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.      

Organization and differentiation of the segmentary plate in common toad embryo Bufo bufo L., following heat shock (author's transl)

A heat shock greatly disturbs the shaping and the growth of embryos with 4 or 5 somites. One part of a segmentary plate with a size including four control somites stays inorganized, whereas posterior segmentation gets on normally. The differentiation of the unsegmented somitic block (fusing myoblasts, myogenesis) is the same as the one of the previous somites; the dermatome and the sclerotome issued from the unsegmented block are not cut up. Ultrastructural observations of treated segmentary plates show that the somitic block undergoes important changes. The non-segmented somitic mesoderm of the control animals obtains a loose aspect; its constitutive cells separated by lacunae are brought into contact by the means of filopods and junctions. 18 hours after the heat shock, the cells of the unsegmented block keep close to each other and are tightened together by many "pseudo-desmosomes", the intercellular spaces are reduced to small meatus. The nuclei of the somitic cells are clear and provided with a restricted amount of chromatine spots; dark granular nuclear like chromatin material is thrown out of the nucleus. In embryos fixed 40 hours after heat shock, several large plurinucleated cells, are formed in the non-segmented somitic block. Inside these plurinucleated cells, there is synthesis of myofilaments and differentiation of myofibrilles. Numerous intercellular lacunae are formed, some yet apparent "pseudo-desmosomes" form "pinchings" between the membranes of muscular cells and therefore confine series of intercellular lacunae.     

Influence of cyclic adenosine monophosphate on the migration of primordial germ cells of the anuran Amphibians (author's transl)]

After the treatment in toto of the embryos from various species of Anura by cAMP, the number of primordial germ cells (PGC) in genital ridges is strongly reduced; the most part of the PGC are found in the endoderm. A ventral implant of agar impregnated with a solution of cAMP attracts numerous PGC in the same way as grafted chordomesoderm. The chordomesoderm itself, incubated with 3'-5' cyclic nucleotide phosphodiesterase, then grafted on to the ventral area of normal embryos attracts very few PBC compared with the non-incubated chordomesoderm. The results are analyzed and discussed along the following hypothesis: the migration of the PGC of the Anura is guided by cAMP which, diffusing from the chordomesoderm, is distributed along a concentration gradient increasing in a ventrodorsal direction. The PGC go up the gradient by a chemiotactic mechanism and reach the dorsal parts of the embryo.     

Detection, using fluorescent lectins, of specific carbohydrate chains in primordial germ cells of anuran amphibians

A study of primordial germ cells (PGC) of Amphibia Anura was carried out after treatment of sections by different fluorescein isothiocyanate conjugated lectins (FITC-lectins). Specific labelling on the PGC is obtained with lectins, the activity of which is inhibited by D-galactose or N-acetyl-galactosamine. These osidic groups appear to be located more specifically on the PGC. The same labelling pattern is not obtained with lectins possessing major affinity for mannose, glucose, fucose and N-acetyl-glucosamine. Furthermore, changes in labelling pattern are observed during migration of PGC. It is suggested that D-galactose and N-acetyl-galactosamine might be related to membrane activity of PGC during migration. Ultrastructural study of the visualization of cell surface carbohydrates supplies some information on the localisation of these lectins receptors.