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91.
Six species of albatrosses breed sympatrically at the Crozet Islands. The population size, masses and measurements of adults, nesting habitats and coloniality, laying, hatching and fledging dates, duration of incubation and brooding shifts are compared. The growth of chicks, diets and feeding methods of the six species are reviewed. Their distribution in the south Indian Ocean is described in relation to the feeding frequency of chicks. Various aspects of ecological isolation among the species are analysed. Overlaps exist in the timing of breeding in the small albatrosses and to a lesser extent in their diet. Differences in the foraging zones at sea appear to be the most important factor in reducing interspecific competition. It is shown that the effective division of resources results from a relative scarcity of resources around the Crozet Islands. Finally the close interrelationship between foraging strategy, breeding biology, diet, chick growth and breeding frequency in the small albatrosses is demonstrated. 相似文献
92.
JEFFERSON HALL BILA-ISIA INOGWABINI ELIZABETH WILLIAMSON ILAMBU OMARI CLAUDE SIKUBWABO LEE WHITE 《African Journal of Ecology》1997,35(3):213-223
There has been considerable uncertainty about the abundance estimation of Loxodonta africana within tropical lowland moist forests in Zaire. We surveyed a 15,570 km2 area within the forests of eastern Zaire using transect sampling methods and estimated the elephant population to be 3720 (range 2300–5000) individuals. Dung pile densities were significantly different between adjacent settlement, deep forest, and deep forest core strata, with the most remote area harbouring the highest density. Evidence of elephant poaching was encountered throughout the survey area suggesting that elephant populations continue to be at severe risk. 相似文献
93.
CLAUDE ARNAULT 《Entomologia Experimentalis et Applicata》1982,32(2):116-122
L'importance des pressions de sélection au cours des premières générations, dans des élevages en alimentation artificielle, est mise en évidence par l'étude de souches d 'Acrolepiopsis assectella Zeller soumises à des changements de régime alimentaire. l'évolution du taux de survie et de la durée du développement des larves a été suivie pendant les premières générations après le changement, et ultérieurement contrôlée au cours de plusieurs années d'élevage dans les mêmes conditions. Le taux de survie semble atteindre assez rapidement un équilibre, dont le niveau n'est pas indépendant de l'aliment consommé, tandis qu la durée du développement larvaire devient identique pour toutes les souches dès la quatrième génération. Ces phénomènes semblent correspondre à une adaptation des insectes à leurs conditions d'élevage, qui provoquent une sélection dans les populations d'origine. 相似文献
94.
JEAN-CLAUDE DAVID CLAUDE PIEAU DANIÈLE S. CARRÉ 《Differentiation; research in biological diversity》1979,15(1-3):169-175
In the course of chick neural retina development, several forms of DNA ligase have been found. During embryonic life the major DNA ligase activity that is found at seven days is form I (8.2 S) which gradually decreases and disappears by 14 days after incubation, whereas form II (6.2 S) increases to reach a maximum at the time of hatching. Form II then decreases reaching a constant level by Day 7 and from that time new slow sedimenting forms also appear (forms III and IV). Form III (2 S) is first detectable at seven days and increases up to 90 days, whereas form IV (3 S) is the only form detected in the 17- and 18-month-old and also in the 5-year-old birds. These four forms display different elution patterns on phosphocellulose column chromatography. They also differ in their thermal stability and sensitivity towards N-ethylmaleimide. 相似文献
95.
ROLAND VERGILINO CLAUDE BELZILE FRANCE DUFRESNE 《Biological journal of the Linnean Society. Linnean Society of London》2009,97(1):68-79
Genome size was estimated in 49 clones of the Daphnia pulex complex from temperate and subarctic locations using flow cytometry and microsatellite DNA analyses. Significant genome size differences were found in diploid species belonging to the two genetically distinct groups (the pulicaria and the tenebrosa groups), with clones from the tenebrosa group having genome sizes 22% larger than those in the pulicaria group. Combined flow cytometry and microsatellite DNA analyses revealed that nearly all polyploid clones in the D. pulex complex are triploid and not tetraploid, as was previously suggested. Sequencing analyses of the ND5 gene to position clones in their respective clades within the D. pulex complex have uncovered three triploid clones of Daphnia middendorffiana with a D. pulex maternal parent. This result was unexpected because Daphnia pulicaria has always been identified as the maternal parent of these hybrid polyploid clones. Triploid clones likely owe their origins to interactions between sexual and asexual populations. Further interactions in the tenebrosa group have generated tetraploid clones but these events have been rare. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 68–79. 相似文献
96.
97.
CLAUDE MASSIN 《Zoologica scripta》1992,21(3):311-324
Two new species Mesothuria edwardensis sp.n. and Paradota marionensis sp.n., and four little-known species Cucumaria kerguelensis Théel, 1886, Cladodactyla crocea croceoides (Vaney, 1908), Psolidium incertum (Théel, 1886) and Synallactes challengeri (Théel, 1886) of holothurians are described from Marion and Prince Edward Islands. 相似文献
98.
Cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses (CMGs) is one of the most devastating crop diseases and a major constraint for cassava cultivation. CMD has been reported only from the African continent and Indian subcontinent despite the large-scale cultivation of cassava in Latin America and several South-East Asian countries. Seven CMG species have been reported from Africa and two from the Indian subcontinent and, in addition, several strains have been recognized. Recombination and pseudo-recombination between CMGs give rise not only to different strains, but also to members of novel virus species with increased virulence and a new source of biodiversity, causing severe disease epidemics. CMGs are known to trigger gene silencing in plants and, in order to counteract this natural host defence, geminiviruses have evolved suppressor proteins. Temperature and other environmental factors can affect silencing and suppression, and thus modulate the symptoms. In the case of mixed infections of two or more CMGs, there is a possibility for a synergistic interaction as a result of the presence of differential and combinatorial suppressor proteins. In this article, we provide the status of recent research findings with regard to the CMD complex, present the molecular biology knowledge of CMGs with reference to other geminiviruses, and highlight the mechanisms by which CMGs have exploited nature to their advantage. 相似文献
99.
SUMMARY. 1. Based on in situ gutter trials we related the drift of caddis flies to their benthic densities and to various abiotic factors in streams in the Ivory Coast (West Africa). Members of the families Hydropsychidae, Philopotamidae. Hydroptilidae and Leptoceridae were considered in detail.
2. The drift of larvae peaked at night in both early and late larval instars.
3. Drift of a larval group (a certain instar, species or higher taxon) was more often related to the benthic density of other larval groups than to its own benthic density.
4. Self-regulation of an upper benthic density of a larval group by emigration through drift was not statistically evident.
5. There was no straightforward relationship between drift and abiotic factors.
6. Drift rates differed between taxa as well as between larval instars (size groups) within a taxon. Newly hatched larvae had very high drift rates, whereas the last larval instar usually had the lowest drift rate.
7. We related these results to the violently fluctuating discharge of the streams in the study area and the consequent variability of space for lotic insects.
8. Drift estimates, made at the same time as a monitoring programme on possible side-effects of insecticides (Onchocerciasis Control Programme), failed to reflect benthic densities except in the night drift of Hydropsychidae. 相似文献
2. The drift of larvae peaked at night in both early and late larval instars.
3. Drift of a larval group (a certain instar, species or higher taxon) was more often related to the benthic density of other larval groups than to its own benthic density.
4. Self-regulation of an upper benthic density of a larval group by emigration through drift was not statistically evident.
5. There was no straightforward relationship between drift and abiotic factors.
6. Drift rates differed between taxa as well as between larval instars (size groups) within a taxon. Newly hatched larvae had very high drift rates, whereas the last larval instar usually had the lowest drift rate.
7. We related these results to the violently fluctuating discharge of the streams in the study area and the consequent variability of space for lotic insects.
8. Drift estimates, made at the same time as a monitoring programme on possible side-effects of insecticides (Onchocerciasis Control Programme), failed to reflect benthic densities except in the night drift of Hydropsychidae. 相似文献
100.
Geminivirus classification and nomenclature: progress and problems 总被引:13,自引:0,他引:13
During the last few years there has been some confusion among geminivirologists about how to determine the taxonomic status of a geminivirus and provide appropriate names for newly discovered viruses. The Seventh Report of the International Committee on Taxonomy of Viruses (ICTV) published in 2000, that provides guidelines for classification within the family Geminiviridae, is rapidly becoming obsolete, due mainly to the large number of complete genomic sequences that have become available. These sequences have provided a wealth of information with which to establish a coherent and durable taxonomic system, although the realisation that frequent inter‐species recombination events occur has introduced an additional level of complexity. This has resulted in a number of individual initiatives that were not fully compatible with current classification. The Geminiviridae Study Group of the ICTV exploited the last two International Geminivirus Workshops, held in Puerto Rico (1998) and Norwich, UK (2001), to debate some of the issues arising, allowing taxonomic proposals to be formulated that are in the process of being accepted by the ICTV for publication in the Eighth Report due in 2004. The present paper reviews these established principles and provides a reference with which to name and classify geminiviruses appropriately. 相似文献