• Circadian Rhythms, Neuroanatomy Of The Superchiasmatic Nucleus And Selective Breeding Of The Northern Red -Backed Vole (Clethrionomys Rutilus)

      Tavernier, Ronald J., Jr.; Bult-Ito, Abel (2007)
      The experiments performed in this thesis investigated the circadian rhythms and neuroanatomy of a subarctic rodent, the northern red-backed vole ( Clethrionomys rutilus). Arctic and subarctic light regimes are extreme, with long periods of light and dark and large daily changes in day-length, but very little is known about circadian rhythms of mammals at high latitudes. A colony of C. rutilus was established and proper husbandry techniques were developed to allow voles to reproduce in captivity. Wild-caught and laboratory reared animals were tested for circadian rhythms in a 16:8 hour light:dark (LD) cycle, constant dark (DD) and constant light (LL). Voles displayed predominantly nocturnal patterns of wheel-running in 16:8 LD. In LL and DD, animals displayed large phenotypic variation in circadian rhythms with many becoming non-circadian (60% in DD, 72% in LL), indicating highly labile circadian organization. The distributions of eight common neurotransmitters in the suprachiasmatic nucleus (SCN), the brain's master circadian clock, were characterized. The SCN of C. rutilus is similar to that found in other rodents. Larger quantities of cholecystokinin and neuropeptide Y are found in the SCN of C. rutilus pointing to the possible importance of non-photic cues in resetting the phase of the internal clock. An additional study also found a distinct distribution of Substance P fibers and neurokinin-1 receptors in the SCN of C. rutilus. Starting with the 5th generation, laboratory-bred voles were selectively bred to create two lines of voles that maintained a circadian rhythm in DD, two lines that lost their circadian rhythm in DD, and a randomly bred control line. After three additional generations no significant differences were found among the lines due to the variability in the response to selection over the first few generations. With a large phenotypic variation in circadian wheel-running rhythms and an SCN similar to other rodents studied, C. rutilus is an ideal candidate to study subarctic circadian adaptations. Continued selective breeding will develop a useful tool for elucidating natural genetic variation in circadian rhythm characteristics in a subarctic mammal.
    • Contaminant Exposure And Associated Biological Responses In Southern Beaufort Sea Polar Bears

      Knott, Katrina K.; O'Hara, Todd; Miller, Debra; O'Brien, Diane; Hueffer, Karsten (2011)
      Concentrations of mercury (Hg) and polychlorinated biphenyls (PCBs) were examined in polar bear (Ursus marititnus) to assess variations among sex and age cohorts, and evaluate possible adverse impacts of combined toxicant exposures. Biomarkers of selenium (Se) status (whole blood and serum Se concentrations, glutathione peroxidase activity), and thyroid status (total and free concentrations of thyroxine and tri-iodothyronine) were examined in Southern Beaufort Sea (SBS) polar bears. Both Hg and PCBs tended to be greater in female than in male polar bears and likely related to the type and proportion of marine-based prey in their overall diet. Significant positive relationships between circulating concentrations of PCBs, specific blood lipids (e.g., triglycerides and free fatty acids) and reduced body condition scores suggest combined contaminant-environmental stressors for SBS polar bears. Polar bear milk contained detectable concentrations of both Hg and PCBs. Estimated tolerable daily intake levels for PCBs through milk consumption by cubs of the year (< 6 months of age) exceeded available toxicity thresholds and could indicate possible adverse consequences of contaminant exposure during critical stages of neonatal development. Significantly positive and negative associations between contaminants and biomarkers indicated a possible oxidative stress response and thyroid disruption in SBS polar bears. Definitive relationships between contaminants and these physiologically-based biomarkers, however, could not exclude natural variations and equally possible impacts of nutritional stress and changes in physiological status. Female and young polar bears are the cohorts of concern for chronic low-level exposure to chemical mixtures. These data provide a better understanding of the physiological interactions underlying toxicity, and the multiple environment-toxicant stressors projected for arctic species with changes in climate.
    • Epizootic Of Beak Deformities In Alaska: Investigation Of An Emerging Avian Disease

      Van Hemert, Caroline; O'Hara, Todd; O'Brien, Diane; Handel, Colleen; Blake, John; Sharbaugh, Susan (2012)
      The sudden appearance of morphological abnormalities in a wild population is often associated with underlying ecological disturbances, including those related to introduction of new pathogens or pollutants. An epizootic of beak deformities recently documented among Black-capped Chickadees (Poecile atricapillus) and other resident bird species in Alaska has raised concern about underlying causes. This dissertation describes results from several recent studies of what we have termed "avian keratin disorder." The primary objectives of the research were to characterize the physiology and pathology of beak deformities and to address specific ecological questions related to this emerging avian disease. In a study of beak growth rates in captive chickadees, I determined that accelerated epidermal growth is the primary physical mechanism by which beak deformities develop and are maintained. Affected birds also exhibited high rates of mortality and skin lesions, suggesting that this disorder significantly compromises individual health. I used radiography, histopathology, and electron microscopy to describe the pathology of avian keratin disorder. As part of this effort, I established baseline information about normal passerine beak and claw structure and developed methods for processing hard-cornified tissues. The suite of lesions that I observed in affected chickadees does not correspond with any known avian diseases, suggesting the presentation of a novel disorder in wild birds. In addition, the detailed characterization of gross and microscopic changes has allowed me to eliminate a number of likely etiologies, including nutritional problems, microbial pathogens, and select toxicants. As a complement to diagnostic pathology, I conducted field studies to investigate possible causes and patterns of occurrence of beak deformities. I used stable isotope analysis to investigate the association between diet and beak deformities. I found that winter dietary patterns differed between chickadees with normal beaks and those with beak deformities, but that such differences are more likely a result than a cause of avian keratin disorder. My field research on Northwestern Crows in Alaska confirmed high prevalence of a nearly identical condition to that observed in chickadees. These findings indicate that avian keratin disorder affects multiple, ecologically-distinct species across a large geographic area. Together, the studies presented in this dissertation provide new insights and identify priority research areas for a rapidly emerging disease in wild birds.
    • Expression And Mechanisms Of Hibernation In The Artic: The Alaska Marmot And Arctic Ground Squirrel

      Lee, Trixie Nicole; O'Brien, Diane; Buck, Loren; Taylor, Barbara; Barnes, Brian (2012)
      The Arctic is home to animals that have taken adaptations to overwintering to extremes. In this dissertation, I have investigated one of these adaptations, hibernation, in two species from the Arctic, the Alaska marmot (Marmota broweri) and the arctic ground squirrel (Urocitellus parryii ). The expression of hibernation under natural conditions in these species was compared by collecting body temperature records of free-living individuals. The Alaska marmot, a highly social species, demonstrated extreme synchrony in body temperature patterns among a family group, indicating a strong reliance on social thermoregulation. In contrast, the arctic ground squirrel was confirmed to be a solitary hibernator that reduces body temperature below freezing during torpor. Both species must produce heat when soil temperatures are significantly below freezing for most of the winter. At these subfreezing ambient temperatures, the arctic ground squirrel has shown an increasing reliance on nonlipid fuel during torpor, driving a loss of lean mass during hibernation of ~20%. I calibrated deuterium dilution to repeatedly estimate body composition in this species, which dramatically changes adiposity through its annual cycle, and used this technique to quantify lean mass loss throughout hibernation in a study of tissue metabolism. I also developed and applied the natural abundance of nitrogen and carbon stable isotopes as tools for monitoring differential tissue metabolism and differentiating mixed metabolic fuel use in the arctic ground squirrel. These data clarified the mechanism of change in nitrogen stable isotopes and indicated that hibernating ground squirrels rebuild organ tissues while breaking down muscle tissue to meet energetic demands. Furthermore, I corroborated a shift in metabolic fuel use toward nonlipid sources during torpor at low ambient temperatures by using the carbon isotope ratio in exhaled breath in combination with respiratory quotient. This dissertation combines studies of hibernation patterns in free-living animals with experimental data on the tissues and fuels being catabolized at very low temperatures to broaden our understanding of how small mammals successfully hibernate in severe winter conditions. It also presents the development and use of stable isotope ratios as physiological tools in hibernating species.
    • Health Assessment In The Bowhead Whale

      Rosa, Cheryl; Blake, John E. (2006)
      Tissue samples and morphometric data were collected from 64 bowhead whales landed during the 1998-2002 subsistence hunts in Barrow and Kaktovik, Alaska. Our primary goal was to assess the health status of the Bering-Chukchi-Beaufort Seas stock of bowhead whales. Ages of whales were determined via aspartic acid racemization of the eye lens nucleus, baleen stable carbon isotope analysis and morphometric and histologic indices. We investigated the gross and microscopic anatomy of organs and blubber, thyroid hormone concentrations, serum haptoglobin, vitamin A and E concentrations in liver, blubber and serum and essential element concentrations in liver and kidney. Thyroid hormone and vitamin A were also evaluated as potential biomarkers of organochlorine (OC) concentrations in blubber, liver and serum. Neither of these substances was found to correlate with the relatively low OC concentrations found in these mysticetes. Histological changes of interest included renal interstitial fibrosis, hepatic periportal fibrosis/pigmentation/lipidosis, splenic extramedullary hematopoiesis and pulmonary fibromuscular hyperplasia. Changes in the kidney and lung were related to both age and renal and hepatic Cd concentrations. Most of the histological differences observed did not appear to adversely affect organ function or health of the individual. Thyroid hormone concentrations were stable over age/sex/seasonal groups, however, pregnant females had significantly lower total and free thyroxine than non-pregnant adult females and other age-sex classes. Serum haptoglobin was measured as an indirect determinant of acute inflammation, with three reactors found among 51 whales examined. Liver contained the highest mean concentrations of vitamins A and E (followed by epidermis, blubber, and serum and serum, epidermis, and blubber, in order). Finally, blubber percent collagen was measured at 30 locations on each whale and was found to be stable by site and most depths, with the most internal region of the reticular dermis being the only exception. Overall, the bowhead whales were healthy. However, climate change, offshore development and increases in arctic pollution emphasize the importance of baseline data collection. An ongoing surveillance effort is recommended to ensure that the species will be viable for generations to come and to assure subsistence users of the robust and healthy status of this stock of whales.
    • Heat Increment And Methane Production By Muskoxen Fed Browse

      Lawler, James Patrick; White, Robert G. (2001)
      Many browse species contain anti-herbivory compounds that deter consumers by their toxicity or digestive inhibitory effects. Animals that consume browse are assumed to pay a detoxification energy cost, which increases the heat increment of feeding (HIF). Ruminants also lose potentially metabolizable energy as methane (CH4); but browse may lower CH4 production. I hypothesized that increases in energy loss to HIF by animals eating browse could be offset by a reduction in energy lost via CH4 production. Muskoxen eat both graminoids and browse and are considered to be energetically conservative due to their existence in a sparse arctic environment. These traits make them ideal for energetic studies. Muskoxen were fasted for 24 h and then fed a test meal composed of hay mixed with graded percentages of one of three browse species (Willow: S. alaxensis, S. pulchra, birch: Betula nana). Browse consisted of twigs in winter and leaves in the summer. Heat increment of feeding and CH4 production were estimated with an indirect calorimeter. Muskoxen had a 33% lower metabolic rate in winter in comparison to summer. The main increase in EE from winter to summer occurred between April and May, and the summer to winter decrease between August and September. Addition of woody twigs or leaves of birch to hay diets tended to depress HIF following the test meal. Woody twigs and leaves of willow added to hay diets tended to increase HIF. Woody browse tended to lower CH4 production when fed at >20% of the meal. Leafy browse had variable effects on CH4 production; S. alaxensis was stimulatory, S. pulchra was inhibitory, while B. nana showed not consistent pattern. Generally, CH 4 production by muskoxen was low at 2.0--3.2% of GE intake when compared with estimates for sheep and cattle (2--12% of GE intake). Although diets high in fermentable carbohydrates stimulated methane production, secondary compounds apparently had a suppressing effect as deduced from the relation of in vitro digestibility to methane production. Given the low overall CH4 production in muskoxen, and the inconsistency of the relationship of CH4 to HIF, it is unlikely that significant gains in energy retention are made by reductions in CH4 production through browse consumption.
    • Identification And Function Of Male Moose Urinary Pheromones

      Whittle, Chris L.; Clausen, Thomas P. (2005)
      Olfactory communication and associated scent-marking activities play a major role in the behavioral ecology of many mammals. During the mating season (rut), scent marking associated with urine of male cervids is an important chemical cue to relay information to conspecifics. Specifically, adult male moose (Alces alces) dig rutting pits in which they urinate, and females respond strongly to urine deposited in pits. A behavioral bioassay was developed to aid in the identification and function of adult male moose urinary pheromones, which elicited the behaviors observed in females during rut. Several behavioral bioassays were conducted to delineate the putative pheromones(s). It was experimentally established that when female moose were presented with urine from the pre-rut and rut periods, females preferred the urine from rut. Moreover, this experiment documented that females responded markedly to constituent(s) in rut urine by wallowing. Rut urine can be chemically extracted and maintain its bioactivity when presented to female moose, the partition of the urine that had bioactivity was delineated. Information was provided on the chemical and physical nature of the chemosignal---not a protein, or carbohydrate, relatively non-polar, and of low molecular weight. Urinary constituents that may function as the putative pheromone(s) were characterized. Some of the chemical differences that existed in rut urine and may not function as chemical signals were eliminated. Also provided, was evidence that female moose may utilize the main olfactory system to detect chemosignals present in rut urine.
    • Molecular phylogenetics of arvicoline rodents

      Conroy, Christopher John; Cook, Joseph A. (1998)
      The impetus for this dissertation was an interest in geographic variation in Microtus longicaudus with a particular focus on populations in the Alexander Archipelago of southeastern Alaska. To establish a framework for interpreting intraspecific variation in M. longicaudus, I examined the phylogenetics of 28 species of the genus Microtus, including all North American species (Chapters 2 and 4). That study, which corroborates a rapid pulse of diversification noted in the fossil record, necessitated a deeper phylogenetic perspective. Thus, a third objective of the dissertation was to investigate relationships among genera of arvicolines within the framework of other murid rodents. I examined variation in the mitochondrial cytochrome b and ND4 genes using maximum parsimony, distance, and maximum likelihood phylogenetic analyses. Relationships at several taxonomic levels appear intractable due to rapid accumulation and survival of genetic lineages. These rapid radiations were found among species, genera, and possibly subfamilies; however, strong support at these levels for other taxa (e.g., the monophyly of Microtus) suggests these genes have strong phylogenetic signal. Many of the well-supported sister species pairs within Microtus (Chapters 2 and 4) had been previously identified based on morphologic or allozyme work (e.g., M. pennsylvanicus and M. montanus, M. pinetorum and M. quasiater). The sequence data supported a clade of taiga dwelling species in North America and a clade of eastern and central Asian species. The southernmost arvicoline species of Mexico and Guatemala, though previously suggested to be derived from a single ancient invasion, did not appear to be either ancient or monophyletic. Within M. longicaudus, a large east-west phylogeographic break was detected that is equivalent in genetic distance to other sister species pairs in the genus. This break may indicate mid to late-Pleistocene differentiation (Chapter 3) within the genus. At higher latitudes, populations of M. longicaudus exhibited evidence of recent range expansion including absence of correlation between geographic and genetic structure; and pairwise mismatches among DNA sequences with a single peak and few differences.
    • Nmda Receptors In Hibernating Arctic Ground Squirrels

      Zhao, Huiwen; Drew, Kelly (2005)
      Hibernation is a unique physiological state characterized by suppressed metabolism and body temperature that is interrupted by multiple, brief periods of arousal throughout the hibernation season. Blood flow fluctuates during hibernation and arousal in a reperfusion-like manner without causing neurological damage. Previous studies show that hippocampal slices from hibernating animals tolerate experimental oxygen nutrient deprivation and N-methyl-D-aspartate (NMDA) toxicity better than slices from euthermic animals. However, the cellular mechanisms underlying these examples of tolerance remain unclear. Tolerance to NMDA toxicity suggests that modulation of NMDA receptors (NMDAR) contributes to intrinsic tissue tolerance in slices from hibernating Arctic ground squirrels (hAGS, Spermophilus parryii). NMDAR are one subtype of glutamate receptors. NMDAR play critical roles in excitatory synaptic transmission, synaptic plasticity, learning and memory, and excitotoxicity. NMDAR1 (NR1) is a fundamental subunit of NMDAR and required for receptor function. The main focus of the current project was to test the hypothesis that NMDAR are down-regulated in hAGS compared with interbout euthermic AGS (ibeAGS) and to explore the potential mechanisms of this down-regulation. NMDAR function can be modulated by protein phosphorylation, subunit composition, and internalization. Hence, the aim of chapter 2 was to determine the distribution of NRl in hAGS and ibeAGS using immunohistochemistry. The aim of chapter 3 was to examine NMDAR function in cultured hippocampal slices from hAGS, ibeAGS, and rats using calcium imaging, and to investigate potential modulation of NMDAR such as phosphorylation and internalization for altered function using western blot analysis. Given that synaptic remodeling and functional changes after arousal from hibernation, and NMDAR play an important role in learning and memory, the aim of chapter 4 was to address the effects of hibernation on learning and memory in AGS using an active avoidance task. Here, we report that NMDAR in hAGS are down-regulated via decreased phosphorylation of NR1. This down-regulation is not due to changes in NR1 distribution and internalization. In addition, the fraction of NR1 in the functional membrane pool in AGS is less than in rats. These findings provide evidence that modulation of NMDAR contributes to neuroprotection observed in hAGS.
    • Physiological adaptations for overwintering by the black-capped chickadee (Parus atricapillus) in interior Alaska (64 degrees North latitude)

      Sharbaugh, Susan Marie (1997)
      Winter in interior Alaska (64$\sp\circ$N) is characterized by short photoperiod (LD 5:19) and chronic subfreezing temperatures. These conditions present a physiological challenge to overwintering animals. This challenge increases as body size decreases. In small animals, higher surface to volume ratio and concomitant higher mass-specific metabolic rate (compared to larger animals) vastly increase energetic demand. This thesis focuses on the physiological adaptations of the smallest (12 g) overwintering bird in interior Alaska, the Black-capped Chickadee (Parus atricapillus). To determine if seasonal acclimatization of Black-capped Chickadees at high latitude differs from that of conspecifics at lower latitudes, standard metabolic rates (SMR), metabolic response to low temperature (${-}30\sp\circ$C), use of nocturnal hypothermia, body mass, fat reserves, and conductance were measured over two winters and one summer in three groups of seasonally acclimatized captive birds. Body mass and conductance did not vary with season, but furcular fat levels were higher in winter. Birds used nocturnal hypothermia when exposed to ${-}30\sp\circ$C in summer or winter. Although SMR did not vary seasonally, winter SMRs differed between the two winters studied. Nocturnal hypothermia in summer and decreased SMR during winter have not been reported in conspecifics at lower latitudes. Lipid reserves play an important role in fueling the energy demands of overwintering birds. Black-capped Chickadees exhibit a daily and seasonal cycle of fattening. At high latitudes (64$\sp\circ$N), fat to fuel an 18 hour nocturnal fast is deposited during 6 hours of daylight available for foraging. Daily fattening rates are highest in December when ambient conditions are most limiting. Activity of the fat deposition-promoting enzyme, adipose lipoprotein lipase (ALPL), was measured in furcular fat samples from seasonally acclimatized captive birds to determine its role in daily and seasonal fattening cycles. ALPL activity levels were 20-30 times higher than those previously reported for passerines. Seasonal variation in enzyme activity positively correlated with changes in fattening rates from December to April. Alaskan birds displayed the highest level of activity when compared to conspecifics at lower latitudes. All subpopulations measured exhibited activity higher than previously reported for small birds.
    • Physiological ecology of the arctic ground squirrel: Energy metabolism, torpor, and behavioral endocrinology

      Buck, Charles Loren (1998)
      I monitored seasonal changes in body condition and dates of immergence into and emergence from hibernation in a natural population of arctic ground squirrels (Sphermophilus parryii kennicottii) living on the North Slope of Alaska. Age and sex differences in changes of body condition and hibernation chronology are attributable to sex differences in energetic costs associated with preparation for reproduction and differences in reproductive status within males. While winters are long and environmental conditions faced by arctic ground squirrels in northern Alaska are extreme, the timing of hibernation did not differ appreciably from patterns observed in Sciurid populations living in temperate latitudes. To determine the environmental conditions faced by S. parryii during hibernation and to investigate the effect of overwinter temperature on change in body condition of the individual, I instrumented 18 burrow sites with temperature-sensitive data loggers to record soil temperature at hibernacula depth. Burrow sites did not differ significantly in soil temperature over years, but significant thermal differences were observed among burrows. Burrows with more shrubby vegetation accumulated deeper snow and had higher overwinter temperatures than did windswept sites. Females hibernated at warmer sites than did males and adults hibernated at warmer sites than juveniles. Repeated measures of overwinter changes in body condition were not significantly correlated with winter soil temperatures for any age or sex class. To determine the energetic cost associated with hibernation under arctic conditions, I measured metabolic rate, respiratory quotient, and body temperature of arctic ground squirrels in steady-state torpor. At ambient temperatures below 0$\sp\circ$C, body temperature remained constant and metabolic rate increased proportional to the gradient between body and ambient temperatures. With increased metabolic rate associated with decreased ambient temperature, animals switched from catabolism of exclusively lipid fuel to mixed fuels. To test the effects of male-male aggressive behavior on circulating testosterone and corticosterone concentrations during the breeding season, I staged encounters between free-living males and sampled them for blood following the interaction. Levels of testosterone and corticosterone significantly increased following the encounter compared to in control animals, and the magnitude of increase significantly correlated with the intensity of the interaction.
    • The Effects Of Perchlorate Exposure On A Model Vertebrate Species: The Threespine Stickleback

      Bernhardt, Richard R.; Von Hippel, Frank A.; O'Hara, Todd (2008)
      Few studies have examined the effects of chronic perchlorate exposure during multiple stages of development, and fewer still have analyzed the effects of perchlorate over multiple generations. Perchlorate exposure is known to cause thyrocyte hypertrophy (suggesting glandular stimulation), interference with thyroid hormone synthesis, and ultimately altered levels of circulating thyroid hormones, but whether these effects represent adaptive mechanisms or actual impairment is often debated within the scientific community. My research attempts to clarify whether exposure to environmentally relevant concentrations of perchlorate cause impairment at the organismal level. I examine ecologically significant endpoints to provide an indication if a contaminated population would be able to sustain itself I exposed threespine stickleback fish (Gasterosteus aculeatus) to one of eight perchlorate treatments and compared them to each other and to fish raised in water without detectable levels of perchlorate (<1.1 mug/L). I present patterns for two separate generations (G2,2002 and G2,2003 ) of stickleback that were spawned and raised in control or perchlorate treated water and a third generation (G3,2004) that was not directly exposed to perchlorate but whose parents (G2,2003) were raised from syngamy through sexual maturity in control or perchlorate treated water. When warranted, I make comparisons with their wild-caught ancestors (G 1,2002 and G1,2003) that were exposed to perchlorate as adults for up to 22 days. Exposure of mature adult stickleback to perchlorate had no noticeable effect on survival, behavioral, or reproductive endpoints. However, chronic exposure of their offspring (G2,2002 and G2,2003) to perchlorate impaired nearly every aspect of fitness. Aberrant developmental patterns of somatic characters were primarily associated with growth, reproduction, locomotion, anti-predatory structures, and vision. Impaired stickleback (G 2,2003) that produced offspring in water without detectable levels of perchlorate (<1.1 mug/L) gave rise to offspring (G3,2004) without the suite of abnormalities noted among treated fish. These findings suggest that perchlorate exposure during sensitive developmental periods has negative effects on critical life history characteristics of threespine stickleback, but remediation efforts are likely to restore healthy ecosystems. Effects noted among stickleback provide a useful model to assess effects that are likely to occur among other contaminated fishes and perhaps to other vertebrates.