Transformation by Polyoma Virus affects Adhesion of Fibroblasts

WHEN freshly trypsinized hamster fibroblasts (BHK 21, Clone 13¹) are shaken in suspension, intercellular adhesions are rapidly formed and there is some support for the view that this process is the expression of an adhesive property of the cells in culture which has survived the procedures used to separate them and is not simply an artefact of the use of trypsin². Transformation of animal cells in culture by tumour viruses alters the cell surfaces, as various techniques have shown^3–9 and we have investigated whether intercellular adhesiveness, as defined by the particular assay we have been using, is also affected.     

Landscapes of Settlement in Northern Iceland: Historical Ecology of Human Impact and Climate Fluctuation on the Millennial Scale

Early settlement in the North Atlantic produced complex interactions of culture and nature. The sustained program of interdisciplinary collaboration is intended to focus on ninth- to 13th-century sites and landscapes in the highland interior lake basin of Mývatn in Iceland and to contribute a long-term perspective to larger issues of sustainable resource use, soil erosion, and the historical ecology of global change.     

The incidence of viruses in wild Brassica rapa ssp. sylvestris in southern England

Using enzyme‐linked immunosorbent assays, the frequency of occurrence of six viruses was determined in Brassica rapa ssp. sylvestris collected from two Thameside sites (Abingdon and Culham) in Oxfordshire and one near the Avon (Claverton) in Bath & North East Somerset. During 2000–2001, the viruses detected were: Beet western yellows virus (genus Polerovirus) (BWYV), Cauliflower mosaic virus (genus Caulimovirus) (CaMV), Turnip crinkle virus (genus Carmovirus) (TCV), Turnip rosette virus (genus Sobemovirus) (TRoV), and Turnip yellow mosaic virus (genus Tymovirus) (TYMV). BWYV and TYMV were the most frequently detected viruses at the Oxford shire sites, both as single infections (20/1743 and 66/1743 respectively) and as dual infections (7/1743). Turnip mosaic virus (genus Potyvirus) (TuMV) was not detected in the field‐grown plants assayed from any of the sites. There was a highly significant (x²_[1]=30.07, P<0.001) difference in the proportion of plants at each Oxfordshire site in which one or more viruses were detected, and essentially the same pattern of virus infection was observed in tests on B. rapa from the site near Claverton. At least one representative isolate of each detected virus was tested for its morphological and serological effects on glasshouse‐grown individuals from different half‐sib families of B. rapa from both Oxfordshire sites. Except for TRoV, where there was a large difference in the frequency of successful infection in B. rapa from the two locations (1/15 vs 11/15), no clear evidence of resistance or immunity to challenge was observed, although tolerance (virus invasion without symptoms) was frequent. Fewer of the plants from Abingdon were infected than those from Culham, when mechanically challenged with TRoV, but the two B. rapa populations were not otherwise consistently different, either in their infectibility by this virus or in their responses to challenge. However, with TCV, viral antigen concentration was closely linked to the severity of disease and the B. rapa from both Oxfordshire sites segregated into two classes: those with symptoms and most viral antigen, and those without symptoms and least viral antigen. These results suggest that generic risk assessments cannot be made due to differences in the way distinct B. rapa populations react to virus challenge.     

Innate aversion to ants (Hymenoptera: Formicidae) and ant mimics: experimental findings from mantises (Mantodea)

Field data suggest that ants may be important predators of mantises which, in turn, may be important predators of jumping spiders (Salticidae). Using a tropical fauna from the Philippines as a case study, the reactions of mantises to ants, myrmecomorphic salticids (i.e. jumping spiders that resemble ants) and ordinary salticids (i.e. jumping spiders that do not resemble ants) were investigated in the laboratory. Three mantis species ( Loxomantis sp., Orthodera sp., and Statilia sp.) were tested with ten ant species, five species of Myrmarachne (i.e. myrmecomorphic salticids), and 23 ordinary salticid species. Two categories of the myrmecomorphic salticids were recognized: (1) 'typical Myrmarachne ' (four species with a strong resemblance to ants) and (2) Myrmarachne bakeri (a species with less strong resemblance to ants). Ants readily killed mantises in the laboratory, confirming that, for the mantises studied, ants are dangerous. In alternate-day testing, the mantises routinely preyed on the ordinary salticids, but avoided ants. The mantises reacted to myrmecomorphic salticids similarly to how they reacted to ants (i.e. myrmecomorphic salticids appear to be, for mantises, Batesian mimics of ants). Although myrmecomorphic salticids were rarely eaten, M . bakeri was eaten more often than typical Myrmarachne . Because the mantises had no prior experience with ants, ant mimics or ordinary salticids, our findings suggest that mantises have an innate aversion to attacking ants and that this aversion is generalized to myrmecomorphic salticids even in the absence of prior experience with ants. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 23–32.     

Mitochondrial gene order is not conserved in arthropods: prostriate and metastriate tick mitochondrial genomes

The entire mitochondrial genome was sequenced in a prostriate tick, Ixodes hexagonus, and a metastriate tick, Rhipicephalus sanguineus. Both genomes encode 22 tRNAs, 13 proteins, and two ribosomal RNAs. Prostriate ticks are basal members of Ixodidae and have the same gene order as Limulus polyphemus. In contrast, in R. sanguineus, a block of genes encoding NADH dehydrogenase subunit 1 (ND1), tRNA(Leu)(UUR), tRNA(Leu)(CUN), 16S rDNA, tRNA(Val), 12S rDNA, the control region, and the tRNA(Ile) and tRNA(Gln) have translocated to a position between the tRNA(Glu) and tRNA(Phe) genes. The tRNA(Cys) gene has translocated between the control region and the tRNA(Met) gene, and the tRNA(Leu)(CUN) gene has translocated between the tRNA(Ser)(UCN) gene and the control region. Furthermore, the control region is duplicated, and both copies undergo concerted evolution. Primers that flank these rearrangements confirm that this gene order is conserved in all metastriate ticks examined. Correspondence analysis of amino acid and codon use in the two ticks and in nine other arthropod mitochondrial genomes indicate a strong bias in R. sanguineus towards amino acids encoded by AT-rich codons.      

Nucleotide polymorphism at the alcohol dehydrogenase locus of pocket gophers, genus Geomys

Using the strictly neutral model as a null hypothesis, we tested for deviations from expected levels of nucleotide polymorphism at the alcohol dehydrogenase locus (Adh-1) within and among four species of pocket gophers (Geomys bursarius major, G. knoxjonesi, G. texensis llanensis, and G. attwateri). The complete protein-encoding region was examined, and 10 unique alleles, representing both electromorphic and cryptic alleles, were used to test hypotheses (e.g., the neutral model) concerning the maintenance of genetic variation. Nineteen variable sites were identified among the 10 alleles examined, including 9 segregating sites occurring in synonymous positions and 10 that were nonsynonymous. Several statistical methods, including those that test for within-species variation as well as those that examine variation within and among species, failed to reject the null hypothesis that variation (both within and between species of Geomys) at the Adh locus is consistent with the neutral theory. However, there was significant heterogeneity in the ratio of polymorphism to divergence across the gene, with polymorphisms clustered in the first half of the coding region and fixed differences clustered in the second half of the gene. Two alternative hypotheses are discussed as possible explanations for this heterogeneity: an old balanced polymorphism in the first half of the gene or a recent selective sweep in the second half of the gene.      

Lower Devonian coalified sporangia from Shropshire: Salopella Edwards & Richardson and Tortilicaulis Edwards

A diverse assemblage of coalified sporangia from Lochkovian/Gedinnian, fluvial rocks imicrornatus-newportensis Spore Biozone) contains fusiform forms assignable to Salopella Edwards & Richardson and Tortilicaulis Edwards. Both show bifurcation within some sporangia. In specimens assigned to Salopella cf. marcensis , longitudinal dehiscence produces two equal valves revealing spores resembling Aneurospora , although trilete marks may be difficult to distinguish. The spores are in two forms with distal ornament of either coarse or fine coni, each occurring in separate sporangia. A further sporangium of Salopella shape contains distally apiculate, hilate cryptospores. Elongate sporangia exhibiting spiralling of superficial cells and sometimes gross twisting, are placed in a new species of Tortilicaulii, T. offaeus. Anatomical data include details of irregularly thickened epidermal cells, sporangial wall and in situ spores. The latter are trilete, equatorially thickened and highly distinctive, because the entire exospore surface is covered with grana, a feature not common in dispersed spores of this age. The nomenclatural and curatorial problems associated with these small, coalified fossils, whose anatomical examination by scanning electron microscope necessitates elimination of gross morphology, are discussed.