Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Mammals

  • adult mammal
  • american mammal
  • australian mammal
  • endangered mammal
  • eutherian mammal
  • female mammal
  • forest mammal
  • large mammal
  • larger mammal
  • marine mammal
  • neotropical mammal
  • non-volant mammal
  • north american mammal
  • other mammal
  • placental mammal
  • polygynous mammal
  • small mammal
  • terrestrial mammal
  • wild mammal

  • Terms modified by Mammals

  • mammal abundance
  • mammal assemblage
  • mammal community
  • mammal fauna
  • mammal population
  • mammal prey
  • mammal species
  • mammal species richness

  • Selected Abstracts


    Michael Moore
    Abstract Rehabilitation of stranded marine mammals elicits polarized attitudes: initially done alongside display collections, but release of rehabilitated animals has become more common. Justifications include animal welfare, management of beach use conflict, research, conservation, and public education. Rehabilitation cost and risks have been identified that vary in degree supported by data rather than perception. These include conflict with fisheries for resources, ignorance of recipient population ecology, poor understanding of long-term survival, support of the genetically not-so-fit, introduction of novel or antibiotic-resistant pathogens, harm to human health, and cost. Thus facilities must balance their welfare appeal against public education, habitat restoration, human impact reduction, and other conservation activities. Benefits to rehabilitating marine mammals are the opportunity to support the welfare of disabled animals and to publish good science and so advance our understanding of wild populations. In specific cases, the status of a population may make conservation the main reason for rehabilitation. These three reasons for rehabilitation lead to contrasting, and sometimes conflicting, management needs. We therefore outline a decision tree for rehabilitation managers using criteria for each management decision, based on welfare, logistics, conservation, research, and funding to define limits on the number of animals released to the wild. [source]


    Abigail K. Caudron
    First page of article [source]


    Gerald L. Kooyman
    Presented on 12 December 2005 San Diego, California Abstract This paper reviews past and current work on diving behavior, effects of pressure, and the aerobic diving limit from the perspective of the Ken Norris Lifetime Achievement Award. Because of the influence of Norris to marine mammalogy in general, and to my career in particular, I want to emphasize the important tradition of mentors and colleagues as keystones to a successful career in science, and ultimately to the success of science itself. These two related activities are illustrated by studies on marine mammals that were conducted in an endeavor to understand: (1) the behavioral traits associated with deep diving, (2) the mechanical and physiological effects of pressure during routine dives to great depth, and (3) the degree of oxygen depletion that they routinely endure while diving. The search for answers has resulted in numerous physiological and ecological experiments, along with accompanying theoretical analyses. Currently it appears that some deep-diving mammals may suffer from bends, and some may resort more often than what seems physiologically possible to anaerobic metabolism while diving. Above all, the way divers manage their nitrogen and oxygen stores remains a mystery. [source]


    Douglas P. Nowacek


    PALAEONTOLOGY, Issue 5 2008
    Abstract:, The extinct, Cretaceous,Paleogene Gondwanatherians have previously been considered to be early xenarthrans, multituberculates and more recently Mammalia incertae sedis. However, the phylogenetic relationships of Gondwanatheria have yet to be resolved. In this paper, additional dental specimens of the gondwanatherian Sudamerica ameghinoi from the Early Paleocene Salamanca Formation of Argentina are described. These specimens provide additional information on Gondwanatheria affinities, sudamericid morphology and help support earlier hypotheses on Sudamerica dental formula and tooth categories. Sudamericid dental functional morphology and body mass estimates, based on measurements of isolated teeth, are inferred. Dental morphology such as hypsodonty, enamel microstructure and crown features do support a robust clade for Sudamericidae. [source]

    Early ontogeny and placentation of the grey short-tailed opossum, Monodelphis domestica (Didelphidae: Marsupialia): contribution to the reconstruction of the marsupial morphotype

    This study provides new findings on the placenta of Monodelphis domestica and a reconstruction of the marsupial morphotype. To achieve this, early ontogeny and placentation of the grey short-tailed opossum, M. domestica, from 3 h after copulation until birth (day 15), were studied and compared with other mammals. Both the ultrastructure and histochemistry of egg membranes, foetal membranes, oviduct and uterus were examined. The results of this study provide the first detailed ultrastructural description of a trophoblastic syncytium in a marsupial. In addition, this is the first original documentation of an invasive trophectoderm and an inflammatory reaction at parturition in M. domestica. These findings were compared with literature data and included into the reconstruction of the marsupial morphotype. Based on marsupial phylogeny as proposed by Luckett (J. Mammal. Evol. 2, 255,283, 1994), characters that are consistent at least within didelphids and dasyurids were determined to be characters of the marsupial morphotype. These characters are a central yolk separated from the peripheral yolk-poor cytoplasm in the unfertilized oocyte, the presence of a zona pellucida, a mucoid coat and a shell coat, the absence of a corona radiata, oviductal mucoid secretion, no shell secretion distal to the isthmus of the oviduct, uterine shell secretion, a short tubal passage (1 day at maximum), the apposition of blastomeres to the zona pellucida prior to intercellular association, the absence of a morula stage, the polarity of the zygotic yolk, the localized segmentation of deutoplasm (yolk) during the first cleavage and subsequent extrusion of yolk vesicles during the first two cleavage stages. With regard to the marsupial morphotype, the non-polarized yolk distribution in the zygote [Hartman (J. Morphol. 27, 1,84, 1916); McCrady (Am. Anat. Mem. 16, 1,233, 1938)] is a derived character of Didelphis virginiana. Didelphis virginiana [Hartman (J. Morphol. 27, 1,84, 1916); Hartman (J. Morphol. 32, 1,139, 1919); McCrady (Am. Anat. Mem. 16, 1,233, 1938)] and Didelphis marsupialis (Hill, Q. J. Micr. Sci. 63, 91,139, 1918) share the synapomorphous reduction of deutoplasmolysis to a generalized extrusion of vesicles. The absence of separated yolk and consequently a cleavage without yolk extrusion (Renfree and Lewis, Reprod. Fert. Dev. 8, 725,742, 1996) are apomorphies of macropodids. This is possibly correlated with the association of blastomeres in early cleavage stages (Renfree and Lewis, Reprod. Fert. Dev. 8, 725,742, 1996). A yolk sac placenta and a vascularized allantochorion can be assumed for part of the ontogeny in the marsupial morphotype, irrespective of the formation of an allantoic placenta at near term stages. The character polarization of the mode of placentation and parturition needs further investigation. Frühe Ontogenie und Plazentation der grauen Hausspitzmausbeutelratte, Monodelphis domestica (Didelphidae: Marsupialia): Ein Beitrag zur Rekonstruktion des Grundplans der Marsupialia Die vorliegende Arbeit beschreibt die frühe Ontogenese und Plazentation von 3 Stunden nach der Kopulation bis zur Geburt der Beutelratte Monodelphis domestica. Es wird die Ultrastruktur und Histochemie der Eihäute, der Fetalmembranen, des Oviductes und des Uterus beschrieben. Erstmalig wird die Ultrastruktur eines trophoblastischen Syncytiums bei einem Beuteltier beschrieben. Weiterhin wird ein invasives Trophektoderm und eine Entzündungsreaktion zum Zeitpunkt der Geburt bei M. domestica festgestellt. Die Befunde dieser Studie und Literaturdaten werden verglichen und in eine Grundplanrekonstruktion integriert. Merkmale, die mindestens zwischen Vertretern der Didelphidae und Dasyuridae übereinstimmen, werden basierend auf dem phylogenetischen System der Marsupialia nach Luckett, J. Mammal. Evol. 2, 255,283, 1994, für den Grundplan der Marsupialia angenommen. Diese Merkmale sind zentral separierter Dotter und peripheres dotterarmes Zytoplasma in der unbefruchteten Eizelle, das Vorhandensein von Zona pellucida, Mucoidschicht und Schalenhaut, das Fehlen einer Corona radiata, die Mucoidsekretion durch den Oviduct, die Schalensekretion durch den Uterus und nicht distal der Isthmusregion des Oviductes, eine kurze Tubenwanderung (maximal einen Tag), die Anlagerung der Blastomeren an die Zona pellucida vor der interzellulären Verbindung, das Fehlen eines Morulastadiums, die Dotterpolarität in der Zygote, die lokale Dotterabtrennung bei der ersten Teilung und die anschließende Dotterextrusion während der ersten beiden Teilungen. In Bezug auf den Grundplan der Marsupialia ist die unpolare Dotterverteilung in der Zygote ein abgeleitetes Merkmal von Didelphis virginiana. Didelphis virginiana und Didelphis marsupialis teilen als Synapomorphie die Reduktion der Deutoplasmolyse auf eine generelle Vesikelextrusion. Das Fehlen separierten Dotters in der Oocyte und die resultierende Furchung ohne Dotterextrusion [Renfree and Lewis, Reprod. Fert. Dev. 8, 725,742, 1996] ist eine Apomorphie der Macropodidae. Hiermit hängt möglicherweise die frühe Zusammenlagerung der Blastomeren zusammen [Renfree and Lewis, Reprod. Fert. Dev. 8, 725,742, 1996]. Ein vaskularisiertes Allantochorion und eine Dottersackplazenta können für einen Teil der Ontogenese im Grundplan der Marsupialia angenommen werden. Ob das Allantochorion neben der Respiration auch dem Stoffaustausch diente ist unklar. Die Lesrichtung für den Modus der Plazentation und der Geburt bedarf weiterer Untersuchungen. [source]

    A New Symmetrodont Mammal with Fur Impressions from the Mesozoic of China

    Guillermo W. ROUGIER
    Abstract, Western Liaoning of northeastern China is world-renowned for the Mesozoic Jehol biota, especially for yielding many feathered dinosaurs, primitive birds, mammals and fossil angiosperm. This paper describes a complete specimen of a symmetrodont mammal with well-preserved hairs and soft tissue from the basal part of the Yixian Formation in the Sihetun area, Beipiao, western Liaoning. It is significant for understanding the morphology, osteology, phylogeny and life habits of Mesozoic symmetrodont mammals. [source]

    What Is Known about Mountain Goats and a Model for Studying Large Mammals

    Jon E. Swenson
    No abstract is available for this article. [source]

    Summary and Synthesis for Neotropical Mammals

    Rurik List
    No abstract is available for this article. [source]

    Body Size and Risk of Extinction in Australian Mammals

    Marcel Cardillo
    For Australian terrestrial mammals this link is of particular interest because it is widely believed that species in the intermediate size range of 35,5500 g (the "critical weight range") have been the most prone to recent extinction. But the relationship between body size and extinction risk in Australian mammals has never been subject to a robust statistical analysis. Using a combination of randomization tests and phylogenetic comparative analyses, we found that Australian mammal extinctions and declines have been nonrandom with respect to body size, but we reject the hypothesis of a critical weight range at intermediate sizes. Small species appear to be the least prone to extinction, but extinctions have not been significantly clustered around intermediate sizes. Our results suggest that hypotheses linking intermediate body size with high risk of extinction in Australian mammals are misguided and that the focus of future research should shift to explaining why the smallest species are the most resistant to extinction. Resumen: El vínculo entre el tamaño del cuerpo y el riesgo de extinción ha sido el centro de mucha atención reciente. Para los mamíferos terrestres australianos este vínculo es de particular interés debido a que se cree ampliamente que las especies en un rango intermedio de tamaño de 35,5500 g (el rango de peso crítico) ha sido el más susceptible a extinciones recientes. Sin embargo, la relación entre extinciones, el tamaño y el riesgo de extinción en mamíferos australianos nunca ha sido sometida a un análisis estadístico robusto. Usando una combinación de pruebas aleatorizadas y análisis filogenéticos comparativos, encontramos que las extinciones y disminuciones de mamíferos australianos han sido no aleatorias con respecto al tamaño del cuerpo, pero rechazamos la hipótesis de un rango crítico a tamaños intermedios. Las especies pequeñas aparentan ser las menos susceptibles de extinción, pero las extinciones no se han agrupado significativamente alrededor de tamaños intermedios. Nuestros resultados sugieren que la hipótesis que vincula el tamaño intermedio de cuerpo con un alto riesgo de extinción en mamíferos australianos está mal planteada y que el centro de la investigación a futuro deberá enfocarse a explicar el porqué las especies más pequeñas son las más robustas a la extinción. [source]

    Patch Occupancy and Potential Metapopulation Dynamics of Three Forest Mammals in Fragmented Afromontane Forest in South Africa

    Michael J. Lawes
    We recorded patch occupancy of blue duiker ( Philantomba monticola), tree hyrax ( Dendrohyrax arboreus), and samango monkey (Cercopithecus mitis labiatus) in 199 forest patches. Their rarity is ascribed to the fragmentation and destruction of their forest habitat. Incidence functions, derived from presence and absence data, were formulated as generalized linear models, and environmental effects were included in the fitted logistic models. The small and mostly solitary hyrax and duiker persisted in smaller patches than the large and social monkey. Although this result follows expectations based on relative home-range sizes of each species, the incidence probability of the samango monkey was invariant with increasing isolation, whereas a gradual decrease with increasing isolation was observed for the hyrax and duiker. Group dynamics may inhibit dispersal and increase the isolation effect in social species such as samango monkeys. A mainland-island metapopulation model adequately describes patterns of patch occupancy by the hyrax and duiker, but the monkeys' poor dispersal ability and obvious area-dependent extirpation suggest that they exist in transient, nonequilibrium (declining) metapopulations. Through identification of large forest patches for careful protection and management, the survival of all three species,especially the monkey,could be prolonged. Because no functional metapopulation may exist for the monkey, however, this is an emergency measure. For the duiker and hyrax, larger patches should form part of a network of smaller and closer patches in a natural matrix. Resumen: Investigamos la persistencia de tres mamíferos forestales raros de tamaño mediano (2,9 kg) en los bosques fragmentados de cinturón de niebla Podocarpus en la región central de la provincia KwaZulu-Natal, Sudáfrica. Registramos la ocupación del duiker azul ( Philantomba monticola), el hyrax arborícola ( Dendrohyrax arboreus) y el mono samango (Cercopithecus mitis labiatus) en 199 parches forestales. Su rareza se atribuye a la fragmentación y destrucción de su hábitat forestal. Las funciones de incidencia, derivadas de datos de presencia y ausencia, fueron formuladas como modelos lineales generalizados, y los efectos ambientales fueron incluidos en los modelos logísticos ajustados. Los pequeños y mayormente solitarios hyrax y duiker persistieron en parches más pequeños que los monos, que son más grandes y más sociables. A pesar de que este resultado obedece a expectativas basadas en tamaños de rango de hogar relativos de cada especie, la probabilidad de incidencia del mono samango no cambió con un incremento en el aislamiento, mientras que una disminución gradual al crecer el aislamiento se observó en hyrax y duiker. Las dinámicas de grupos podrían inhibir la dispersión e incrementar el efecto de aislamiento en especies sociables como lo es el mono samango. Un modelo de metapoblación continente-isla describe adecuadamente los patrones de la ocupación de parches por hyrax y duiker; sin embargo, la pobre capacidad de dispersión de los monos y la obvia extirpación área-dependente sugiere que estos existen en metapoblaciones transitorias, desequilibradas (en disminución). Mediante la identificación de parches forestales grandes para la protección y manejo cuidadosos, la supervivencia de las tres especies ( pero especialmente la de los monos) podría ser prolongada. Sin embargo, debido a que no existen metapoblaciones funcionales de monos, esta es una medida de emergencia. Para el duiker y el hyrax, los parches grandes deberán formar parte de una red de parches más pequeños y más cercanos en una matriz natural. [source]

    A minor ,-tubulin essential for mammalian cell proliferation

    CYTOSKELETON, Issue 9 2008
    Rajat Bhattacharya
    Abstract Mammals use tubulin from multiple genes to construct microtubules. Some genes are expressed in a tissue specific manner, while others are expressed in almost all cell types. ,5-Tubulin is a minor, ubiquitous isoform whose overexpression was recently shown to disrupt microtubules. Using inhibitory RNA, we now report that suppression of ,5 production in both human and hamster cells blocks cell proliferation. Cells depleted of ,5 either trigger the mitotic checkpoint and undergo apoptosis; or they experience a transient mitotic block, a high incidence of lagging chromosomes, and progression into G1 without cytokinesis to become large, flat cells with elevated DNA content. Microtubules appear to be normally organized in cells depleted of ,5, but they are rich in acetylated ,-tubulin indicating that they may be more stable than normal. The results provide the first evidence that a specific isoform of ,-tubulin is required for mitosis. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source]

    Mammals of Russia and Adjacent Regions: Lagomorphs

    ACTA ZOOLOGICA, Issue 3 2010
    Irina Ruf
    No abstract is available for this article. [source]

    Individual Acoustic Variation in Fallow Deer (Dama dama) Common and Harsh Groans: A Source-Filter Theory Perspective

    ETHOLOGY, Issue 3 2007
    Elisabetta Vannoni
    Mammals are able to distinguish conspecifics based on vocal cues, and the acoustic structure of mammal vocalizations is directly affected by the anatomy and action of the vocal apparatus. However, most studies investigating individual patterns in acoustic signals do not consider a vocal production-based perspective. In this study, we used the source-filter model of vocal production as a basis for investigating the acoustic variability of fallow deer groans. Using this approach, we quantified the potential of each acoustic component to carry information about individual identity. We also investigated if cues to individual identity carry over among the two groan types we describe: common and harsh groans. Using discriminant function analysis, we found that variables related to the fundamental frequency contour and the minimum frequencies of the highest formants contributed most to the identification of a given common groan. Common groans were individually distinctive with 36.6% (53.6% with stepwise procedure) of groans assigned to the correct individual. This level of discrimination is approximately six times higher than that predicted by chance. In addition, univariate anovas showed significant inter-individual variation in the minimum formant frequencies when common and harsh groans were combined, suggesting that some information about individuality is shared between groan types. Our results suggest that the sound source and the vocal tract resonances act together to determine groan individuality and that enough variation exists to potentially allow individual recognition based on groans. [source]

    Germ Line Transformation of Mammals by Pronuclear Microinjection

    T. Rülicke
    The most popular approach for generating transgenic mammals is the direct injection of transgenes into one pronucleus of a fertilized oocyte. In the past 15 years microinjection has been successfully applied in laboratory as well as in farm animals. The frequency of transgenic founders, although highly different between the species, is efficient enough to render this technique applicable to a wide range of mammals. The expression levels and patterns of a transgene are initially influenced by the construction of the transgene. However, the overall phenotype of a transgenic organism is influenced by several genetic and environmental factors. Due to the features of this technique not all of the genetic factors can be experimentally controlled by the scientist. In this article we will emphasize some peculiarities which have to be taken into account for the successful performance of transgenesis by pronuclear microinjection [source]

    Development and characterization of an animal model of carnitine deficiency

    FEBS JOURNAL, Issue 6 2001
    Markus Spaniol
    Mammals cover their carnitine needs by diet and biosynthesis. The last step of carnitine biosynthesis is the conversion of butyrobetaine to carnitine by butyrobetaine hydroxylase. We investigated the effect of N -trimethyl-hydrazine-3-propionate (THP), a butyrobetaine analogue, on butyrobetaine hydroxylase kinetics, and carnitine biosynthesis and body homeostasis in rats fed a casein-based or a vegetarian diet. The Km of butyrobetaine hydroxylase purified from rat liver was 41 ± 9 µmol·L,1 for butyrobetaine and 37 ± 5 µmol·L,1 for THP, and THP was a competitive inhibitor of butyrobetaine hydroxylase (Ki 16 ± 2 µmol·L,1). In rats fed a vegetarian diet, renal excretion of total carnitine was increased by THP (20 mg·100 g,1·day,1 for three weeks), averaging 96 ± 36 and 5.3 ± 1.2 µmol·day,1 in THP-treated and control rats, respectively. After three weeks of treatment, the total carnitine plasma concentration (8.8 ± 2.1 versus 52.8 ± 11.4 µmol·L,1) and tissue levels were decreased in THP-treated rats (liver 0.19 ± 0.03 versus 0.59 ± 0.08 and muscle 0.24 ± 0.04 versus 1.07 ± 0.13 µmol·g,1). Carnitine biosynthesis was blocked in THP-treated rats (,0.22 ± 0.13 versus 0.57 ± 0.21 µmol·100 g,1·day,1). Similar results were obtained in rats treated with the casein-based diet. THP inhibited carnitine transport by rat renal brush-border membrane vesicles competitively (Ki 41 ± 3 µmol·L,1). Palmitate metabolism in vivo was impaired in THP-treated rats and the livers showed mixed steatosis. Steady-state mRNA levels of the carnitine transporter rat OCTN2 were increased in THP-treated rats in skeletal muscle and small intestine. In conclusion, THP inhibits butyrobetaine hydroxylase competitively, blocks carnitine biosynthesis in vivo and interacts competitively with renal carnitine reabsorption. THP-treated rats develop systemic carnitine deficiency over three weeks and can therefore serve as an animal model for human carnitine deficiency. [source]

    Mammals in South American drylands: faunal similarity and trophic structure

    GLOBAL ECOLOGY, Issue 2 2000
    Ricardo A. Ojeda
    Abstract We compared the fauna of small mammals (less than 500 g body weight) among five major South American drylands (Atacama, Altiplano, Monte, Patagonia and Caatinga) and found considerable heterogeneity and distinctiveness in species richness and composition between these biomes. From a total of 89 recorded species, 76 of them are restricted to only one of these drylands. The highland desert, or Altiplano, is the biome with the highest number of species. Despite the marked differences in the composition of the mammalian fauna, the trophic structure shows a rather consistent pattern: herbivores are the most important trophic group in all drylands. This consistency seems to be more the result of phylogenetic inertia than of similar ecological processes. Our results are compared with recent studies on desert small mammals across continents. [source]

    The Exploitation and Cultural Importance of Sea Mammals, Edited by Gregory G. Monks

    No abstract is available for this article. [source]

    Factors controlling the spatial species richness pattern of four groups of terrestrial vertebrates in an area between two different biogeographic regions in northern Spain

    David Nogués-Bravo
    Abstract Aim, To examine the influence of environmental variables on species richness patterns of amphibians, reptiles, mammals and birds and to assess the general usefulness of regional atlases of fauna. Location, Navarra (10,421 km2) is located in the north of the Iberian Peninsula, in a territory shared by Mediterranean and Eurosiberian biogeographic regions. Important ecological patterns, climate, topography and land-cover vary significantly from north to south. Methods, Maps of vertebrate distribution and climatological and environmental data bases were used in a geographic information systems framework. Generalized additive models and partial regression analysis were used as statistical tools to differentiate (A) the purely spatial fraction, (B) the spatially structured environmental fraction and (C) the purely environmental fraction. In this way, we can evaluate the explanatory capacity of each variable, avoiding false correlations and assessing true causality. Final models were obtained through a stepwise procedure. Results, Energy-related features of climate, aridity and land-cover variables show significant correlation with the species richness of reptiles, mammals and birds. Mammals and birds exhibit a spatial pattern correlated with variables such as aridity index and vegetation land-cover. However, the high values of the spatially structured environmental fraction B and the low values of the purely environmental fraction A suggest that these predictor variables have a limited causal relationship with species richness for these vertebrate groups. An increment in land-cover diversity is correlated with an increment of specific richness in reptiles, mammals and birds. No variables were found to be statistically correlated with amphibian species richness. Main conclusions, Although aridity and land-cover are the best predictor variables, their causal relationship with species richness must be considered with caution. Historical factors exhibiting a similar spatial pattern may be considered equally important in explaining the patterns of species richness. Also, land-cover diversity appears as an important factor for maintaining biological diversity. Partial regression analysis has proved a useful technique in dealing with spatial autocorrelation. These results highlight the usefulness of coarsely sampled data and cartography at regional scales to predict and explain species richness patterns for mammals and birds. The accuracy of models appears to be related to the range perception of each group and the scale of the information. [source]

    Epigenetic pre-patterning and dynamics during initial stages of mammalian preimplantation development

    Theodore P. Rasmussen
    Mammals, like all multicellular organisms, develop from a single cell,the totipotent zygote. During preimplantation development and subsequent development in utero, over 200 distinct cell types are established and integrated into the organ systems and tissues of the developing organism. Much of the field of mammalian developmental biology is devoted to investigation of mechanisms that govern the formation of complete organs and tissues. In contrast to later development, which consumes the vast majority of time associated with development in utero, preimplantation development and germ layer specification occur rapidly. Yet knowledge is limited regarding the regulatory mechanisms that specify the transient, but pluripotent, cellular lineages that form during the initial stages of mammalian development. Gametogenesis and preimplantation development are marked by dramatic and pervasive epigenetic changes rooted in chromatin dynamics. The fundamental mechanisms that specify subsequent cellular lineages of the conceptus are only now becoming understood, and tend to rely relatively heavily upon broad epigenetic mechanisms in addition to master transcription factors. This review considers epigenetic regulation in the very earliest stages of preimplantation development. In addition, recent advances which indicate that some epigenetic coding is imposed during gametogenesis and maintained during preimplantation development are considered. J. Cell. Physiol. 225: 333,336, 2010. © 2010 Wiley-Liss, Inc. [source]

    Evidence That Gonadotropin-Releasing Hormone II Is Not a Physiological Regulator of Gonadotropin Secretion in Mammals

    P. M. Gault
    Abstract Gonadotropin-releasing hormone (GnRH)-II stimulates luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion when administered at high doses in mammals, and this effect has been assumed to be mediated through the GnRH-II receptor expressed on gonadotropes. This study used two selective GnRH-I receptor antagonists to test the alternative hypothesis that GnRH-II acts through the GnRH-I receptor to elicit gonadotropin secretion. The antagonist, antide, was used to characterize the receptor-relay because it was a pure antagonist in vitro based on inositol phosphate responses in COS-7 cells transfected with either mammalian GnRH-I and GnRH-II receptors and, in vivo, potently antagonized the gonadotropin-releasing effect of a single injection of 250 ng GnRH-I in our sexually inactive sheep model. In a series of studies in sheep, antide (i) blocked the acute LH response to a single injection of GnRH-II (20 µg antide: 10 µg GnRH-II); (ii) blocked both the acute, pulsatile LH response and the FSH priming response to 2-hourly injections of GnRH-II over 36 h (100 µg antide/8 h: 4 µg GnRH-II/2 h); and (iii) chronically blocked both the pulsatile LH response and the marked FSH priming response to 4-hourly injections of GnRH-II over 10 days (75 µg antide/8 h: 4 µg GnRH-II/4 h). In two final experiments, the GnRH-I antagonist 135-18, shown previously to agonize the mammalian GnRH-II receptor, blocked the gonadotropin-releasing effects of GnRH-I (250 ng) but failed to elicit an LH response when given alone, and simultaneous administration of GnRH-II (250 ng) failed to alter the LH-releasing effect of GnRH-I (50,500 ng). These data thus support our hypothesis. Based on additional literature, it is unlikely that the GnRH-II decapeptide is a native regulator of the gonadotrope in mammals. [source]

    Marine Mammals: Evolutionary Biology

    M. S. Fischer
    No abstract is available for this article. [source]

    Support for a metapopulation structure among mammals

    MAMMAL REVIEW, Issue 3 2009
    ABSTRACT 1The metapopulation metaphor is increasingly used to explain the spatial dynamics of animal populations. However, metapopulation structure is difficult to identify in long-lived species that are widely distributed in stochastic environments, where they can resist extinctions. The literature on mammals may not provide supporting evidence for classic metapopulation dynamics, which call for the availability of discrete habitat patches, asynchrony in local population dynamics, evidence for extinction and colonization processes, and dispersal between local populations. 2Empirical evidence for metapopulation structure among mammals may exist when applying more lenient criteria. To meet these criteria, mammals should live in landscapes as discrete local breeding populations, and their demography should be asynchronous. 3We examined the literature for empirical evidence in support of the classical criteria set by Hanski (1999), and for the more lenient subset of criteria proposed by Elmhagen & Angerbjörn (2001). We suggest circumstances where metapopulation theory could be important in understanding population processes in mammals of different body sizes. 4The patchy distribution of large (>100 kg) mammals and dispersal often motivate inferences in support of a metapopulation structure. Published studies seldom address the full suite of classical criteria. However, studies on small mammals are more likely to record classic metapopulation criteria than those on large mammals. The slow turnover rate that is typical for medium-sized and large mammals apparently makes it difficult to identify a metapopulation structure during studies of short duration. 5To identify a metapopulation structure, studies should combine the criteria set by Hanski (1999) and Elmhagen & Angerbjörn (2001). Mammals frequently live in fragmented landscapes, and processes involved in the maintenance of a metapopulation structure should be considered in conservation planning and management. [source]

    Mammals, agri-environment schemes and set-aside , what are the putative benefits?

    MAMMAL REVIEW, Issue 4 2007
    ABSTRACT 1The impacts of agricultural intensification on farmland wildlife have been the subject of increasing concern, particularly over the last two decades. Population declines have occurred for a number of mammalian species, sometimes drastically so, and changes in farming practice are believed to be significant contributory factors. 2The major policy instruments for delivering environmental benefits on farmland are agri-environment schemes. These encourage farmers to adopt more environmentally sensitive farming practices to promote farmland biodiversity. Additionally, compulsory set-aside, which reduces agricultural surplus, could also have positive impacts on wildlife. In this paper we consider some of the putative benefits of agri-environment schemes and set-aside for mammals. 3We review how establishment and management options within agri-environment schemes and set-aside might affect habitat resources for mammals. For example, conservation headlands increase plant and invertebrate resources within the crop edge for mammals such as wood mice. Grassy field margins can support communities of smaller mammals, and hedgerows may act as important commuting and hunting routes. Their potential will depend on factors such as seed mixtures used, timing and severity of cutting, and length of time they have been in place. 4At a farm level, habitat heterogeneity may be increased through organic agriculture, which is supported by some agri-environment schemes. Studies suggest significant benefits to mammals, including wood mice and bats. However, it is increasingly recognized that effective conservation of farmland mammals must seek solutions at the landscape scale, addressing such issues as habitat connectivity between farms. One approach may be the better targeting of scheme agreements. 5We suggest that agri-environment schemes and set-aside can contribute to the conservation of mammals on farmland. Recent policy changes are likely to have further positive impacts on farmland wildlife but appropriate mammal monitoring programmes must be developed rigorously to assess their effects. [source]

    Intraperitoneal Insemination in Mammals: A Review

    JL Yaniz
    Contents This review focuses on factors associated with the development of intraperitoneal insemination in mammals. Findings to date indicate that fertility improves as the sperm cell concentration rises, but that the optimal sperm number differs in each species. Sperm washing before intraperitoneal insemination favours fertility. Peritoneal fluid shows a variable effect on spermatozoa, depending on the hormonal status of the female. The optimal time for insemination appears to be just prior to ovulation. The technique may be performed either through the abdominal or the vaginal wall. Verification of sperm deposition in the proximity of the ovaries improves fertility rates. Although associated with some risk of infection and an immune reaction against spermatozoa, the intraperitoneal technique rarely gives rise to severe anaphylactic shock, peritonitis, adhesion formation and the production of anti-sperm antibodies and these complications may be prevented by adequate sperm pretreatment and antibiotic therapy. The success of intraperitoneal insemination in humans, with results comparable with those of intrauterine insemination in the treatment of infertility, suggest the potential use of this technique in domestic mammals, especially in those in which intrauterine insemination poses practical difficulties. Some of the methods applied in human intraperitoneal insemination, such as confirming the position of the needle in the peritoneal cavity, and sperm pre-treatments might also improve results in domestic species. Conversely, the use of the animal model should help to develop some aspects of this technique in humans. [source]

    A Note on Langerhans Cells in the Oesophagus Epithelium of Domesticated Mammals

    W. Meyer
    With 3 figures Summary Using the zinc-iodide osmium tetroxide (ZIO) method, TEM and immunohistochemistry (for CD1a and langerin), the study demonstrates Langerhans cells in the oesophageal epithelium of domesticated mammals (herbivores: horse, cattle, goat; omnivores: pig, dog, laboratory rat; carnivores: cat), although with variations between the species. The ZIO method and TEM showed this cell type in the cat and, sporadically, in the horse; CD1a (+) Langerhans cells were demonstrated in the ovine, porcine and murine oesophagus. Positive staining for langerin was detected in single cells of the caprine, canine, murine and feline oesophagus and more distinct in almost all the cell layers of the equine and porcine oesophagus epithelium. The findings are discussed comparing specifically the results for CD1a and langerin, whereby the latter C-type lectin may be of importance in species with a rather thick oesophagus epithelium, such as that present in the plantivorous and most of the omnivorous animals, where antigenic pressure is reduced. [source]

    Introduced Mammals of the World: Their History, Distribution and Influence

    AUSTRAL ECOLOGY, Issue 2 2005
    No abstract is available for this article. [source]

    Australian Mammals: Biology and Captive Management

    AUSTRAL ECOLOGY, Issue 1 2005
    No abstract is available for this article. [source]

    BOOK REVIEW: Parasitic Diseases of Wild Mammals

    PJ Duignan
    No abstract is available for this article. [source]

    X-chromosome upregulation and inactivation: two sides of the dosage compensation mechanism in mammals

    BIOESSAYS, Issue 1 2009
    Elena V. Dementyeva
    Abstract Mammals have a very complex, tightly controlled, and developmentally regulated process of dosage compensation. One form of the process equalizes expression of the X-linked genes, present as a single copy in males (XY) and as two copies in females (XX), by inactivation of one of the two X-chromosomes in females. The second form of the process leads to balanced expression between the X-linked and autosomal genes by transcriptional upregulation of the active X in males and females. However, not all X-linked genes are absolutely balanced. This review is focused on the recent advances in studying the dosage compensation phenomenon in mammals. [source]