Petersburg Area Research Articles

Advances in the Ordovician graptolite biostratigraphy of the St Petersburg area, Russia

The Ordovician shallow-water shelf deposits rich in benthic fauna are exposed along the Russian part of the Baltic- Ladoga Klint. Graptolites occur only at some stratigraphic levels, being comparatively numerous in marls and clays and very rare in carbonate layers. Since the 19th century graptolites have been collected from exposures of the Pakerort, Hunneberg, Billingen, and Volkhov regional stages (Tremadocian-Dapingian), while in the Uhaku-Idavere stratigraphic interval (Darriwilian-lower Sandbian) rare graptolites have been found in boreholes. Up to now, only some collections have been systematically studied. On the basis of new graptolite finds, recently the Pterograptus elegans Biozone was established in the upper Aseri Stage and the Nemagraptus gracilis Biozone in the lower Kukruse Stage. Detailed sampling of the Shundorovo Formation (upper Idavere Stage) resulted in the discovery of numerous diplograptids at five stratigraphic levels, in association with various dendroids. These diplograptids were provisionally assigned to ?Archiclimacograptus antiquus lineatus Elles & Wood. A systematic description of the late Darriwilian and early Sandbian diplograptids is under preparation.

Mycobacterium tuberculosis co-existence with humans: making an imprint on the macrophage P2X7 receptor gene?

The development of tuberculosis (TB) infection in humans depends on the mycobacterial strain and the human host, and is multigenically controlled in both. ATP ligation of P2X(7) receptors expressed on human macrophages infected with mycobacteria induces cell death and subsequent loss of intracellular bacterial viability. This study analysed the allelic distribution of two single-nucleotide polymorphisms (SNPs) in the P2RX7 gene in the Slavic population of the St Petersburg area of Russia. Analysis of the -762 C/T P2RX7 promoter SNP revealed no significant association between pulmonary TB patients and control subjects (3x2 chi(2)=3.2, 1 d.f., P=0.2). The -762C allele was highly and almost equally represented in both groups in this study (68.2 % in patients and 69.3 % in controls). This result differs strikingly from a Gambian study where this allele was found in only 7 and 12 % of pulmonary TB patients and controls, respectively [Li, C. M., Campbell, S. J., Kumararatne, D. S., Bellamy, R., Ruwende, C., McAdam, K. P. W. J., Hill, A. V. S. & Lammas, D. A. (2002). J Infect Dis 186, 1458-1462]. In contrast, the frequency of the C allele at position 1513 in exon 13, resulting in a loss of P2X(7) function, was significantly higher among pulmonary TB patients in this study (P=0.02). Thus, analysis of the P2X(7) receptor gene in the Russian Slavic population showed that the 1513C allele, acting dominantly, is a possible risk factor for clinical TB, whereas the -762 P2RX7 polymorphism did not appear to be associated with human susceptibility to TB.

Morphology, evolution and stratigraphic distribution in the Middle Ordovician conodont genus Microzarkodina

ABSTRACTMicrozarkodina is a genus of mainly Middle Ordovician conodonts that has its centre of distribution in Baltoscandia, and much less commonly occurs in southern China, Australia, Argentina and Laurentia. In Baltica a series of species, Microzarkodina russica n. sp., M. flabellum, M. parva, M. bella, M. hagetiana and M. ozarkodella, established themselves successfully. The succession of species ranges from just below the base of the Middle Ordovician (M. russica) to the upper part of the Middle Ordovician (M. ozarkodella). The species are frequently used for biostratigraphical purposes. The largely contemporaneous species Microzarkodina bella and M. hagetiana probably both evolved from M. parva and mostly occurred in separate areas. Microzarkodina ozarkodella probably evolved from M. hagetiana. This present investigation is based on a total of 94,208 elements, collected from 20 sections and one drill-core site in Sweden, one drill-core site and one outcrop in Estonia and two sections in the St Petersburg area in Russia. The Microzarkodina apparatus probably consisted of 15 or 17 elements: four P, two or four M and nine S elements. The S elements include different Sa, Sb1, Sb2, and Sc element types.

A redescription of Eucyclops serrulatus (Fischer, 1851) (Crustacea: Copepoda: Cyclopoida) and some related taxa, with a phylogeny of the E. serrulatus‐group

Eucyclops serrulatus (Fischer, 1851), the type species of the genus Eucyclops, is redescribed from specimens found in the St. Petersburg area, Russia (type locality) and compared with specimens from Siberia, western Europe and North Africa. A neotype is selected. Cultures were set up, and interpopulation hybridization as well as hybridization with related species was attempted. The classical description of external body morphology was combined with pore signature mapping and with DNA nuclear small subunit (18S) ribosomal gene sequence analysis. Comparisons with E. dumonti Alekseev, 2000, E. hadjebensis Kiefer, E. speratus Lilljeborg, E. turcomanus Lindberg, and E. pectinifer (Cragin, 1883) were carried out. A phylogenetic tree based on molecular information shows that E. serrulatus and E. speratus should be regarded as separate species. E. dumonti also deserves species status, but not E. hadjebensis. A cladistic tree based on the pore pattern of the cephalosome agrees well with a tree based on the sequence of the 18S rDNA gene. Cephalosome (and probably metasome) pore patterns seem useful to elucidate relationships within genera, while urosomal pore patterns better reflect the relationship between genera. E. serrulatus occurs in three morphological forms over most of its range; one of these (C) might be a rare (‘recessive’) morphotype, while forms A and B differ in microhabitat choice, but hybridize when living together. The same polymorphism also occurs in an American species (E. prionophorus), and therefore two hypotheses regarding its origin are advanced: either forms A and B evolved during the glacial episode (Pleistocene origin), separately on both sides of the Atlantic, or the polymorphism was already present in the ancestor of the serrulatus‐group, and was later lost in some but not in all species (Pliocene origin.)

Efficient Discrimination within aCorynebacterium diphtheriaeEpidemic Clonal Group by a Novel Macroarray-Based Method

A large diphtheria epidemic in the 1990s in Russia and neighboring countries was caused by a clonal group of closely related Corynebacterium diphtheriae strains (ribotypes Sankt-Peterburg and Rossija). In the recently published complete genome sequence of C. diphtheriae strain NCTC13129, representative of the epidemic clone (A. M. Cerdeno-Tarraga et al., Nucleic Acids Res. 31:6516-6523, 2003), we identified in silico two direct repeat (DR) loci 39 kb downstream and 180 kb upstream of the oriC region, consisting of minisatellite (27- to 36-bp) alternating DRs and variable spacers. We designated these loci DRA and DRB, respectively. A reverse-hybridization macroarray-based method has been developed to study polymorphism (the presence or absence of 21 different spacers) in the larger DRB locus. We name it spoligotyping (spacer oligonucleotide typing), analogously to a similar method of Mycobacterium tuberculosis genotyping. The method was evaluated with 154 clinical strains of the C. diphtheriae epidemic clone from the St. Petersburg area in Russia from 1997 to 2002. By comparison with the international ribotype database (Institut Pasteur, Paris, France), these strains were previously identified as belonging to ribotypes Sankt-Peterburg (n = 79) and Rossija (n = 75). The 154 strains were subdivided into 34 spoligotypes: 14 unique strains and 20 types shared by 2 to 46 strains; the Hunter Gaston discriminatory index (HGDI) was 0.85. DRB locus-based spoligotyping allows fast and efficient discrimination within the C. diphtheriae epidemic clonal group and is applicable to both epidemiological investigations and phylogenetic reconstruction. The results are easy to interpret and can be presented and stored in a user-friendly digital database (Excel file), allowing rapid type determination of new strains.

Emplacement, rapid burial, and exhumation of 90-Ma plutons in southeastern Alaska

In southeastern Alaska, granodiorite–tonalite plutons of the Admiralty–Revillagigedo belt intruded the Jurassic–Cretaceous Gravina belt along the eastern side of the Alexander terrane around 90 Ma. These plutons postdate some deformation related to a major contractional event between the previously amalgamated Wrangellia and Alexander terranes and the previously accreted terranes of the North American margin. We studied the aureole mineral assemblages of these plutons near Petersburg, Alaska, determined pressure and temperature of equilibration, and examined structures that developed within and adjacent to these plutons. Parallelism of magmatic and submagmatic fabrics with fabrics in the country rock indicates synchroneity of pluton emplacement with regional deformation and suggests that magma transport to higher crustal levels was assisted by regional deformation. Replacement of andalusite by kyanite or sillimanite indicates crustal thickening soon after pluton emplacement. Regional structural analysis indicates the crustal thickening was accomplished by thrust burial. Thermobarometric analyses indicate the aureoles reached near-peak temperatures of 525 to 635 °C at pressures of 570 to 630 MPa. Consideration of the rate of thermal decay of the aureoles suggests that burial was rapid and occurred at rates around 5 to 8 mm/year. Structural observations indicate there was contractional deformation before, during, and after emplacement of the 90-Ma plutons. Initial exhumation of the Admiralty–Revillagigedo belt in the Petersburg area may have occurred along a thrust west of the pluton belt within the Gravina belt.

Plagganthrepts in northwest Russia? Genesis, properties and classification

To clarify the properties, genesis and classification of typical anthropedogenic soils of St. Petersburg area, exemplary five profiles were thoroughly investigated. The soils are characterised by humus-rich, well-structured and biologically active anthropedogenic epipedons, reaching depths of 52 and 55 cm. The texture, the mineral distribution and the XRD analysis confirmed the multiple geological composition of the profiles. The bulk densities of the anthropedogenic epipedons were 1.0–1.3 g cm −3 and down to 1.9 g cm −3 in the underlying horizons. The pH values were 4.9–6.8 (CaCl 2). Small lime amounts were found in two cases. The C org contents were 23.5–74.0 g kg −1 and the N contents 2.0–3.9 g kg −1 in the anthropedogenic horizons and 0.8–4.9 g kg −1 and 0.1–0.3 mg kg −1 in the underlying ones. Decreased humus contents in the root zone indicated degradation processes. The base saturation was mostly 100% and the CEC 9.3–17.1 cmol c kg −1 in the top and 3.0–9.3 cmol c kg −1 in the subsoils. The total P contents were 884–1835 mg kg −1 and the citric acid soluble P content 321–776 mg kg −1 in the anthropedogenic epipedons and 189–355 and 46–321 mg kg −1 in the underlying horizons. Thus, the anthropedogenic St. Petersburg soils showed distinct similarities to the Plagganthrepts of northwest Europe in respect of C org enrichment, surface raise and P enrichment. The same is true regarding the main management aims: increase of soil fertilisation combined with an overcome of lacking bedding materials. Hence, the genesis and most properties of the anthropedogenic St. Petersburg soils support a classification as Agrosems (Russian taxonomy) Plaggeneschs (German taxonomy) Plagganthrepts (U.S. taxonomy) or terric Anthrosol (World Reference Base for Soil Resources [WRB] taxonomy). But the required thickness of the anthropedogenic epipedon is barely achieved. Thus, Plagganthrepts occur as small patches, which may even decrease, because of soil degradation.

Taxonomy and distribution of the Ordovician conodontDrepanodus arcuatus Pander, 1856, and related species

Drepanodus arcuatusPander, 1856, is one of the geographically most widely distributed conodont species in the Ordovician, and has been reported to range practically throughout the entire Ordovician System. Topotype material from thePrioniodus elegans Zone in the St. Petersburg area of Russia has been studied in order to better define the species, and largeD. arcuatus collections from Sweden, ranging in age from the TremadocianPaltodus deltifer Zone and into the basalPygodus serra Zone in the Darriwilian, have been examined to estimate the limits of variation. Most of the investigated material is of Arenigian age. In this process, two additional speciesof Drepanodus were identified in the Swedish collections, and at least one of these,Drepanodus reclinatus (Lindstrom, 1955), also has a rather wide distribution in North America and southern China. This species and the new species,Drepanodus parformis n. sp., are much less common thanD. arcuatus in the great majority of the investigated samples, but they seem to have largely the same stratigraphical range asD. arcuatus. Biofacies patterns as well as palaeogeo-graphic distribution of the taxa discussed are documented.

Early Ordovician acritarchs of the Lierneux Member (Stavelot Inlier, Belgium): stratigraphy and palaeobiogeography

Abstract The messaoudensis-trifidum acritarch microflora is currently considered to be characteristic of latest Tremadocian-earliest Arenigian cold-water environments on the periphery of Gondwana, at high latitudes in the southern hemisphere. Integrated biostratigraphical studies on both acritarchs and graptolites are available from two areas of peri-Gondwana, the Lake District (northwestern England) and the Sierra Morena (southwestern Spain). The assemblage was also recorded from other areas on the northern border of the Gondwana continent where macrofossils are generally not available: from southern Ireland, the Isle of Man, southern Wales, the island of Rügen in northern Germany, the Prague Basin in the Czech Republic, and southern Turkey. While it appears that the messaoudensis-trifidum acritarch assemblage is limited to cold-water environments in localities on the periphery of Gondwana, some of its elements can be found in other areas. Some taxa, but not the complete assemblage, have been identified in the eastern Cordillera of Argentina, and some species of the assemblage are cited from continents which were situated at intermediate latitudes in warmer waters: some elements of the assemblage are described from localities of Baltica (from Norway, Estonia and the St. Petersburg area in northwestern Russia) and from the Yangzte Platform in southern China. In these regions, typical representatives of the messaoudensis-trifidum assemblage co-occur with taxa typical of temperate and warm-water areas. The present paper reports the discovery of the messaoudensis-trifidum acritarch assemblage in the Lierneux Member (Stavelot Inlier, Belgium). The Lierneux Member, which constitutes the uppermost part of the Jalhay Formation (formerly Salmian 1c) in the Stavelot Inlier, was first dated as late Tremadocian by Vanguestaine [1992a]. Following recent stratigraphical conclusions based on the detailed investigations of the messaoudensis-trifidum assemblage from different sequences of peri-Gondwana, the age of the Lierneux Member recovered from the Chevron borehole in the Stavelot Massif can now be confirmed as being probably latest Tremadocian. The discovery of the messaoudensis-trifidum assemblage in the Stavelot Inlier provides further evidence for the palaeogeographical distribution of the assemblage on the northern border of Gondwana and allows tentative correlations between eastern Belgium and northern Germany.

Detection of embB306 mutations in ethambutol-susceptible clinical isolates of Mycobacterium tuberculosis from Northwestern Russia: implications for genotypic resistance testing.

A total of 183 epidemiologically unlinked Mycobacterium tuberculosis isolates collected in the St. Petersburg area of Russia from 1996 to 2001 were screened for alterations in codon 306 of the embB gene; mutations in this codon are reported to confer resistance to ethambutol (EMB). The embB306 mutations were detected in 14 (48.3%) of 29 EMB-resistant strains and, quite surprisingly, in 48 (31.2%) of 154 EMB-susceptible strains. A discrepancy between the results of phenotypic and genotypic EMB resistance tests was restricted to the strains already resistant to other antitubercular (anti-TB) drugs. In particular, 40 (60%) of the 69 EMB-susceptible strains resistant to rifampin, isoniazid, and streptomycin but none of the 43 pansusceptible strains harbored an embB306 mutation. We hypothesize that the phenomenon observed could reflect the presence of a target other than EmbB for the drug in tubercle bacilli; this unknown target could be sensitized and affected, sensu lato, by EMB during treatment with other first-line anti-TB drugs. Comparison with DNA fingerprinting data showed that, irrespectively of the phenotypic susceptibility profiles, 46 (50.6%) of 91 Beijing family strains and 16 (17.4%) of 92 strains of other genotypes had a mutation in embB306.

Nosocomial outbreak of multidrug-resistant tuberculosis caused by a strain of Mycobacterium tuberculosis W-Beijing family in St. Petersburg, Russia.

A molecular epidemiologic study of 35 Mycobacterium tuberculosis isolates from 19 patients was conducted to define a nosocomial outbreak of multidrug-resistant tuberculosis in St. Petersburg, Russia. IS 6110-restriction fragment length polymorphism (RFLP) fingerprinting, together with investigations to detect mutations conferring drug resistance, revealed relationships between the isolates and links between the cases. Three patients and a nurse exposed to active tuberculosis were proved to be involved in the outbreak; the source case was identified. The outbreak strain possessed a 17-band RFLP pattern and a spoligoprofile (signals 35-43) characteristic of the W-Beijing family as well as distinctive mutations in katG315, rpoB531, embB306 and rpsL43. This specific RFLP pattern has previously been identified among Mycobacterium tuberculosis W-Beijing strains isolated across the former Soviet Union and in the St. Petersburg area of Russia. The spread of multidrug-resistant strains of W-Beijing genotype in the general population and in hospital settings presents a serious threat for public health in Russia. Specific pathogenic properties of W-Beijing genotype strains, such as enhanced transmissibility and the ability to cause reinfection and to readily acquire drug resistance to major antituberculosis drugs, along with special features of host response, have yet to be investigated.

Novel IS6110 insertion sites in the direct repeat locus of Mycobacterium tuberculosis clinical strains from the St. Petersburg area of Russia and evolutionary and epidemiological considerations.

A modification of spoligotyping with primers derived from the direct repeat (DR) and IS6110 sequences was used to identify IS6110 insertions in the DR locus of Mycobacterium tuberculosis clinical strains from the St. Petersburg area of Russia. Novel IS6110 insertions were identified: (i) in two epidemiologically unlinked Beijing family strains, an asymmetrical direct insertion in DR37; (ii) in a non-Beijing strain, an asymmetrical insertion in the opposite orientation in DR38; (iii) in another non-Beijing strain, a direct insertion in DR38 and one in the opposite orientation in DR14 (DR numbering is according to standard spoligotyping). Our results strengthen an observation that the DR locus structure is extremely conserved in the Beijing genotype. Asymmetrical insertions prevented detection of the adjacent spacer by standard spoligotyping. This, therefore, should be taken into consideration when similar spoligoprofiles that differ only in signals 37 and 38 are interpreted.

Nordic investments in the former soviet baltic frontier: a survey of firms and selected case studies

Nordic companies have been leaders in the rapid expansion of Western business into Estonia, Latvia, Lithuania, and the St Petersburg area of Russia. While joint ventures were being developed prior to the demise of the USSR, investment rose sharply in early 1992. Our survey of companies from Nordic countries revealed a pattern of location and of adaptation to the conditions of former Soviet infrastructure, culture, politics and economy. Initial Nordic investment has renewed economic ties across the Baltic Sea, with inter‐country links stronger between specific countries. Frustrations with changing government rules, communications, work ethic, quality expectations and other conditions were expressed in interviews with managers of Nordic companies in the Baltic area. Optimism was tempered by continued uncertainty about Russian governmental policies and market potential.

Relative sea-level changes in Baltoscandia in the Cumbrian and early Ordovician: the predominance of tectonic factors and the absence of large scale eustatic fluctuations

Fluctuations in sea depth within a magnitude 20–100 m and a duration of 1–10 m.y. are often explained by rapid eustatic changes — so called ‘third-order eustatic events’. Considerable influence of regional tectonics on relative sea-level changes has been demonstrated by many authors, but because of uncertainties in the timing of short events in widely separated regions, the problem of separating tectonic and eustatic factors still remains unsolved. In this paper, a new and simple approach is used to reveal the presence or absence of eustatic events. We consider the St. Petersburg area and North Estonia in the north-eastern region of the East Baltic. From the late Early Cambrian until the middle of the Tremadoc (early Ordovician), deposition was extremely slow and the sea bed remained for a long time in a well defined peritidal zone in a water depth ≤10 m. Under such environmental conditions, a sea-level rise of ≥10 m would result in marked changes in the character of faunas and sedimentation. In the time interval considered here, significant sea deepening in the north-eastern Baltic region occurred only twice, and its magnitude did not exceed 10–20 m. A fall of sea level by ≥10 m would result in complete regression in the peritidal zone. This situation also occurred in region. However, the preservation of a sequence of unconsolidated sands, which is only a few tens of metres thick and includes all the main stratigraphic subdivisions on a regional scale, indicates that the crustal surface reached a very low altitude ≤10–20 m above sea level. These data show that in the late Late Cambrian to the middle of the Tremadoc, over a period of ∼40 m.y. long, eustatic sea-level changes did not exceed ±10–20 m. This limits the magnitude of several third-order cycles — eustatic events with duration of a few million years, which have been proposed previously for the epoch of the transition from the Cambrian to the Ordovician. In the late Early Cambrian to the Late Cambrian, transgressions and regressions with a magnitude of ∼50–150 m took place in southern Sweden and Lithuania. Since these phenomena occurred when there were no comparable eustatic sea-level changes, they must be associated with regional tectonic movements. Some were rapid and could be easily misinterpreted as indications of third-order eustatic changes. It is probable that some of the other eustatic events that have been proposed for the Phanerozoic were actually not of eustatic but of tectonic origin. Such rapid tectonic movements with magnitude of ∼50–100 m in cratonic areas can be caused by changes in the forces in the lithospheric layer with a laterally variable thickness, and by phase transitions in the mafic lower crust. Depending on the spatial distribution of vertical crustal movements, both these mechanisms could have been operating in the East Baltic and southern Sweden in the Cambrian.

Eucyclops dumonti sp.nov. from Central Mongolia

Eucyclops dumonti sp.nov. is described from a shallow spring-fed lake in Central Mongolia. Data on its morphological variability are given, a comparison with the type population of Eucyclops serrulatus (Fischer, 1853) from St. Petersburg area is made, and its position relative to some closely related congeners is discussed.

Recognizing explosion sites with a self-organizing network for unsupervised learning

A self-organizing neural network model has been developed for identifying mining explosion locations in different environments in Finland and adjacent areas. The main advantage of the method is its ability to automatically find a suitable network structure and naturally correctly identify explosions as such. The explosion site recognition was done using extracted waveform attributes of various kind event records from the small-aperture array FINESS in Finland. The recognition was done by using P–S phase arrival differences and rough azimuth estimates to provide a first robust epicentre location. This, in turn, leads to correct mining district identification where more detailed tuning was performed using different phase amplitude and signal-to-noise attributes. The explosions studied here originated in mines and quarries located in Finland, coast of Estonia and in the St. Petersburg area, Russia. Although the Helsinki bulletins in 1995 and 1996 listed 1649 events in these areas, analysis was restricted to the 380 (ML≥2) events which, besides, were found in the reviewed event bulletins (REB) of the CTBTO/UN prototype international data centre (pIDC) in Arlington, VA, USA. These 380 events with different attributes were selected for the learning stage. Because no `ground-truth' information was available the corresponding mining, `code' coordinates used earlier to compile Helsinki bulletins were utilized instead. The novel self-organizing method was tested on 18 new event recordings in the mentioned area in January–February 1997, out of which 15 were connected to correct mines. The misconnected three events were those which did not have all matching attributes in the self-organizing maps (SOMs) network.

Latitudinal Variation in Cold Hardiness and Body Size in the Boreal Ant species Leptothorax acervorum (Hymenoptera: Formicidae)

The Myrmicinae species Leptothorax acervorum (Fabricius 1793) is among the ants ranging farthest north in both North America and Eurasia. Workers from 3 populations living in areas with greatly different climates differ in cold hardiness and individual size. Workers from Cape Kindo on the shore of the White Sea (66° 33'N) survived best at low temperatures and were significantly larger than workers from Nurnberg Reichswald (49.5°N), with workers from the St. Petersburg area (60°N) lying between the two extremes. The significance of the findings is discussed.

Clay varve chronology in the Eastern Baltic area

The clay varve chronologies of the Eastern Baltic and NW Russia are discussed, and an attempt is made on the basis of the revised Swedish Time Scale and direct correlation with the Swedish and Finnish clay varve chronologies, to date Markov's chronologies for the St. Petersburg area and southern Karelia via Sauramo's chronology for Finland. A mean annual rate of ice recession is used to overcome the distance of 100 km between the sites investigated by Sauramo and Markov. It is proposed that the area north of L. Onega was deglaciated approximately between 13,940 and 13,140 varve years BP, the Neva basin between 12,600 and 12,520 varve years BP and the Luga basin between 12,440 and 12,360 varve years BP. Accordingly, the Weichselian ice sheet would have retreated from the Pandivere/Neva ice marginal zone about 12,330 varve years BP. The weakness of some of the arguments used in correlating the chronologies for NW Russia means that the deglaciation chronology of the Eastern Baltic remains open for further discussion. Hang, T., 1997: Clay varve chronology in the Eastern Baltic area. GFF, Vol. 119 (Pt. 4, December), pp. 295–300. Stockholm. ISSN 1103–5897.

A new stem-chordate solute fromthe Middle Ordovician of Estonia

The solute Maennilia estonica nov. gen. et nov. sp. (Maenniliidae, nov. fam.) from the middle Caradoc Keila Horizon of the village of Vasalemma, near the town of Keila, near Tallin, Estonia is reconstructed and described. Remarkable features include: the hydropore developed as a madreporite and penetrated by the gonopore; ringshaped major plates in the fore tail, visibly formed by the fusion of smaller plates; a symmetrical mid tail, with dorsal and ventral series of ossicles extending forwards to meet the fore-tail rings in the mid line; an anterior lobe projecting leftwards and better developed in large than small individuals; and large size. Maennilia estonica may have lived with the ventral face up. The presence of a branchial pore could not be established. Ontogenetic changes in the anterior lobe suggest that the gonad was anteriorly located in the head, as in other solutes. Maenniliidae nov. fam. comprising M. estonica and Heckericystis kuckersiana (Hecker) 1940, and with Maennilia estonica as the type species, is proposed with three autapomorphies: the gonopore penetrates the hydropore, the mid tail has a peculiar symmetrical structure and the head skeleton is relatively rigid. The Maeniliidae have rings in the fore tail visibly formed by the fusion of smaller plates. Among other solutes, only Dendrocystites sedgwickiBarrande, 1887 seems to share this feature which should therefore probably be seen as a synapomorphy of the Maenniliidae with that species. Within the chordate stem group, the Maenniliidae with Dendrocystites sedgwicki probably represent a plesion crownward of the Iowacystidae and anti-crownward of Dendrocystoides scoticus (Bather) 1913. Hecker's reconstruction of H. kuckersiana is partly mistaken. Isolated hind-tail ossicles of ”Dendrocystites” rossicusJaekel, 1901, from the Llanvirn near Pavlovsk in the St. Petersburg area of Russia, suggest a solute of very great size i.e. with a guessed total length of perhaps 300 mm, making it by far the largest known solute.

Selection of Rhizobium leguminosarum bv. viceae strains for inoculation of Pisum sativum L. cultivars: Analysis of symbiotic efficiency and nodulation competitiveness

From an analysis of 481 Rhizobium leguminosarum bv. viceae strains with 7 pea cultivars in pot and field experiments, we demonstrated that effective strains could be isolated from a rich medium-acid grey forest soil of the Orol area (Central region of the European part of Russia) but not from a poor acid podzolic soil of the St. Petersburg area (North-West Russia). The proportion of the isolates significantly increasing N accumulation in pea plants (10.2%) is higher than that of strains increasing the shoot dry mass (4.6%) in the pot experiments. The mean values of the increase for N accumulation (33.8%) upon inoculation are also higher than for shoot mass (27.0%) in these experiments. N accumulation in the inoculated pea plants in the pot experiments was significantly correlated with seed yield and seed N accumulation in field experiments, while for shoot dry mass these correlations were either weak or not significant. Two-factor analysis of variance demonstrated that the contribution of plant cultivars to the variation of the major symbiotic efficiency parameters is higher (30.8–31.6%) and contributions of cultivar-strain specificity is lower (5.4–8.8%) than the contributions of strain genotypes (13.4–14.9%). We identified an ineffective R. leguminosarum bv. viceae strain 50 which can be used as a tester for assessing the nodulation competitiveness of the effective strains by an indirect method (analysis of dry mass and N accumulation in pea plants inoculated with the mixture of the tested effective strains and the tester strain). The relative competitive ability (RCA) determined by this method was 75.7–82.8% for strain 52 but only 10.5–13.8% for strain 250a; this difference was confirmed by a direct method (use of the streptomycin-resistant mutants). Results of screening of the diverse collection of 53 effective R. leguminosarum bv. viceae strains by the indirect method permits us to divide them into 3 groups (32 high-competitive, 10 medium-competitive and 11 low-competitive strains) but reveals no correlation between the competitiveness and symbiotic efficiency. N accumulation in the pea shoots is demonstrated to be a much more suitable criterion than the shoot mass for selection either of the highly-effective or of highly-competitive (by the indirect estimation) R. leguminosarum bv. viceae strains in the pot experiments.