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Marina B. Blanco - One of the best experts on this subject based on the ideXlab platform.
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Conservation genomic analysis reveals ancient introgression and declining levels of genetic diversity in Madagascar’s hibernating Dwarf Lemurs
Heredity, 2019Co-Authors: Rachel C Williams, Marina B. Blanco, Jelmer W. Poelstra, Kelsie E. Hunnicutt, Aaron A. Comeault, Anne D. YoderAbstract:Madagascar's biodiversity is notoriously threatened by deforestation and climate change. Many of these organisms are rare, cryptic, and severely threatened, making population-level sampling unrealistic. Such is the case with Madagascar's Dwarf Lemurs (genus Cheirogaleus), the only obligate hibernating primate. We here apply comparative genomic approaches to generate the first genome-wide estimates of genetic diversity within Dwarf Lemurs. We generate a reference genome for the fat-tailed Dwarf Lemur, Cheirogaleus medius, and use this resource to facilitate analyses of high-coverage (~30×) genome sequences for wild-caught individuals representing species: C. sp. cf. medius, C. major, C. crossleyi, and C. sibreei. This study represents the largest contribution to date of novel genomic resources for Madagascar's Lemurs. We find concordant phylogenetic relationships among the four lineages of Cheirogaleus across most of the genome, and yet detect a number of discordant genomic regions consistent with ancient admixture. We hypothesized that these regions could have resulted from adaptive introgression related to hibernation, indeed finding that genes associated with hibernation are present, though most significantly, that gene ontology categories relating to transcription are over-represented. We estimate levels of heterozygosity and find particularly low levels in an individual sampled from an isolated population of C. medius that we refer to as C. sp. cf. medius. Results are consistent with a recent decline in effective population size, which is evident across species. Our study highlights the power of comparative genomic analysis for identifying species and populations of conservation concern, as well as for illuminating possible mechanisms of adaptive phenotypic evolution.
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Conservation genomic analysis reveals ancient introgression and declining levels of genetic diversity in Madagascar's hibernating Dwarf Lemurs.
Heredity, 2019Co-Authors: Rachel C Williams, Marina B. Blanco, Jelmer W. Poelstra, Kelsie E. Hunnicutt, Aaron A. Comeault, Anne D. YoderAbstract:Madagascar's biodiversity is notoriously threatened by deforestation and climate change. Many of these organisms are rare, cryptic, and severely threatened, making population-level sampling unrealistic. Such is the case with Madagascar's Dwarf Lemurs (genus Cheirogaleus), the only obligate hibernating primate. We here apply comparative genomic approaches to generate the first genome-wide estimates of genetic diversity within Dwarf Lemurs. We generate a reference genome for the fat-tailed Dwarf Lemur, Cheirogaleus medius, and use this resource to facilitate analyses of high-coverage (~30×) genome sequences for wild-caught individuals representing species: C. sp. cf. medius, C. major, C. crossleyi, and C. sibreei. This study represents the largest contribution to date of novel genomic resources for Madagascar's Lemurs. We find concordant phylogenetic relationships among the four lineages of Cheirogaleus across most of the genome, and yet detect a number of discordant genomic regions consistent with ancient admixture. We hypothesized that these regions could have resulted from adaptive introgression related to hibernation, indeed finding that genes associated with hibernation are present, though most significantly, that gene ontology categories relating to transcription are over-represented. We estimate levels of heterozygosity and find particularly low levels in an individual sampled from an isolated population of C. medius that we refer to as C. sp. cf. medius. Results are consistent with a recent decline in effective population size, which is evident across species. Our study highlights the power of comparative genomic analysis for identifying species and populations of conservation concern, as well as for illuminating possible mechanisms of adaptive phenotypic evolution.
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Conservation genomic analysis reveals ancient introgression and declining levels of genetic diversity in Madagascar’s hibernating Dwarf Lemurs
2019Co-Authors: Rachel C Williams, Marina B. Blanco, Jelmer W. Poelstra, Kelsie E. Hunnicutt, Aaron A. Comeault, Anne D. YoderAbstract:Abstract Madagascar’s biodiversity is notoriously threatened by deforestation and climate change. Many of these organisms are rare, cryptic, and severely threatened, making population-level sampling unrealistic. Such is the case with Madagascar’s Dwarf Lemurs (genus Cheirogaleus), the only obligate hibernator within the primates. We here apply comparative genomic approaches to generate the first genome-wide estimates of genetic diversity within species of Cheirogaleus. We generate a reference genome for the fat-tailed Dwarf Lemur, Cheirogaleus medius, and use this resource to facilitate analyses of high-coverage (~30x) genomes for wild-caught individuals representing four Dwarf Lemur species: Cheirogaleus sp. cf. medius, C. major, C. crossleyi and C. sibreei. This study therefore represents the largest contribution to date of novel genomic resources for Madagascar’s Lemurs. We show that phylogenetic relationships among the four lineages of Cheirogaleus demonstrate broad-scale concordance across the genome, and yet we detect a number of discordant genomic regions. Using the size distribution of introgressed regions, we estimate that admixture, and subsequent introgression, occurred between species an average of 4.1 Mya. Introgressed regions contain genes associated with hibernation, though most significantly, show over-represented gene ontology categories relating to transcription. Finally, we estimate levels of heterozygosity and find particularly low levels in an individual sampled from an isolated population of C. medius that we refer to as C. sp. cf. medius. Our study highlights the power of comparative genomic analysis for identifying species and populations of conservation concern, as well as for illuminating possible mechanisms of adaptive phenotypic evolution - in this case, hibernation.
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Transcriptomics in the wild: Hibernation physiology in free-ranging Dwarf Lemurs.
Molecular ecology, 2018Co-Authors: Sheena L. Faherty, Marina B. Blanco, José Luis Villanueva-cañas, M. Mar Albà, Anne D. YoderAbstract:Hibernation is an adaptive strategy some mammals use to survive highly seasonal or unpredictable environments. We present the first investigation on the transcriptomics of hibernation in a natural population of primate hibernators: Crossley's Dwarf Lemurs (Cheirogaleus crossleyi). Using capture-mark-recapture techniques to track the same animals over a period of 7 months in Madagascar, we used RNA-seq to compare gene expression profiles in white adipose tissue (WAT) during three distinct physiological states. We focus on pathway analysis to assess the biological significance of transcriptional changes in Dwarf Lemur WAT and, by comparing and contrasting what is known in other model hibernating species, contribute to a broader understanding of genomic contributions of hibernation across Mammalia. The hibernation signature is characterized by a suppression of lipid biosynthesis, pyruvate metabolism and mitochondrial-associated functions, and an accumulation of transcripts encoding ribosomal components and iron-storage proteins. The data support a key role of pyruvate dehydrogenase kinase isoenzyme 4 (PDK4) in regulating the shift in fuel economy during periods of severe food deprivation. This pattern of PDK4 holds true across representative hibernating species from disparate mammalian groups, suggesting that the genetic underpinnings of hibernation may be ancestral to mammals.
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two new species of sucking lice phthiraptera anoplura polyplacidae from endangered hibernating Lemurs primates cheirogaleidae
Journal of Medical Entomology, 2017Co-Authors: Lance A Durden, Marina B. Blanco, Matthew H SeaboltAbstract:: Lemurpediculus robbinsi sp. nov. is described from Crossley's Dwarf Lemur, Cheirogaleus crossleyi A. Grandidier, and Lemurpediculus claytoni sp. nov. is described from Sibree's Dwarf Lemur, Cheirogaleus sibreei Forsyth Major, from Madagascar. Both sexes of each new louse species are illustrated and distinguished from the two previously known species of Lemurpediculus: L. verruculosus (Ward) and L. petterorum Paulian. With the addition of two new species to the genus, an amended description of Lemurpediculus is provided. The two hosts of the new louse species are morphologically similar, endangered, obligately hibernating Lemurs. These two species of Lemurs are sometimes sympatric in rainforests in eastern Madagascar. Despite the morphological similarity of the two host species, their lice are morphologically distinct and are easiest to identify based on the shape of the subgenital plate of the female and the shape of the genitalia in the male. Both new species of lice should be considered to be endangered because their hosts are endangered. It is not known if either of the new species of lice are vectors of pathogens or parasites to their hosts.
Alexandra E. Müller - One of the best experts on this subject based on the ideXlab platform.
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Biology of the fat‐tailed Dwarf Lemur (Cheirogaleus medius E.Geoffroy 1812): New results from the field
Evolutionary Anthropology, 2003Co-Authors: Alexandra E. Müller, Urs ThalmannAbstract:The two currently recognized Dwarf Lemur species of the genus Cheirogaleus—the fat-tailed Dwarf Lemur (C. medius, Fig. 1) and the greater Dwarf Lemur (C. major)—belong to the family Cheirogaleidae. All cheirogaleids are arboreal and strictly nocturnal, forage solitarily, and weigh between 30–600 g.1–3 Until very recently, Dwarf Lemurs were poorly studied. Knowledge of their biology was based on occasional field observations,1,4 two short-term field studies,2,5 and investigations in captivity.6–11 Longer-term studies on general aspects of the biology of Cheirogaleus were lacking until the late 1990s, when two field studies on C. medius were carried out at Ampijoroa Forestry Station in northwestern Madagascar12–15 and in the Kirindy Forest in western Madagascar.16–18 While there is still only sparse information on the biology of C. major, our knowledge of C. medius has increased significantly in the last several years. Here, we present a summary of what is known to date about the biology of the fat-tailed Dwarf Lemur.
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biology of the fat tailed Dwarf Lemur cheirogaleus medius e geoffroy 1812 new results from the field
Evolutionary Anthropology, 2003Co-Authors: Alexandra E. Müller, Urs ThalmannAbstract:The two currently recognized Dwarf Lemur species of the genus Cheirogaleus—the fat-tailed Dwarf Lemur (C. medius, Fig. 1) and the greater Dwarf Lemur (C. major)—belong to the family Cheirogaleidae. All cheirogaleids are arboreal and strictly nocturnal, forage solitarily, and weigh between 30–600 g.1–3 Until very recently, Dwarf Lemurs were poorly studied. Knowledge of their biology was based on occasional field observations,1,4 two short-term field studies,2,5 and investigations in captivity.6–11 Longer-term studies on general aspects of the biology of Cheirogaleus were lacking until the late 1990s, when two field studies on C. medius were carried out at Ampijoroa Forestry Station in northwestern Madagascar12–15 and in the Kirindy Forest in western Madagascar.16–18 While there is still only sparse information on the biology of C. major, our knowledge of C. medius has increased significantly in the last several years. Here, we present a summary of what is known to date about the biology of the fat-tailed Dwarf Lemur.
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Social Organization of the Fat-Tailed Dwarf Lemur (Cheirogaleus Medius) in Northwestern Madagascar
New Directions in Lemur Studies, 1999Co-Authors: Alexandra E. MüllerAbstract:The strictly nocturnal Dwarf Lemurs(Cheirogaleus)are extraordinary among primates in showing extensive torpor phases during the austral winter, which is thought to be an adaptation to seasonal variation in food availability. The Fat-tailed Dwarf Lemur(C. medius)is found throughout the west and south of Madagascar and enters torpor for six to eight months. Such a long period of dormancy may influence their social organization. A 20-month field study carried out at the Station Forestiure d’ Ampijoroa revealed a monogamous social pattern forC. medius.
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Aspects of social life in the fat-tailed Dwarf Lemur (Cheirogaleus medius): inferences from body weights and trapping data.
American journal of primatology, 1999Co-Authors: Alexandra E. MüllerAbstract:Body weight is an important attribute of any animal and influences its biology in many ways. In the case of the fat-tailed Dwarf Lemur (Cheirogaleus medius), this is of special interest because animals of this species store fat to survive extended torpor phases during the austral winter and, as a result, show extreme seasonal variation in body weight. In this paper, I present field data from a 20-month study at the Forestry Station of Ampijoroa in northwestern Madagascar on body weights of repeatedly trapped individuals combined with trapping results to investigate the general biology and notably the social life of C. medius. The most remarkable physical characteristic of wild C. medius is a dramatic weight-loss in males in September following emergence from torpor. Trapping results showed that adult males emerge from torpor earlier than females and offspring, even though food is still scarce. Early emergence from torpor puts males at an energetic disadvantage and confers no advantage in terms of access to females. Observation data from nightly follows indicate that males patrol their home range, probably to guarantee its integrity for the coming active season and to secure the food supply for their families. The high energetic costs of this strategy is argued to represent a form of paternal investment. Body weight data of repeatedly captured individuals showed that they may reach adult size and sexual maturity at 2 years of age but are not socially mature before the age of 3 years. The data presented may serve as a guide for keeping C. medius at a suitable weight in captivity.
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a preliminary report on the social organisation of cheirogaleus medius cheirogaleidae primates in north west madagascar
Folia Primatologica, 1998Co-Authors: Alexandra E. MüllerAbstract:Key WordsLemuriformes · Madagascar · Nocturnal prosimians · Cheirogaleus medius ·Dwarf Lemur · Radio-tracking · Social organisation · Solitary speciesIntroductionBoth currently recognised species of the genus Cheirogaleus, C. majorand C.medius, are notable for seasonal storage of fat (especially in the tail) and for extendedtorpor phases during the austral winter, i.e. the dry season [1, 2]. The fat-tailed DwarfLemur, C. medius, has been reported to hibernate for 6–8 months and such a longperiod would inevitably have a major influence on social organisation [2]. Firstly, theanimals have only a few months to reproduce and rear offspring. Secondly, the ani-mals have to ensure sufficient fat storage to survive during the following dry season.To date, knowledge of the ecology and behaviour of C. mediushas been based onoccasional field observations [1–3], a few longer-term studies [4], investigations incaptivity [for citations see 2, 5, 6] and zoo reports [7], but social organisation has sofar been poorly documented [2, 8].Inferences concerning the social organisation of nocturnal prosimians can bemade from range overlap between individuals, associations within ranges (at particu-lar sleeping sites) and patterns of dispersal of individuals from their natal areas [9].For C. medius , Hladik et al. [4] determined individual ranges with a maximal diameterof 200 m and a population density of 300–400 animals/km
Peter M. Kappeler - One of the best experts on this subject based on the ideXlab platform.
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Mouse Lemurs in an Assemblage of Cheirogaleid Primates in Menabe Central, Western Madagascar – Three Reasons to Coexist
Frontiers in Ecology and Evolution, 2021Co-Authors: Livia Schäffler, Peter M. Kappeler, John M. HalleyAbstract:Ecological communities are structured by interactions between coexisting species that mutually influence their distribution and abundance. Ecologically similar species are expected to exclude one another from suitable habitat, so the coexistence of two mouse Lemur species in an assemblage of several closely related cheirogaleid primates in the central Menabe region of Madagascar requires explanation. We assessed the occurrence of Madame Berthe’s mouse Lemurs (Microcebus berthae) and Gray mouse Lemurs (Microcebus murinus), and of two larger cheirogaleids, Coquerel’s giant mouse Lemur (Mirza coquereli) and the western fat-tailed Dwarf Lemur (Cheirogaleus medius), by nocturnal line transect walks between 2003 and 2007. We explored interspecific interactions for four different scenarios with varying resource availability (degraded and non-degraded habitat in the wet and dry season), both on the regional spatial scale and on a finer local (transect) scale. We tested whether the interspecific distribution of mouse Lemur individuals indicates interspecific competition and whether their regional coexistence might be stabilized by interactions with M. coquereli or C. medius. We developed the “Inter-Species Index of Attraction” (ISIA) to quantify the observed interspecific interactions within transects and determined if these were significantly different from a null model generated by a combination of randomization and bootstrapping to control for intraspecific aggregation. For the two mouse Lemurs, interspecific spatial exclusion was most pronounced during the resource-poor dry season, consistent with the hypothesis of feeding competition. Seasonally varying distribution patterns indicated resource tracking in a spatio-temporally heterogeneous environment. The interspecific distribution of individuals suggested that the larger cheirogaleids benefit M. berthae at the expense of the more abundant M. murinus: spatial associations of both, M. coquereli and C. medius, with M. murinus were negative in most scenarios and across spatial scales, but neutral or even positive with M. berthae. Thus, our study revealed that coexistence among ecologically similar heterospecifics can rely on complex density-mediated interspecific processes varying with habitat quality and season. With regard to the stability of animal assemblages, this insight has major implications for biodiversity conservation.
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MtDNA and nDNA corroborate existence of sympatric Dwarf Lemur species at Tsinjoarivo, eastern Madagascar
Molecular phylogenetics and evolution, 2010Co-Authors: Linn F. Groeneveld, Marina B. Blanco, Laurie R. Godfrey, Vololonirina Rahalinarivo, Jean-luc Raharison, Rodin M. Rasoloarison, Peter M. Kappeler, Mitchell T. IrwinAbstract:Madagascar is a biodiversity hotspot, well known for its endemic primates, the Lemurs. Numbers of recognized Lemur species have increased drastically in some genera (e.g. Microcebus), while field-based studies revealed low species diversity in the Dwarf Lemurs (genus Cheirogaleus). Only three (C. medius, C. major, C. crossleyi) of seven described species have to date been identified in field-based studies. Blanco et al. (2009) reported two sympatric Cheirogaleus species at Tsinjoarivo based on morphological data, one of which they attributed to C. crossleyi and the other of which they described as C. sibreei-like, or possibly a new species. Based on comparative analyses of mtDNA (cytb) and nDNA (vWF, fiba, adora3), we confirm the presence of C. crossleyi and show that the C. sibreei-like individuals form a well-defined fourth clade, basal to the three recognized species. Whereas these molecular analyses demonstrate that a non-holotype museum specimen considered by Groves (2000) to belong to C. sibreei does not cluster with the C. sibreei-like individuals from Tsinjoarivo, morphometric analysis of one Tsinjoarivo individual, the C. sibreei holotype from Ankeramadinika, and samples of C. medius, C. major, and C. crossleyi strongly suggests that the fourth (and basal) clade is indeed C. sibreei. Tsinjoarivo therefore becomes the only known field site harboring C. sibreei today. Given ongoing forest loss and fragmentation at Tsinjoarivo we can surmise that this population, critical to our understanding of the evolution of the genus Cheirogaleus, is also critically endangered.
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Species delimitation in Lemurs: multiple genetic loci reveal low levels of species diversity in the genus Cheirogaleus
BMC Evolutionary Biology, 2009Co-Authors: Linn F. Groeneveld, Anne D. Yoder, Rodin M. Rasoloarison, David W Weisrock, Peter M. KappelerAbstract:Background Species are viewed as the fundamental unit in most subdisciplines of biology. To conservationists this unit represents the currency for global biodiversity assessments. Even though Madagascar belongs to one of the top eight biodiversity hotspots of the world, the taxonomy of its charismatic Lemuriform primates is not stable. Within the last 25 years, the number of described Lemur species has more than doubled, with many newly described species identified among the nocturnal and small-bodied cheirogaleids. Here, we characterize the diversity of the Dwarf Lemurs (genus Cheirogaleus ) and assess the status of the seven described species, based on phylogenetic and population genetic analysis of mtDNA ( cytb + cox2 ) and three nuclear markers ( adora3 , fiba and vWF ). Results This study identified three distinct evolutionary lineages within the genus Cheirogaleus . Population genetic cluster analyses revealed a further layer of population divergence with six distinct genotypic clusters. Conclusion Based on the general metapopulation lineage concept and multiple concordant data sets, we identify three exclusive groups of Dwarf Lemur populations that correspond to three of the seven named species: C. major , C. medius and C. crossleyi . These three species were found to be genealogically exclusive in both mtDNA and nDNA loci and are morphologically distinguishable. The molecular and morphometric data indicate that C. adipicaudatus and C. ravus are synonymous with C. medius and C. major , respectively. Cheirogaleus sibreei falls into the C. medius mtDNA clade, but in morphological analyses the membership is not clearly resolved. We do not have sufficient data to assess the status of C. minusculus . Although additional patterns of population differentiation are evident, there are no clear subdivisions that would warrant additional specific status. We propose that ecological and more geographic data should be collected to confirm these results.
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Species delimitation in Lemurs: multiple genetic loci reveal low levels of species diversity in the genus Cheirogaleus
BMC evolutionary biology, 2009Co-Authors: Linn F. Groeneveld, Anne D. Yoder, Rodin M. Rasoloarison, David W Weisrock, Peter M. KappelerAbstract:Species are viewed as the fundamental unit in most subdisciplines of biology. To conservationists this unit represents the currency for global biodiversity assessments. Even though Madagascar belongs to one of the top eight biodiversity hotspots of the world, the taxonomy of its charismatic Lemuriform primates is not stable. Within the last 25 years, the number of described Lemur species has more than doubled, with many newly described species identified among the nocturnal and small-bodied cheirogaleids. Here, we characterize the diversity of the Dwarf Lemurs (genus Cheirogaleus) and assess the status of the seven described species, based on phylogenetic and population genetic analysis of mtDNA (cytb + cox2) and three nuclear markers (adora3, fiba and vWF). This study identified three distinct evolutionary lineages within the genus Cheirogaleus. Population genetic cluster analyses revealed a further layer of population divergence with six distinct genotypic clusters. Based on the general metapopulation lineage concept and multiple concordant data sets, we identify three exclusive groups of Dwarf Lemur populations that correspond to three of the seven named species: C. major, C. medius and C. crossleyi. These three species were found to be genealogically exclusive in both mtDNA and nDNA loci and are morphologically distinguishable. The molecular and morphometric data indicate that C. adipicaudatus and C. ravus are synonymous with C. medius and C. major, respectively. Cheirogaleus sibreei falls into the C. medius mtDNA clade, but in morphological analyses the membership is not clearly resolved. We do not have sufficient data to assess the status of C. minusculus. Although additional patterns of population differentiation are evident, there are no clear subdivisions that would warrant additional specific status. We propose that ecological and more geographic data should be collected to confirm these results.
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Genetic structure, lack of sex-biased dispersal and behavioral flexibility in the pair-living fat-tailed Dwarf Lemur, Cheirogaleus medius
Behavioral Ecology and Sociobiology, 2007Co-Authors: Tina Fredsted, Linn F. Groeneveld, Mikkel H. Schierup, Peter M. KappelerAbstract:Mating system and dispersal patterns influence the spatio-genetic structure within and between populations. Among mammals, monogamy is rare, and its socio-genetic consequences have not been studied in detail before. The goal of our study was to investigate population history, demographic structure, and dispersal patterns in a population of pair-living fat-tailed Dwarf Lemurs, Cheirogaleus medius, a small, nocturnal primate from western Madagascar, and to infer their underlying behavioral mechanisms. Tissue samples for DNA extraction were obtained from a total of 140 individuals that were captured in two subpopulations about 3 km apart. Analyses of mtDNA variability at the population level revealed very low levels of genetic variability combined with high haplotype diversity, which is indicative of a recent population bottleneck. We found no evidence for spatial clustering of same-sexed individuals with identical haplotypes within each of two subpopulations but significant clustering between them. Thus, a high level of local subpopulation differentiation was observed (F ST = 0.230). The sexes showed equal variances in the number of individuals representing each haplotype, as well as equal levels of aggregation of identical haplotypes. Hence, both sexes disperse from their natal area, one pattern expected in a pair-living mammal. There is a possibility of behavioral and social flexibility in this species, however, because we documented pronounced differences in density and sex ratio between the two subpopulations, suggesting that single study sites or populations may not be representative of a given local population or even species.
Joerg U Ganzhorn - One of the best experts on this subject based on the ideXlab platform.
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physiology hibernation in a tropical primate
Nature, 2004Co-Authors: Kathrin H. Dausmann, Joerg U Ganzhorn, Julian Glos, Gerhard HeldmaierAbstract:Even in the wound-down hibernating state, this Lemur can warm up without waking up. The Madagascan fat-tailed Dwarf Lemur, Cheirogaleus medius, hibernates in tree holes for seven months of the year, even though winter temperatures rise to over 30 °C. Here we show that this tropical primate relies on a flexible thermal response that depends on the properties of its tree hole: if the hole is poorly insulated, body temperature fluctuates widely, passively following the ambient temperature; if well insulated, body temperature stays fairly constant and the animal undergoes regular spells of arousal. Our findings indicate that arousals are determined by maximum body temperatures and that hypometabolism in hibernating animals is not necessarily coupled to a low body temperature.
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White adipose tissue composition in the free-ranging fat-tailed Dwarf Lemur (Cheirogaleus medius; Primates), a tropical hibernator.
Journal of comparative physiology. B Biochemical systemic and environmental physiology, 2002Co-Authors: Joanna Fietz, F Tataruch, Kathrin H. Dausmann, Joerg U GanzhornAbstract:In temperate species, hibernation is enhanced by high levels of essential fatty acids in white adipose tissue. Essential fatty acids cannot be synthesized by mammals, thus nutritional ecology should play a key role in physiological adaptations to hibernation. Tropical hibernators are exposed to different physiological demands than hibernators in temperate regions and are expected to be subject to different constraints. The aims of this study were to assess whether or not the tropical hibernator Cheirogaleus medius shows biochemical changes in its white adipose tissue before and during hibernation. A capture-recapture study was combined with feeding observations in western Madagascar. Before and after hibernation, 77 samples of white adipose tissue from 57 individuals of C. medius, as well as dietary items eaten during pre-hibernation fattening, were sampled and analyzed for their fatty acid composition. In contrast to temperate hibernators, C. medius exhibits extremely low essential fatty acid concentrations in its white adipose tissue (2.5%) prior to hibernation. The fatty acid pattern of the white adipose tissue did not change during pre-hibernation fattening and did not reflect dietary fatty acid composition. During hibernation, fat stores showed only minor but significant compositional changes. Because of its prevalence, the main fuel during hibernation was the monounsaturated oleic acid, which seemed to be preferentially synthesized from dietary carbohydrates. Results suggest that essential fatty acids do not represent an ecological limitation for hibernation in the tropics, at least not in the fat-tailed Dwarf Lemur.
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High rates of extra-pair young in the pair-living fat-tailed Dwarf Lemur, Cheirogaleus medius
Behavioral Ecology and Sociobiology, 2000Co-Authors: Joanna Fietz, Kathrin H. Dausmann, Hans Zischler, Claudia Schwiegk, Jürgen Tomiuk, Joerg U GanzhornAbstract:Cheirogaleids are one of the most primitive extant primate taxa in the world. Their lifestyle and mating system, therefore, have been considered to be representative for social systems in primate ancestors. Accepted models of social evolution in primates state that pair-bonding has evolved secondarily from diurnal group-living taxa and should therefore be constrained primarily to diurnal species. In contrast to these assumptions, the nocturnal fat-tailed Dwarf Lemur (Cheirogaleus medius) lives in permanent pairs, with obligate paternal care probably representing the evolutionary basis of pair-living. In this sociobiological field study, we analyzed the reproduction strategy of C. medius in the tropical forest of western Madagascar. In the rainy seasons from 1995 to 1999, 173 individuals of C. medius were captured and individually marked and 131 were genetically characterized through seven microsatellite loci. Additionally, 36 of these individuals were radio-tracked and observed. For 53 genotyped individuals, including 16 offspring, information about pair-bonding and family structure was known from field observations. Genetic analyses revealed that yearlings and infants living with an adult pair were in all cases sibs of the social mother. However, C. medius does not restrain from extra-pair copulations (EPCs) and a high rate of extra-pair paternity (44%) was detected. Males sired offspring with their female partners as well as with extra-pair females within the same year, indicating that males may increase their reproductive success by EPCs without necessarily running the risk of cuckoldry. Females on the other hand do not seem to run the risk of reduced paternal care, either because males cannot detect relatedness of young, or because they might even increase their inclusive fitness by raising offspring of closely related males. Since females reproduce preferentially with territory holders and no paternity could be assigned to floating males, superior genetic quality of the males might be crucial for female choice.
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Feeding ecology of the hibernating primate Cheirogaleus medius: how does it get so fat?
Oecologia, 1999Co-Authors: Joanna Fietz, Joerg U GanzhornAbstract:The fat-tailed Dwarf Lemur (Cheirogaleus medius; Cheirogaleidae) lives in the tropical forests of Madagascar. It is exceptional among primates, because this small nocturnal Lemur hibernates during the dry season from the end of April until October. This field study was carried out to assess seasonal changes in body mass and behavioral traits (locomotor activity, feeding ecology) of C. medius that enable this species to accumulate large quantities of fat within weeks. Feeding observations of 36 radio-collared individuals were combined with a mark-recapture study in western Madagascar during the rainy seasons from 1995 to 1998. Pulp of fruit species not consumed, as well as fruit species eaten by C. medius was analyzed for lipid and sugar contents. Body mass changes of recaptured individuals revealed that C. medius may double its body mass within a few weeks. Most of the increase in body mass took place between March and April after infants had been weaned and directly before the onset of hibernation. Locomotor activity was significantly reduced during the period of body mass gain. During the entire study, fruits, nectar, and flowers of 34 different plant species comprised about 80% of the diet, supplemented by a seasonally varying intake of animal prey. Lipid contents of consumed fruits were comparatively low throughout the study period. No difference in lipid content was detectable between fruit species consumed and not consumed by C. medius. During prehibernation fattening, C. medius consumed mostly fruit species with a high sugar content, significantly higher than that of fruit species that were not consumed. The results suggest that a reduction in locomotor activity as well as a preference for fruit species with a high sugar content enable C. medius to deposit large quantities of fat in a few weeks.
John M Allman - One of the best experts on this subject based on the ideXlab platform.
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topographical localization of lipofuscin pigment in the brain of the aged fat tailed Dwarf Lemur cheirogaleus medius and grey lesser mouse Lemur microcebus murinus comparison to iron localization
American Journal of Primatology, 1999Co-Authors: Emmanuel P Gilissen, Russell E Jacobs, Evelynn Mcguinness, John M AllmanAbstract:The present study was undertaken to explore the distribution of lipofuscin in the brain of cheirogaleids by autofluorescence and compare it to other studies of iron distribution. Aged Dwarf (Cheirogaleus medius) and mouse (Microcebus murinus) Lemurs provide a reliable model for the study of normal and pathological cerebral aging. Accumulation of lipofuscin, an age pigment derived by lipid peroxidation, constitutes the most reliable cytological change correlated with neuronal aging. Brain sections of four aged (8–15 year old) and 3 young (2–3 year old) animals were examined. Lipofuscin accumulation was observed in the aged animals but not in the young ones. Affected regions include the hippocampus (granular and pyramidal cells), where no iron accumulation was observed, the olfactory nucleus and the olfactory bulb (mitral cells), the basal forebrain, the hypothalamus, the cerebellum (Purkinje cells), the neocortex (essentially in the pyramidal cells), and the brainstem. Even though iron is known to catalyse lipid oxidation, our data indicate that iron deposits and lipofuscin accumulation are not coincident. Different biochemical and morphological cellular compartments might be involved in iron and lipofuscin deposition. The nonuniform distribution of lipofuscin indicates that brain structures are not equally sensitive to the factors causing lipofuscin accumulation. The small size, the rapid maturity, and the relatively short life expectancy of the cheirogaleids make them a good model system in which to investigate the mechanisms of lipofuscinogenesis in primates.
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magnetic resonance microscopy of iron in the basal forebrain cholinergic structures of the aged mouse Lemur
Journal of the Neurological Sciences, 1999Co-Authors: Emmanuel P Gilissen, Russell E Jacobs, John M AllmanAbstract:Increased non-heme iron levels in the brain of Alzheimer’s disease (AD) patients are higher than the levels observed in age matched normal subjects. Iron level in structures that are highly relevant for AD, such as the basal forebrain, can be detected post mortem with histochemistry. Because of the small size of these structures, in vivo MR detection is very difficult at conventional field magnets (1.5 and 4 T). In this study, we observed iron deposits with histochemistry and MR microscopy at 11.7 T in the brain of the mouse Lemur, a strepsirhine primate which is the only known animal model of aging presenting both senile plaques and neurofibrillary degeneration. We also examined a related species, the Dwarf Lemur. Iron distribution in aged animals (8 to 15 years old) agrees with previous findings in humans. In addition, the high iron levels of the globus pallidus is paralleled by a comparable contrast in basal forebrain cholinergic structures. Because of the enhancement of iron-dependent contrast with increasing field strength, microscopic magnetic resonance imaging of the mouse Lemur appears to be an ideal model system for studying in vivo iron changes in the basal forebrain in relation to aging and neurodegeneration.
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topographical localization of iron in brains of the aged fat tailed Dwarf Lemur cheirogaleus medius and gray lesser mouse Lemur microcebus murinus
American Journal of Primatology, 1998Co-Authors: Emmanuel P Gilissen, Russell E Jacobs, Pratik Ghosh, John M AllmanAbstract:Iron deposits in the human brain are characteristic of normal aging but have also been implicated in various neurodegenerative diseases. Among nonhuman primates, strepsirhines are of particular interest because hemosiderosis has been consistently observed in captive aged animals. In particular, the cheirogaleids, because of their small size, rapid maturity, fecundity, and relatively short life expectancy, are a useful model system for the study of normal and pathological cerebral aging. This study was therefore undertaken to explore iron localization in the brain of aged cheirogaleids (mouse and Dwarf Lemurs) with histochemistry and magnetic resonance microscopy. Results obtained with both techniques were comparable. There was no difference between old animals in the two species. The young animals (3 years old) showed no iron deposits. In the old animals (8–15 years old), iron pigments were mainly localized in the globus pallidus, the substantia nigra, the neocortical and cerebellar white matter, and anterior forebrain structures, including the nucleus basalis of Meynert. This distribution agrees with previous findings in monkeys and humans. In addition, we observed iron in the thalamus of these aged nonhuman primates. Microscopic NMR images clearly reveal many features seen with the histochemical procedure, and magnetic resonance microscopy is a powerful method for visualizing age-related changes in brain iron.
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Xanthogranuloma of the Choroid Plexus in the Fat-Tailed Dwarf Lemur (Cheirogaleus medius)
American journal of primatology, 1996Co-Authors: Jason T. Lee, Carol A. Miller, Colin T. Mcdonald, John M AllmanAbstract:This report documents the death of two fat-tailed Dwarf Lemurs (Cheirogaleus medius) maintained over 6 years each in our laboratory. Postmortem studies revealed xanthogranuloma of the choroid plexus, a mass replete with stored lipids, including cholesterol crystals. Six months prior to their deaths, both animals developed a peculiar head tilt and signs suggestive of neurological dysfunction. At autopsy, each had masses projecting into the lateral and IVth ventricles and an associated obstructive hydrocephalus. Cryostat sections of the brains of both Lemurs showed histological features consistent with xanthogranuloma of the choroid plexus, a histologically benign and usually asymptomatic lesion found in up to 7% of human autopsies. This case is of special interest because of the unique feeding strategies in the fat-tailed Dwarf Lemur. Since C. medius remains in torpor for 6 months out of the year during the time of food scarcity in the forests of Madagascar, the animal must accumulate large reserves of fat during its active period. In the laboratory, however, Dwarf Lemurs do not normally go into torpor, and the accumulated fat is not used. The finding of this tumor, therefore, suggests that the combination of a captive high-fat diet and the unusual fat-storage mechanisms utilized by C. medius contributed to the buildup of lipids and might be etiologically related to the development of those lesions. © 1996 Wiley-Liss, Inc.
