Observations on Chromosomes of Dicrostonyx torquatus stevensoni Nelson and Chromosomal Diversity in Varying Lemmings = Untersuchungen an den Chromosomen von Dicrostonyx torquatus stevensoni Nelson und chromosomale Unterschiede bei Halsbandlemmingen

English abstract: The cytogenetic characteristics of the varying lemming, Dicrostonyx torquatus stevensoni, (2n = 34), were investigated, and diploid chromosomal numbers were reported for four other nominal subspecies (exsul, nelsoni, richardsoni, and rubricatus) of the torquatus-group in North America. The diploid complements ranged from 30 to 44 chromosomes, and the fundamental number from 50 to 55. Chromosomal polymorphism was observed in all forms. In cross-breeding experiments, the mating of F1 progeny was not productive. The findings support the zoogeographic concept that populations of Dicrostonyx became fragmented or displaced southward during Würm time, with relict stocks persisting in unglaciated refugia or periglacial tundra. Speciation in the isolates led to chromosomal evolution, with the result that populations spreading from refugia in post-glacial time are reproductively isolated. The torquatus-group in North America appears to be a superspecies. German title: Untersuchungen an den Chromosomen von Dicrostonyx torquatus stevensoni Nelson und chromosomale Unterschiede bei Halsbandlemmingen German abstract: Die cytogenetischen Merkmale des Halsbandlemmings, Dicrostonyx torquatus stevensoni, (2n = 34) wurden eingehend untersucht, und für vier andere nordamerikanische Unterarten der torquatus-Gruppe wurden die somatischen Chromosomensätze festgestellt. Die Chromosomenzahl der untersuchten Populationen schwankte zwischen 30 und 44, der NF (Nombre Fondamental) zwischen 50 und 55. Zuchttiere der verschiedenen Populationen wurden erfolgreich gekreuzt, aber Sterilität der F1 Unterartbastarde war typisch. Die Halsbandlemminge wiesen Karyotypenverschiedenheiten auf, die sich durch Variationen des Robertsonschen Typus, Deletionen oder möglicherweise durch perizentrische Inversionen erklären. Die Ergebnisse sprechen dafür, daß das ursprüngliche Verbreitungsgebiet von Dicrostonyx in Nordamerika durch die letzte (Würm) Vereisung getrennt wurde, und daß die Reliktpopulationen die letzte Glazial-Phase in eisfreien Refugien oder in periglazialer Tundra überlebten, wo Karyotypevolution durch lokale Anpassungsbedürfnisse gefördert wurde. Die in der Postglazialzeit aus den Refugien sich verbreitenden Populationen von Dicrostonyx scheinen reproduktiv isoliert zu sein. Die torquatus-Gruppe in Nordamerika gilt also als Superspecies.

Heligmosomoides johnsoni sp. nov. (Nematoda: Heligmosomatidae) from the Heather Vole, Phenacomys intermedius Merriam

Heligmosomoides johnsoni sp. noy. is described from the cecum of the heather vole, Phenacomys intermedius Merriam, from the Olympic Mountains, Washington. The absence of longitudinal cuticular ridges dorsally separates H. johnsoni from species of Heligmosomoides other than H. hudsoni (Cameron, 1937), which occurs in varying lemmings, Dicrostonyx spp., and from which H. johnsoni is distinguished by its longer spicules, form of the dorsal ray, and other characters. Both Phenacomys and Dicrostonyx have a specialized cecum, with long villi around which the nematodes are found tightly coiled. The zoogeography of heligmosomid nematodes in Phenacomys is briefly discussed. French abstract: On décrit Heligmosomoides johnsoni sp. nov. parasite du caecum du rongeur néarctique, Phenacomys intermedius Merriam, des Montagnes Olympiques de Washington. L'absence de crêtes cuticulaires sur la face dorsaIe sépare H. johnsoni des autres Heligmosomoides à I'exception d'H. hudsoni (Cameron, 1937) qui se trouve chez Dicrostonyx spp., et duquel H. johnsoni se distingue par ses spicules plus longs, par la forme différente de la côte dorsale et par d'autres caractères. Phenacomys et Dicrostonyx ont un caecum spécialisé, muni de villosités allongées, autour desquelles les nématodes s'enroulent étroitement. La zoogéographie des nematodes héligmosomes chez Phenacomys est discutée.

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.

On the Ecology and Distribution of Echinococcus spp. (Cestoda: Taeniidae), and Characteristics of Their Development in the Intermediate Host. II. Comparative Studies on the Development of Larval E. multilocularis Leuckart, 1863, in the Intermediate Host

This paper reports the results of a comparative study of the development of the larval Echinococcus multilocularis Leuckart, 1863), and associated tissue reaction in naturally and experimentally infected mammals representing 31 species. The histogenesis of the larval cestode was traced in detail in arvicoline rodents of several species, and interspecific differences were defined. In arvicoline rodents, the developing larva exhibited host-specific characteristics within about a month after infection was established. The tissue reaction in Microtus oeconomus was characterized by the production of a large quantity of detritus around the larva, and by the formation of a thick epithelioid zone. In one subspecies, M. oeconomus innuitus, development of the larva was retarded, and the detrital mass was often calcified; in another, M. oeconomus operarius, the detritus rarely became calcified and the larva proliferated more rapidly. In M. pennsylvanicus, the tissue reaction was minimal, and little detritus was present. The characteristics of the tissue reaction in M. montebelli placed it in an intermediate position between the aforementioned species. In Clethrionomys rutilus, a thin epithelioid zone and an outer zone of loose collagenous fibers composed the adventitial layer; exogenous budding was retarded in this vole. A minimal tissue reaction occurred in Lagurus curtatus. In Lemmus spp., larger cysts were characteristic, but areas of small-cystic proliferation were always present. Similar differences in species or subspecies of Citellus and Dicrostonyx were described. Lesions of alveolar bydatid disease in man also were studied. The invasive growth of the larval cestode in the human liver involves a process comparable to small-cystic proliferation in the natural intermediate hosts. Although the later stages of development of the larval cestode are inhibited in man, exogenous proliferation of vesicles continues for the life of the host. The lesion in man was compared with a morphologically similar formation produced by anomalous development of the larval E. granulosus in the bovine liver. The latter is distinguished by the absence of areas of small-cystic proliferation. Non-echinococcal lesions found in the tissues studied, some of which resembled foci caused by the larval E. multilocularis, were briefly discussed.

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.

Zoonotic Diseases in the Changing Arctic

Compatible with the biotic uniformity of northern regions, the occurrence of certain organisms which cause zoonotic diseases is general throughout the Arctic. In the past, most frequently affected by such diseases have been aboriginal peoples whose way of life involved encroachment upon naturally occurring parasite-host assemblages. Now, as changes take place in socioeconomic conditions in the Arctic, the importance of zoonotic diseases as a cause of morbidity may lessen among such peoples, but on the other hand, more nonaborigines may be affected. Although my remarks relate mainly to Alaska, again the biotic uniformity of the North seems to have its effect even with regard to man's activity, for similar changes are occurring throughout the arctic zone. Thus far, the natural environment has not been extensively disrupted at higher latitudes, and the arctic regions remain important for basic research in the natural history of zoonotic diseases. Because of the biotic peculiarities of these regions, conditions there especially favor the investigation of parasite-host relationships and the transmission of disease among the inhabitants. Significant benefit to the human population, in the temperate zone as well, can be expected to accrue from future studies in an undisturbed arctic wilderness.

Cytogenic Evidence for the Specific Distinction of an Alaskan Marmot, Marmota broweri Hall and Gilmore (Mammalia: Sciuridae)

Cytogenetic studies based upon somatic cells (bone marrow) have disclosed that the marmot hitherto designated Marmota caligata broweri Hall and Gilmore, occurring in the Brooks Range of Arctic Alaska, differs from M. c. caligata (Eschscholtz) in number of chromosomes (2n=36 as compared with 2n=42 in M. caligata) and in proportions of chromosomal types. Typical karyograms for the two species are presented. It is concluded that the Brooks Range marmot is specifically distinct from M. caligata, the applicable name being Marmota broweri Hall and Gilmore. Also determined were diploid chromosome numbers for two other Nearctic species of marmots, M. flaviventris (Audubon and Bachman), with 42, and M. olympus (Merriam), with 40. It is suggested that M. broweri survived the last (Wisconsin) glaciations in the amphi-Beringian refugium, and that its closest affinities may be with one of the Eurasian species of Marmota.

Virus-Associated Tumours of the Harderian Gland in Laboratory-Reared Voles, Clethrionomys rutilis (Pallas)

Tumors of the Harderian gland occurred frequently in red-backed voles, Clethrionomys rutilus (Pallas), in a captive colony maintained since 1957. Although the tumors became obvious only in animals about a year old and older, early stage changes were histologically evident in glands from younger, clinically normal voles. The tumors ranged in type from poorly differentiated adenoma to adenocarcinoma, with invasion of adjacent tissues and characteristic deformation of the zygomata. Electron micrographs disclosed viral particles in the cytoplasm of glands from clinically normal animals as well as in glands showing malignant changes. The tumor was not observed in arvicoline rodents of other species maintained in the same rooms with the red-backed voles.

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.

Seasonal Carbon Dioxide and Oxygen Concentrations in the Dens of Hibernating Mammals (Sciuridae)

This paper reports seasonal changes in respiratory gases in artificial dens of two species of hibernators indigenous to central and northern Alaska: Citellus parryi ablusus(Osgood) and Marmota broweri Hall and Gilmore (Sciuridae).

Taxonomic Characters in the Genus Echinococcus (Cestoda: Taenlidae)

Not more than four species of cestodes of the genus Echinococcus Rudolphi, 1801, are recognized as valid. The larval stage of at least three of them is able to develop in man, causing respective types of hydatid disease. Accurate characterization of these cestodes, including both larval and adult stages, is essential for identification, upon which depends development of methods for preventing infection of man and domestic animals. Because morphological characteristics of the larval cestodes may be modified according to the species of host in which they develop, identification should be based upon taxonomic characters of specimens from the respective natural hosts, which can be identified by means of ecological investigations in endemic areas in combination with controlled infection of experimental animals. The morphological and biological characteristics of the known species are discussed, and the two species most important to public health and economically--E. granulosus (Batsch, 1786) and E. multilocularis Leuckart, 1863--are distinguished. French résumé: Trois espèces de cestodes du genre Echinococcus Rudolphi, 1801 ont été identifiées: E. granulosus (Batsch, 1786); E. multilocularis Leuckart, 1863; et E. oligarthrus (Diesing, 1863). On n'a pas encore déterminé avec certitude s'il fallait leur adjoindre E. patagonicus Szidat, 1960. Ce dernier mis à part, tous ces ténias sont connus pour provoquer chez l'homme des formes spécifiques d'échinococcose hydatique; l'infestation par les larves de E. granulosus est également fréquente chez les ongulés domestiques et la répartition de ce cestode est presque cosmopolite. E. multilocularis est très largement répandu dans l'hémisphère nord, tandis que E. oligarthrus ne se trouve que dans le centre et le sud de I'Amérique. Pour définir des critères morphologiques qui permettent de distinguer avec précision les différentes espèces d'Echinococcus, il convient de prendre les spécimens sur leurs hôtes naturels, sinon l'évolution du stade strobilaire se trouve habituellement retardée et le stade larvaire présente une gamme étendue de variations morphologiques. Pour identifier les hôtes naturels, il faut étudier l'écologie dans les zones d'éndemicité, ainsi que les manifestations de l'infection contrôlée chez des animaux d'expérience. Le stade strobilaire des ténias peut présenter plusieurs caractères spécifiques importants qui concernent notamment la taille, le nombre et la répartition des testicules, la position du pore génital dans les segments gravides, la forme de l'utérus gravide et, dans certains cas, la taille et la forme des crochets du rostre. La structure de la larve normalement développée est caractéristique de chacune des trois espèces relativement bien connues. Les caractéristiques biologiques jouent également un rôle important dans la différenciation de ces cestodes. Au stade larvaire, le laps de temps nécessaire au développement des scolex infectants est directement fonction de la durée de vie de l'hôte intermédiaire. La larve de E. multilocularis présente des scolex infectants dès le deuxième ou le troisième mois, alors qu'ils n'apparaissent qu'au bout d'un ou deux ans chez la larve de E. granulosus. Un tableau donne la liste comparative des caractéristiques taxonomiques qui permettent de faire la distinction entre ces deux espèces.

Rabies in Experimentally Infected Bears, Ursus spp., with Epizootiologic Notes

Ten black bears, Ursus americanus Pallas, and three brown bears, U. arctos Linnaeus, were inoculated with rabies virus from naturally infected foxes in Alaska. The bears were more resistant than canine species, requiring at least 1,000 MLD50 of virus for infection. Low titres or negative results were obtained in salivary glands titrated in mice. Clinical course of the disease, post mortem findings, and microscopic lesions are described. Microscopic lesions were more· severe in brown bears, in which the inflammatory response was distinguished by the presence of numerous eosinophils in the perivascular infiltrate and among cells diffusely infiltrating the parenchyma. In both species, inclusion bodies were found only in the Purkinje cells of the cerebellum. Rabies is discounted as a factor in unprovoked attacks by bears on man at high latitudes. The epizootiology of rabies in a region where bears are numerous is discussed, with the conclusion that rabid foxes usually do not excrete sufficient quantities of virus in the saliva to infect bears. German title: Tollwut bei experimentell infizierten Bären, Ursus spp., mit epizootiologischen Anmerkungen German abtract: Zehn Schwarzbären, Ursus americanus Pallas, und drei Braunbären, U. arctos Linnaeus, wurden mit einem von Füchsen in Alaska isolierten Feldstamm des Tollwutvirus infiziert. Die Untersuchungsergebnisse lassen erkennen, daß Bären eine größere Resistenz gegenüber Tollwutinfektion aufweisen als hundeartige Karnivoren, und zwar konnten sie nicht mit weniger als 1000 MLD50 des Tollwutvirus infiziert werden. Das Virus war selten nachweisbar in den Speicheldrüsen der tollwuterkrankten Bären. Klinik und Pathologie der Tollwut bei Bären wurden kurz beschrieben. Die im Gehirn vorkommenden entzündlichen Veränderungen waren bei Braunbären besonders schwer und unterschieden sich durch die Häufigkeit der eosinophilen Leukozyten in den perivasculären und Gewebs-Infiltraten. Bei beiden Arten wurden Einschlußkörperchen nur in den Purkinje-Zellen beobachtet. Die Epizootiologie der Tollwut auf der Alaska-Halbinsel, wo Bären häufig vorkommen, wurde besprochen. Die Ergebnisse deuten an, daß Füchse wenig Virus mit dem Speichel ausscheiden, und selten soviel, daß es für die Infektion von Bären ausreicht. French title: La rage expérimentale chez les ours, Ursus spp., avec observations épizootiologiques French abstract: Dix ours noirs, Ursus americanus Pallas, et trois ours bruns, U. arctos Linnaeus, ont été inoculés avec de virus rabique provenant des renards infectés naturellement dans l'Alaska. Les ours Ont été plus résistants au virus que des espèces canines, et pour produire l'infection chez les ours, au moins 1000 MLD50 ont été requis. La titration des glandes salivaires chez des souris a données des titres peu éléves ou des résultats négatifs. La course clinique de la maladie, les observations des autopsies, et les lésions microscopiques sont decrites. Les lésions microscopiques les plus sévères ont été observées chez les ours bruns, dans lesquels la réponse inflammatoire a été distinguée par la présence de nombreux éosinophiles dans l'infiltration périvasculaire et parmi les cellules infiltrées diffusément dans Ie parenchyme. Chez les deux espèces des ours, des corps d'inclusion ont été trouvés seulement dans les cellules de Purkinje du cervelet. On a discuté l'épizootiologie de la rage dans une région où des ours sont nombreux, avec la conclusion qu'il y a dans la salive des renards rabiques une quantité de virus insuffisante pour infecter les ours. é ó í á ú Spanish title: Rabia en osos, Ursus spp., infectados experimentalmente, con anotaciones epizootológicas Spanish abstract: Diez osos negros, Ursus americanus Pallas, y tres osos pardos, U. arctos Linea, se infectaron con una estirpe campal de virus rábico aislada de zorros en Alasca. Los resultados de la experiencia permiten reconocer que los osos presentan una resistencia mayor frente a la infección rábica que los carnívoros cánidos, pues no se pudieron infectar con menos de 1.000 DML50 de virus rábico. El virus era muy raras veces identificable en las glándulas salivales de los osos enfermos de rabia. Se describen sucintamente la clínica y patología de la rabia en los osos. Las modificaciones inflamatorias en el cerebro eran muy graves en el oso pardo y se distinguían por la frecuencia de los leucocitos eosinófilos en los infiltrados perivasculares e hísticos. En ambas especies solo se hallaron corpúsculos de inclusión en las células de Purkinje. Se discute la epizootología de la rabia en la península de Alasca, donde es frecuente Ia presencia de osos. Los resultados señalan que los zorros eliminan poco virus con la saliva y casi nunca en cantidad tal que fuese suficiente para infectar los osos.

An Ecological Study of Helminths of Some Wyoming Voles (Microtus spp.) with a Description of a New Species of Nematospiroides (Heligmosomidae: Nematoda)

An ecological and taxonomic study of the helminth parasites of voles (Microtus spp.) in the Jackson Hole region of Wyoming is reported. Nematospiroides microti n. sp. from Microtus montanus nanus and M. richardsoni macropus is described and figured. A cestode, Paranoplocephala infrequens, and a nematode, Syphacia obvelata, were generally distributed throughout the region in all habitats except the sage flats. A trematode, Quinqueserialis hassalli, was recovered only from voles collected near streams at low altitudes. This was presumably due to the localized distribution of the molluscan intermediate host. Four helminths, viz., Hymenolepis horrida, Heligmosomum costellatum, Nematospiroides microti and Trichuris opaca, were restricted in their distribution to the alpine and sub-alpine meadows. Of these parasites, H. horrida and H. costellatum are reported for the first time from North America. Most of the other host and locality records are new. Available data indicate that host specificity was not a factor in restricting the distribution of parasites. Although the greatest numbers of parasites, both qualitative and quantitative, occurred in habitats where host density was greatest, it seems unlikely that host density is the only factor involved.

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.

The Taxonomic Value and Variability of Certain Structures in the Cestode Genus Echinococcus (Rudolphi, 1801) and a Review of Recognized Species

Although cestodes of the genus Echinococcus have been much studied in the past, there is need for an evaluation of these morphological characters used as the basis for species differentiation. The generous cooperation of other investigators in providing necessary foreign material and the results of nearly five years of field work in Alaska make possible such a study. It is the purpose of the paper to evaluate morphological characters used at the species level to differentiate these cestodes, and to review the status of species currently considered valid.