Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Proposal for adoption of the base of the Undulograptus austrodentatus Biozone as a global Ordovician stage and series boundary level

The base of the Undulograptus austrodentatus Biozone appears to be a synchronous event that is widely recognizable within graptolitic facies around the world. It occurs within an interval in which graptolite species ranges are now well known and in which there is a rapid turnover in the composition of graptolite faunas. This turnover reflects the rapid evolutionary radiation of the Diplograptacea simultaneously with the appearance of several distinctive pseudisograptid and glossograptid species. These events provide the basis for the recognition of two thin but widely applicable subzones; a lower Arienigraptus zhejiangensis Subzone and an upper U. sinicus Subzone. The occurrence of the lower boundary of the U. austrodentatus Biozone within a succession of first appearances also permits accurate and reliable identification of the boundary as well as assessment of stratigraphic completeness across the boundary interval in correlated sections. Diverse graptolite faunas of late Yapeenian and early Darriwilian age occur in association with the Histiodella altifrons Biozone of the North American midcontinent conodont zonation and the Paroistodus originalis and Microzarkodina parva biozones of the North Atlantic conodont zonation. They also occur in association with the shelly-fossil zonations developed for several different continents. These features of the base of the U. austrodentatus Biozone make it a suitable level for use as the boundary level for a global stage. Its stratigraphic position within the Ordovician System relative to other likely global stages as well as its coincidence with one of the major events in graptolite evolutionary history suggest that this level also may be a suitable level for the base of a global Middle Ordovician Series.Ordovician System, Ordovician stages, graptolite zonation, chronostratigraphy, international correlation. Charles E. Mitchell and Jörg Maletz, Department of Geology, State University of New York at Buffalo, Buffalo, New York 14260-1550, USA; 13th July, 1994; revised 22nd May, 1995.     

Heterogeneity of Intermediate Filament Expression in Vascular Smooth Muscle: A Gradient in Desmin Positive Cells from the Rat Aortic Arch to the Level of the Arteria Iliaca Communis

The display of the two distinct intermediate filament proteins, desmin and vimentin, in rat vascular smooth muscle tissue was studied by immunofluorescence microscopy on frozen sections of aorta and other blood vessels. Vascular smooth muscle cells present in these vessels always appeared rich in vimentin. However, staining of sections covering six distinct but contiguous parts of the aorta showed that the number of desmin containing cells was low distal to the truncus brachiocephalicus, but increases until in distal parts of the aorta and in the arteria iliaca communis almost all cells appear positive for desmin. Thus blood vessels show heterogeneity of intermediate filament expression not only in cross-section but can also display heterogeneity along their length. Muscular arteries such as the renal artery and the arteria femoralis, as well as arterioles and veins including the vena jugularis and the vena cava also contain desmin. Thus it may be that low numbers of desmin-positive cells are typical of elastic arteries, while muscular arteries and other blood vessels are characterized by large numbers of desmin-positive cells. We discuss whether desmin-positive and desmin-negative vascular smooth muscle cells may perform different functions and raise the possibility that desmin expression may coincide with the turn on of a specially regulated contractility program.     

Comparative analysis of the localization and mobility of retrotransposons in sibling species Drosophila simulans and Drosophila melanogaster]

The distribution of four retrotransposon families (MDG1, MDG3, MDG4 and copia) on polytene chromosomes of different (from 9 to 15) Drosophila simulans strains is studied. The mean number of MDG1 and copia euchromatic hybridization sites (3 sites for each element) is drastically decreased in D. simulans in comparison with D. melanogaster (24 and 18 sites respectively). The mean number of MDG3 sites of hybridization is 5 in D. simulans against 12 in D. melanogaster. As for MDG4 both species have on the average about 2-3 euchromatic sites. The majority of MDG1 and copia and about a half of MDG3 euchromatic copies are localized in restricted number of sites (hot spots) on D. simulans polytene chromosomes. In D. melanogaster these elements are scattered along the chromosomes though there are some hot spots too. It appears that euchromatic copies of MDG1 and copia are considerably less mobile in D. simulans in contrast to D. melanogaster. Some common hot spots of retrotransposon localization in D. simulans and D. melanogaster were earlier described as intercalary heterochromatin regions in D. melanogaster. The level of interstrain variability of MDG4 hybridization sites is comparable in both species. Comparative blot-analysis of adult and larval salivary gland DNA shows that MDG1 and copia are situated mainly in euchromatic regions of D. melanogaster chromosomes. In D. simulans genome they are located mainly in heterochromatic regions underreplicated in salivary gland polytene chromosomes. There are interspecies differences in the distribution of retrotransposons in beta-heterochromatic chromosome regions.     

Cellular energy functions of a subline of mouse fibroblasts resistent to the action of ethidium bromide]

The respiration of subline Leb-25 cells, resistant to ethidium bromide (EB, 25 g/ml), is 2.5 times slower than the respiration of parental L cells of mouse fibroblasts. The EB resistant cells have a normal level of ATP. Disturbances of mitochondrial functions can be observed such as a defect of the succinate dehydrogenase complex and the uncoupling of respiration and oxidative phosphorylation in mitochondria of Leb-25 cells.