Experimental hybridization between catfishes of the families Clariidae and Pangasiidae in Thailand

Synopsis Hybrids between the clariid speciesClarias macrocephalus andC. batrachus and the pangasiid speciesPangasius sutchi were obtained by hormone injection of brood stock and artificial fertilization. Pure parental crosses as well as all possible hybrid combinations were obtained. Fertility, hatchability, and post-yolk absorption survival was high (66–99%) in all pure parental crosses and in all crosses between the two species ofClarias. In crosses betweenClarias andPangasius fertilization was also very high (68–97%) but hatchability varied from 11 to 23% and post-yolk absorption survival from 0% inPangasius sutchi ×Clarias batrachus to about 50% inPangasius sutchi ×Clarias macrocephalus . The longest-lived hybrids ofPangasius andClarias were those ofPangasius sutchi ×Clarias macrocephalus which survived until the experiment was prematurely terminated due to contaminated food after 4 1/2 months, at which point they had grown to total lengths of 8–14cm. The hybrids comprised four morphotypes, two relativelyPangasius-like and two relativelyClarias-like, but all markedly different from the parental species.     

Phylohydrax (Rubiaceae-Spermacoceae)—a new genus to accommodate the African and Madagascan“Hydrophylax” species

Hydrophylax, a genus of maritime strand or dune plants, was previously thought to comprise three species, one from India, Sri Lanka and Thailand (H. maritima), and two from Africa and Madagascar (H. carnosa and H. madagascariensis respectively). Evidence is presented that the African and Madagascan species are better placed into a separate genus (Phylohydrax). Differential characters betweenH. maritima andP. carnosa—P. madagascariensis, the relationships between the three species, and the affinities ofPhylohydrax andHydrophylax to otherSpermacoceae are discussed in detail.     

Elektronenmikroskopische Analyse der Musterbildung im Antheridium derPolypodiaceae

An electron microscopical investigation of the cell walls in young antheridia ofPolypodium crassifolium andPlatycerium alcicorne confirms the classical developmental model as postulated byStrasburger and byKny. The structure of the basal cell walls, both of the funnel cell and of the operculum, and especially the evidence of plasmodesmata in those walls, disprove the widely accepted interpretation presented 1951 byDavie.

     

Comparative studies on the teliospore morphology and ontogeny ofSpumula serispora,spec. nova,andRavenelia texensis (Uredinales,Raveneliaceae)

A new rust fungus,Spumula serispora, is described. The morphology of the teliospores and the telia was studied. In the teliospores ofS. serispora andS. quadrifida, the type species of the genus, sterile cells could be found, which are comparable to apical cells of otherRaveneliaceae. Similar sterile cells were also present in the telial heads ofRavenelia texensis. The ontogeny of the teliospores ofS. serispora and the teliospore heads ofRavenelia texensis was studied and compared. In both species the ontogeny of the spores heads was similar. InR. texensis hygroscopic cysts sustaining the spore heads were produced by division and not by conversion of basal sterile cells of the teliospore heads.Part 114 of the series Studies inHeterobasidiomycetes.     

Role ofCandida in indirect pathogenesis of antibiotic associated diarrhoea in infants

One hundred and thirty seven isolates ofCandida species were isolated from antiobiotic associated diarrhoea cases and were examined to study the role ofCandida in the pathogenesis of diarrhoea in infants. The quantitative estimation of yeast population by simple gram stain smear revealed more than 70% of the cases had 3+ score. The isolates further screened for detection of-lactamases. Among the isolatedCandida sp,-lactamases was secreted byC. albicans, C. tropicalis, C. krusei andC. parapsilosis. Further, 46% of theCandida isolates were found to be produced 741–1110 mU/ml of-lactamases, suggesting that these enzyme would inactivate penicillin group of drugs and cause failure in the therapy directed against other diarrhoegenic bacteria.Abbreviation AAD antibiotic associated diarrhoea     

Meiotic studies ofElymus nutans andE. jacquemontii (Poaceae,Triticeae) and their hybrids withPseudoroegneria spicata and seventeenElymus species

Hybridizations ofElymus nutans andE. jacquemontii were carried out with one species ofPseudoroegneria (S genome), and 20Elymus species, each containing either of the SH, SY, SYH, or SYW genomes. Chromosome configurations were analysed at metaphase I of the two target taxa and their interspecific hybrids. It is concluded that (i)E. nutans is an allohexaploid containing the SYH genomes, andE. jacquemontii is an allotetraploid having the SY genomes; (ii) the genomic affinity is associated with the geographic distance between the species studied; (iii) minor genomic structural rearrangements have occurred within the hexaploid taxon ofE. nutans.     

DNA base composition within the genusScenedesmus (Chlorophyta)

The DNA base compositions of 60 strains ofScenedesmus were determined and found to be a valuable indicator for the differentiation within this genus (except for the very closely related species of the subsect.Desmodesmus). The range for allScenedesmus species was 49.9–69.3 mol% GC for nuclear DNA and 36.8–39.9 mol% GC for chloroplast DNA. The separation of the genusTetradesmus cannot be verified by GC values, becauseS. obliquus andS. (Tetradesmus)wisconsinensis have a similar GC content.S. (Chlorella)ultrasquamata, S. costato-granulatus (sect.Costato-granulati) andS. lunatus are separated clearly from all other species of the genus because of their high GC content.     

Orbicules and the ektexine are homologous sporopollenin concretions inSpermatophyta

During microsporogenesis sporopollenin becomes accumulated independently by the only two sporopollenin-producing cell types in the higher plants—the anther tapetum and the microspores—not only within the exine, but also within the orbicules. In Spermatophytes usually only a single orbicule type is found, but sometimes, e.g., inEuphorbia palustris, two different types exist within a single species. Very interestingly, most orbicules are strikingly similar in their structure, sculpture, shape and dimension to the respective ektexine: e.g., smooth sporopollenin globules are found near the totally smooth exines ofEupomatia laurina andPentaphragma sinense respectively, while inDelonix elata andEuphorbia palustris the orbicules often look like some incomplete tectum pieces. All these parallelisms can be attributed to the homologous and therefore highly similar genetic information to form sporopollenin in the sporogeneous tissue and the anther tapetum. The orbicules should be seen neither as sporopollenin storage, as sporopollenin transfer vehicle, nor as sporopollenin surplus.     

Globin evolution in the genusXenopus: Comparative analysis of cDNAs coding for adult globin polypeptides ofXenopus borealis andXenopus tropicalis

Summary Globin mRNAs ofXenopus borealis andXenopus tropicalis have been cloned and sequenced. The nucleotide and derived amino acid sequences were compared with each other and with already available data fromXenopus laevis. This analysis rendered clear evidence that the common ancestor ofX. laevis andX. borealis, but not ofX. tropicalis, had lost one amino acid of the -globins prior to a genome duplication event that preceded the segregation of the former two species. Replacement-site substitutions were used to calculate a rough time scale of genome duplication and species segregation. The results suggest an ancient separation between theX. laevis and theX. tropicalis groups occurring approximately 110–120 million years ago. Analysis of the amino acid chains demonstrated various alterations. However, some functional domains, like heme-binding sites and₁₂ contact sites, were subject to a high degree of conservation, indicating the existence of functional constraints on them also in the genusXenopus.     

A phylogenetic and allozyme approach to understanding rarity in three “green ash” eucalypts (Myrtaceae)

Phylogenetic relationships among the 12 species of the green ash group of eucalypts were examined using allozyme data, to investigate the causes of rarity in three localized endemics of the group. The relationships suggested by the allozyme data showed both similarities to and differences from those estimated from morphological data byLadiges and coworkers. The phylogenetic relationships suggest that rarity inEucalyptus burgessiana may be related to recent divergence, whileE. paliformis andE. rupicola are relatively old species, more likely to be relicts, and/or restricted to a rare habitat.     

Relationships between external nitrate availability,nitrate uptake and expression of nitrate reductase in roots of barley grown in N-limited split-root cultures

Despite the large number of studies of nitrate metabolism in plants, it remains undetermined to what extent this key plant system is controlled by overall plant N nutrition on the one hand, and by the nitrate ion itself on the other hand. To investigate these questions, V _max for nitrate uptake (high-affinity range), and nitrate reductase (NR) mRNA and activity, were measured in roots of N-limited barley (Hordeum vulgare L. cv. Golf) grown under conditions of constant relative addition of nitrate, with the seminal roots split between two culture compartments. The total amount of nitrate added per unit time (0.09·d^-1) was distributed between the two root parts (subroots) in ratios of 1000, 982, 955, 9010, 8020, and 5050. These nitrate-addition ratios resulted in nitrate fluxes ranging from 0 to 23 mol nitrate·g^-1 DW root·h^-1, while the external nitrate concentrations varied between 0 and 1.2 M. The apparent V _max for net nitrate uptake showed saturation-type responses to nitrate flux maintained during preceding growth. The flux resulting in half-maximal induction of nitrate uptake was approximately 4 mol nitrate·g^-1 DW root·h^-1, corresponding to an external nitrate concentration of 0.7 M. The activity of NR and levels of NR mRNA did not saturate within the range of nitrate fluxes studied. None of the parameters studied saturated with respect to the steady-state external nitrate concentration. At the zero nitrate addition — the 0%-root — initial uptake activity as determined in short-term ¹⁵N-labelling experiments was insignificant, and NR activity and NR mRNA were not detectable. However, nitrate uptake was rapidly induced, showing that the 0%-root had retained the capacity to respond to nitrate. These results suggest that local nitrate availability has a significant impact on the nitrate uptake and reducing systems of a split-root part when the total plant nitrate nutrition is held constant and limiting.Abbreviation NR nitrate reductase This work was supported by the Lars Hierta Memory Foundation, the Royal Swedish Academy of Sciences, and by the Swedish Natural Science Research Council via project grants (to C.-M.L. and B.I.) and visiting scientist grant (to W.H.C.). We thank Mrs. Ellen Campbell for technical advice, and Mrs. Judith V. Purves, Long Ashton Research Station, Long Ashton, UK, for analyses of ¹⁵N-labelling in tissue samples.     

Chemotaxonomical investigations of the generaBlackstonia andCentaurium (Gentianaceae)

Methanolic extracts from aerial parts and capsules of plants of 5 populations ofBlackstonia perfoliata and 99 populations of nine European and two AmericanCentaurium species (Gentianaceae) have been screened by means of TLC for the secoiridoid glucosides: sweroside, swertiamarin, gentiopicroside and the m-hydroxybenzoyl esters of sweroside, namely centapicrin, desacetylcentapicrin, decentapicrin A and B as well as for the xanthones: 1,8-dihydroxy-3,5-dimethoxyxanthone, 1,8-dihydroxy-3,7-dimethoxyxanthone, 1,8-dihydroxy-3,5,6,7-tetramethoxyxanthone and xanthone--mono-glucosides. The taxonomical significance of the results is discussed. On the basis of chemotaxonomical evidence twoCentaurium species,C. pulchellum andC. tenuiflorum, are placed in sect.Parviflora instead of sect.Centaurium subsect.Parviflora. Part 8 in the series Secoiridoids and Xanthones in the genusCentaurium. For part 7 see:Van der Sluis & Labadie (1985). — Parts of this study were presented at the 10th annual congress of Farmacognosie en Natuurstofchemie in Utrecht, Nederland, Nov. 11, 1983. For summary see:van der Sluis, W. G., & Labadie, R. P. (1984), Pharm. Weekbl.119, 905–906.     

Observations on the morphogenetic capacity of “residual nuclei” inAcetabularia

Summary Stalks ofAcetabularia mediterranea cells after cyst formation contain residual nuclei,e.g., secondary nuclei not used for cyst formation. Residual nuclei may lead to the formation in the stalk of direct germlings (Hämmerling 1955), cysts, and—without preceeding cyst formation—of biflagellate swarmers, identical in appearance with gametes.     

Evolution of thedec-1 eggshell locus inDrosophila. I. Restriction site mapping and limited sequence comparison in themelanogaster species subgroup

Summary We have analyzed 18 kb of DNA in and upstream of thedefective chorion-1 (dec-1) locus of the eight known species of themelanogaster species subgroup ofDrosophila. The restriction maps ofD. simulans, D. mauritiana, D. sechellia, D. erecta, andD. orena are shown to have basically the restriction map ofD. melanogaster, whereas the maps ofD. teissieri andD. yakuba were more difficult to align. However, the basic amount of DNA and sequence arrangement appear to have been conserved in these species. A small deletion of varying length (65–200 bp) is found in a repeated sequence of the central transcribed region ofD. melanogaster, D. simulans, andD. erecta. Restriction site mapping indicated that thedec-1 gene is highly conserved in themelanogaster species subgroup. However, sequence comparison revealed that the amount of nucleotide and amino acid substitution in the repeated region is much larger than in the 5 translated region. The 5 flanking region showed noticeable restriction site polymorphisms between species. Based on calculations from the restriction maps a dendrogram was derived that supports earlier published phylogenetic relationships within themelanogaster species subgroup except that theerecta-orena pair is placed closer to themelanogaster complex than toD. teissieri andD. yakuba.     

Effects of several metals on spore,biomass, and geosmin production byStreptomyces tendae andPenicillium expansum

Cultures ofStreptomyces tendae andPenicillium expansum grown on Actinomyces and Czapek's media, respectively, were exposed to 5 mg L^–1 of manganese, magnesium, iron, cobalt, nickel, copper and zinc, supplied as sulfate salts. Only copper markedly increased geosmin (1, 10-dimethyl-9-decalol), biomass, and spore production. inductively coupled plasma-atomic emission spectrometric analysis ofS. tendae andP. expansum cells did not indicate an accumulation of copper. Both 1 and 5 mg L^–1 copper, as copper sulfate, increased total geosmin production in cultures ofS. tendae on several media, but decreased production on others, suggesting that substrate composition affects responses to copper.     

Genetics of esterases in Drosophila. IV. Slow-migrating S-esterase in Drosophila of the virilis group

A slow-migrating -esterase (S-esterase) is described which has been detected in Drosophila montana, Drosophila imeretensis, and some stocks of Drosophila virilis when mixtures of - and -naphthyl acetate are used as substrates in histochemical reactions after electrophoresis. Sexual dimorphism for S-esterase has been demonstrated. This esterase is contained in male genitalia only, predominantly in the ejaculatory bulb (waxy plug). It appears 3–4 days after emergence of flies. In hybrids between S⁺ and S⁰ species, the activity of the slow esterase is either decreased or inhibited. An autonomous synthesis of the S-esterase in the ejaculatory bulb was established by transplantation of imaginal genital discs into larvae of different Drosophila stocks. Based on analysis of physicochemical and immunochemical properties, S-esterase is suggested to be an independent fraction of esterase, possibly dimeric, which does not cross-react with -esterase antiserum.     

Karyosystematics of thePhleum alpinum polyploid complex (Poaceae)

The karyotypes of three taxa from thePhleum alpinum group of sect.Phleum (P. alpinum subsp.rhaeticum, 2n = 14,P. commutatum, 2n = 28, and informally namedP. commutatum, 2n = 14) were investigated by Giemsa C-banding. The overall similarity of diploid genomes suggests thatP. alpinum subsp.rhaeticum andP. commutatum are closely related — their karyotypes vary only with respect to their average amounts of telomeric heterochromatin. TheP. commutatum genome contains less telomeric heterochromatin than the genome ofP. alpinum subsp.rhaeticum, but in theP. alpinum group as a whole almost fluent transition between low (1.5%) and high (25.5%) amounts of telomeric heterochromatin was observed among populations. In the karyotype of tetraploidP. commutatum, seven distinguishable chromosome types were observed. Each of them is represented at somatic metaphase by four chromosomes. C-band structure of karyotype and average amount of telomeric heterochromatin suggest that this taxon has originated from hybridization between two related diploid forms of theP. commutatum — P. alpinum complex.     

Phylogeny and habitat adaptations within a monophyletic group of wetland moss genera (Amblystegiaceae)

Genus level phylogenetic patterns within a monophyletic group of wetland mosses consisting ofTomentypnum, Hamatocaulis, Scorpidium, Conardia, Calliergon, Warnstorfia, Straminergon, andLoeskypnum (Amblystegiaceae) are cladistically analysed, usingPalustriella and partlyCratoneuron as outgroups. The ingroup consists of two clades, one withTomentypnum, Hamatocaulis andScorpidium, the other with the other ingroup genera. The second clade gets completely resolved only with the inclusion of habitat data. The adaptation to relatively dry wetland habitats probably evolved in the ancestor ofStraminergon andLoeskypnum, the species ofCalliergon andWarnstorfia, which are more ancestral, growing in wetter habitats. The more primitive taxa of the ingroup, as well asPalustriella species, occur in relatively mineral-rich habitats and adaptations to poorer habitats occurred several times in the two clades.     

Nuclear DNA changes,genome differentiation and evolution inNicotiana (Solanaceae)

A survey of 51 species fromNicotiana subgg.Tabacum, Rustica andPetunioides has shown that evolution was accompanied by a five-fold variation in nuclear DNA amounts. This variation, however, was not directly correlated with the changes in chromosome number. Drastic rearrangement of karyotypes is characteristic for the evolution ofNicotiana spp. Significant gain or loss in nuclear DNA has often accompanied such changes, but DNA variation has also occurred without significant changes in karyotype arrangements.—The distribution of nuclear DNA is discontinuous inNicotiana, species cluster into DNA groups with consistently regular increments in the mean DNA amounts. The discontinuities are viewed as steady states in terms of genomic balance and biological fitness.—Changes in the amount of nuclear DNA and in the heterochromatin are compared with the morphological, chromosomal and adaptive changes which accompanied speciation in 14 subgeneric sections. The evolutionary significance of DNA variation is discussed.     

Fruiting studies in species ofCapronia (Herpotrichiellaceae)

A recently described protocol for thein vitro production of ascomata was employed to determine the sexual incompatibility systems of five species ofCapronia. The formation of mature ascomata in isolates derived from single ascospores demonstrated thatC. epimyces, C. mansonii, andC. munkii n. sp. are homothallic. In contrast, fertile ascomata were observed only in mass-ascospore isolates and pairwise crosses between specific single-ascospore isolates inC. dactylotricha n. sp. andC. moravica. TheExophiala anamorphs ofC. dactylotricha andC. munkii are described and aPhialophora-like synanamorph is reported for the former species. Germinating ascospores ofC. munkii formed conidiogenous cells directly, while the ascospores of the remaining species germinated to produce germ tubes and hyphae. The application of the terms microcyclic conidiation to secondary conidium production and sclerotial body and stroma to the multicellular structures produced by species ofCapronia andExophiala are discussed.