首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
We compared the use of olfactory, visual, and spatial cues for learning the location of stored food by gray squirrels (Sciurus carolinensis). All experimental cues were extrinsic, that is, they originated from the environment around the food rather than from the food itself. In training trials, artificial caches with one of two odors, one of two colors, and six of 12 spatial locations contained sunflower seeds. In experimental trials, the odors, colors, and sets of spatial locations associated with food were reversed one at a time, so that only two of the three training cues gave evidence of the food rewards. Consequent declines in food localization by the squirrels revealed differential use of particular cue modalities. The data show that squirrels used visual cues the most and olfactory cues the least with this design. These results, along with other evidence, suggest that gray squirrels use spatial memory in food recovery.  相似文献   

2.
The distributions of the Red and Grey Squirrel were surveyed in Northern Ireland and the Republic of Ireland between 1994 and 1996. Survey methods differed between the two studies. In the former, all suitable habitat, of at least 15 ha, was inspected for species presence or absence. In the Republic, data were gathered through questionnaires to governmental and independent wildlife bodies. The combined results indicate that the Red Squirrel remains widespread and locally abundant, and is present in all but two counties. The Grey Squirrel is now more widespread than ever before, and can be found in 22 of the 32 counties. Its range expansion has varied from 0 km/yr to an estimated 13.4 km/yr, as various geographical features, principally rivers, have hindered its progress in certain directions.  相似文献   

3.
SYNOPSIS. Eimerians from 27 gray squirrels Sciurus carolinensis sampled in Waterloo County were studied. Two double-walled species, E. ontarioensis n. sp. which was piriform (36.8 × 23.5) and E. confusa Joseph which was subspherical (35.7 × 28.4), were described and compared with similar species from the genus Sciurus. Eimeria sp., ellipsoidal (24.9 × 14.4), from Ontario gray squirrels resembled E. ascotensis and E. neosciuri and was a new eimerian record from Ontario. The zoogeographic significance of E. ontarioensis n. sp. and E. sp. in North American gray squirrels is discussed.  相似文献   

4.
5.
Rat-bite fever is an over-looked, global zoonotic disease that has a mortality rate of up to 13%, if untreated. Historically, this rat-borne disease has been attributed to one of two causative agents, Streptobacillus moniliformis or Spirillum minus. Given the confirmed presence of multiple invasive Rattus host species, high rat densities in urban, informal human settlements and increasing reports of rat bites in South Africa, we undertook a retrospective assessment of Streptobacillus in rats sampled from 16 urban sites, in Gauteng, the smallest but most populous Province in South Africa. Using a multi-gene PCR-sequencing approach, we confirmed Streptobacillus presence in 50.9% of oral swabs from three rat species and the presence of two Streptobacillus species, viz. S. moniliformis and S. notomytis. The two members of the cryptic Rattus rattus species complex (R. rattus and R. tanezumi), which are morphologically indistinguishable from each other, had markedly different colonization rates. Whereas 48.6% of rats from this species complex were Streptobacillus-positive, only 32.3% of Rattus tanezumi were positive compared to 61.5% R. rattus. Rattus norvegicus had an intermediate prevalence of 55.6%. Phylogenetic analysis of four gene regions (16S rRNA, gyrB, groEL, recA) identified two discrete lineages; S. moniliformis occurred exclusively in R. norvegicus, and S. notomytis was restricted to the two members of the R. rattus species complex; this represents the first report of Streptobacillus in R. tanezumi. These results highlight a largely overlooked zoonotic threat posed by invasive rats and confirm the presence of two discrete and potentially host-specific Streptobacillus lineages in South Africa.  相似文献   

6.
The rare ospC allele L was detected in 30% of Borrelia burgdorferi sensu stricto strains cultured from a tick species, Ixodes affinis, and two rodent host species, Peromyscus gossypinus and Sigmodon hispidus, collected in a coastal plain area of Georgia and South Carolina, in the southeastern United States.  相似文献   

7.
Dromedary camels (Camelus dromedarius) play a major economic role in many countries in Africa and Asia. Although they are resistant to harsh environmental conditions, they are susceptible to a wide range of zoonotic agents. This study aimed to provide an overview on the prevalence of selected zoonotic pathogens in blood and tissues of camels in central Iran. Blood, liver, portal lymph node, and brain were collected from 100 apparently healthy camels at a slaughterhouse in Qom city to assess the presence of DNA of Brucella spp., Trypanosoma spp., Coxiella burnetii, and Bartonella spp. PCR products were sequenced bidirectionally and phylogenetic analyses were performed. Eleven percent of camels tested positive for Brucella abortus (3%) and Trypanosoma evansi (8%). Coxiella burnetii and Bartonella spp. DNA was not detected. Our data demonstrate that camels from Iran contribute to the epidemiology of some zoonotic pathogens. Performing proper control strategies, such as vaccination of camels and humans in contact with them, test-and-slaughter policy, and education of the general population is necessary for minimizing the risk of zoonotic infection.  相似文献   

8.
Extracts of squirrel plasma have been chromatographed on partition columns (using a hydrophilic stationary phase) at atmospheric pressure (Celite support) and a reversed phase system at high pressure (HPLC). Both methods effectively separated testosterone, 17 beta-hydroxy-5 alpha-androstan-3-one (DHT) and 4-androstene-3,17-dione; they gave elution patterns that differed considerably. Chromatographic mobility of the three androgens on the two systems was identical with that of fractions of squirrel plasma extracts that gave responses measured by appropriate androgen radioimmunoassays; good evidence for the occurrence of these androgens in squirrel plasma is thus provided. Plasma testosterone levels were 300 pmol/l in juvenile males, 800-7000 pmol/l in sexually-active males but undetectable (less than 50 pmol/l) in sexually-regressed males. Plasma DHT levels were also high in sexually-active males, but undetectable in other males except for one regressed individual. Plasma androstenedione was higher in juvenile males than in adult males, in which it was similar whether or not they were sexually regressed. Plasma testosterone and DHT, unlike androstenedione, were totally dependent on the presence of the testes. In females testosterone and DHT were undetectable in plasma but androstenedione levels were high, especially at oestrus. Androstenedione was dependent on the presence of the ovaries.  相似文献   

9.
10.

Background

The uptake of sulphur-containing compounds plays a pivotal role in the physiology of bacteria that live in aerobic soils where organosulfur compounds such as sulphonates and sulphate esters represent more than 95% of the available sulphur. Until now, no information has been available on the uptake of sulphonates by bacterial plant pathogens, particularly those of the Xanthomonas genus, which encompasses several pathogenic species. In the present study, we characterised the alkanesulphonate uptake system (Ssu) of Xanthomonas axonopodis pv. citri 306 strain (X. citri), the etiological agent of citrus canker.

Methodology/Principal Findings

A single operon-like gene cluster (ssuEDACB) that encodes both the sulphur uptake system and enzymes involved in desulphurisation was detected in the genomes of X. citri and of the closely related species. We characterised X. citri SsuA protein, a periplasmic alkanesulphonate-binding protein that, together with SsuC and SsuB, defines the alkanesulphonate uptake system. The crystal structure of SsuA bound to MOPS, MES and HEPES, which is herein described for the first time, provides evidence for the importance of a conserved dipole in sulphate group coordination, identifies specific amino acids interacting with the sulphate group and shows the presence of a rather large binding pocket that explains the rather wide range of molecules recognised by the protein. Isolation of an isogenic ssuA-knockout derivative of the X. citri 306 strain showed that disruption of alkanesulphonate uptake affects both xanthan gum production and generation of canker lesions in sweet orange leaves.

Conclusions/Significance

The present study unravels unique structural and functional features of the X. citri SsuA protein and provides the first experimental evidence that an ABC uptake system affects the virulence of this phytopathogen.  相似文献   

11.

Background

Recipient NK cells may detect the lack of recipient''s (i.e., self) HLA antigens on donor renal tissue by means of their killer cell immunoglobulin-like receptors (KIRs). KIR genes are differently distributed in individuals, possibly contributing to differences in response to allogeneic graft.

Methodology/Principal Findings

We compared frequencies of 10 KIR genes by PCR-SSP in 93 kidney graft recipients rejecting allogeneic renal transplants with those in 190 recipients accepting grafts and 690 healthy control individuals. HLA matching results were drawn from medical records. We observed associations of both a full-length KIR2DS4 gene and its variant with 22-bp deletion with kidney graft rejection. This effect was modulated by the HLA-B,-DR matching, particularly in recipients who did not have glomerulonephritis but had both forms of KIR2DS4 gene. In contrast, in recipients with glomerulonephritis, HLA compatibility seemed to be much less important for graft rejection than the presence of KIR2DS4 gene. Simultaneous presence of both KIR2DS4 variants strongly increased the probability of rejection. Interestingly, KIR2DS5 seemed to protect the graft in the presence of KIR2DS4fl but in the absence of KIR2DS4del.

Conclusions/Significance

Our results suggest a protective role of KIR2DS5 in graft rejection and an association of KIR2DS4 with kidney rejection, particularly in recipients with glomerulonephritis.  相似文献   

12.
The study deals with a new sample of the mammalian fossils from the Pleistocene deposits of the Ignatievskaya Cave in Southern Urals (54°53' N, 57°46' E). Among the rodent fossils, the teeth of red squirrel (Sciurus vulgaris) and forest dormouse (Dryomys nitedula) have been identified. The enamel differentiation quotient (SDQ) of the water vole teeth matches the Arvicola terrestris species from locations of the end of Middle and Late Pleistocene (oxygen isotope stages, OIS 6 and OIS 5–2, respectively). The high SDQ value for the water vole and the presence of the squirrel and dormouse in the fauna allow dating the finding near the end of the Middle Pleistocene and beginning of the Late Pleistocene (OIS 6 and OIS 5e, respectively). The widespread open and forest landscapes were inhabited by this fauna.  相似文献   

13.
There is a concern on how emerging pests and diseases will affect the distribution range and adaptability of their host species, especially due to different conditions derived from climate change and growing globalization. Fusarium circinatum, which causes pitch canker disease in Pinus species, is an exotic pathogen of recent introduction in Spain that threatens its maritime pine (P. pinaster) stands. To predict the impact this disease will have on the species, we examine host resistance traits and their genetic architecture. Resistance phenotyping was done in a clonal provenance/progeny trial, using three-year-old cuttings artificially inoculated with the pathogen and maintained under controlled environmental conditions. A total number of 670 ramets were assessed, distributed in 10 populations, with a total of 47 families, 2 to 5 half-sibs per family, and 3–7 ramets per clone. High genetic variation was found at the three hierarchical levels studied: population, family and clone, being both additive and non-additive effects important. Narrow-sense and broad-sense heritability estimates were relatively high, with respective values of 0.43–0.58 and 0.51–0.8, depending on the resistance traits measured (lesion length, lesion length rate, time to wilting, and survival). These values suggest the species'' high capacity of evolutionary response to the F. circinatum pathogen. A population originated in Northern Spain was the most resistant, while another from Morocco was the most susceptible. The total number of plants that did not show lesion development or presented a small lesion (length<30 mm) was 224 out of 670, indicating a high proportion of resistant trees in the offspring within the analyzed populations. We found large differences among populations and considerable genetic variation within populations, which should allow, through natural or artificial selection, the successful adaptation of maritime pine to pitch canker disease.  相似文献   

14.
World distribution of the cereal-cyst nematode is herein reviewed. It is suggested that Heterodera avenae originated in Europe and has been widely disseminated, largely by the activities of Man but also by wind movement of cysts. So far, it may not have spread to some major wheat-growing regions of the New World, but a non-friable soil structure limits population level and disease. Yield loss could result from the introduction of new cultivars to developing countries where H . avenae has not been detected or where existing cultivars possess tolerance.  相似文献   

15.
The common marmoset (Callithrix jacchus) is a small-bodied Neotropical primate and a useful preclinical animal model for translational research into autoimmune-mediated inflammatory diseases (AIMID), such as rheumatoid arthritis (RA) and multiple sclerosis (MS). The animal model for MS established in marmosets has proven their value for exploratory research into (etio) pathogenic mechanisms and for the evaluation of new therapies that cannot be tested in lower species because of their specificity for humans. Effective usage of the marmoset in preclinical immunological research has been hampered by the limited availability of blood for immunological studies and of reagents for profiling of cellular and humoral immune reactions. In this paper, we give a concise overview of the procedures and reagents that were developed over the years in our laboratory in marmoset models of the above-mentioned diseases.  相似文献   

16.
The nymphs of Antillotolania Ramos and Deiroderes Ramos are described for the first time, along with the first host record for the genus Antillotolania, represented by Antillotolania myricae, sp. n. Nymphal features of both genera, such as a ventrally fused, cylindrical tergum IX (anal tube), the presence of abdominal lamellae, and heads with foliaceous ventrolateral lobes confirm their placement in Membracidae and are consistent with phylogenetic analyses placing them in Stegaspidinae but in conflict with a cladistic analysis showing a closer relationship to Nicomiinae. Head processes and emarginate forewing pads in the last instars of both genera support an earlier estimate, based on nuclear genes, that the two genera form a monophyletic group in Stegaspidinae. Distinguishing features of the four species of Antillotolania are tabulated.  相似文献   

17.
Invasive species often display different patterns of parasite burden and virulence compared to their native counterparts. These differences may be the result of variability in host-parasite co-evolutionary relationships, the occurrence of novel host-parasite encounters, or possibly innate differences in physiological responses to infection between invasive and native hosts. Here we examine the adaptive, humoral immune responses of a resistant, native bird and a susceptible, invasive bird to an arbovirus (Buggy Creek virus; Togaviridae: Alphavirus) and its ectoparasitic arthropod vector (the swallow bug; Oeciacus vicarius). Swallow bugs parasitize the native, colonially nesting cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that occupies nests in cliff swallow colonies. We measured levels of BCRV-specific and swallow bug-specific IgY levels before nesting (prior to swallow bug exposure) and after nesting (after swallow bug exposure) in house sparrows and cliff swallows in western Nebraska. Levels of BCRV-specific IgY increased significantly following nesting in the house sparrow but not in the cliff swallow. Additionally, house sparrows displayed consistently higher levels of swallow bug-specific antibodies both before and after nesting compared to cliff swallows. The higher levels of BCRV and swallow bug specific antibodies detected in house sparrows may be reflective of significant differences in both antiviral and anti-ectoparasite immune responses that exist between these two avian species. To our knowledge, this is the first study to compare the macro- and microparasite-specific immune responses of an invasive and a native avian host exposed to the same parasites.  相似文献   

18.
Mitogen-activated protein kinases (MAPKs) have been demonstrated to be involved in fungal development, sexual reproduction, pathogenicity and/or virulence in many filamentous plant pathogenic fungi, but genes for MAPKs in the fungal cereal pathogen Bipolaris sorokiniana have not been characterized. In this study, orthologues of three MAPK genes (CsSLT2, CsHOG1 and CsFUS3) and one MAPK kinase kinase (MAPKKK) gene (CsSTE11) were identified in the whole genome sequence of the B. sorokiniana isolate ND90Pr, and knockout mutants were generated for each of them. The ∆Csfus3 and ∆Csste11 mutants were defective in conidiation and formation of appressoria-like structures, showed hypersensitivity to oxidative stress and lost pathogenicity on non-wounded leaves of barley cv. Bowman. When inoculated on wounded leaves of Bowman, the ∆Csfus3 and ∆Csste11 mutants were reduced in virulence compared to the wild type. No morphological changes were observed in the ∆Cshog1 mutants in comparison with the wild type; however, they were slightly reduced in growth under oxidative stress and were hypersensitive to hyperosmotic stress. The ∆Cshog1 mutants formed normal appressoria-like structures but were reduced in virulence when inoculated on Bowman leaves. The ∆Csslt2 mutants produced more vegetative hyphae, had lighter pigmentation, were more sensitive to cell wall degrading enzymes, and were reduced in virulence on Bowman leaves, although they formed normal appressoria like the wild type. Root infection assays indicated that the ∆Cshog1 and ∆Csslt2 mutants were able to infect barley roots while the ∆Csfus3 and ∆Csste11 failed to cause any symptoms. However, no significant difference in virulence was observed for ∆Cshog1 mutants while ∆Csslt2 mutants showed significantly reduced virulence on barley roots in comparison with the wild type. Our results indicated that all of these MAPK and MAPKKK genes are involved in the regulation of fungal development under normal and stress conditions and required for full virulence on barley plants.  相似文献   

19.
Since 1984, Anopheles (Kerteszia) lepidotus has been considered a mosquito species that is involved in the transmission of malaria in Colombia, after having been incriminated as such with epidemiological evidence from a malaria outbreak in Cunday-Villarrica, Tolima. Subsequent morphological analyses of females captured in the same place and at the time of the outbreak showed that the species responsible for the transmission was not An. lepidotus, but rather Anopheles pholidotus. However, the associated morphological stages and DNA sequences of An. pholidotus from the foci of Cunday-Villarrica had not been analysed. Using samples that were caught recently from the outbreak region, the purpose of this study was to provide updated and additional information by analysing the morphology of female mosquitoes, the genitalia of male mosquitoes and fourth instar larvae of An. pholidotus, which was confirmed with DNA sequences of cytochrome oxidase I and rDNA internal transcribed spacer. A total of 1,596 adult females were collected in addition to 37 larval collections in bromeliads. Furthermore, 141 adult females, which were captured from the same area in the years 1981-1982, were analysed morphologically. Ninety-five DNA sequences were analysed for this study. Morphological and molecular analyses showed that the species present in this region corresponds to An. pholidotus. Given the absence of An. lepidotus, even in recent years, we consider that the species of mosquitoes that was previously incriminated as the malaria vector during the outbreak was indeed An. pholidotus, thus ending the controversy.  相似文献   

20.
Updated data on the distribution, ecology and taxonomy of Euphaedra cyparissa (Cramer) and Euphaedra sarcoptera (Butler) are presented. Three new subspecies of Euphaedra cyparissa and one of Euphaedra sarcoptera are described and their geographic distribution is presented. The monophyly of the genus Euphaedra sensu Hecq is assessed based on morphological, in particular male and female genitalia, and behavioural traits. Possible evolutionary reasons for the convergence of colour pattern between the sympatric subspecies of Euphaedra cyparissa and Euphaedra sarcoptera are discussed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号