SUMMARY Most aquatic insects do not survive subzero temperatures and, for those that do, the phys... more SUMMARY Most aquatic insects do not survive subzero temperatures and, for those that do, the physiology has not been well characterized. Nemoura arctica is a species of stonefly widely distributed throughout arctic and subarctic Alaska. We collected nymphs from the headwaters of the Chandalar River, where we recorded streambed temperatures as low as –12.7°C in midwinter. When in contact with ice, autumn-collected N. arctica cool to –1.5±0.4°C before freezing, but individuals survived temperatures as low as –15°C, making this the first described species of freeze-tolerant stonefly. N. arctica clearly survive freezing in nature, as winter-collected nymphs encased in ice demonstrated high survivorship when thawed. In the laboratory, 87% of N. arcticanymphs frozen to –15°C for 2.5 weeks survived and, within one month of thawing, 95% of the last-instar nymphs emerged. N. arctica produce both glycerol and ice-binding factors (e.g. antifreeze protein) in response to low temperature. Hemoly...
SUMMARY Larvae of the freeze-avoiding beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) in... more SUMMARY Larvae of the freeze-avoiding beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) in Alaska have mean supercooling points in winter of –35 to –42°C, with the lowest supercooling point recorded for an individual of –58°C. We previously noted that some larvae did not freeze when cooled to –80°C, and we speculated that these larvae vitrified. Here we present evidence through differential scanning calorimetry that C. c. puniceus larvae transition into a glass-like state at temperatures <–58°C and can avoid freezing to at least –150°C. This novel finding adds vitrification to the list of insect overwintering strategies. While overwintering beneath the bark of fallen trees, C. c. puniceus larvae may experience low ambient temperatures of around –40°C (and lower) when microhabitat is un-insulated because of low snow cover. Decreasing temperatures in winter are correlated with loss of body water from summer high levels near 2.0 to winter lows near 0.4 mg mg–1 dry mass and co...
SUMMARY The beetle Cucujus clavipes is found in North America over a broad latitudinal range from... more SUMMARY The beetle Cucujus clavipes is found in North America over a broad latitudinal range from North Carolina (latitude ∼35°N) to near tree line in the Brooks Range in Alaska (latitude, ∼67°30′ N). The cold adaptations of populations from northern Indiana (∼41°45′N) and Alaska were compared and, as expected, the supercooling points (the temperatures at which they froze) of these freeze-avoiding insects were significantly lower in Alaska insects. Both populations produce glycerol, but the concentrations in Alaska larvae were much higher than in Indiana insects(∼2.2 and 0.5 mol l–1, respectively). In addition, both populations produce antifreeze proteins. Interestingly, in the autumn both populations have the same approximate level of hemolymph thermal hysteresis,indicative of antifreeze protein activity, suggesting that they synthesize similar amounts of antifreeze protein. A major difference is that the Alaska larvae undergo extreme dehydration in winter wherein water content dec...
Proceedings of the National Academy of Sciences, 2009
Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that ... more Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that is indicative of the presence of large-molecular-mass antifreezes (e.g., antifreeze proteins), has been described in animals, plants, bacteria, and fungi. Although all previously described TH-producing biomolecules are proteins, most thermal hysteresis factors (THFs) have not yet been structurally characterized, and none have been characterized from a freeze-tolerant animal. We isolated a highly active THF from the freeze-tolerant beetle, Upis ceramboides , by means of ice affinity. Amino acid chromatographic analysis, polyacrylamide gel electrophoresis, UV-Vis spectrophotometry, and NMR spectroscopy indicated that the THF contained little or no protein, yet it produced 3.7 ± 0.3 °C of TH at 5 mg/ml, comparable to that of the most active insect antifreeze proteins. Compositional and structural analyses indicated that this antifreeze contains a β-mannopyranosyl-(1→4) β-xylopyranose backbo...
Cucujus clavipes puniceus is a freeze avoiding beetle capable of surviving the long, extremely co... more Cucujus clavipes puniceus is a freeze avoiding beetle capable of surviving the long, extremely cold winters of the Interior of Alaska. Previous studies showed that some individuals typically supercool to mean values of approximately -40 °C, with some individuals supercooling to as low as -58 °C, but these non-deep supercooling (NDSC) individuals eventually freeze if temperatures drop below this. However, other larvae, especially if exposed to very cold temperatures, supercool even further. These deep supercooling (DSC) individuals do not freeze even if cooled to -100 °C. In addition, the body water of the DSC larvae vitrifies (turns to a glass) at glass transition temperatures of -58 to -70 °C. This study examines the proteomes of DSC and NDSC larvae to assess proteins that may contribute to or inhibit the DSC trait. Using high throughput proteomics, we identified 138 proteins and 513 Gene Ontology categories in the DSC group and 104 proteins and 573 GO categories in the NDSC group. GO categories enriched in DSC include alcohol metabolic process, cellular component morphogenesis, monosaccharide metabolic process, regulation of biological quality, extracellular region, structural molecule activity, and antioxidant activity. Proteins unique to DSC include alpha casein precursor, alpha-actinin, vimentin, tropomyosin, beta-lactoglobulin, immunoglobulins, tubulin, cuticle proteins and endothelins.
Prior to this study, antifreeze proteins (AFPs) had not been identified in terrestrial arthropods... more Prior to this study, antifreeze proteins (AFPs) had not been identified in terrestrial arthropods from the Arctic or anywhere in Alaska. The hemolymph of 75 species of insects and six spiders from interior and arctic Alaska were screened for thermal hysteresis (a difference between the freezing and melting points), characteristic of the presence of AFPs. Eighteen species of insects and three spiders were shown to have AFPs. Ten of the insects with AFPs were beetles including the first species from the families Chrysomelidae, Pythidae, Silphidae and Carabidae. In addition, the first Neuropteran to have AFPs was identified, the lacewing Hemerobius simulans together with the second and third Diptera (the first Tipulids) and the second and third Hemiptera, the stinkbug Elasmostethus interstinctus (the first Pentatomid), and the water strider Limnoporus dissortis (the first Gerrid). Prior to this study, 33 species of insects and three spiders had been reported to have AFPs. Most AFP-producing terrestrial arthropods are freeze avoiding, and the AFPs function to prevent freezing. However, some of the AFP-producing insects identified in this study are known to be freeze tolerant (able to survive freezing) to very low temperatures (À40 to À70 v C).
Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies fo... more Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies for overwintering in animals. Here we show an insect species that combines both strategies. Individual fungus gnats, collected in Fairbanks, Alaska, display two freezing events when experimentally cooled and diVerent rates of survival after each event (mean § SEM: ¡31.5 § 0.2°C, 70% survival and ¡50.7 § 0.4°C, 0% survival). To determine which body compartments froze at each event, we dissected the abdomen from the head/thorax and cooled each part separately. There was a signiWcant diVerence between temperature levels of abdominal freezing (¡30.1 § 1.1°C) and head/thorax freezing (¡48.7 § 1.3°C). We suggest that freezing is initially restricted to one body compartment by regional dehydration in the head/thorax that prevents inoculative freezing between the freeze-tolerant abdomen (71.0 § 0.8% water) and the supercooled, freeze-sensitive head/thorax (46.6 § 0.8% water).
The presence of large-molecular-mass, thermal hysteresis (TH)-producing antifreezes (e.g., antifr... more The presence of large-molecular-mass, thermal hysteresis (TH)-producing antifreezes (e.g., antifreeze proteins) has been reported in numerous and diverse taxa, including representative species of fish, arthropods, plants, fungi, and bacteria. However, relatively few of these antifreeze molecules have been chemically characterized. We screened diverse species by subjecting their homogenates to ice-affinity purification and discovered the presence of a newly identified class of antifreeze, a xylomannan-based TH-producing glycolipid that was previously reported in one species of freeze-tolerant Alaskan beetle. We isolated xylomannan-based antifreeze glycolipids from one plant species, six insect species, and the first frog species to be shown to produce a large-molecular-mass antifreeze. 1 H NMR spectra of the ice-purified molecules isolated from these diverse freeze-tolerant and freeze-avoiding organisms were nearly identical, indicating that the chemical structures of the glycolipids were highly similar. Although the exact functions remain uncertain, it appears that antifreeze glycolipids play a role in cold tolerance. Keywords Freeze tolerance Á Antifreeze proteins Á Cryoprotection Á Cold adaptation Á Antifreeze glycolipid Abbreviations TH Thermal hysteresis AF(G)Ps Antifreeze (glyco)proteins AFGLs Antifreeze glycolipids Communicated by H.V. Carey.
We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relatio... more We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relationships between mass and passive cooling rate, wing loading, minimum flight temperature (MFT) and thermoregulating ability were examined. These properties were also compared between the behavioural classes: perchers and fliers. All factors with the addition of seasonal and daily flight activity were related to generalized thermal strategies.
Manned aerial surveys are routinely used to assess cetacean distribution and density, often over ... more Manned aerial surveys are routinely used to assess cetacean distribution and density, often over large geographic areas. Unmanned aircraft systems (UAS) have been identified as a technology that could augment or replace manned aerial surveys for cetaceans. To understand what research questions involving cetacean distribution and density can be addressed using manned and UAS technology in the Arctic, we conducted paired aerial surveys for cetaceans near Utqiaġvik (Barrow), Alaska. We present the methods and operational results from the project, and challenges encountered during the field work. Fall arctic weather varied dramatically over small spatiotemporal scales and harsh environmental conditions increased the maintenance required for repeated UAS operations. Various technologies, such as temperature and humidity sensors, a software system that provided near-term forecasts of highly variable weather, and a surface-based air traffic radar feed, directly contributed to the ability t...
The objective of this paper is to report on the demography and pathology of 131 Pacific walruses ... more The objective of this paper is to report on the demography and pathology of 131 Pacific walruses (Odobenus rosmarus divergens), primarily calves, found dead on the northwest coast of Alaska in September 2009. The walrus carcasses extended over approximately 120 km, but most were found where walruses had hauled out for several days on the beach at Icy Cape. The remote location and severe weather made access to the site difficult and limited the number and extent of necropsies. A total of 71 carcasses were examined: nine were necropsied, and 62 were classified externally for age, gender, blubber depth, and other parameters. The most likely causes of death were crushing trauma, particularly of the upper thorax, neck and head, or asphyxiation due to being trampled by larger animals.
Potential responses of marine mammals to anthropogenic underwater sound are usually assessed by r... more Potential responses of marine mammals to anthropogenic underwater sound are usually assessed by researchers and regulators on the basis of exposure to a single, relatively loud sound source. However, marine mammals typically receive sounds from multiple, dynamic sources. We developed a method to aggregate modeled sounds from multiple sources and estimate the sound levels received by individuals. To illustrate the method, we modeled the sound fields of 9 sources associated with oil development and estimated the sound received over 47 d by a population of 10 000 simulated bowhead whales Balaena mysticetus on their annual migration through the Alaskan Beaufort Sea. Empirical data were sufficient to parameterize simulations of the distribution of individual whales over time and their range of movement patterns. We ran 2 simulations to estimate the sound exposure history and distances traveled by bowhead whales: one in which they could change their movement paths (avert) in response to set levels of sound and one in which they could not avert. When animals could not avert, about 2% of the simulated population was exposed to root mean square (rms) sound pressure levels (SPL) ≥180 dB re 1 µPa, a level that regulators in the U.S. often associate with injury. When animals could avert from sound levels that regulators often associate with behavioral disturbance (rms SPL >160 dB re 1 µPa), <1% of the simulated population was exposed to levels associated with injury. Nevertheless, many simulated bowhead whales received sound levels considerably above ambient throughout their migration. Our method enables estimates of the aggregated level of sound to which populations are exposed over extensive areas and time periods.
The increased scientific interest in the Arctic due to climate change and potential oil and gas d... more The increased scientific interest in the Arctic due to climate change and potential oil and gas development has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also examined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthesis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other species. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for surveys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter season surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed.
• Premise of the study: Cold tolerance is a critically important factor determining how plants wi... more • Premise of the study: Cold tolerance is a critically important factor determining how plants will be infl uenced by climate change, including changes in snowcover and extreme weather events. Although a great deal is known about cold tolerance in Arabidopsis thaliana , it is not highly cold tolerant. This study examined cold tolerance and its genetic diversity in an herbaceous subarctic relative, Arabidopsis kamchatica , which generally occurs in much colder climates. • Methods: Thermal analysis and electrolyte leakage were used to estimate supercooling points and lethal temperatures (LT 50) in cold-acclimated and nonacclimated families from three populations of A. kamchatica. • Key results: Arabidopsis kamchatica was highly cold tolerant, with a mean LT 50 of −10.8 ° C when actively growing, and −21.8 ° C when cold acclimated. It also was able to supercool to very low temperatures. Surprisingly, actively growing plants supercooled more than acclimated plants (−14.7 vs. −12.7 ° C). There was signifi cant genetic variation for cold tolerance both within and among populations. However, both cold tolerance and genetic diversity were highest in the midlatitude population rather than in the far north, indicating that adaptations to climate change are most likely to arise in the center of the species range rather than at the edges. • Conclusions: Arabidopsis kamchatica is highly cold tolerant throughout its range. It is far more freeze tolerant than A. thaliana , and supercooled to lower temperatures, suggesting that A. kamchatica provides a valuable complement to A. thaliana for cold tolerance research.
1. We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The rela... more 1. We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relationships between mass and passive cooling rate, wing loading, minimum flight temperature (MFT) and thermoregulating ability were examined. These properties were also compared between the behavioural classes: perchers and fliers. All factors with the addition of seasonal and daily flight activity were related to generalized thermal strategies. 2. Passive cooling rate decreased while wing loading and MFT increased with mass. 3. While all species were able to elevate thoracic temperature, larger species were better able to maintain a constant temperature. 4. Both the smallest and largest species of dragonflies were capable of activity at ambient temperatures of approximately 14 ° C by employing different thermal strategies: low MFT and physiological heat production, respectively. 5. For small species active in cool conditions low MFT may be favoured even if accompanied by poor thermoregulating ability. By contrast, thermoregulation and specialization for high-temperature performance may be favoured in both small and large species during the warmer summer flight season. 6. The smallest and largest dragonflies in Interior Alaska have the shortest and longest daily activity periods, respectively. However this pattern does not hold for the intermediatesized dragonflies. Thermal strategy displays no clear relationship to daily activity pattern.
SUMMARY Most aquatic insects do not survive subzero temperatures and, for those that do, the phys... more SUMMARY Most aquatic insects do not survive subzero temperatures and, for those that do, the physiology has not been well characterized. Nemoura arctica is a species of stonefly widely distributed throughout arctic and subarctic Alaska. We collected nymphs from the headwaters of the Chandalar River, where we recorded streambed temperatures as low as –12.7°C in midwinter. When in contact with ice, autumn-collected N. arctica cool to –1.5±0.4°C before freezing, but individuals survived temperatures as low as –15°C, making this the first described species of freeze-tolerant stonefly. N. arctica clearly survive freezing in nature, as winter-collected nymphs encased in ice demonstrated high survivorship when thawed. In the laboratory, 87% of N. arcticanymphs frozen to –15°C for 2.5 weeks survived and, within one month of thawing, 95% of the last-instar nymphs emerged. N. arctica produce both glycerol and ice-binding factors (e.g. antifreeze protein) in response to low temperature. Hemoly...
SUMMARY Larvae of the freeze-avoiding beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) in... more SUMMARY Larvae of the freeze-avoiding beetle Cucujus clavipes puniceus (Coleoptera: Cucujidae) in Alaska have mean supercooling points in winter of –35 to –42°C, with the lowest supercooling point recorded for an individual of –58°C. We previously noted that some larvae did not freeze when cooled to –80°C, and we speculated that these larvae vitrified. Here we present evidence through differential scanning calorimetry that C. c. puniceus larvae transition into a glass-like state at temperatures <–58°C and can avoid freezing to at least –150°C. This novel finding adds vitrification to the list of insect overwintering strategies. While overwintering beneath the bark of fallen trees, C. c. puniceus larvae may experience low ambient temperatures of around –40°C (and lower) when microhabitat is un-insulated because of low snow cover. Decreasing temperatures in winter are correlated with loss of body water from summer high levels near 2.0 to winter lows near 0.4 mg mg–1 dry mass and co...
SUMMARY The beetle Cucujus clavipes is found in North America over a broad latitudinal range from... more SUMMARY The beetle Cucujus clavipes is found in North America over a broad latitudinal range from North Carolina (latitude ∼35°N) to near tree line in the Brooks Range in Alaska (latitude, ∼67°30′ N). The cold adaptations of populations from northern Indiana (∼41°45′N) and Alaska were compared and, as expected, the supercooling points (the temperatures at which they froze) of these freeze-avoiding insects were significantly lower in Alaska insects. Both populations produce glycerol, but the concentrations in Alaska larvae were much higher than in Indiana insects(∼2.2 and 0.5 mol l–1, respectively). In addition, both populations produce antifreeze proteins. Interestingly, in the autumn both populations have the same approximate level of hemolymph thermal hysteresis,indicative of antifreeze protein activity, suggesting that they synthesize similar amounts of antifreeze protein. A major difference is that the Alaska larvae undergo extreme dehydration in winter wherein water content dec...
Proceedings of the National Academy of Sciences, 2009
Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that ... more Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that is indicative of the presence of large-molecular-mass antifreezes (e.g., antifreeze proteins), has been described in animals, plants, bacteria, and fungi. Although all previously described TH-producing biomolecules are proteins, most thermal hysteresis factors (THFs) have not yet been structurally characterized, and none have been characterized from a freeze-tolerant animal. We isolated a highly active THF from the freeze-tolerant beetle, Upis ceramboides , by means of ice affinity. Amino acid chromatographic analysis, polyacrylamide gel electrophoresis, UV-Vis spectrophotometry, and NMR spectroscopy indicated that the THF contained little or no protein, yet it produced 3.7 ± 0.3 °C of TH at 5 mg/ml, comparable to that of the most active insect antifreeze proteins. Compositional and structural analyses indicated that this antifreeze contains a β-mannopyranosyl-(1→4) β-xylopyranose backbo...
Cucujus clavipes puniceus is a freeze avoiding beetle capable of surviving the long, extremely co... more Cucujus clavipes puniceus is a freeze avoiding beetle capable of surviving the long, extremely cold winters of the Interior of Alaska. Previous studies showed that some individuals typically supercool to mean values of approximately -40 °C, with some individuals supercooling to as low as -58 °C, but these non-deep supercooling (NDSC) individuals eventually freeze if temperatures drop below this. However, other larvae, especially if exposed to very cold temperatures, supercool even further. These deep supercooling (DSC) individuals do not freeze even if cooled to -100 °C. In addition, the body water of the DSC larvae vitrifies (turns to a glass) at glass transition temperatures of -58 to -70 °C. This study examines the proteomes of DSC and NDSC larvae to assess proteins that may contribute to or inhibit the DSC trait. Using high throughput proteomics, we identified 138 proteins and 513 Gene Ontology categories in the DSC group and 104 proteins and 573 GO categories in the NDSC group. GO categories enriched in DSC include alcohol metabolic process, cellular component morphogenesis, monosaccharide metabolic process, regulation of biological quality, extracellular region, structural molecule activity, and antioxidant activity. Proteins unique to DSC include alpha casein precursor, alpha-actinin, vimentin, tropomyosin, beta-lactoglobulin, immunoglobulins, tubulin, cuticle proteins and endothelins.
Prior to this study, antifreeze proteins (AFPs) had not been identified in terrestrial arthropods... more Prior to this study, antifreeze proteins (AFPs) had not been identified in terrestrial arthropods from the Arctic or anywhere in Alaska. The hemolymph of 75 species of insects and six spiders from interior and arctic Alaska were screened for thermal hysteresis (a difference between the freezing and melting points), characteristic of the presence of AFPs. Eighteen species of insects and three spiders were shown to have AFPs. Ten of the insects with AFPs were beetles including the first species from the families Chrysomelidae, Pythidae, Silphidae and Carabidae. In addition, the first Neuropteran to have AFPs was identified, the lacewing Hemerobius simulans together with the second and third Diptera (the first Tipulids) and the second and third Hemiptera, the stinkbug Elasmostethus interstinctus (the first Pentatomid), and the water strider Limnoporus dissortis (the first Gerrid). Prior to this study, 33 species of insects and three spiders had been reported to have AFPs. Most AFP-producing terrestrial arthropods are freeze avoiding, and the AFPs function to prevent freezing. However, some of the AFP-producing insects identified in this study are known to be freeze tolerant (able to survive freezing) to very low temperatures (À40 to À70 v C).
Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies fo... more Freeze tolerance and freeze avoidance are typically described as mutually exclusive strategies for overwintering in animals. Here we show an insect species that combines both strategies. Individual fungus gnats, collected in Fairbanks, Alaska, display two freezing events when experimentally cooled and diVerent rates of survival after each event (mean § SEM: ¡31.5 § 0.2°C, 70% survival and ¡50.7 § 0.4°C, 0% survival). To determine which body compartments froze at each event, we dissected the abdomen from the head/thorax and cooled each part separately. There was a signiWcant diVerence between temperature levels of abdominal freezing (¡30.1 § 1.1°C) and head/thorax freezing (¡48.7 § 1.3°C). We suggest that freezing is initially restricted to one body compartment by regional dehydration in the head/thorax that prevents inoculative freezing between the freeze-tolerant abdomen (71.0 § 0.8% water) and the supercooled, freeze-sensitive head/thorax (46.6 § 0.8% water).
The presence of large-molecular-mass, thermal hysteresis (TH)-producing antifreezes (e.g., antifr... more The presence of large-molecular-mass, thermal hysteresis (TH)-producing antifreezes (e.g., antifreeze proteins) has been reported in numerous and diverse taxa, including representative species of fish, arthropods, plants, fungi, and bacteria. However, relatively few of these antifreeze molecules have been chemically characterized. We screened diverse species by subjecting their homogenates to ice-affinity purification and discovered the presence of a newly identified class of antifreeze, a xylomannan-based TH-producing glycolipid that was previously reported in one species of freeze-tolerant Alaskan beetle. We isolated xylomannan-based antifreeze glycolipids from one plant species, six insect species, and the first frog species to be shown to produce a large-molecular-mass antifreeze. 1 H NMR spectra of the ice-purified molecules isolated from these diverse freeze-tolerant and freeze-avoiding organisms were nearly identical, indicating that the chemical structures of the glycolipids were highly similar. Although the exact functions remain uncertain, it appears that antifreeze glycolipids play a role in cold tolerance. Keywords Freeze tolerance Á Antifreeze proteins Á Cryoprotection Á Cold adaptation Á Antifreeze glycolipid Abbreviations TH Thermal hysteresis AF(G)Ps Antifreeze (glyco)proteins AFGLs Antifreeze glycolipids Communicated by H.V. Carey.
We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relatio... more We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relationships between mass and passive cooling rate, wing loading, minimum flight temperature (MFT) and thermoregulating ability were examined. These properties were also compared between the behavioural classes: perchers and fliers. All factors with the addition of seasonal and daily flight activity were related to generalized thermal strategies.
Manned aerial surveys are routinely used to assess cetacean distribution and density, often over ... more Manned aerial surveys are routinely used to assess cetacean distribution and density, often over large geographic areas. Unmanned aircraft systems (UAS) have been identified as a technology that could augment or replace manned aerial surveys for cetaceans. To understand what research questions involving cetacean distribution and density can be addressed using manned and UAS technology in the Arctic, we conducted paired aerial surveys for cetaceans near Utqiaġvik (Barrow), Alaska. We present the methods and operational results from the project, and challenges encountered during the field work. Fall arctic weather varied dramatically over small spatiotemporal scales and harsh environmental conditions increased the maintenance required for repeated UAS operations. Various technologies, such as temperature and humidity sensors, a software system that provided near-term forecasts of highly variable weather, and a surface-based air traffic radar feed, directly contributed to the ability t...
The objective of this paper is to report on the demography and pathology of 131 Pacific walruses ... more The objective of this paper is to report on the demography and pathology of 131 Pacific walruses (Odobenus rosmarus divergens), primarily calves, found dead on the northwest coast of Alaska in September 2009. The walrus carcasses extended over approximately 120 km, but most were found where walruses had hauled out for several days on the beach at Icy Cape. The remote location and severe weather made access to the site difficult and limited the number and extent of necropsies. A total of 71 carcasses were examined: nine were necropsied, and 62 were classified externally for age, gender, blubber depth, and other parameters. The most likely causes of death were crushing trauma, particularly of the upper thorax, neck and head, or asphyxiation due to being trampled by larger animals.
Potential responses of marine mammals to anthropogenic underwater sound are usually assessed by r... more Potential responses of marine mammals to anthropogenic underwater sound are usually assessed by researchers and regulators on the basis of exposure to a single, relatively loud sound source. However, marine mammals typically receive sounds from multiple, dynamic sources. We developed a method to aggregate modeled sounds from multiple sources and estimate the sound levels received by individuals. To illustrate the method, we modeled the sound fields of 9 sources associated with oil development and estimated the sound received over 47 d by a population of 10 000 simulated bowhead whales Balaena mysticetus on their annual migration through the Alaskan Beaufort Sea. Empirical data were sufficient to parameterize simulations of the distribution of individual whales over time and their range of movement patterns. We ran 2 simulations to estimate the sound exposure history and distances traveled by bowhead whales: one in which they could change their movement paths (avert) in response to set levels of sound and one in which they could not avert. When animals could not avert, about 2% of the simulated population was exposed to root mean square (rms) sound pressure levels (SPL) ≥180 dB re 1 µPa, a level that regulators in the U.S. often associate with injury. When animals could avert from sound levels that regulators often associate with behavioral disturbance (rms SPL >160 dB re 1 µPa), <1% of the simulated population was exposed to levels associated with injury. Nevertheless, many simulated bowhead whales received sound levels considerably above ambient throughout their migration. Our method enables estimates of the aggregated level of sound to which populations are exposed over extensive areas and time periods.
The increased scientific interest in the Arctic due to climate change and potential oil and gas d... more The increased scientific interest in the Arctic due to climate change and potential oil and gas development has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also examined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthesis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other species. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for surveys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter season surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed.
• Premise of the study: Cold tolerance is a critically important factor determining how plants wi... more • Premise of the study: Cold tolerance is a critically important factor determining how plants will be infl uenced by climate change, including changes in snowcover and extreme weather events. Although a great deal is known about cold tolerance in Arabidopsis thaliana , it is not highly cold tolerant. This study examined cold tolerance and its genetic diversity in an herbaceous subarctic relative, Arabidopsis kamchatica , which generally occurs in much colder climates. • Methods: Thermal analysis and electrolyte leakage were used to estimate supercooling points and lethal temperatures (LT 50) in cold-acclimated and nonacclimated families from three populations of A. kamchatica. • Key results: Arabidopsis kamchatica was highly cold tolerant, with a mean LT 50 of −10.8 ° C when actively growing, and −21.8 ° C when cold acclimated. It also was able to supercool to very low temperatures. Surprisingly, actively growing plants supercooled more than acclimated plants (−14.7 vs. −12.7 ° C). There was signifi cant genetic variation for cold tolerance both within and among populations. However, both cold tolerance and genetic diversity were highest in the midlatitude population rather than in the far north, indicating that adaptations to climate change are most likely to arise in the center of the species range rather than at the edges. • Conclusions: Arabidopsis kamchatica is highly cold tolerant throughout its range. It is far more freeze tolerant than A. thaliana , and supercooled to lower temperatures, suggesting that A. kamchatica provides a valuable complement to A. thaliana for cold tolerance research.
1. We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The rela... more 1. We examined the thermal ecology of Interior Alaska dragonflies (Odonata: Anisoptera). The relationships between mass and passive cooling rate, wing loading, minimum flight temperature (MFT) and thermoregulating ability were examined. These properties were also compared between the behavioural classes: perchers and fliers. All factors with the addition of seasonal and daily flight activity were related to generalized thermal strategies. 2. Passive cooling rate decreased while wing loading and MFT increased with mass. 3. While all species were able to elevate thoracic temperature, larger species were better able to maintain a constant temperature. 4. Both the smallest and largest species of dragonflies were capable of activity at ambient temperatures of approximately 14 ° C by employing different thermal strategies: low MFT and physiological heat production, respectively. 5. For small species active in cool conditions low MFT may be favoured even if accompanied by poor thermoregulating ability. By contrast, thermoregulation and specialization for high-temperature performance may be favoured in both small and large species during the warmer summer flight season. 6. The smallest and largest dragonflies in Interior Alaska have the shortest and longest daily activity periods, respectively. However this pattern does not hold for the intermediatesized dragonflies. Thermal strategy displays no clear relationship to daily activity pattern.
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