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1.
Otolith Sr:Ca ratios were examined to evaluate the contribution of the stocked eel Anguilla anguilla elvers, which have been stocked in Lithuanian waters and mixed with naturally recruited eels for several decades, to the native eel population. Stocked eels were identified by the freshwater signature (Sr:Ca ratios <2·24 × 10−3) on the otolith after the glass eel stage. Naturally recruited eels, that had migrated through the North and Baltic Seas, were characterized by an extended seawater and brackish-water signature (Sr:Ca ratios >3·23 × 10−3) after the glass eel stage. Of 108 eels analysed, 21 eels had otolith Sr:Ca ratio profiles consistent with stocking while 87 showed patterns of natural recruitment. The ages of naturally recruited eels arriving in Lithuanian fresh waters varied from 1 to 10 years, with a mean ±  s.d . age of 5·2 ± 2·1 years. Eels from the inland Lake Baluošai were all freshwater residents of stocked origin. Stocked eels, however, accounted for only 20% of the eels from the Curonian Lagoon and 2% of eels sampled in Baltic coastal waters. This finding does not support the hypothesis that the eel fishery in the Curonian Lagoon depends mostly on stocking.  相似文献
2.
Torpid common dormice (Muscardinus avellanarius) were found in nestboxes during all the activity period from early April until late October. Prevalence of torpor among dormice was highest in spring, decreased considerably in summer and increased again in October. The proportion of adult dormice that were torpid was inversely related to mean monthly air temperature, except in September, when dormice prepare for hibernation by accumulating fat reserves. In spring and summer, torpid dormice were found when ambient temperature was up to 14–15 °C and in the arousal phase of torpor – up to 19–20 °C. In autumn, dormice were active at much lower ambient temperatures compared to spring and summer, and only dormice that were fat enough and ready for hibernation were torpid. Torpor bouts usually lasted only until noon, but also in the afternoon during persistently low ambient temperatures in April and October. In April–July, torpor was more frequent among adult males than females (75% vs. 46%), and pregnant females were never found in deep torpor. Prevalence of torpor among young-of-the-year was lower compared to adult dormice at the same time. In October, the average weight of torpid young-of-the-year dormice was significantly higher compared to the weight of active dormice (22.3 vs. 17.5 g).

Zusammenfassung

Tagestorpor bei frei lebenden Haselmäusen (Muscardinus avellanarius) in LitauenHaselmäuse (Muscardinus avellanarius) im Torpor wurden während der gesamten aktiven Saison zwischen zeitigem April und Ende Oktober in Nistkästen gefunden. Im Frühjahr war die Torporfrequenz am höchsten, während des Sommers ging sie beträchtlich zurück, und im Oktober stieg sie wieder deutlich. Der Anteil an Haselmäusen im Torpor war umgekehrt abhängig von der mittleren Monatslufttemperatur, mit Ausnahme des Septembers, wo sich die Haselmäuse Fettreserven in Vorbereitung des Winterschlafes anlegen. Während des Frühlings und des Sommers konnten Haselmäuse im Torpor gefunden werden, wenn die Umgebungstemperatur bis 14–15 °C war, und in der Aufwachphase bei Temperaturen bis 19–20 °C. Im Herbst waren die Haselmäuse bei viel tieferen Temperaturen als im Sommer oder Frühjahr aktiv und nur die Haselmäuse die fett genug waren, um in den Winterschlaf gehen zu können, waren lethargisch. Die Torporphasen dauerten in der Regel nur bis zum Mittag, aber im April und Oktober während lang anhaltenden tiefen Umgebungstemperaturen auch bis in den Nachmittag hinein. Zwischen April und Juli konnten mehr adulte Männchen als Weibchen im Torpor nachgewiesen werden (75% vs 46%). Tragende Weibchen waren niemals im tiefen Torpor zu finden. Die Torporfrequenz war bei Haselmäusen in ihrem ersten Lebensjahr geringer als bei adulten im selben Zeitraum. Im Oktober war bei den lethargischen Jungtieren des Jahres das Durchschnittsgewicht höher als bei den aktiven Haselmäusen (22.3 vs. 17.5 g).  相似文献
3.
Two populations of Sphaerium corneum were sampled from River Vilnelė and small pond in Vilnius, Lithuania. The chromosomes were studied using conventional Giemsa staining and karyometric analysis. Inter- and intra-individual variation in the diploid chromosome numbers was revealed and two different sources of chromosome variability were identified: B chromosomes and the structural changes of chromosomes of the basic (A) set. The chromosome set of the more common karyotypic form, 2 n  = 30, found in both populations, consists of all biarmed metacentric and meta-submetacentric chromosomes of gradually decreasing size. Small, biarmed, mitotically unstable B chromosomes were found in the cells of this karyotypic form. Specimens with 2 n  = 36 were found only in pond. No B chromosomes were detected in their cells. The karyotype is characterized by presence of two pairs of medium telocentrics and four pairs of small subtelocentrics. The remaining chromosomes are biarmed. Robertsonian fusions appear to be involved in formation of two karyotypic forms of S. corneum . DNA sequence analyses showed that ITS1 is identical in both karyotypic forms. On the other hand, differences in 16S sequence were revealed and two haplotypes, corresponding to two karyotypic forms, were identified. The present study opens new perspectives in establishing species-specific characters for confident identification of Sphaerium species and provides insights to the genetic intraspecific variability and possible mechanisms of speciation.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 53–64.  相似文献
4.
Daphnids of ex-ephippial and parthenogenetic origin differ substantially in life-history. Possible maternally transmitted ex-diapause effects of differing female origin on the fitness of their offspring were studied across multiple clones in Daphnia magna. Ex-ephippial daphnids responded in egg size to different constant food concentrations with the same pattern as parthenogenetic females. Significant differences in egg characteristics between females of different origin were only found for the first clutch produced under high food. The smaller size of eggs in ex-ephippial females, however, did not translate into size differences of first-clutch neonates. A trend for lower mass density per body volume was detected in offspring from ex-ephippial females in comparison with parthenogenetic daphnids. Hence, an ex-diapause effect transmitted by ex-ephippial mothers to their parthenogenetic offspring is likely. However, there was no difference in life-histories and fitness between offspring produced by females of ex-ephippial and parthenogenetic origin at both, high and low food concentrations across multiple clones. Thus, a significant ex-diapause effect on fitness in successive parthenogenetic generations may not be expected in D. magna at the population level.  相似文献
5.
Karyotypes of three dilepidid species: Molluscotaenia crassiscolex, Anomotaenia bacilligera and Dilepis undula, which have not been recorded previously, were studied using conventional Giemsa staining and comparative karyometric analysis. Twelve small biarmed chromosomes were observed in mitotic cells of M. crassiscolex, 16 biarmed chromosomes of gradually decreasing size were found in cells of A. bacilligera, while 18 elements were characteristic for D. undula. These data, together with information available in literature, prove the heterogeneity and possible polyphyletic nature of the family Dilepididae.  相似文献
6.
Numerous polymerase chain reaction (PCR)-based methods have been developed and used increasingly to screen vertebrate blood samples for the diagnosis of haemosporidian blood parasites (Sporozoa, Haemosporida), but a rigorous evaluation of the sensitivity of these methods for detecting mixed infections of different haemosporidian species belonging to the same and different genera and subgenera is lacking. This study links the information obtained by nested cytochrome b PCR and traditional microscopy in determining mixed haemosporidian infections in naturally infected birds. Samples from 83 individual passerine birds with single infections of Haemoproteus or Plasmodium spp., as determined by mitochondrial DNA amplification, also were investigated by microscopic examination of stained blood films. Thirty-six samples (43%) were found to harbor mixed Haemoproteus, or Plasmodium spp. infections, or both. Thus, the PCR assays alone underestimate the occurrence of mixed infections of haemosporidian parasites in naturally infected birds. To determine the true species composition of the haemosporidians in each individual host, PCR diagnostics need to be improved. Specific primers for Haemoproteus spp. and Plasmodium spp. should be developed. Ideally, a combination of the approaches of both microscopy and PCR-based methods is recommended for this purpose.  相似文献
7.
The effect of initial Haemoproteus belopolskyi infection on the weight of its natural host, the blackcap Sylvia atricapilla, was investigated. Fourteen blackcap nestlings were taken at the age of 4-5 days and raised by hand in the laboratory. They were free of blood parasites. Seven 20- to 21-day-old nestlings were infected experimentally by inoculation in their pectoral muscle with approximately 45 sporozoites, which had developed in the experimentally infected biting midge Culicoides impunctatus. Seven nestlings were used as negative controls. Parasitemia developed in 6 inoculated nestlings, with a prepatent period of 11-12 days. No infections were detected in the controls during this study. The weight of experimentally infected and control birds was measured 2 days before parasitemia became patent and for a 45-day period after patency. Blood smears were prepared from all birds on the days when they were weighed. When compared with controls, there was a significant weight loss of experimentally infected blackcaps during 6 days after the decline of parasitemia at 10-16 days of patency, indicating a short-term influence of the infection on the birds' body mass. Clinical symptoms of the infection were not recorded. All birds from both groups survived until the end of the experiment.  相似文献
8.
A parasite's shift to a new host may have serious evolutionary consequences, since host switching usually is associated with a change in virulence and may lead to the evolution of emerging diseases. This phenomenon remains insufficiently studied in wildlife. Here, we combine microscopic examination of blood films and PCR-based methods to investigate the natural host specificity of Haemoproteus and Plasmodium spp. in birds of 4 families of the Passeriformes within a small geographic area. The material was collected on the Curonian Spit in the Baltic Sea between May and July in 2003-2004. A nested-PCR protocol was used for amplifying and sequencing a fragment of 480 nucleotides of the cytochrome b gene of the mtDNA of these parasites. Blood samples from 282 birds, which were positive both by microscopic examination of blood films and mtDNA amplification, were used in this study. We found that Haemoproteus majoris (lineages hPARUS1, hCCF5, hWW2, and hPHSIB1), Haemoproteus sp. (hWW1), Plasmodium (Haemamoeba) sp. (pSGS1), and Plasmodium (Haemamoeba) sp. (pGRW11) are capable of infecting birds belonging to different families of passeriform birds. Some species of Haemoproteus are less specific than have been traditionally believed. Haemoproteus majoris appears to have a genetic predisposition to have a broad host range. The level of host specificity varies markedly among different species of hemosporidian parasites of birds. The natural host range is thus not a reliable taxonomic character in the systematics of these parasites in the form in which it is still accepted in some recent taxonomic studies.  相似文献
9.
Birds from three National Parks (Bwindi Impenetrable, Kibale, and Queen Elizabeth) in western Uganda were surveyed during the dry season in July 2003 and investigated for hematozoa by microscopic examination of stained blood films. Of 307 birds examined, representing 68 species of 15 families and four orders, 61.9% were found to be infected with blood parasites. Species of Haemoproteus (15.3% prevalence), Plasmodium (20.5%), Leucocytozoon (40.1%), Trypanosoma (11.4%), Hepatozoon (2.6%), Atoxoplasma (0.3%), and microfilariae (3.9%) were recorded. Except for Haemoproteus spp. infections, the overall prevalence of hematozoa belonging to all genera was significantly higher in this study than was previously reported in Uganda. Thirty-six species of birds were examined for blood parasites for the first time and 112 new host-parasite associations were identified. Eighty-one were at the generic and 31 at the specific level of the hematozoa. Hepatozoon and Atoxoplasma spp. were detected for the first time in Uganda.  相似文献
10.
Birds from the Area de Conservacion Guanacaste in northwestern Costa Rica were surveyed for blood parasites in June 2001 and December 2001-January 2002. Of 354 birds examined, representing 141 species of 35 families and 15 orders, 44 (12.4%) were infected with blood parasites. Species of Haemoproteus (4.8% prevalence), Plasmodium (0.6%), Leucocytozoon (0.3%), Trypanosoma (2.0%), and microfilariae (7.6%) were recorded. Twelve species of birds in this survey were examined for blood parasites for the first time. Several new host-parasite associations were identified.  相似文献
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