Observations on a Cyclic Decline of Lemmings (Lemmus) on the Arctic Coast of Alaska during the Spring of 1949

The importance to the biotic community of various species of lemmings in arctic and subarctic regions has long been recognized, but there is little known about the ecology of these mammals. of the two species that occur on the Arctic Slope of Alaska, namely, the collared lemming, Dicrostonyx groenlandicus rubricatus (Richardson), and the brown lemming, Lemmus trimucronatus alascensis Merriam, during the spring of 1949 the writer had the good fortune to observe a cyclic decline in the population of the brown lemming on the Arctic Coast of Alaska. Observations were made during the peak density preceding this decline and were continued for more than a year subsequent to it. It is the purpose of this paper to present the results of these studies.

Studies on the Helminth Fauna of Alaska. XLI. Observations on Cestodes of the Genus Diplogonoporus Lönnberg, 1892 (Diphyllobothriidae)

The study of a collection of cestodes assigned to the genus Diplogonoporus Lönnberg, 1892 disclosed but two species, D. balaenopterae Lönnberg, 1892, and D. tetrapterus (von Siebold, 1848) (provis.). These cestodes occur characteristically in marine mammals but occasionally are found in terrestrial hosts; D. balaenopterae is recorded for the first time from the domestic dog, and it is concluded that D. grandis (Blanchard, 1894), from man, is conspecific with D. balaenopterae. The latter species is recorded for the first time from the humpback whale, Megaptera novaeangliae (Borowski). The relatively small D. tetrapterus, a common parasite of the Steller sea lion, Eumetopias jubata (Schreber), is reported for the first time from the sea otter, Enhydra lutris Linnaeus, and from the domestic mink, Mustela vison Schreber. Descriptions of representative specimens are presented, and the taxonomic status of other species assigned to Diplogonoporus is discussed. Although the diplogonadic organization of these cestodes is somewhat variable, it is nevertheless constant and serves to characterize the genus Diplogonoporus. The process of asexual reproduction by means of transverse subdivision of primary segments is described. This ability and the diplogonadic structure of these cestodes are considered to be adaptations that increase the production of eggs and thereby the probability of reproductive success in the marine habitat.

Studies on the Helminth Fauna of Alaska. XXV. The Ecology and Public Health Significance of Echinococcus sibiricensis Rausch & Schiller, 1954, on St. Lawrence Island

The occurrence of a species of Echinococcus (Rudolphi, 1801) on St Lawrence Island was noted by the writers in early 1950. Recognition of its unusual host relationships led to an investigation of the ecology of this cestode, E. sibiricensis Rausch & Schiller, 1954. It is the purpose of this paper to report the results of this work, with emphasis on alveolar hydatid disease in man, of which this cestode is the etiologic agent.

Observations on Some Natural-Focal Zoonoses in Alaska

In Alaska, as in arctic and subarctic Eurasia, important natural-focal zoonoses are rabies, brucellosis, tularemia, trichinosis, alveolar hydatid disease, cystic hydatid disease, and diphyllobothriasis. Most frequently affected are aboriginal peoples in villages within biocenoses that include the natural parasite-host assemblages. Pathogens are transmitted to man from wild animals and from dogs, which are important as synanthropic hosts. The prevalence and rate of transmission of certain pathogens in natural foci are related to the numerical density of small mammals, especially rodents, which may themselves be involved as hosts, and on which the numbers of their predators ultimately depend, such as is evident in the natural cycles of Echinococcus multilocularis and of rabies virus. Some pathogens in northern regions exhibit biological Characteristics that separate them from morphologically indistinguishable strains at lower latitudes (e.g., Trichinella spiralis and E. granulosus). Host-parasite relationships may also differ, as in the Arctic where rabies virus is maintained in populations of foxes, without significant involvement of mammals of other groups. Faunal interchanges during and after the Pleistocene period have influenced the distribution of parasite-host assemblages in Alaska.

Contribution à l'étude des Microphallidae Travassos, 1920 (Trematoda). XXVI. -De quelques espèces d'Alaska

French abstract: La faune des Trématodes Microphallidés d'Alaska étudiée comporte neuf espèces différentes, distribuées en quatre genres: 1° Microphallus oblonga Ching, 1965, M. pygmaeum (Levinsen, 1881) et M. similis (Jaegerskioeld, 1900). 2° Levinseniella (Lev.) propinqua Jaegerskioeld, 1907. 3° Maritrema acadiae (Swales, 1933). M. afanassjewi Belopolskaia, 1952. M. gratiosum Nicoll, 1907. M. megametrios Deblock et Rausch, 1968 et enfin, 4° Pseudospelotrema sp. n° 1. Les caractéristiques morphologiques essentielles de ces Trématodes sont décrites, sauf celles de la dernière espèce citée qui a déjà fait l'objet d'une étude antérieure. English abstract: Microphallid trematodes of nine species, representing four genera, have been studied from birds and mammals collected in Alaska: 1° Microphallus oblonga Ching, 1965, M. pygmaeum (Levinsen, 1881) and M. similis (Jaegerskioeld, 1900). 2° Levinseniella (Lev.) propinqua Jaegerskioeld, 1907. 3° Maritrema acadiae (Swales, 1933), M. afanassjewi Belopolskaia, 1952, M. gratiosum, Nicoll, 1907 and M. megametrios Deblock and Rausch, 1968 and 4° Pseudospelotrema sp. n° 1. Morphological characteristics of these trematodes are described, with the exception of Pseudospelotrema sp. to be considered elsewhere.

Notes on Microtine Rodents from the Brooks Range, Arctic Alaska

In connection with parasitological studies carried on during 1949 for the U.S. Public Health Service, the writer collected a considerable number of mammals from the northern edge of the "Endicott" section of the Brooks Range, in Arctic Alaska. The mammalian fauna of this region is poorly known, since apparently no previous collecting has been done here. About 200 microtine rodents were collected, mostly near Tolugak Lake (latitude 68° 24' N, longitude 151° 26' W), near the head of the Anaktuvuk River Valley. A few specimens were also taken at Umiat, on the Colville River, about 80 miles north of Tolugak Lake (latitude 69° 23' N, longitude 152° 10' W). Five species are represented: Clethrionomys rutilis dawsoni (Merriam), Microtus oeconomus macfarlani Merriam, Microtus miurus paneaki, n. subsp., Lemmus trimucronatus alascensis Merriam and Dicrostonyx groenlandicus rubricatus (Richardson). More complete details concerning their ecology and reproduction will be presented in a later paper, at which time the other mammals obtained will also be considered. The specimens have been deposited in the U.S. National Museum.

Studies on the Helminth Fauna of Alaska. XXXVIl. Description of Schizorchis caballeroi n. sp. (Cestoda: Anoplocephalidae), with Notes on Other Parasites of Ochotona

Schizorchis caballeroi n. sp. has been described from the collared pika, Ochotona collaris (Nelson), from Alaska, and has been distinguished morphologically from its congeners, S. ochotonae Hansen, 1948, and S. altaica Gvozdev, 1951. Nine species of helminths have been described 10 dale from North American pikas, O. collaris and O. princeps (Richardson). These mammals are markedly allopatric and do not share any species of helminth. Nematodes of two genera, Eugenuris Shults and Labiostomum Akhtar, 1941, occur in O. collaris as weIl as in palearctic species of Ochotona. This, along with other pertinent information, is taken to suggest that O. collaris has invaded North American more recently than did O. princeps or its precursor.

Studien an der Helminthenfauna von Alaska. IV. Haploparaxis galli n. sp., Ein Cestode aus dem Schneehuhn, Lagopus rupestris (Gmelin) = Studies on the Helminth Fauna of Alaska. IV.

Eine neue Haploparaxis--Art, H. galli, aus dem Darm des Schneehuhns, Lagopus rupestris (Gmelin), wird beschrieben und von den verwandten Formen differenziert. Die typische Lokalität ist Tolugaksee, Brooksgebirge, arktisches Alaska.

Maximal exercise and muscle oxygen extraction in acclimatizing lowlanders and high altitude natives

[EN] The tight relation between arterial oxygen content and maximum oxygen uptake (Vv(o2max)within a given person at sea level is diminished with altitude acclimatization. An explanation often suggested for this mismatch is impairment of the muscle O(2) extraction capacity with chronic hypoxia, and is the focus of the present study. We have studied six lowlanders during maximal exercise at sea level (SL) and with acute (AH) exposure to 4,100 m altitude, and again after 2 (W2) and 8 weeks (W8) of altitude sojourn, where also eight high altitude native (Nat) Aymaras were studied. Fractional arterial muscle O(2) extraction at maximal exercise was 90.0+/-1.0% in the Danish lowlanders at sea level, and remained close to this value in all situations. In contrast to this, fractional arterial O(2) extraction was 83.2+/-2.8% in the high altitude natives, and did not change with the induction of normoxia. The capillary oxygen conductance of the lower extremity, a measure of oxygen diffusing capacity, was decreased in the Danish lowlanders after 8 weeks of acclimatization, but was still higher than the value obtained from the high altitude natives. The values were (in ml min(-1) mmHg(-1)) 55.2+/-3.7 (SL), 48.0+/-1.7 (W2), 37.8+/-0.4 (W8) and 27.7+/-1.5 (Nat). However, when correcting oxygen conductance for the observed reduction in maximal leg blood flow with acclimatization the effect diminished. When calculating a hypothetical leg V(o2max)at altitude using either the leg blood flow or the O(2) conductance values obtained at sea level, the former values were almost completely restored to sea level values. This would suggest that the major determinant V(o2max)for not to increase with acclimatization is the observed reduction in maximal leg blood flow and O(2) conductance.

The lactate paradox revisited in lowlanders during acclimatization to 4100 m and in high-altitude natives

[EN] Chronic hypoxia has been proposed to induce a closer coupling in human skeletal muscle between ATP utilization and production in both lowlanders (LN) acclimatizing to high altitude and high-altitude natives (HAN), linked with an improved match between pyruvate availability and its use in mitochondrial respiration. This should result in less lactate being formed during exercise in spite of the hypoxaemia. To test this hypothesis six LN (22-31 years old) were studied during 15 min warm up followed by an incremental bicycle exercise to exhaustion at sea level, during acute hypoxia and after 2 and 8 weeks at 4100 m above sea level (El Alto, Bolivia). In addition, eight HAN (26-37 years old) were studied with a similar exercise protocol at altitude. The leg net lactate release, and the arterial and muscle lactate concentrations were elevated during the exercise in LN in acute hypoxia and remained at this higher level during the acclimatization period. HAN had similar high values; however, at the moment of exhaustion their muscle lactate, ADP and IMP content and Cr/PCr ratio were higher than in LN. In conclusion, sea-level residents in the course of acclimatization to high altitude did not exhibit a reduced capacity for the active muscle to produce lactate. Thus, the lactate paradox concept could not be demonstrated. High-altitude natives from the Andes actually exhibit a higher anaerobic energy production than lowlanders after 8 weeks of acclimatization reflected by an increased muscle lactate accumulation and enhanced adenine nucleotide breakdown.

Pulmonary gas exchange at maximal exercise in Danish lowlanders during 8 wk of acclimatization to 4,100 m and in high-altitude Aymara natives

[EN] We aimed to test effects of altitude acclimatization on pulmonary gas exchange at maximal exercise. Six lowlanders were studied at sea level, in acute hypoxia (AH), and after 2 and 8 wk of acclimatization to 4,100 m (2W and 8W) and compared with Aymara high-altitude natives residing at this altitude. As expected, alveolar Po2 was reduced during AH but increased gradually during acclimatization (61 +/- 0.7, 69 +/- 0.9, and 72 +/- 1.4 mmHg in AH, 2W, and 8W, respectively), reaching values significantly higher than in Aymaras (67 +/- 0.6 mmHg). Arterial Po2 (PaO2) also decreased during exercise in AH but increased significantly with acclimatization (51 +/- 1.1, 58 +/- 1.7, and 62 +/- 1.6 mmHg in AH, 2W, and 8W, respectively). PaO2 in lowlanders reached levels that were not different from those in high-altitude natives (66 +/- 1.2 mmHg). Arterial O2 saturation (SaO2) decreased during maximum exercise compared with rest in AH and after 2W and 8W: 73.3 +/- 1.4, 76.9 +/- 1.7, and 79.3 +/- 1.6%, respectively. After 8W, SaO2 in lowlanders was not significantly different from that in Aymaras (82.7 +/- 1%). An improved pulmonary gas exchange with acclimatization was evidenced by a decreased ventilatory equivalent of O2 after 8W: 59 +/- 4, 58 +/- 4, and 52 +/- 4 l x min x l O2(-1), respectively. The ventilatory equivalent of O2 reached levels not different from that of Aymaras (51 +/- 3 l x min x l O2(-1)). However, increases in exercise alveolar Po2 and PaO2 with acclimatization had no net effect on alveolar-arterial Po2 difference in lowlanders (10 +/- 1.3, 11 +/- 1.5, and 10 +/- 2.1 mmHg in AH, 2W, and 8W, respectively), which remained significantly higher than in Aymaras (1 +/- 1.4 mmHg). In conclusion, lowlanders substantially improve pulmonary gas exchange with acclimatization, but even acclimatization for 8 wk is insufficient to achieve levels reached by high-altitude natives.

Provenance signature of a forearc basin modified by spreading ridge subduction: Detrital zircon geochronology and detrital modes from the Paleogene Arkose Ridge Formation, southern Alaska

Upper Paleocene–Eocene boulder conglomerate, cross-stratified sandstone, and laminated carbonaceous mudstone of the Arkose Ridge Formation exposed in the southern Talkeetna Mountains record fluvial-lacustrine deposition proximal to the volcanic arc in a forearc basin modified by Paleogene spreading ridge subduction beneath southern Alaska. U-Pb ages of detrital zircon grains and modal analyses were obtained from stratigraphic sections spanning the 2,000 m thick Arkose Ridge Formation in order to constrain the lithology, age, and location of sediment sources that provided detritus. Detrital modes from 24 conglomerate beds and 54 sandstone thin sections aredominated by plutonic and volcanic clasts and plagioclase feldspar with minor quartz, schist, hornblende, argillite, and metabasalt. Westernmost sandstone and conglomerate strata contain <5% volcanic clasts whereas easternmost sandstone and conglomerate strata contain 40 to >80% volcanic clasts. Temporally, eastern sandstones andconglomerates exhibit an upsection increase in volcanic detritus from <40 to >80% volcanic clasts. U-Pb ages from >1400 detrital zircons in 15 sandstone samples reveal three main populations: late Paleocene–Eocene (60-48 Ma; 16% of all grains), Late Cretaceous–early Paleocene (85–60 Ma; 62%) and Jurassic–Early Cretaceous (200–100 Ma; 12%). A plot of U/Th vs U-Pb ages shows that >97% of zircons are <200 Ma and>99% of zircons have <10 U/Th ratios, consistent with mainly igneous source terranes. Strata show increased enrichment in late Paleocene–Eocene detrital zircons from <2% in the west to >25% in the east. In eastern sections, this younger age population increases temporally from 0% in the lower 50 m of the section to >40% in samples collected >740 m above the base. Integration of the compositional and detrital geochronologic data suggests: (1) Detritus was eroded mainly from igneous sources exposed directly north of the Arkose Ridge Formation strata, mainly Jurassic–Paleocene plutons and Paleocene–Eocenevolcanic centers. Subordinate metamorphic detritus was eroded from western Mesozoic low-grade metamorphic sources. Subordinate sedimentary detritus was eroded from eastern Mesozoic sedimentary sources. (2) Eastern deposystems received higher proportions of juvenile volcanic detritus through time, consistent with construction of adjacent slab-window volcanic centers during Arkose Ridge Formation deposition. (3)Western deposystems transported detritus from Jurassic–Paleocene arc plutons that flank the northwestern basin margin. (4) Metasedimentary strata of the Chugach accretionaryprism, exposed 20-50 km south of the Arkose Ridge Formation, did not contribute abundant detritus. Conventional provenance models predict reduced input of volcanic detritus to forearc basins during exhumation of the volcanic edifice and increasing exposure ofsubvolcanic plutons (Dickinson, 1995; Ingersoll and Eastmond, 2007). In the forearc strata of these conventional models, sandstone modal analyses record progressive increases upsection in quartz and feldspar concomitant with decreases in lithic grains, mainly volcanic lithics. Additionally, as the arc massif denudes through time, theyoungest detrital U-Pb zircon age populations become significantly older than the age of forearc deposition as the arc migrates inboard or ceases magmatism. Westernmost strata of the Arkose Ridge Formation are consistent with this conventional model. However, easternmost strata of the Arkose Ridge Formation contain sandstone modes that record an upsection increase in lithic grains accompanied by a decrease in quartz and feldspar, and detrital zircon age populations that closely match the age of deposition. This deviation from the conventional model is due to the proximity of the easternmost strata to adjacent juvenile volcanic rocks emplaced by slab-window volcanic processes. Provenance data from the Arkose Ridge Formation show that forearc basins modified by spreading ridge subduction may record upsection increases in non-arc, syndepositional volcanic detritusdue to contemporaneous accumulation of thick volcanic sequences at slab-window volcanic centers. This change may occur locally at the same time that other regions of the forearc continue to receive increasing amounts of plutonic detritus as the remnant arc denudes, resulting in complex lateral variations in forearc basin petrofacies and chronofacies.