Editor's column: Tnternational Geological Correlation Programme

The International Geological Correlation Programme (IGCP) offers great opportunities to geologists but suffers from a marked lack of identity in both public and professional perspective. This can be remedied by organizing the programme into a number of reasonably large projects with an identity of their own. Such a structure has to be attained according to a differentiated pattern, adjusted to accommodate groups and persons with initiative and dedication. The Board of the IGCP now has its great chance to act creatively by structurizing the programme. Now that the IGCP has become more widely known, geologists should make increased use of their formal powers to influence the programme, through the IUGS and individually.     

The moult of Barred Warblers Sylvia nisoria in Kenya—evidence for a split wing-moult pattern initiated during the birds' first winter*

The moult of Barred Warblers Sylvia nisoria was studied during three winter seasons in southeastern Kenya at a southward passage site (Ngulia) and a wintering site (Mtito Andei). Most Barred Warblers migrating through Ngulia in November had yet to commence winter moult. These birds probably moulted subsequently in winter in northern Tanzania. In December, birds were found in heavy moult at Mtito Andei, and some of these birds were known to stay throughout the winter. By contrast, most birds reaching southeastern Kenya from late December onwards had already completed part or all of their winter moult, presumably at stopover sites in northern and eastern Kenya or in Ethiopia. Thus, winter moult in Barred Warblers takes place mainly in late November and December, either just before or soon after the final leg of autumn migration. In general, first-year birds renewed all tertials and tail feathers, about three to five secondaries per wing and commonly also the outer one to four large primaries per wing. Adults renewed all tertials and tail feathers, almost all secondaries and only occasionally an outer primary. The replacement of relatively fresh juvenile secondaries during the birds' first winter implies that the split moult pattern of this species (secondaries, tertials and tail moulted in winter; primaries and tertials in summer) is endogenously controlled.     

Migration, stopover and moult of the Great Reed Warbler Acrocephalus arundinaceus in Ghana, West Africa

We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid-November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March-April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.     

Prey Capture and Feeding in the Social Spider Anelosimus eximius

Wild colonies of the social spider Anelosimus eximius (Araneae, Theridiidae) appear often to be food-limited and not all females come to reproduction. Using a limited number of marked females in an artificial colony, set up in the laboratory, this study attempts a first analysis of the participation in prey capture and ingestion. Marked females of the same age and experience were observed during the attack of prey insects, the ensuing transportation of the prey to the retreat, and the feeding session. No correlation was found between the time females spent hunting and the time they spent feeding. Females that laid eggs had fed longer and imbibed more nutrients, but had not hunted more than those females that did not reproduce. These, it is speculated, were denied access to the prey by the reproducing females.     

An Ultrastructural Study of Mitosis in a Marine Dinoflagellate: Prorocentrum minimum1

An ultrastructural study on mitosis in the marine dinoflagellate Prorocentrum minimum is described. Early in mitosis the nuclear membrane invaginates in the area of the Golgi apparatus. Additional membrane-lined channels form within the nucleus as the Golgi apparatus separates and moves toward opposite spindle poles. Microtubules appear within the channels and make contact with distinct kinetochore-like structures on the cytoplasmic side of the channels adjacent to the site of chromosome attachment. By mid-mitosis two or three parallel channels dissect the nucleus perpendicular to the suture plane of the cell. Chromosome separation thus occurs perpendicular to the suture plane. An additional group of microtubules extends posteriorly from the flagellar apparatus towards the nucleus but has no apparent role in mitosis. Mitosis in P. minimum is compared to that of P. micans and to other dinoflagellates.     

Tumor Gene Expression and Interphase Chromatin Appearance in Xiphophorus

SYNOPSIS. Xiphophorus maculatus (platyfish) exhibits spots whichconsist of neoplastically transformed pigment cells (T-cells).The spots actually represent extreme benign melanomas. Transformationto T-cells is mediated by a "tumor gene" (Tu). Platyfish whichdevelop from X-irradiated embryos reveal an increase of Tu-expressionresulting in an overproduction of T-cells to benign melanomaswhich can be compared to that observed in certain hybrids betweenthe platyfish and Xiphophorus helleri (swordtail). Both theX irradiation-induced and the crossing conditioned increaseof Tu-expression represent a heritable alteration which mightbe related to a conversion from dispersed to condensed chromatinin the interphase nuclei.     

How is host egg mimicry maintained in the cuckoo (Cuculus canorus)?

To investigate the evolutionary mechanism (host specificity vs. random searching) maintaining mimicry between cuckoo egg appearance and that of different European cuckoo Cuculus canorus hosts, we studied the level of mimicry between the appearance of C. canorus eggs and that of their hosts' eggs in different habitats in southern Finland by using ultraviolet-visible reflectance spectrophotometry. In the main habitat used by C. canorus for reproduction, eggs laid in nests of different host species differed in appearance. Host use by C. canorus was not related to the abundance of hosts, and the level of mimicry was not related to host abundance in the habitat. Furthermore, a close match between C. canorus egg appearance and that of host eggs within habitats was detected after removing the potentially confounding effect of host abundance. In the only two suitable host species nesting in trees (namely chaffinch Fringilla coelebs and brambling Fringilla montifringilla ) we detected changes in C. canorus egg appearance that paralleled those of the two host species. Thus our findings suggest the existence of a correlation between the appearance of C. canorus eggs and that of their hosts' eggs within different habitat types, and suggest that mimicry is maintained by strict host preferences by each C. canorus female when laying.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 57–68.     

Comparison of Mitomycin C and X-irradiation as Blocking Agents in One-way Mixed Leucocyte Cultures

THE mixed leucocyte culture (MLC) test^1,2 has been widely used as a measure of histocompatibility in man and as a model for the recognition phase of the homograft response in vitro. Two methods have been proposed to achieve unidirectional stimulation in MLC: treatment of stimulating cells with either mitomycin C³ or X-irradiation³. The mitomycin C method has the advantage of not requiring expensive X-ray equipment and being immediately available in the laboratory; the X-ray method has the advantage of not requiring washing of the cells following treatment. Although much of the quantitative MLC work for histocompatibility testing in man has been done using mitomycin C, the general impression gained from the literature as well as the studies we report here would support the use of either method. A previous study⁴ suggested that irradiation is superior to mitomycin C treatment for a number of reasons, but we question those conclusions.     

Coiled Supercoiled DNA in Critical Point Dried and Thin Sectioned Human Chromosome Fibres

SUPERCOILING of the DNA double helix in the deoxynucleo-histone fibril (100 Â in diameter with a pitch of 120 Â) has been well documented by X-ray diffraction^1–3. The main structural element of eukaryotic metaphase chromosomes and inactive interphase chromatin, however, is a long, irregularly folded fibre, 200 to 300 Â in diameter, as electron microscopy has shown^4–10. The arrangement of DNA within this fibre has not yet been established clearly. I wish to present electron micrographs of critical point dried and thin sectioned fibres of human metaphase chromosomes, which demonstrate more or less regularly distributed electron densities which could be explained by supercoiling of the 100 Â deoxynucleohistone fibril.