty-nine wild-caught Sanderling (Calidris alba) were exposed to 0 (control), 12.6 (low), 126 (medium), or 1260 (high) μg total PAH/kg body weight/day. Birds were dosed during a 21-day period of autumn pre-migratory fuelling to mimic the typical staging duration of Sanderling. We measured daily changes in mass and fat loads, as well as ethoxyresorufin-O-deethylase (EROD) activity, serum biochemical profiles, and liver mass and lipid content following dosing. All dose groups gained fat and increased in mass (size-corrected) during the study period, with females having a higher average body mass than males. However, mass gain was 3.9, 5.4, and 3.8 times lower in the low, medium, and high dose groups, respectively, relative to controls, and body mass in the medium and high dose groups significantly declined near the end of the experiment. EROD activity showed a dose-dependent increase and was significantly elevated in the high dose group relative to controls. Higher individual EROD activity was associated with reduced serum bile acid and elevated serum creatine kinase concentrations in both sexes, and with elevated serum lipase concentrations in females. These results suggest that PAH exposure in Sanderling can interfere with mechanisms of lipid transport and metabolism, can cause muscle damage, and can lead to reduced overall fat loads that are critical to staging duration, departure decisions, migratory speed, and flight range. Given that many shorebirds migrate thousands of kilometers between the breeding and wintering grounds and frequently aggregate at key staging sites that are subject to contamination, PAH exposure likely represents a significant threat to shorebird migratory success.

A probabilistic risk assessment for the Kirtland's warbler potentially exposed to chlorpyrifos and malathion during the breeding season and migration

Two organophosphate pesticides, chlorpyrifos and malathion, are currently undergoing reregistration in the United States and were recently used by the US Environmental Protection Agency (USEPA) as case studies to develop a national procedure for evaluating risks to endangered species. One of the endangered bird species considered by the USEPA was the Kirtland's warbler (Setophaga kirtlandii). The Kirtland's warbler is an endangered migratory species that nests exclusively in young jack pine stands in Michigan and Wisconsin, and winters in the Bahamas. We developed probabilistic models to assess the risks of chlorpyrifos and malathion to Kirtland's warblers during the breeding season and the spring and fall migrations. The breeding area model simulates acute and chronic exposure and risk to each of 10 000 birds over a 60-d period following initial pesticide application. The model is highly species specific with regard to the foraging behavior of Kirtland's warblers during the breeding season. We simulated the maximum application rate and number of applications allowed on the labels for representative use patterns that could be found within 3 km of the breeding areas of Kirtland's warbler. The migration model simulates 10 000 birds during the course of their 12- to 23-d migration between their breeding area and the Bahamas. The model takes advantage of more than a century of observations of when, where, and for how long Kirtland's warblers forage in different habitats during the course of their migration. The data indicate that warblers only infrequently stop over in habitats that could be treated with chlorpyrifos and malathion. The breeding area and migration models resulted in predictions of very low acute and chronic risk for both pesticides to Kirtland's warblers. These results were expected, given that field observations indicate that the Kirtland's warbler has dramatically increased in abundance in recent decades. Integr Environ Assess Manag 2018;14:252-269. © 2017 SETAC.

Dietary exposure to methylmercury affects flight endurance in a migratory songbird

Although there has been much speculation in the literature that methylmercury (MeHg) exposure can reduce songbird fitness, little is known about its effects on migration. Migrating songbirds typically make multiple flights, stopping to refuel for short periods between flights. How refueling at MeHg-contaminated stopover sites would contribute to MeHg bioaccumulation, and how such exposure could affect subsequent flight performance during migration has not been determined. In a dosing experiment we show that migratory yellow-rumped warblers (Setophaga coronata) rapidly accumulate dietary MeHg in blood, brain and muscle, liver and kidneys in just 1-2 weeks. We found that exposure to a 0.5 ppm diet did not affect vertical takeoff performance, but in 2-h wind tunnel flights, MeHg-treated warblers had a greater median number of strikes (landing or losing control) in the first 30 min, longer strike duration, and shorter flight duration. The number of strikes in the first 30 min of 0.5 ppm MeHg-exposed warblers was related to mercury concentration in blood in a sigmoid, dose-dependent fashion. Hyperphagic migratory songbirds may potentially bioaccumulate MeHg rapidly, which can lead to decreased migratory endurance flight performance.

Low level exposure to crude oil impacts avian flight performance: The Deepwater Horizon oil spill effect on migratory birds

In 2010, the Deepwater Horizon oil spill released 134 million gallons of crude oil into the Gulf of Mexico making it the largest oil spill in US history. The three month oil spill left tens of thousands of birds dead; however, the fate of tens of thousands of other migratory birds that were affected but did not immediately die is unknown. We used the homing pigeon as a surrogate species for migratory birds to investigate the effects of a single external oiling event on the flight performance of birds. Data from GPS data loggers revealed that lightly oiled pigeons took significantly longer to return home and spent more time stopped en route than unoiled birds. This suggests that migratory birds affected by the oil spill could have experienced long term flight impairment and delayed arrival to breeding, wintering, or crucial stopover sites and subsequently suffered reductions in survival and reproductive success.

Body mass change in flying homing pigeons externally exposed to Deepwater Horizon crude oil

The Deepwater Horizon oil spill contaminated thousands of miles of habitat valuable to hundreds of species of migratory and resident birds of the Gulf of Mexico. Many birds died as a direct result of the oil spill; however, the indirect effects of oil exposure on the flight ability and body condition of birds are difficult to assess in situ. This study utilizes the homing pigeon as a surrogate species for migratory birds to investigate the effect of multiple external oil exposures on the flight performance and body mass change of birds over a series of repeated flights from 136.8km flight distance. Oiled pigeons took significantly longer to return home, lost more weight during flight, and were unable to recover their weight, resulting in reduction of body weight overtime. Based on our data, migratory birds that were oiled, even partially, by the Deepwater Horizon oil spill likely took longer to complete migration and were likely in poor body condition, increasing their risk of mortality and reproductive failure.

Imidacloprid and chlorpyrifos insecticides impair migratory ability in a seed-eating songbird

Birds that travel long distances between their wintering and breeding grounds may be particularly susceptible to neurotoxic insecticides, but the influence of insecticides on migration ability is poorly understood. Following acute exposure to two widely used agricultural insecticides, imidacloprid (neonicotinoid) and chlorpyrifos (organophosphate), we compared effects on body mass, migratory activity and orientation in a seed-eating bird, the white-crowned sparrow (Zonotrichia leucophrys). During spring migration, sparrows were captured, held and dosed by gavage daily for 3 days with either the vehicle control, low (10% LD50) or high (25% LD50) doses of imidacloprid or chlorpyrifos and tested in migratory orientation trials pre-exposure, post-exposure and during recovery. Control birds maintained body mass and a seasonally appropriate northward orientation throughout the experiment. Imidacloprid dosed birds exhibited significant declines in fat stores and body mass (mean loss: -17% low, -25% high dose) and failed to orient correctly. Chlorpyrifos had no overt effects on mass but significantly impaired orientation. These results suggest that wild songbirds consuming the equivalent of just four imidacloprid-treated canola seeds or eight chlorpyrifos granules per day over 3 days could suffer impaired condition, migration delays and improper migratory direction, which could lead to increased risk of mortality or lost breeding opportunity.

Effects of diluted bitumen exposure on juvenile sockeye salmon: From cells to performance

Diluted bitumen (dilbit; the product of oil sands extraction) is transported through freshwater ecosystems critical to Pacific salmon. This is concerning, because crude oil disrupts cardiac development, morphology, and function in embryonic fish, and cardiac impairment in salmon can have major consequences on migratory success and fitness. The sensitivity of early life-stage salmon to dilbit and its specific cardiotoxic effects are unknown. Sockeye salmon parr were exposed to environmentally relevant concentrations of the water-soluble fraction (WSF) of dilbit for 1 wk and 4 wk, followed by an examination of molecular, morphological, and organismal endpoints related to cardiotoxicity. We show that parr are sensitive to WSF of dilbit, with total polycyclic aromatic hydrocarbon (PAH) concentrations of 3.5 µg/L sufficient to induce a liver biomarker of PAH exposure, and total PAH of 16.4 µg/L and 66.7 µg/L inducing PAH biomarkers in the heart. Furthermore, WSF of dilbit induces concentration-dependent cardiac remodeling coincident with performance effects: fish exposed to 66.7 µg/L total PAH have relatively fewer myocytes and more collagen in the compact myocardium and impaired swimming performance at 4 wk, whereas the opposite changes occur in fish exposed to 3.5 µg/L total PAH. The results demonstrate cardiac sensitivity to dilbit exposure that could directly impact sockeye migratory success. Environ Toxicol Chem 2017;36:354-360. © 2016 SETAC.

Mercury and drought along the lower Carson River, Nevada: IV. Snowy egret post-fledging dispersal, timing of migration and survival, 2002-2004

This telemetry study is an extension of our 1997-2006 research on historical mercury contamination on snowy egrets (Egretta thula) up to ~ 20 days of age. Findings from initial studies at the mercury-contaminated Carson River colony at Lahontan Reservoir (LR) and a similar-sized reference (REF) colony on the Humboldt River included mercury-related physiological, biochemical, histopathological and reproductive effects up to ~20 days of age; with poor water years (2000-04), i.e., reduced prey availability, exacerbating effects. Herein, we compare timing of dispersal and migration at LR vs. REF, but the primary question now addressed is "whether survival of young mercury-exposed snowy egrets from LR would be further compromised beyond ~20 days of age? " Based upon telemetry signals until 90-110 days of age (including dead bird counts and survival rate estimates), we conclude that mercury did not further compromise survival. Dead bird counts and survival rate estimates included time in the colony when fed by adults, plus the critical period when young dispersed from the colony to forage independently. The extended drought during this 3-year study was most critical in 2002 when production of ~20d old egrets at LR was only 0.24 young/nest. In 2002, survival rates were low at both colonies and we documented the highest counts of dead egrets for both colonies. We suggest the losses in 2002 beyond 20 days of age were more a function of prey availability influenced by drought than exposure to mercury, especially at LR, because higher mercury concentrations, higher survival rates and fewer dead birds were documented at LR in 2003 when water conditions improved. Furthermore, total mercury (THg) in blood in 2003 was more than double 2002 (geometric mean, 3.39 vs 1.47µg/g wet weight (ww). This higher THg exposure at LR in 2003 was associated with a redistribution of parent and post-dispersal feeding activities upstream (where there was higher mercury from historic mining) related to slightly improved water levels. When comparing the 3-year telemetry findings based upon ~20d old young at LR (blood THg, geo. means 1.47, 3.39 and 1.89µg/g ww), we found no evidence that age at dispersal, Julian date at dispersal, timing of migration, or pre-migration survival (~20 to ~100 days post-hatch) were adversely affected by elevated mercury.

Honey Bee Swarms Aboard the USNS Comfort: Recommendations for Sting Prevention, Swarm Removal, and Medical Readiness on Military Ships

The article provides observations of multiple honey bee (Apis mellifera) swarms aboard the USNS Comfort (TAH-20) during the Continuing Promise 2015 mission. A brief overview of swarming biology is given along with control/removal recommendations to reduce sting exposures. The observations suggest that preventive medicine personnel should provide adequate risk communications about the potential occurrence of bee swarms aboard military ships, and medical department personnel should be prepared for the possibility of treating of multiple sting exposures, especially in the Southern Command Area of Operations where the Africanized genotype of A mellifera is common.

Effects of developmental exposure to bisphenol A and ethinyl estradiol on spatial navigational learning and memory in painted turtles (Chrysemys picta)

Developmental exposure of turtles and other reptiles to endocrine disrupting chemicals (EDCs), including bisphenol A (BPA) and ethinyl estradiol (EE2, estrogen present in birth control pills), can induce partial to full gonadal sex-reversal in males. No prior studies have considered whether in ovo exposure to EDCs disrupts normal brain sexual differentiation. Yet, rodent model studies indicate early exposure to these chemicals disturbs sexually selected behavioral traits, including spatial navigational learning and memory. Thus, we sought to determine whether developmental exposure of painted turtles (Chrysemys picta) to BPA and EE2 results in sex-dependent behavioral changes. At developmental stage 17, turtles incubated at 26⁰C (male-inducing temperature) were treated with 1) BPA High (100μg /mL), 2) BPA Low (0.01μg/mL), 3) EE2 (0.2μg/mL), or 4) vehicle or no vehicle control groups. Five months after hatching, turtles were tested with a spatial navigational test that included four food containers, only one of which was baited with food. Each turtle was randomly assigned one container that did not change over the trial period. Each individual was tested for 14 consecutive days. Results show developmental exposure to BPA High and EE2 improved spatial navigational learning and memory, as evidenced by increased number of times spent in the correct target zone and greater likelihood of solving the maze compared to control turtles. This study is the first to show that in addition to overriding temperature sex determination (TSD) of the male gonad, these EDCs may induce sex-dependent behavioral changes in turtles.

Developmental Exposure to Aroclor 1254 Alters Migratory Behavior in Juvenile European Starlings (Sturnus vulgaris)

Birds exposed to endocrine disrupting chemicals during development could be susceptible to neurological and other physiological changes affecting migratory behaviors. We investigated the effects of ecologically relevant levels of Aroclor 1254, a polychlorinated biphenyl (PCB) mixture, on moult, fattening, migratory activity, and orientation in juvenile European starlings (Sturnus vulgaris). Birds were orally administered 0 (control), 0.35 (low), 0.70 (intermediate), or 1.05 (high) μg Aroclor 1254/g-body weight by gavage from 1 through 18 days posthatch and later exposed in captivity to a photoperiod shift simulating an autumn migration. Migratory activity and orientation were examined using Emlen funnel trials. Across treatments, we found significant increases in mass, fat, and moulting and decreasing plasma thyroid hormones over time. We observed a significant increase in activity as photoperiod was shifted from 13L:11D (light:dark) to 12L:12D, demonstrating that migratory condition was induced in captivity. At 12L:12D, control birds oriented to 155.95° (South-Southeast), while high-dosed birds did not. High-dosed birds showed a delayed orientation to 197.48° (South-Southwest) under 10L:14D, concomitant with apparent delays in moult. These findings demonstrate how subtle contaminant-induced alterations during development could lead to longer-scale effects, including changes in migratory activity and orientation, which could potentially result in deleterious effects on fitness and survival.

Methylmercury effects on migratory behaviour in glass eels (Anguilla anguilla): an experimental study using isotopic tracers

The effect of methylmercury (MeHg) on glass eels' propensity to migrate, mitochondrial activity and antioxidative defence systems was investigated. Marine glass eels were first sorted in an experimental flume according to their response to dusk. Fish responding to the decrease in light intensity by ascending in the water column and moving with or against the flow were considered as having a high propensity to migrate (migrant). Glass eels still sheltering at the end of the 24 h catching period were considered as having a low propensity to migrate and were called non-migrant. Migrant and non-migrant glass eels were then individually tagged and exposed to isotopically enriched (201)MeHg (50 ng L(-1)) for 11 days. The effect of contamination was studied on muscle fibre structure, and the expression level of genes involved in mitochondrial activity and antioxidative defence systems. To investigate the effect of MeHg on glass eel behaviour, migrant and non-migrant glass eels were sorted again and the bioaccumulation of (201)MeHg and its demethylation product ((201)Hg(II)) were determined for each individual. MeHg exposure increased activity in non-migrant glass eels but not migratory behaviour. Contamination affected mitochondrial structure and metabolism and suggests a higher oxidative stress and activation of antioxidative defence systems in non-migrant glass eels. Overall, our results suggest that exposure to MeHg might induce an increase in energy expenditure and a higher vulnerability to predation in non-migrant glass eels in the wild.

Experimental and observational studies of seasonal interactions between overlapping life history stages in a migratory bird

Prior to reproduction, migratory animals are at the juxtaposition of three life history stages in which they must finish the non-breeding stage, initiate and complete migration, and prepare for the onset of breeding. However, how these stages interact with one another is not fully understood. We provide evidence that, for migratory birds that begin breeding development prior to departure from non-breeding sites, the level of breeding preparation can drive migration phenology, a critical behavioral determinant of reproductive success. Specifically, male American redstart (Setophaga ruticilla) plasma androgen levels, which increase in males during the period leading into migration, were positively correlated with energetic condition. We empirically tested the hypothesis that elevated androgen simultaneously supports migratory and breeding preparation in a hormone manipulation field experiment. Males with testosterone implants showed advanced preparation for migration and breeding, and ultimately departed on migration earlier than controls. It is assumed that early departure leads to early arrival at breeding areas, which increases breeding success. Collectively, our observational and experimental results demonstrate how overlapping life history stages can interact to influence important components of an individual's fitness. This highlights the critical need for understanding population processes across the full life cycle of an organism to better understand the ecological and evolutionary origins of complex life history events.

Polybrominated diphenyl ethers in birds from Chongming Island, Yangtze estuary, China: insight into migratory behavior

Sum-PBDEs concentrations in shorebirds and Anatidae ducks muscles from Chongming Dongtan National Nature Reserve ranged from 21-324 to 14-159ngg(-1) lw, respectively. PBDEs were detected in muscles of all the studied species. Compared with flyways around the world, migratory waterbirds on the East Asian-Australasian flyway exhibited lower PBDEs burdens than those reported on Black Sea-Mediterranean flyway in Europe and Pacific, Atlantic, Mississippi flyway in North America. Residential Eurasian tree sparrow samples indicated few PBDE products were used in Chongming Island developed in the idea of world famous eco-island. There was no significant difference in PBDEs concentrations between shorebirds and ducks. However, PBDEs composition varied between them. BDE 209 (29-44%) contributed to sum-PBDEs more than BDE 47 (17-19%) in muscles of ducks, while BDE 47 was the predominant congener in shorebirds contributing 32-48%. Stable nitrogen and carbon isotopes and stomach content analysis indicated shorebirds and ducks had the same dietary composition, but showed different preference to bivalves, gastropods and crustaceans for shorebirds and aquatic plant material for ducks. Migratory species had inherent migratory routes and thus had exposure to PBDEs during their stay in breeding grounds, stopover sites and wintering grounds with high use of different commercial PBDE mixtures. Higher percentage of BDE 209 in ducks than shorebirds suggested that breeding ranges and wintering grounds of ducks comprise wetlands in inland and coastal China and Korea where decaBDEs pollution was serious in Asian-Pacific region. Our findings reveal the influence of migratory behavior on PBDEs distribution in migratory waterbirds.

Glyphosate applications on arable fields considerably coincide with migrating amphibians

Glyphosate usage is increasing worldwide and the application schemes of this herbicide are currently changing. Amphibians migrating through arable fields may be harmed by Glyphosate applied to field crops. We investigated the population-based temporal coincidence of four amphibian species with Glyphosate from 2006 to 2008. Depending on a) age- and species-specific main migration periods, b) crop species, c) Glyphosate application mode for crops, and d) the presumed DT50 value (12 days or 47 days) of Glyphosate, we calculated up to 100% coincidence with Glyphosate. The amphibians regularly co-occur with pre-sowing/pre-emerging Glyphosate applications to maize in spring and with stubble management prior to crop sowing in late summer and autumn. Siccation treatment in summer coincides only with early pond-leaving juveniles. We suggest in-depth investigations of both acute and long-term effects of Glyphosate applications on amphibian populations not only focussed on exposure during aquatic periods but also terrestrial life stages.

Potential impact of low-concentration silver nanoparticles on predator-prey interactions between predatory dragonfly nymphs and Daphnia magna as a prey

This study investigated the potential impacts of low-concentration citrate-coated silver nanoparticles (citrate-nAg; 2 μg L(-1) as total Ag) on the interactions of Daphnia magna Straus (as a prey) with the predatory dragonfly ( Anax junius : Odonata) nymph using the behavioral, survival, and reproductive end points. Four different toxicity bioassays were evaluated: (i) horizontal migration; (ii) vertical migration; (iii) 48 h survival; and (iv) 21 day reproduction; using four different treatment combinations: (i) Daphnia + citrate-nAg; (ii) Daphnia + predator; (iii) Daphnia + citrate-nAg + predator; and (iv) Daphnia only (control). Daphnia avoided the predators using the horizontal and vertical movements, indicating that Daphnia might have perceived a significant risk of predation. However, with citrate-nAg + predator treatment, Daphnia response did not differ from control in the vertical migration test, suggesting that Daphnia were unable to detect the presence of predator with citrate-nAg treatment and this may have potential implication on daphnids population structure owing to predation risk. The 48 h survival test showed a significant mortality of Daphnia individuals in the presence of predators, with or without citrate-nAg, in the test environment. Average reproduction of daphnids increased by 185% with low-concentration citrate-nAg treatment alone but was severely compromised in the presence of predators (decreased by 91.3%). Daphnia reproduction was slightly enhanced by approximately 128% with citrate-nAg + predator treatment. Potential mechanisms of these differential effects of low-concentration citrate-nAg, with or without predators, are discussed. Because silver dissolution was minimal, the observed toxicity could not be explained by dissolved Ag alone. These findings offer novel insights into how exposure to low-concentration silver nanoparticles could influence predator-prey interactions in the fresh water systems.

Behavioural and physiological responses of Gammarus pulex exposed to cadmium and arsenate at three temperatures: individual and combined effects

This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and 15 °C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na(+)] and [Cl(-)] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na(+)] and [Cl(-)] while AsV alone had a weak impact only on [Cl(-)]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as 'additive' for all the tested binary mixtures and temperatures (except for the lowest combination at 10 °C considered as "antagonistic"). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl(-)] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na(+)] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity mechanisms of these metals and their interaction with rising temperature.

Predator cues and an herbicide affect activity and emigration in an agrobiont wolf spider

Animals use chemical cues for signaling between species. However, anthropogenic chemicals might interrupt this natural chemical information flow, with potential impacts on predator-prey interactions. Our goal was to explore how Buccaneer® Plus, a common herbicide similar to Round-up® (active ingredient glyphosate), affected the interactions between intraguild predators. The wolf spider Pardosa milvina (Hentz, 1844) is numerically dominant in agricultural systems across the eastern United States, and often falls prey to or competes with the larger wolf spider, Hogna helluo (Walckenaer, 1837) and/or the carabid beetle, Scarites quadriceps (Chaudoir, 1843). We tested the effects of chemical cues from these intraguild predators and exposure to herbicide on the activity, emigration, and survival of P. milvina using a full-factorial laboratory experiment. Both predator cues and herbicide led to a decrease in movement by P. milvina. However, although H. helluo cues alone decreased movement, S. quadriceps cues only decreased movement when combined with herbicide. These results indicate that predation risk and herbicide application likely interact in complex ways to affect the movement of a major arthropod predator in agricultural systems, and thus may have complex effects on the food web.

Behavioral and physiological effects of photoperiod-induced migratory state and leptin on a migratory bird, Zonotrichia albicollis: I. Anorectic effects of leptin administration

The hormone leptin is involved in the regulation of energy balance in mammals, mainly by reducing food intake and body adiposity and increasing energy expenditure. During energetically demanding periods, leptin's action is often altered to facilitate fat deposition and maintain high rates of food intake. Despite the present controversy over the existence of an avian leptin, there is evidence that a leptin receptor exists in birds and its activation influences energy intake and metabolism. However, it is unknown whether the effects of the activation of leptin receptor on energy balance are modulated during migration. We manipulated photoperiod to induce migratory behavior in captive white-throated sparrows (Zonotrichia albicollis) and injected migratory and wintering sparrows with either murine leptin or PBS for 7 days. We measured food intake, changes in body composition and foraging behavior to test if leptin's effects are altered during migratory state. Leptin decreased foraging behavior, food intake and fat mass in wintering sparrows, but had no effect on foraging behavior or food intake in migratory sparrows. Migratory sparrows injected with leptin maintained fat better than sparrows injected with PBS. Thus, sparrows' responses to leptin changed with migratory state, possibly to aid in the increase and maintenance of rates of food intake and fat deposition. We also found that long-form leptin receptor and SOCS3 were expressed in tissues of sparrows, including the hypothalamus, but their expression did not change with migratory state. Further study of the leptin receptor system and other regulators of energy balance in migratory birds will increase our understanding of the physiological mechanisms that are responsible for their ability to complete energetically demanding journeys.

Non-migratory stonechats show seasonal changes in the hormonal regulation of non-seasonal territorial aggression

In many birds and mammals, male territorial aggression is modulated by elevated circulating concentrations of the steroid hormone testosterone (T) during the breeding season. However, many species are territorial also during the non-breeding season, when plasma T levels are basal. The endocrine control of non-breeding territorial aggression differs considerably between species, and previous studies on wintering birds suggest differences between migratory and resident species. We investigated the endocrine modulation of territorial aggression during the breeding and non-breeding season in a resident population of European stonechats (Saxicola torquata rubicola). We recorded the aggressive response to a simulated territorial intrusion in spring and winter. Then, we compared the territorial aggression between seasons and in an experiment in which we blocked the androgenic and estrogenic action of T. We found no difference in the aggressive response between the breeding and the non-breeding season. However, similarly to what is found in migratory stonechats, the hormonal treatment decreased aggressive behaviors in resident males in the breeding season, whereas no effects were recorded in the non-breeding season. When we compared the aggressive responses of untreated birds with those obtained from migratory populations in a previous study, we found that territorial aggression of resident males was lower than that of migratory males during the breeding season. Our results show that in a resident population of stonechats T and/or its metabolites control territorial aggression in the breeding but not in the non-breeding season. In addition, our study supports the hypothesis that migratory status does modulate the intensity of aggressive behavior.

[The adaptive strategy of rodent populations living in conditions of radioactive and chemical environmental pollution]

The comparative analysis of demographic, morphological and physiological processes in mouselike rodents in pollution zones (90Sr + 90Y, 137Cs) on East-Ural radioactive track (EURT) and (Cu + Cd + Pb + Zn + SO2) on a site near copper-smelting factory is carried out. The direct (not mediated) defeat of animals by an irradiation leads to inherited adaptation (density preservation, tolerance increase to pollution, migration decrease and so forth). The mediated defeat of animals at pollution by metals influences animals as a result of degradation of a vegetative cover, reducing a forage reserve, shelters and reproduction places. Population is decreasing, migration is increasing. Hence, population reacts onto direct defeat of animals or on inhabitancy locuses degradation, id est unspecifically, without dependence from the physical and chemical nature of pollution.

Effects of chlorpyrifos and aldicarb on flight activity and related cholinesterase inhibition in homing pigeons, Columba livia: potential for migration effects

Homing pigeons (Columba livia) were used as a model to assess the effects of chlorpyrifos and aldicarb on flight times at sub-lethal, environmentally relevant concentrations. A significant increase in flight times of birds dosed with aldicarb and with chlorpyrifos was observed. Plasma cholinesterase activity was measured over time following exposure to either compound. The results suggest that the time of peak inhibition would correlate with migratory flight activity after exposure. In total, the results of these studies show that sub-lethal exposure to cholinesterase-inhibiting pesticides can affect the flying ability of non-target avian species.

PCBs and the energy cost of migration in the European eel (Anguilla anguilla L.)

The effect of polychlorinated biphenyls (PCBs) on the energy consumption of fasting silver European eel (Anguilla anguilla L.) was studied over a 27-day period during which the animals were at rest or were swimming 800 km in Blazka swim tunnels. Three-year-old female hatchery eels (silver stage) between 73 and 80 cm long weighing around 1 kg were dosed intraperitoneally with PCBs at a nominal dosage of 10x the consumption standard as a mixture representative for planar (7 microg PCB126/kg eel), non-planar (5 mg PCB153/kg eel) and metabolizable PCBs (50 microg PCB77/kg eel) found in wild eel, or only with the vehicle (corn oil, 10 ml/kg eel). Four major observations were made: (1) PCB-exposed animals lose less weight compared to their unexposed controls; (2) PCB-concentrations on a lipid basis are 2.8-14 times higher in swimming compared to resting animals; (3) the standard metabolic rate is significantly lower in the PCB-exposed animals than in unexposed controls. In addition, PCB-exposure significantly reduces oxygen consumption during swimming, and starting at 400 km (18 days) this effect increases with time; (4) the relative spleen and liver weight significantly increased in the PCB-swim animals but not in the PCB-rest animals. The swimming animals lost about 75% more weight compared to resting animals and had about 50% lower plasma fat content. Hematocrit, haemoglobin, plasma pH, ion levels (sodium and potassium), and plasma lactate were not affected by PCB-exposure or swimming. Apparently, the current levels of PCBs and other dioxin-like compounds may seriously impair the reproduction of the European eel.

Impacts of frequent, acute pulses of corticosterone on condition and behavior of Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii)

Little is known about how frequent, acute stressors affect wild animals. We present two experiments conducted on captive, Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii) that explore how frequent, acute doses of corticosterone (CORT) affect condition and behavior. CORT was administered either once or three times a day to birds in pre-breeding, early-breeding, or late-breeding life-history stages. Two additional groups were included to control for the CORT delivery vehicle, DMSO, and the treatment process. Our results indicate that CORT treatment decreases condition, but that its effects are dependent on frequency and life stage. Specifically, CORT-treated birds delayed the onset of molt and had reduced body mass, flight muscle, and food consumption. CORT treatment did not affect fat stores, bile retention in the gallbladder, or the expression of migratory restlessness behavior. These results increase our understanding of the effects of frequent, acute stressors and the development of chronic stress states.

Raptor ecotoxicology in Spain: a review on persistent environmental contaminants

Initial studies on the pressure from environmental contaminants on raptor populations in Spain date back to the 1980s, and they have been carried out from a range of viewpoints using a range of sentinel raptor species. However, there is no national monitoring scheme, and therefore the research carried out has been sporadic both spatially and temporally. The exposure to metals has not varied over time, except in the case of lead, whose concentration in eggs and tissues has diminished. In general, the concentrations of metals detected in raptor samples from Spain are generally low and not sufficient to produce toxic effects. Excepting DDT and DDE, most organochlorine-based pesticides in raptors from Spain have diminished over the last 2 decades. The concentrations of DDE found in the eggs of various species could in part explain problems in the reproductive success of raptors in Spain.

How cadmium could compromise the completion of the European eel's reproductive migration

The European eel (Anguilla anguilla L.) is severely threatened with extinction. Surprisingly, even though their unusual life cycle makes them particularly vulnerable to pollution, the possible contribution of contamination remains especially poorly known. Here we have investigated the possible effect of cadmium (Cd), a widespread nonessential metal, on eel reproductive capacities. Both control and Cd precontaminated female silver eels were experimentally matured and forced to swim in metal-free conditions to mimic their reproductive migration. Cd pre-exposure was found to strongly stimulate the pituitary-gonad-liver axis of maturing female silver eels leading to early and enhanced vitellogenesis. This was followed by a strong phenomenon of oocyte atresia and eel mortality. These phenomena occurred before oocytes could reach full maturation and were associated with a large entry of both vitellogenin and Cd into the ovaries. Indeed, a redistribution of previously stored cadmium, even from the low Cd levels of control eels, was observed during sexual maturation. Atresia and mortality phenomena were also associated with an overexpression of the pituitary gene encoding the growth hormone, a marker of physiological stress and energy reserves exhaustion. Significantly, these devastating effects of Cd were observed in organisms that presented liver and kidney Cd concentrations still below those observed in eels from Cd contaminated hydrosystems. Our research shows how common levels of cadmium contamination could disrupt endocrine pathways implicated in gonad maturation and subsequently impair reproductive capacity of eel future genitors.

Factors promoting marine invasions: a chemoecological approach

The Mediterranean Sea is losing its biological distinctiveness, and the same phenomenon is occurring in other seas. It gives urgency to a better understanding of the factors that affect marine biological invasions. A chemoecological approach is proposed here to define biotic conditions that promote biological invasions in terms of enemy escape and resource opportunities. Research has focused on the secondary metabolite composition of three exotic sea slugs found in Greece that have most probably entered the Mediterranean basin by Lessepsian migration, an exchange that contributes significantly to Mediterranean biodiversity. We have found toxic compounds with significant activity as feeding deterrents both in the cephalaspidean Haminoea cyanomarginata and in the nudibranch Melibe viridis. These findings led us to propose aposematism in the former and dietary autonomy in producing defensive metabolites in the latter case, as predisposing factors to the migration. In the third mollusk investigated, the anaspidean Syphonota geographica, the topic of marine invasions has been approached through a study of its feeding biology. The identification of the same compounds from both the viscera of each individual, separately analyzed, and their food, the seagrass Halophila stipulacea, implies a dietary dependency. The survival of S. geographica in the Mediterranean seems to be related to the presence of H. stipulacea. The initial invasion of this exotic pest would seem to have paved the way for the subsequent invasion of a trophic specialist that takes advantage of niche opportunities.

Treating hop plants with (Z)-jasmone increases colonization by Phorodon humuli (Hemiptera: Aphididae) spring migrants

Hop plants were sprayed with (Z)-jasmone, at a rate of 50 g ha(-1), during the spring migration of the damson-hop aphid Phorodon humuli (Schrank) in 2002 and 2003. Numbers of P. humuli spring migrants colonizing hop plants, Humulus lupulus L., 2-6 and 7-11 days after applying this treatment were assessed in both years. During the first five-day period, significantly more spring migrants were found on hop plants treated with (Z)-jasmone, in comparison with control plants, in 2002. By contrast, no significant difference was evident in the second five-day period. Although the migration in 2003 was much lighter than in 2002, greater numbers of migrants were again removed from treated plants. Indeed, more spring migrants were removed from plants sprayed with (Z)-jasmone in this year during both five-day periods (11 and 44%, respectively) compared with the 23% greater numbers removed in the first five-day period in 2002. Therefore, unlike some other species of aphid, where numbers were consistently lower on plots sprayed with (Z)-jasmone, spraying the secondary host of P. humuli with this compound appears to increase colonization by spring migrants.

Impairment of lipid storage by cadmium in the European eel (Anguilla anguilla)

Because European silver eels (Anguilla anguilla) fast during their reproductive migration to the Sargasso Sea, the successful completion of their unusual life cycle depends on quantity of lipids stored beforehand. These lipids are mainly accumulated during the growth phase stage of the animals, called yellow eel, as triglycerides in muscle. They are then catabolized to provide sufficient energy to enable migration, gonad maturation and spawning. In the laboratory, we investigated the possible impact of cadmium on the lipid storage efficiency of yellow eels in order to evaluate the possible contribution of this pollutant to the reported decline of European eel populations. Eels were exposed to dissolved cadmium at nominal concentrations of 0 and 5 microgL(-1) for 1 month. Cd toxicity was then examined by studying the activity and expression level of several enzymes involved in liver lipolysis and lipogenesis and by determining lipid content in muscle. Contaminated eels showed a lower body weight growth with a lower efficiency of lipid storage compared to controls. Using two complementary approaches, genetic and enzymatic, it was possible to conclude that this impairment is mainly explained by an increased utilisation of triglycerides since cadmium contamination did not trigger a reduced fatty acid synthesis. These observations suggest an increased fat consumption in presence of cadmium, which could compromise successful reproduction.

Mother's timing and duration of corticosterone exposure modulate offspring size and natal dispersal in the common lizard (Lacerta vivipara)

Although multiple condition dependence in dispersal is common, the proximate mechanisms that integrate information from multiple sources remain largely unknown. In the common lizard (Lacerta vivipara), earlier studies have shown that maternal plasma corticosterone level interacts with maternal phenotype to affect offspring phenotype and dispersal strategy, and may reflect the mother's external and/or internal environment. However, the mechanism by which these two types of environmental information are integrated has not been identified. We explored the possibility that the timing and duration of the corticosterone signal are the key factors by which the message is modulated. We found that the timing of corticosterone exposure affects the juvenile phenotype: an exposure to corticosterone early in development has negative effects on juvenile size, weight, and body condition, that can nevertheless be restored in the case of a prolonged exposure. The duration of corticosterone exposure affects the dispersal strategy, although the precise effect depends on the sex ratio of the clutch. That is, in female-biased clutches, a prolonged exposure during gestation promotes philopatry of juveniles, while a short exposure enhances their dispersal, a result that is consistent with kin competition theory. Therefore, our results demonstrate that while corticosterone titer may signal a mother's external and/or internal environment to her developing young, differences in the timing and duration of this endocrine signal produce offspring with specialized phenotypes that exhibit different dispersal strategies.

Differential toxic effects of Carbofuran and Diazinon on time of flight in pigeons (Columba livia): potential for pesticide effects on migration

Cholinesterase inhibiting compounds such as carbamates and organophosphate insecticides have been widely used in agriculture since the ban on organochlorines in the 1970s. Carbofuran, a carbamate, and diazinon, an organophosphate, are among the most commonly implicated cholinesterase inhibitors in episodes of accidental avian toxicity and mortality. Despite the apparent effects of these compounds, little work has been done to study effects of low-level, environmentally relevant doses at the population level in migratory bird species. In this study, homing pigeons were used as surrogate species to assess the differences in the effect of incrementally low doses (0.0, 0.25, 0.5, and 1.0 mg/kg) of carbofuran and diazinon on time of flight and determine whether there was a threshold dose of either or both xenobiotics when orally administered at these levels. The results indicate that there is a significant dose-dependent increase in flight time in pigeons dosed with carbofuran while diazinon exposed pigeons showed little effect. More profound effects were noted with carbofuran with pigeons falling off the pace of the flock and a dose for highly significant increase in flight time elucidated between 0.5 and 1.0 mg/kg. The results of the studies validate the homing pigeon as a good subject for comparative studies of cholinesterase inhibitors in birds and the need for further research on repeated low-level exposures on populations of avian species.

Effect of waterborne exposure to 4-tert-octylphenol and 17beta-estradiol on smoltification and downstream migration in Atlantic salmon, Salmo salar

Groups of Atlantic salmon parr (November, Exp. 1) or pre-smolts (March, Exp. 2) were exposed to estradiol-17beta (E2 conc.: nominal 500 ngl(-1)/actual 8-16 ngl(-1)) and two doses of tert-octylphenol (OP: nominal 25 microgl(-1)/actual 4.5-6.5 microgl(-1) and OP: nominal 100 microgl(-1)/actual 10-30 microgl(-1)) for 26 days in fresh water, and the effects on physiological and behavioural aspects of parr-smolt transformation were investigated. Vitellogenesis was induced by all treatments, as indicated by elevated levels of plasma vitellogenin (Vtg) and hepatosomatic index. Elevated Vtg levels were still found in OP-100 and E2-treated fish 4-5 months after cessation of treatment, indicating a slow clearance of Vtg from circulation. Smolting was compromised by E2 and OP-100 treatment as judged by reduced gill Na(+), K(+)-ATPase activity and impaired ability to regulate plasma osmolality and muscle water content in 24-h sea water (SW) challenge tests during the period of smolting. Downstream migratory behaviour was monitored from late April to July (Exp. 2) by implanting passive integrated transponder tags into subgroups of treated and control smolts and placing them in a stream raceway. Irrespective of treatment, nocturnal downstream movement was initiated in all groups on April 23, switching to diurnal movement in late May. Average swimming speed was estimated to be higher than current speed, indicating active migration. E2 and OP-100 fish migrated at lower frequency than control fish, suggesting a reduced migratory drive. The data suggests that waterborne exposure of salmon to xenoestrogens reduce both physiological and behavioural components of smoltification, even when exposure occurs several months prior to smolting.

Performance-enhancing role of dietary fatty acids in a long-distance migrant shorebird: the semipalmated sandpiper

At the end of summer, semipalmated sandpipers (Calidris pusilla)traveling from the Arctic stop in the Bay of Fundy (east coast of Canada) to build large fat reserves before a non-stop flight to South America. During a 2-week stopover, the body mass of this small shorebird is doubled (∼20 g to 40 g) by feeding on a burrowing amphipod, Corophium volutator,that contains unusually high levels of n-3 polyunsaturated fatty acids (PUFA). In mammals, high n-3 PUFA content of membrane phospholipids (PL) is linked to improved exercise performance due to increased membrane fluidity that accelerates transmembrane lipid transport. We hypothesized that dietary n-3 PUFA could be used as a natural `performance-enhancing substance' by semipalmated sandpipers to prepare their flight muscles for migration. Also,PUFA stored as fuel in neutral lipids (NL) can be mobilized more quickly than saturated fatty acids, but they contain less energy per unit mass. It is therefore unclear whether dietary fatty acids are modified before storage. Birds were collected at various stages of fat loading to examine changes in the composition of tissue PL (membranes) and NL (fuel stores). Results show that dietary n-3 PUFA are incorporated in tissue lipids in less than 2 weeks. During the stopover, the double bond index of muscle PL increases by 25% and the fatty acid profiles of both muscle PL and adipose NL converge with that of the diet. However, >50% of dietary n-3 PUFA are converted to other fatty acids before storage, mainly to oleate (18:1), possibly because monounsaturates offer a compromise between high energy density and ease of mobilization. This study shows that long-distance migrant birds can (1) use natural diets rich in specific lipids to prime flight muscles for endurance exercise, and (2) modify dietary fatty acids before storing them as fuel.

The flagellar motility of Chlamydomonas pf25 mutant lacking an AKAP-binding protein is overtly sensitive to medium conditions

Radial spokes are a conserved axonemal structural complex postulated to regulate the motility of 9 + 2 cilia and flagella via a network of phosphoenzymes and regulatory proteins. Consistently, a Chlamydomonas radial spoke protein, RSP3, has been identified by RII overlays as an A-kinase anchoring protein (AKAP) that localizes the cAMP-dependent protein kinase (PKA) holoenzyme by binding to the RIIa domain of PKA RII subunit. However, the highly conserved docking domain of PKA is also found in the N termini of several AKAP-binding proteins unrelated to PKA as well as a 24-kDa novel spoke protein, RSP11. Here, we report that RSP11 binds to RSP3 directly in vitro and colocalizes with RSP3 toward the spoke base near outer doublets and dynein motors in axonemes. Importantly, RSP11 mutant pf25 displays a spectrum of motility, from paralysis with flaccid or twitching flagella as other spoke mutants to wildtype-like swimming. The wide range of motility changes reversibly depending on the condition of liquid media without replacing defective proteins. We postulate that radial spokes use the RIIa/AKAP module to regulate ciliary and flagellar beating; absence of the spoke RIIa protein exposes a medium-sensitive regulatory mechanism that is not obvious in wild-type Chlamydomonas.

Mixture of new sulfated steroids functions as a migratory pheromone in the sea lamprey

The sea lamprey is an ancient, parasitic fish that invaded the Great Lakes a century ago, where it triggered the collapse of many fisheries. Like many fishes, this species relies on chemical cues to mediate key aspects of its life, including migration and reproduction. Here we report the discovery of a multicomponent steroidal pheromone that is released by stream-dwelling larval lamprey and guides adults to spawning streams. We isolated three compounds with pheromonal activity (in submilligram quantities from 8,000 l of larval holding water) and deduced their structures. The most important compound contains an unprecedented 1-(3-aminopropyl)pyrrolidin-2-one subunit and is related to squalamine, an antibiotic produced by sharks. We verified its structure by chemical synthesis; it attracts adult lamprey at very low (subpicomolar) concentrations. The second component is another new sulfated steroid and the third is petromyzonol sulfate, a known lamprey-specific bile acid derivative. This mixture is the first migratory pheromone identified in a vertebrate and is being investigated for use in lamprey control.

Endocrine control of Anguilla anguilla glass eel dispersal: effect of thyroid hormones on locomotor activity and rheotactic behavior

Dispersal, one of the most important processes in population ecology, is an issue linking physiological and behavioral features. However, the endocrine control of animal dispersal remains poorly understood. Here, we tested whether and how thyroid hormones may influence dispersal in glass eels of Anguilla anguilla, by testing their influence on locomotor activity and rheotactic behavior. Glass eels were caught during their estuarine migration and treated by immersion in either a l-thyroxine (T(4)) or a thiourea (TU) solution. As measured by radioimmunoassay, T(4) and TU treatments induced, respectively, increased and decreased whole-body thyroid hormone levels relative to untreated controls. We tested a total of 960 glass eels distributed into control, and T(4) and TU treatment groups, on their swimming behavior in experimental flume tanks equipped with upstream and downstream traps that allowed us to concurrently measure both the locomotor activity and the rheotactic behavior. Compared to controls, locomotor activity significantly increased among the hyperthyroid, T(4)-treated eels, but significantly decreased among the hypothyroid, TU-treated eels. The results on rheotactic behavior suggested a more complex regulatory mechanism, since TU but not T(4) treatment significantly affected rheotactic behavior. The influence of thyroid hormones on locomotor activity suggests a central role for these hormones in the regulation of mechanisms leading to the colonization of continental habitats by glass eels. Thyroid hormones are also implicated in the control of locomotor activity in mammals and migratory behavior in birds, suggesting that these hormones represent conserved, proximate mediators of dispersal in vertebrates.

Control of planula migration by LWamide and RFamide neuropeptides in Hydractinia echinata

Planula larvae of Hydractinia echinata (Cnidaria) settled on a substratum migrate toward light. We observed that planula migration is not a continuous process. Instead, it consists of repeating cycles of active migration (about 8 min on average) and inactive resting periods (about 26 min on average). This pattern of periodic migration is regulated by LWamide and RFamide neuropeptides. LWamide (10(-8) mol l(-1)) stimulates migration primarily by making the active periods longer, whereas RFamide (10(-7) mol l(-1)) inhibits migration by blocking the initiation and also shortening the length of the active periods. Since sensory neurons containing LWamides and RFamides are present in planula larvae, it appears likely that planula migration is regulated by the release of endogenous neuropeptides in response to environmental cues.

17-Beta estradiol and 4-nonylphenol delay smolt development and downstream migration in Atlantic salmon, Salmo salar

The effect of 17-beta estradiol (E2) and 4-nonylphenol (4-NP) on smoltification and downstream migration of Atlantic salmon was studied in an integrated laboratory and field study. In a stock of hatchery-raised 1-year-old salmon, smoltification progressed from February until late May as judged by increased gill Na+, K+ -ATPase activity and 24 h sea water (SW)-tolerance. Starting late March, three groups of 150 fish were each given 6 serial injections over 20 days of 2 microg/g body weight E2, 120 microg/g 4-NP dissolved in peanut oil or peanut oil (4 microl/g) as control. After the last injection, all fish were individually tagged (Passive Integrated Transponder tags) and a non-lethal gill biopsy was taken. Two days later (8 April), 100 fish per group were transported to the field site and released into a small stream. Smolt migration was registered by measuring arrival time at a trap downstream of the release site. Serum vitellogenin levels increased several-fold in both male and female E2- and 4-NP-treated fish. Overall, E2- and 4-NP-treatment impaired smolting as judged by elevated condition factor, reduced gill Na+, K+ -ATPase activity and alpha-subunit Na+, K+ -ATPase mRNA level, reduced muscle water content and increased mortality following 24 h SW-challenge. After release, control fish initiated downstream migration immediately, with 50% of the total number of migrants appearing in the trap within 10 days. E2- and 4-NP-treated fish appeared in the trap with a delay in comparison to controls of 6 and 8 days, respectively. After the smolt run, no fish were registered by electro-fishing upstream of the trap. The total number of fish reaching the trap and thus post-release survival was in the order control (81%), E2 (53%), 4-NP (12%). Representatives from all treatment groups held under simulated natural conditions in the laboratory survived 100% through the migration period, suggesting that a combination of behavioural and in-stream factors (predation by herons) may contribute to the differential mortality. The study indicates that short-term exposure to natural and environmental estrogens may impair smolt development and survival and delay subsequent downstream migration in Atlantic salmon.

Central administration of corticotropin-releasing hormone alters downstream movement in an artificial stream in juvenile chinook salmon (Oncorhynchus tshawytscha)

We evaluated the effect of corticotropin-releasing hormone (CRH) on spatial distribution and downstream movement in an artificial stream in juvenile Chinook salmon (Oncorhynchus tshawytscha) during the period when the fish were able to tolerate seawater. An intracerebroventricular (ICV) injection of CRH (500 ng) to hatchery fish significantly increased the proportion of fish that were distributed downstream of a mid-stream release site. A second group of hatchery fish were given ICV injections of saline (control) or CRH (500 ng) and released near the top of the stream. The time taken to enter a trap at the lower end of the stream was recorded. In all cases the groups given CRH had a higher proportion of fish that did not enter the trap within 60 min of release. However, in those fish that did enter the trap, treatment with CRH increased the speed of downstream movement to this point relative to control fish. Wild sub-yearling Chinook salmon were captured during their downstream migration to the estuary and given ICV injections of saline or CRH (500 ng) either 2, 3, or 7 days after transport from the river. As with hatchery fish, a significantly higher proportion of wild fish that were administered CRH did not enter the trap at the lower end of the stream. The mean time of passage for control fish decreased on each successive day (day 2 > day 3 > day 7). In contrast, the mean passage time of the wild fish that were given CRH was relatively constant through time, and was only significantly faster than control fish on day 2. The current study provides evidence that CRH alters the downstream movement of juvenile Chinook in a simulated stream environment, and produces behavioral effects similar to those of juvenile salmonids that are stressed during their downstream migration.

Relationship of adipokinetic hormone I and II to migratory propensity in the grasshopper, Melanoplus sanguinipes

This report examines three aspects of adipokinetic hormone (AKH) involvement in migratory flight behavior in the grasshopper, Melanoplus sanguinipes. The titer of hemolymph AKH I during long-duration tethered flight was examined using radioimmunoassay (RIA) after narrow bore RP-HPLC. The hemolymph fraction containing AKH I was assayed using commercially available anti-Tyr1-AKH I serum. Titer determinations of hemolymph AKH were done at rest and after various periods of flight. The amount of AKH I released from the corpora cardiaca during flight was estimated. When resting levels of AKH I and II in corpora cardiaca (CC) of migrants and non-migrants were examined with HPLC, no significant differences in AKH levels were detected between non-migrants, animals that had flown for 1 h to identify them as migrants, and animals that had flown to exhaustion (i.e., voluntary cessation). CC levels of both AKH I and II were less in this species than in locusts. When the lipid mobilization in response to AKH I and II was compared in migrants (animals that had self-identified as migrants in a 1-h tethered flight test) and non-migrants (animals that would not perform a 1-h flight in a tethered flight test), the adipokinetic response to AKH I was greater in migrants than in non-migrants, possibly indicating differences in level of sensitivity or number of receptors in the target tissues. AKH II had little effect on hemolymph lipid levels in either flight group, and may not play a significant role in lipid mobilization in this species.

Inhibition of barnacle larval settlement and crustacean toxicity of some hoplonemertine pyridyl alkaloids

Hoplonemertines are carnivorous marine worms, which prey upon crustaceans and annelids. They paralyze their prey by injecting alkaloids with a stylet-bearing proboscis. The dermis of these animals also secretes alkaloids to repel predators. Besides affecting central and peripheral nervous system nicotinic receptors, some pyridyl alkaloids also activate certain chemoreceptor neurons in crustacean walking legs, which sense environmental chemicals. Anabaseine (2-[3-pyridyl]-3,4,5,6-tetrahydropyridyl) and 2,3'-bipyridyl (2,3'-BP) are two nemertine alkaloids, which potently paralyze crustaceans. Anabaseine is an agonist of vertebrate as well as invertebrate nicotinic receptors. While 2,3'-BP is non-toxic to mice, it is toxic to crustaceans. We tested a variety of nemertine pyridyl alkaloids for inhibition of barnacle (Balanus amphitrite) larval settlement and for crustacean toxicity in order to determine whether toxicity could be dissociated from inhibition of larval settlement. We prepared eight C-methylated 2,3'-BP isomers to determine where substitution is permitted without loss of activity. Anti-settlement and toxicity activities were not always related. For instance, 4'-methyl-2,3'-BP displayed only 3% of the crayfish paralytic activity of 2,3'-BP, but inhibited settlement almost 2-fold more effectively. Two other isomers displaying exceptional anti-settlement activity were the 4- and 5-methyl-2,3'-BPs; these also displayed high crustacean toxicity. Nemertelline inhibited barnacle settlement at concentrations similar to 2,3'-BP but was 136-fold less toxic when injected into crayfish. Thus, certain bipyridyls and tetrapyridyls may be useful anti-fouling additives.