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1.
By contrast with a wide definition of the 'epigenetic variation', including all changes in gene expression that do not result from alteration of the gene structure, a more restricted class had been defined, initially in plants, under the name 'paramutation'. It corresponds to epigenetic modifications distinct from the regulatory interactions of the cell differentiation pathways, mitotically stable and sexually transmitted with non-Mendelian patterns. This class of epigenetic changes appeared for some time restricted to the plant world, but examples progressively accumulated of epigenetic inheritance in organisms ranging from mice to humans. Occurrence of paramutation in the mouse and possible mechanisms were then established in the paradigmatic case of a mutant phenotype maintained and hereditarily transmitted by wild type homozygotes. Together with recent findings in plants indicative of a necessary step of RNA amplification in the reference maize paramutation, the mouse studies point to a new role of RNA, as an inducer and hereditary determinant of epigenetic variation. Given the known presence of a wide range of RNAs in human spermatozoa, as well as a number of unexplained cases of familial disease predisposition and transgenerational maintenance, speculations can be extended to possible roles of RNA-mediated inheritance in human biology and pathology.La paramutation est une modification épigénétique héréditaire, découverte chez des plantes et récemment, chez la souris. C'est un changement héréditaire du phénotype associé avec un allèle sauvage à la suite de son passage dans une structure hétérozygote avec un allèle mutant (phénomène quelquefois appelé "conversation interchromosomique"). Souvent il est considéré comme une exception à la base de lois de Mendel, "les allèles sont retrouvés inchangés lors des ségrégations au cours des croisements". Au contraire la paramutation observée chez la souris résulte d'une modification de l'allèle sauvage du gène Kit après transmission à partir d'un hétérozygote avec un allèle mutant "insertion". Le phénotype des taches blanches visibles aisément par la couleur du pelage est transmis en absence de l'allèle inducteur sur plusieurs générations. Il est corrélé avec une diminution du niveau d'ARNm de Kit et une accumulation d'ARN de taille variable de Kit dans les spermatozo?des des souris paramutantes. La micro-injection de l'ARN de l'hétérozygote, ou de l'ARN et des microARN spécifiques de Kit dans l'oeuf fécondé induit le phénotype "taches blanches". Le r?le de l'ARN dans l'établissement et le maintien d'un état épigénétique héréditaire est proposé et discuté.  相似文献   

2.
Botanical diversity provides value to humans through carbon sequestration, air and water purification, and the provisioning of wild foods and ethnomedicines. Here we calculate the value of botanical ethnomedicines in a rainforest region of Madagascar, the Makira Protected Area, using a substitution method that combines replacement costs and choice modeling. The Makira watershed may comprise approximately 0.8% of global botanical diversity and possesses enormous value both in its ability to provision botanical ethnomedicines to local people and as a source of potentially novel pharmaceutical drugs for society as a whole. Approximately 241 locally-recognized species are used as ethnomedicines, including 113 agricultural or weed species. We equated each ethnomedicinal treatment to the monetary value of a comparable pharmaceutical treatment adjusted by personal preferences in perceived efficacy (rather than from known or assumed medicinal equivalency). The benefit value of these botanical ethnomedicines per individual is $5.40–7.90 per year when using the value of highly subsidized Malagasy pharmaceuticals and $100.60–287.40 when using the value of American pharmaceuticals. Using local pharmaceuticals as substitutes, the value per household is $30.24–44.30 per year, equivalent to 43–63% of median annual household income, demonstrating their local importance. Using the value of American pharmaceuticals, the amount is equivalent to 22–63% of the median annual health care expenditures for American adults under 45 in 2006. The potential for developing novel biomedicines from the Makira watershed’s unique flora ranges in untapped benefit value from Botanical diversity provides value to humans through carbon sequestration, air and water purification, and the provisioning of wild foods and ethnomedicines. Here we calculate the value of botanical ethnomedicines in a rainforest region of Madagascar, the Makira Protected Area, using a substitution method that combines replacement costs and choice modeling. The Makira watershed may comprise approximately 0.8% of global botanical diversity and possesses enormous value both in its ability to provision botanical ethnomedicines to local people and as a source of potentially novel pharmaceutical drugs for society as a whole. Approximately 241 locally-recognized species are used as ethnomedicines, including 113 agricultural or weed species. We equated each ethnomedicinal treatment to the monetary value of a comparable pharmaceutical treatment adjusted by personal preferences in perceived efficacy (rather than from known or assumed medicinal equivalency). The benefit value of these botanical ethnomedicines per individual is $5.40-7.90 per year when using the value of highly subsidized Malagasy pharmaceuticals and $100.60-287.40 when using the value of American pharmaceuticals. Using local pharmaceuticals as substitutes, the value per household is $30.24-44.30 per year, equivalent to 43-63% of median annual household income, demonstrating their local importance. Using the value of American pharmaceuticals, the amount is equivalent to 22-63% of the median annual health care expenditures for American adults under 45 in 2006. The potential for developing novel biomedicines from the Makira watershed's unique flora ranges in untapped benefit value from $0.3-5.7 billion for American pharmaceutical companies, non-inclusive of the importance of providing novel medicines and improved healthcare to society. This study provides evidence of the tremendous current local and prospective global value of botanical ethnomedicines and furthers arguments for the conservation of tropical forests for sustainable use.Botanique de la diversité apporte de la valeur à l'homme par la séquestration du carbone, de l'air et de purification de l'eau, et le provisionnement des aliments sauvages et ethnomedicines. Ici, nous calculons la valeur de ethnomedicines botaniques dans une région de forêt de Madagascar, la zone protégée de Makira, en utilisant une méthode de substitution qui combine les co?ts de remplacement et la modélisation des choix. Le bassin versant de Makira peut comprendre environ 0,8% de la diversité botanique mondiale et possède une valeur énorme à la fois dans sa capacité à fournir ethnomedicines botaniques à la population locale et en tant que source de nouveaux médicaments potentiellement pharmaceutiques pour la société dans son ensemble. Environ 241 espèces localement reconnus sont utilisés comme ethnomedicines, y compris 113 espèces d'agricoles ou de mauvaises herbes. Nous assimilé chaque traitement ethnomédicales à la valeur monétaire d'un traitement comparable pharmaceutique ajusté en fonction des préférences personnelles en matière d'efficacité per?ue (plut?t que de l'équivalence médicament connu ou supposé). La valeur de l'avantage de ces ethnomedicines botaniques par individu est de $5,40 à 7.90 par année lors de l'utilisation de la valeur des produits pharmaceutiques malgaches fortement subventionnés et de $100,60 à 287,40 lors de l'utilisation de la valeur des produits pharmaceutiques américains. Utilisation de produits pharmaceutiques locales comme des substituts, la valeur par ménage est de $30.24 à 44.30 par an, équivalent à 43-63% du revenu médian des ménages annuelle, ce qui démontre leur importance locale. Utilisation de la valeur des produits pharmaceutiques américaines, le montant est équivalent à 22-63% de la médiane des dépenses annuelles de soins de santé pour les adultes américains de moins de 45 en 2006. Le potentiel de développement de nouveaux biomédicaments des fourneaux dans le bassin versant de la flore Makira unqiue de la valeur des avantages inexploité de $0,3 à 5,7 milliards pour les sociétés pharmaceutiques américaines, non compris l'importance de fournir de nouveaux médicaments et de soins de santé amélioré à la société. Cette étude fournit une preuve de l'énorme valeur actuelle globale locale et prospective de ethnomedicines botaniques et des arguments fait avancer pour la conservation des forêts tropicales pour l'utilisation durable.  相似文献   

3.
本文报道产于云南南部的中国蝴蝶2个新记录属及7个新记录种:新记录属为奕弄蝶属Iton de Niceéville, 1895和帕米灰蝶属Pamela Hemming, 1935;新记录种为弄蝶科Hesperiidae的素绿弄蝶Choaspes subcaudatus(C.&R. Felder, 1867)、沃氏奕弄蝶Iton watsonii(de Nicéville, 1890)、暗色梳翅弄蝶Ctenoptilum multiguttatum de Nicéville,1890和马氏陀弄蝶Thoressa masoni(Moore,[1879]),灰蝶科Lycaenidae的雅燕灰蝶Rapala duma(Hewitson, 1878)和帕米灰蝶Pamela dudgeonii(de Nicéville, 1894),蛱蝶科Nymphalidae的坎带蛱蝶Athyma kanwa Moore, 1858。所有种类附简要描述。  相似文献   

4.
Abstracts     
《Biometrics》2007,63(2):632-640
S. M. Stigler 317 The Pedigree of the International Biometric Society Pour le 60(ème) anniversaire de la Société Internationale de Biométrie, nous proposons un regard en arrière sur la vision de la Biométrie posée par son premier Président, R. A. Fisher, à partir de notes prises dans un cours qu'il a donné en 1935-36.  相似文献   

5.
1. The interaction between mutualism, facilitation or interference and exploitation competition is of major interest as it may govern species coexistence. However, the interplay of these mechanisms has received little attention. This issue dates back to Gause, who experimentally explored competition using protists as a model [Gause, G.F. (1935) Vérifications expérimentales de la théorie mathématique de la lutte pour la vie. Actualités Scientifiques et Industrielles, 277]. He showed the coexistence of Paramecium caudatum with a potentially allelopathic species, Paramecium bursaria. 2. Paramecium bursaria hosts the green algae Chlorella vulgaris. Therefore, P. bursaria may benefit from carbohydrates synthesised by the algae. Studying endosymbiosis with P. bursaria is possible as it can be freed of its endosymbiont. In addition, C. vulgaris is known to produce allelochemicals, and P. bursaria may benefit also from allelopathic compounds. 3. We designed an experiment to separate the effects of resource exploitation, endosymbiosis and allelopathy and to assess their relative importance for the coexistence of P. bursaria with a competitor that exploits the same resource, bacteria. The experiment was repeated with two competitors, Colpidium striatum or Tetrahymena pyriformis. 4. Results show that the presence of the endosymbiont enables the coexistence of competitors, while its loss leads to competitive exclusion. These results are in agreement with predictions based on resource equilibrium density of monocultures (R*) supporting the idea that P. bursaria's endosymbiont is a resource provider for its host. When P. bursaria and T. pyriformis coexist, the density of the latter shows large variation that match the effects of culture medium of P. bursaria. Our experiment suggests these effects are because of biochemicals produced in P. bursaria culture. 5. Our results expose the hidden diversity of mechanisms that underlie competitive interactions. They thus support Gauses's speculation (1935) that allelopathic effects might have been involved in his competition experiments. We discuss how a species engaged both in competition for a resource and in costly interference such as allelopathy may counterbalance these costs with a resource-provider endosymbiont.  相似文献   

6.
Paracreptotrema profundulusi n. sp. (Trematoda: Allocreadiidae) is described from the intestine of the freshwater fishes Profundulus punctatus and P. balsanus (Teleostei: Profundulidae) from the Tehuantepec and the Atoyac-Verde River basins, in Oaxaca, México, in the western extreme of Central America. The new species is distinguished from Paracreptotrema blancoi Choudhury, Pérez-Ponce de León, Brooks, and Daverdin, 2006 , to which it is most similar, and from P. mendezi (Sogandares-Bernal, 1955) Choudhury, Pérez-Ponce de León, Brooks, and Daverdin, 2006 , by the caeca extending beyond the testes, vitelline follicles that invade the postesticular area, and uterus with transverse loops located mainly between the testes and the genital pore. Paracreptotrema blancoi was collected from the same host species and also from Profundulus oaxacae. Here, we provide data that show its broad distribution in several river basins of Neotropical southern México, including the Papagayo River basin, Guerrero, México, and the Atoyac-Verde and Tehuantepec river basins, and other rivers in Oaxaca, México. Freshwater fishes of the Profundulidae are endemic to Central America and host a helminth fauna that includes at least 4 species found only in these hosts.  相似文献   

7.
Numerous organizations participate and cooperate on parasitological research in France including the Institut national de la Santé et de la Recherche Médicale (INSERM), the Centre national de la Recherche Scientifique (CNRS), the Institut Pasteur, the Institut Fran?ais de Recherche Scientifique pour le Développement en Coopération (ORSTOMM), the Institut national de la Recherche Agronomique (INRA), the Muséum national d'Histoire naturelle (MNHN), the Universities, the Collège de France, the Ecole Pratique des Hautes Etudes (EPHE) as well as various commercial firms. Exchanges and collaborations with foreign workers are continuous and essential to the success of research on tropical diseases. Here, in their own words, Odile Bain, Daniel Camus and Jacques Prod'hon highlight some aspects of current parasitological research in France.  相似文献   

8.
The pit vipers of the genus Trimeresurus Lacépède, 1804 is one of the largest groups of Asian snakes, distributed from India to China and Indonesia. Recent surveys in Jiangcheng and Simao, Yunnan Province, China resulted in a new species previously allocated to T. albolabris. Combining morphological and molecular data, we describe it as Trimeresurus guoi sp. nov. The new species morphologically differs from T. albolabris in the yellow green ventral color; an indistinct ventrolateral line; the a bsence of a postocular stripe; the firebrickred iris; a dark red stripe on dorsal tail; hemipenes with relatively weak sparse papillae, reaching 23 rd subcaudal when unextruded. Molecularly, the new species forms a clearly divergent lineage(BPP 1.00/UFB 100). Uncorrected pairwise distances of mitochondrial gene Cyt b between the new species and other known species of the subgenus Trimeresurus range from 0.052(T. albolabris) to 0.071(T. insularis).  相似文献   

9.
To investigate the dynamics of the potato-Potato virus Y (PVY) compatible interaction in relation to salicylic acid-controlled pathways we performed experiments using non-transgenic potato cv. Désirée, transgenic NahG-Désirée, cv. Igor and PVY(NTN), the most aggressive strain of PVY. The importance of salicylic acid in viral multiplication and symptom development was confirmed by pronounced symptom development in NahG-Désirée, depleted in salicylic acid, and reversion of the effect after spraying with 2,6-dichloroisonicotinic acid (a salicylic acid-analogue). We have employed quantitative PCR for monitoring virus multiplication, as well as plant responses through expression of selected marker genes of photosynthetic activity, carbohydrate metabolism and the defence response. Viral multiplication was the slowest in inoculated potato of cv. Désirée, the only asymptomatic genotype in the study. The intensity of defence-related gene expression was much stronger in both sensitive genotypes (NahG-Désirée and cv. Igor) at the site of inoculation than in asymptomatic plants (cv. Désirée). Photosynthesis and carbohydrate metabolism gene expression differed between the symptomatic and asymptomatic phenotypes. The differential gene expression pattern of the two sensitive genotypes indicates that the outcome of the interaction does not rely simply on one regulatory component, but similar phenotypical features can result from distinct responses at the molecular level.  相似文献   

10.
The question concerning the food of the hospital staff has drawn attention only tardily. However, food is a faithful mirror in which the knowledge, the capacities, the values and the imaginary ones of an institution are reflected. It is in 1905 that the reform made by the "Administration générale de l'Assistance Publique de Paris" is specifically concerned, for the first time, by the food of the hospital staff. It is a change in the practices, founded until then on the principle of equality in food treatment, resulting probably from the monastic form of the hospital in the earliest times. The introduction of the system into force today was done gradually in the years 1930. From now on, hospital staff pay their meal to the administration which establishes the account of it on the basis of a refectory card. At the end of this evolution, nothing is similar any more in the hospital on the ground of the hierarchical relations between the administration and its staff. The era of self-service restaurants has open, transforming the consumer into an autonomous active and participative individual, in an institution converted into the play of democraty company.  相似文献   

11.
We apply archaeological methods to extend our knowledge of chimpanzee material culture. The cha?ne opératoire conceptual framework, as introduced by ethnography, established technology as a phased process. Prehistoric archaeology adopted this concept to elucidate technological variability in tool-making procedures, based on knowledge of tool functions or subsistence patterns. We focused on the detection of operational sequences by wild chimpanzees (Pan troglodytes verus) when nut cracking with lithic implements at the sites of Bossou and Diecké, Guinea, West Africa. Thus, while it has recently been claimed that chimpanzees leave behind recognizable assemblages of stone hammers that can be morphologically distinguished from Oldowan hammers, this is the first study to focus specifically on the existence of operational sequences during the utilization of stone tools by wild chimpanzees. By combining primatological and archaeological methods and examining ecological areas inhabited by different chimpanzee groups, we sought technological variability and identified variables influencing regional diversity in tool typology and technology. We compared three case studies: (1) Bossou-direct recording of experimental nut-cracking sessions; (2) Bossou- direct and indirect monitoring of nut-cracking sites in the wild; (3) Diecké-indirect monitoring of nut-cracking sites in the wild. Results suggest that chimpanzees perform sequences of repeated tool transport and nut cracking. Data show discrimination of tool functions based on tool features. We identified the most technologically complex tool for nut cracking, which was composed of four stones. We found regional diversity in chimpanzee stone assemblages. Raw-material type and tool mobility constrain technological development in human and nonhuman primates. Spatial analysis of tool distribution indicates a pattern of resource-exploitation strategy, revealing affinities with Oldowan.  相似文献   

12.
1. Ecologists are obtaining ever-increasing amounts of data concerning animal movement. A movement strategy that has been concluded for a broad variety of animals is that of Lévy flights, which are random walks whose step lengths come from probability distributions with heavy power-law tails. 2. The exponent that parameterizes the power-law tail, denoted micro, has repeatedly been found to be within the Lévy range of 1 < micro 相似文献   

13.
In 1990, following an idea arising from an Inserm study section on aging, the Dipl?me d'études approfondies (DEA) de Biologie du vieillissement was created. Since then, more than 300 students have followed these courses which cover the cellular mechanisms of aging and associated diseases, from basic causes of aging to CNS and sensory organs aging, as well as nutritional aspects, sarcopenia and osteoporosis, vascular and neuroendocrine aging. More than 150 thesis have been defended and more than a quarter of students has been recruited on permanent positions in French universities and research institutions (10 %) and hospitals (16 %). Since its creation, one of the particularities of the DEA was the formal links between academia and industry since teaching takes place on private laboratory settings.  相似文献   

14.
Fuchs E 《Cell Stem Cell》2012,10(6):751-752
Cédric Blanpain from the Interdisciplinary Research Institute, Université libre de Bruxelles earned the 2012 ISSCR-University of Pittsburgh Outstanding Young Investigator Award for his exceptional achievements as an early-career stem cell researcher.  相似文献   

15.
The toxicity and immunochemical properties of Tityus pachyurus Pocock scorpion venom was characterized, as well as the neutralization capacity against it by three anti-scorpion antivenoms (Alacramyn, Instituto Bioclón, México; Suero antiescorpiónico, Instituto Butantán, Sao Paulo, Brasil; and Suero antiescorpiónico, Centro de Biotecnología, Universidad Central de Venezuela, Caracas, Venezuela). The venom yield, obtained by manual milking, 680+/-20 microg venom, a 50% lethal dose in mice was 4.8 microg/kg (90 microg for an 18-20 g mouse). The most common symptoms of venom poisoning in mice were sialorrhea, respiratory distress, profuse sweating, ataxia, behavior alterations (restlessness, somnolence) and hyperglycemia at 3 and 24 hours after subcutaneous venom injection (0.5 LD50). The neutralizing capacity of Bioclón (México City) and Butantán (Sao Paulo) antivenoms (for a 50% effective dose) was 330 and 292 microg venom/ml antivenom, respectively. The Biotecnología (Caracas) antivenom did not neutralize the lethal effect of venom. By electrophoresis (SDS-PAGE) was demonstrated that the venom contains proteins from less than 14 kd to 97 kd. The Western blots indicated immunological reactivity of the three antivenoms with most of venom components, including proteins of low molecular mass (<14 kd). The results allow to conclude that T. pachyurus venom is neutralized efficiently by anti-scorpion antivenoms produced in México and Brasil.  相似文献   

16.
记录中国裸眼蚜蝇属Citrogramma 11种 (包括1新种)。文中给出黄色裸眼蚜蝇C. amarilla、阿里山裸眼蚜蝇C.arisanicum、黑腿裸眼蚜蝇C. citrinoides、柑桔裸眼蚜蝇C.citrinum、卡氏裸眼蚜蝇C. currani、吉德裸眼蚜蝇C. gedehanum及新种西藏裸眼蚜蝇Citrogramma xizangensis sp. nov.等种的异名录、形态描述、特征图及分布,研究标本保存于陕西理工学院动植物标本馆。清丽裸眼蚜蝇C. clarum、褐翅裸眼蚜蝇C. fumipenne、松村裸眼蚜蝇C. matsumurai、素木裸眼蚜蝇C.shirakii等作者未见标本,文中仅列出异名录及分布。西藏裸眼蚜蝇,新种Citrogramma xizangensis sp. nov. (图36~41)体长:♂10mm,♀11mm;翅长:♂8mm,♀9mm。本种近似Citrogramma amarilla Mengual,两者颜黄色,后胸腹板具毛,胸部侧板黄色,翅透明,翅膜具微刺,腹部黄色带伸达背板侧缘,但新种雄性前足腿节后腹侧具1列黑色长毛,后者前、中足腿节主要具黑毛,仅基部具黄毛;新种雌性第2背板具1对狭长黄斑,后者第2背板具横带。正模1♂,西藏林芝,2008-09-26,潘朝晖采。副模:1♀,西藏林芝,2008-09-26,潘朝晖采;1♂,西藏林芝,2008-09-24,潘朝晖采。词源:新种种名源自模式产地。  相似文献   

17.
O'Connor, LM and Vozenilek, JA. Is it the athlete or the equipment? An analysis of the top swim performances from 1990 to 2010. J Strength Cond Res 25(12): 3239-3241, 2011-Forty-three world record swims were recorded at the 2009 Fédération Internationale de Natation (FINA) World Championship meet in Rome. Of the 20 FINA recognized long-course (50-m pool) swimming events, men set new world records in 15 of those events, whereas women did the same in 17 events. Each of the men's world records and 14 of the 17 women's records still stand. These performances were unprecedented; never before had these many world records been broken in such a short period of time. There was much speculation that full-body, polyurethane, technical swimsuits were the reason for the conspicuous improvement in world records. Further analysis led the FINA to institute new rules on January 1, 2010, that limited the types of technical swimsuits that could be worn by athletes. No long-course world record has been broken since then. We sought to understand this phenomenon by analyzing publicly available race data and exploring other possible causes including improvements in other sports, improvements in training science, changes in rules and regulations, gender differences, anaerobic vs. aerobic events, unique talent, and membership data.  相似文献   

18.
Phylogenetic relationships among representative species of the family Rhacophoridae were investigated based on 2904bp of sequences from both mitochondrial (12S rRNA, 16S rRNA, the complete t-RNA for valine), and nuclear (tyrosinase, rhodopsin) genes. Maximum parsimony, maximum likelihood, and Bayesian analyses were employed to reconstruct the phylogenetic trees. This analysis, combined with previous phylogenetic studies, serves as a framework for future work in rhacophorid systematics. The monophyly of Rhacophorus is strongly confirmed except for the species R.hainanus, which is the sister taxon to A.odontotarsus. The non-monophyly of the newly designated genus Aquixalus by Delorme et al. [Delorme, M., Dubois, A., Grosjean, S., Ohler, A., 2005. Une nouvelle classification générique et subgénérique de la tribu des Philautini (Amphibia, Anura, Ranidae, Rhacophorinae). Bull. Mens. Soc. Linn. Lyon 74, 165-171] is further confirmed. Aquixalus (Aquixalus) forms a well-supported monophyletic group within Kurixalus, whereas, Aquixalus (Gracixalus) is more closely related to species of Rhacophorus, Polypedates, and Chiromantis. Philautus as currently understood, does not form a monophyletic group. Philautus (Kirtixalus) is the sister group to the clade comprising Kurixalus and Aquixalus (Aquixalus), and more remotely related to Philautus (Philautus). Chiromantisromeri does not cluster with species of Chiromantis, and forms a basal clade to all rhacophorids save Buergeria. We propose some taxonomic changes that reflect these findings, but further revision should await more detailed studies, which include combined morphological and molecular analyses, with greater species sampling.  相似文献   

19.
Ten megaspore species isolated from Moscow Basin lignites of Lower Carboniferous (Viséan) age have been studied by scanning and transmission electron microscopy (SEM and TEM). These species belong to seven megaspore genera: Lagenicula, Sublagenicula, Crassilagenicula, Setosisporites, Zonalesporites, Caudatosporites, and Cystosporites. Megaspores of the genus Caudatosporites have only been described previously from the Duckmantian (Westphalian B); a new species is duly erected. The ultrastructure of megaspore walls from the genera Crassilagenicula and Zonalesporites has not been previously described. This study also places them in context with other contemporaneous megaspores. The study shows that during the Viséan, in the Moscow Basin, megaspores expressed a similar wall ultrastructure despite large differences in external appearance. The genus Crassilagenicula may represent a group of megaspores from plants that had evolved from those bearing gulate megaspores here typified by Lagenicula acuminata, Setosisporites brevispinosus, and Sublagenicula hirsutoida. Zonalesporites brasserti also appears to show affinities to this group, and may be representative of a plant species in a transitional state between the Lagenicula bearing lycopsids and those more isoetalean in nature.  相似文献   

20.
Sueur C 《PloS one》2011,6(1):e16131
The Lévy walk is found from amoebas to humans and has been described as the optimal strategy for food research. Recent results, however, have generated controversy about this conclusion since animals also display alternatives to the Lévy walk such as the Brownian walk or mental maps and because movement patterns found in some species only seem to depend on food patches distribution. Here I show that movement patterns of chacma baboons do not follow a Lévy walk but a Brownian process. Moreover this Brownian walk is not the main process responsible for movement patterns of baboons. Findings about their speed and trajectories show that baboons use metal maps and memory to find resources. Thus the Brownian process found in this species appears to be more dependent on the environment or might be an alternative when known food patches are depleted and when animals have to find new resources.  相似文献   

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