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Danio is a diverse group of small, colourful and easily bred freshwater fishes native to Southern Asia. Biological interest in danios has increased in recent years because the zebrafish, Danio rerio , has become an important model organism, particularly for studies of vertebrate developmental biology and genetics. Though several phylogenetic studies of Danio have been done on a subset of Danio species, the resulting phylogenies conflict in detail. To examine the utility of osteology for systematics of this group at the species level, we studied the axial skeleton for 11 species of Danio. We analyse our morphological data alone and combined with DNA sequence data for five gene sequences generated in earlier phylogenetic studies. The axial skeleton of Danio exhibits 14 characters that prove useful in phylogenetic analysis. Both molecular and morphological data support the monophyly of the danios included in our analysis and both data sets support the monophyly of two subclades: a deep-bodied group and a slender-bodied group. Separate analysis of molecular and morphological data sets show that the molecular data resolves relationships within the slender subclade whereas the topology of the deep-bodied subclade is determined by morphological data. © 2002 The Linnean Society of London. Zoological Journal of the Linnean Society , 2002, 135 , 529–546. 相似文献
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Effects of Cytochalasin B on Muscle Cells in Tissue Culture 总被引:12,自引:0,他引:12
THE antibiotic cytochalasin B induces the formation of binucleated and multinucleated cells by preventing cytokinesis1 and the cleavage furrow filaments in sea urchin eggs, 50-100 Å in diameter, disappear in the presence of this compound2. It has a similar effect on the fine filaments found in embryonic pancreatic cells3 and inhibits cell migration1. Many kinds of cells displaying amoeboid movements have been reported to have 50-100 Å filaments4–6. Ishikawa et al. have demonstrated that 60–80 Å filaments in the cortex of various tissue cells bind heavy-meromyosin in a manner identical to that of actin filaments, which are also 60–80 Å in diameter7. Many investigators have referred to these thin filaments as actin or actin-like and assumed them to be responsible for, or associated with, cellular movements8,9, contraction10,11 and cytokinesis12,13. 相似文献
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Species differences in insulin 总被引:8,自引:0,他引:8
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NICOLA PATRICIA SANGER STEPHEN WAITE 《Botanical journal of the Linnean Society. Linnean Society of London》1998,126(1-2):75-81
Ophrys sphegodes is a rare species in the United Kingdom. The largest extant population of the species, at Castle Hill National Nature Reserve in Sussex, has been monitored each year since 1975. At each annual census, which is conducted during the peak period of flowering (May), the co-ordinates of each plant are recorded, allowing the fate of individuals to be followed from one census to the next. In the present study the population was monitored throughout one complete year. The data collected allow the phenology of the species to be described and the effectiveness of the annual census to be assessed. The study shows that a substantial number of Ophrys sphegodes plants emerge above ground and re-enter the below ground phase before the census date. These results suggest that reliance on annual census records alone may result in the size of the population being underestimated and incorrect life-histories being ascribed to individual plants. True counts of the population may be obtained only if 'dormant' plants are retrospectively added to the population. 相似文献