The Life Histories of Two Temporarily Coexisting,Pond Dwelling Cladocerans

Investigations on the life histories of two cladocerans, Moina brachiata and Daphnia obtusa, in a small, nearly temporary pond in South Germany revealed that M. brachiata is better adapted to fluctuating environmental conditions; the species dominated from May to October. D. obtusa was present in spring and autumn/winter but disappeared completely during the summer months. Both species coexisted for extended periods in spring and autumn; abundance of D. obtusa was generally by an order of magnitute lower. Four periods of low water level were slightly preceded by or coincided with a decrease of clutch size, a decrease of the proportion of egg bearing females indicating that both species suffered from food shortage. Laboratory investigations on life history parameters showed that the two species have different temperature tolerances and preferences. M. brachiata showed its highest reproductive success at 25 and 30°C but died at temperatures <15°C and ≥ 35°C. D. obtusa experienced a broader temperature range (2 to 25°C) but could not withstand temperatures ≥ 30°C. Short term starvation periods (3d) caused the death of M. brachiata females, while D. obtusa soon recovered and reproduced when being refed. M. brachiata is a typical r-species with early reproduction, rapid development, high population growth rates and a high tendency to produce resting eggs; D. obtusa pursues more the concept of k-selection.     

Specific arbuscular mycorrhizal fungi associated with non-photosynthetic Petrosavia sakuraii (Petrosaviaceae)

Mycorrhizal fungi in roots of the achlorophyllous Petrosavia sakuraii (Petrosaviaceae) were identified by molecular methods. Habitats examined were plantations of the Japanese cypress Chamaecyparis obtusa in Honshu, an evergreen broad-leaved forest in Amami Island in Japan and a mixed deciduous and evergreen forest in China. Aseptate hyphal coils were observed in root cortical cells of P. sakuraii, suggesting Paris-type arbuscular mycorrhiza (AM). Furthermore, hyphal coils that had degenerated to amorphous clumps were found in various layers of the root cortex. Despite extensive sampling of P. sakuraii from various sites in Japan and China, most of the obtained AM fungal sequences of the nuclear small subunit ribosomal RNA gene were nearly identical and phylogenetic analysis revealed that they formed a single clade in the Glomus group A lineage. This suggests that the symbiotic relationship is highly specific. AM fungi of P. sakuraii were phylogenetically different from those previously detected in the roots of some mycoheterotrophic plants. In a habitat in C. obtusa plantation, approximately half of the AM fungi detected in roots of C. obtusa surrounding P. sakuraii belonged to the same clade as that of P. sakuraii. This indicates that particular AM fungi are selected by P. sakuraii from diverse indigenous AM fungi. The same AM fungi can colonize both plant species, and photosynthates of C. obtusa may be supplied to P. sakuraii through a shared AM fungal mycelial network. Although C. obtusa plantations are widely distributed throughout Japan, P. petrosavia is a rare plant species, probably because of its high specificity towards particular AM fungi.     

Discovery of the oldest record of Nitellopsis obtusa (Charophyceae,Charophyta) in North America

Studies of the colonization and spread of invasive species improves our understanding of key concepts in population biology as well as informs control and prevention efforts. The characean green alga Nitellopsis obtusa (starry stonewort) is rare in its native Eurasian range but listed by the United States Geological Survey (USGS) as an aggressive invasive in North America. First documented in North America in 1978 from New York, United States, it has since been reported from numerous inland lakes from Minnesota to Vermont, and from Lake Ontario and inland lakes in southern Ontario, Canada. While the ecological impacts of N. obtusa are not clearly understood in its invasive range, initial results show negative environmental effects. We have discovered a liquid‐preserved herbarium specimen that predates the 1978 records by at least 4 years, and is the first confirmed record of N. obtusa in Québec.     

Ureolytic activity of Nitellopsis obtusa (Characeae)

The decomposition of urea by Nitellopsis obtusa from Characeae was investigated. The intact cells were exposed to the inhibition by two typical urease inhibitors: boric acid and fluoride ion, used as a criterion to define if urease or UAL-ase is responsible for the ureolytic activity of the algae. It was found that boric acid and fluoride ion are simple competitive and slow-binding competitive inhibitors of Nitellopsis obtusa enzyme respectively, which is the response characteristic of urease. The inhibition constants equal to 2.3 and 0.1 mM for boric acid and fluoride ion, when compared to those of jack bean urease, indicate that in the observed kinetic behaviour of Nitellopsis obtusa urease partake transport processes taking place in the intact cells.     

Biogeography of living and fossil Nitellopsis (Charophyta) in relationship to new finds from Morocco

Aim To document the distribution of two closely related macrophyte species, the fossil Nitellopsis (Tectochara) merianii (A. Braun ex Unger) Grambast & Soulié‐Märsche and Nitellopsis obtusa (Desvaux) J. Groves, the single living species of genus Nitellopsis and to draw the relationships between first finds of N. merianii in North Africa and previously known records. Location South part of the High Atlas Range, Aït Kandoula basin, Morocco. Methods New finds of fossil charophyte gyrogonites were determined and illustrated. Using a large bibliographic database of both fossil and extant charophytes, we depict the biogeographical distribution N. merianii and N. obtusa and summarize the ecological requirements of N. obtusa as a modern analogue. Results The Aït Kandoula deposits, dated by magnetostratigraphy and vertebrate fossils to Upper Miocene, provided the first fossil populations of N. merianii in Africa. The distribution patterns of the Tertiary N. merianii and the living N. obtusa superimpose on a large area that extends from Spain to East Asia and characterize them as typically Eurasian taxa indicative for permanent, relatively cold and deep freshwater lakes. During the Quaternary, similar palaeolakes in the Sahara were colonized by N. obtusa. Main conclusions The presence of the Eurasian species N. merianii in North Africa is the result of dispersal by migratory waterbirds and attests to N–S migration occurring during the Upper Miocene (10–5 Myr ago). Gyrogonites imported from Southern Europe could germinate and fulfil their life cycle so as to form a new seed bank of gyrogonites because they had been deposited in a suitable environment consisting of a freshwater mountain lake.     

TRANSPORT AND DEFENSIVE ROLE OF ELATOL AT THE SURFACE OF THE RED SEAWEED LAURENCIA OBTUSA (CERAMIALES,RHODOPHYTA)1

Natural within‐thallus concentrations of elatol produced by Laurencia obtusa (Huds.) J. V. Lamour. inhibit herbivory and prevent fouling. However, elatol occurs in larger amounts within the thallus compared with the quantities from the surface of this alga. We evaluated whether the surface elatol concentrations inhibit both herbivory and fouling and whether the content of corps en cerise can be transferred to the external cell walls. Surface elatol concentrations did not inhibit herbivory by sea urchins, settlement of barnacle larvae, or mussel attachment. Evidence of a connection between the corps en cerise, where elatol is probably stored, and the cell wall of L. obtusa was based on channel‐like membranous connections that transport vesicles from the corps to the cell wall region. Therefore, L. obtusa presents a specific process of chemical transport between the cell storage structures and the plant surface. We hypothesized that if high amounts of elatol are capable of inhibiting herbivory and fouling, if the tested organisms are ecologically relevant, and if elatol really occurs on the surface of L. obtusa and this seaweed can transport this compound to its surface, the low natural concentration of defensive chemicals on the surface of L. obtusa is probably not absolute but may be variable according to environmental conditions. We also hypothesized that herbivory and fouling would not exert the same selective force for the production of defensive chemicals on L. obtusa’s surface since the low concentrations of elatol were inefficient to inhibit either processes or distinguish selective pressures.     

Nocodazole inhibits macronuclear infection with Holospora obtusa in Paramecium caudatum

Summary. Holospora obtusa is a Gram-negative bacterium inhabiting the macronucleus of the ciliate Paramecium caudatum. Experimental infection with H. obtusa was carried out under nocodazole treatment. Nocodazole has been shown to cause disassembly of the cytoplasmic microtubules radiating from the cytopharynx and postoral fibers in P. caudatum. Treatment with this drug did not prevent the ingestion of both prey bacteria and H. obtusa, but it reduced the phagosome number and affected cyclosis. In situ hybridization revealed infectious forms of this endobiont very close to the macronucleus, but never inside it. These results indicate that disassembly of microtubules does not impair transportation of the infectious forms of H. obtusa in the cytoplasm, but that it completely blocks the invasion of the nucleus by the bacteria. Correspondence and reprints: Department of Cytology and Histology, Faculty of Biology and Soil Sciences, Saint Petersburg State University, Universitetskaya naberezhnaya 7/9, 199034 Saint Petersburg, Russia.     

Comparison of Cocconeis pseudonotata sp. nov. with two closely related species,C. notata and C. diruptoides,from Posidonia oceanica leaves

Three Cocconeis Ehrenberg species, epiphytic on the leaves of Posidonia oceanica (L.) Delile, were studied by light and electron microscopy. A new species, C. pseudonotata, is described which is closely related to C. notata Petit and C. diruptoides Hustedt. Gross morphology and the presence of a sigmoid raphe and sternum are the characters shared by the three species, whereas the central areas of sternum and raphe-sternum valves, and the stria and areola densities are the main distinctive characters for the species when observed by light microscopy. Scanning and transmission electron microscopic observations revealed that the fine structure of areolae must be also considered in order to identify the species. Comparison among the three species has been carried out by observations on material from our samples, as well as on the type material of C. diruptoides and cleaned samples from the Hustedt collection. The study also provides new information on the geographical distribution of these species.     

Observations of the morphology of some known and new fragilarioid diatoms (Bacillariophyceae) from rivers in the USA

Morphological studies at the light microscopy and scanning electron microscopy levels of selected fragilarioid diatoms occurring in North American streams and lakes are presented herein. The majority of the samples studied were collected by the US Geological Survey's National Water Quality Assessment Program, which concentrates on stream water quality monitoring throughout the continental USA and Hawaii. Two new species (Staurosirella confusa Morales and Punctastriata mimetica Morales) and a new forma (Pseudostaurosiropsis geocollegarum f. triradiatum Morales) are described and two new combinations (Pseudostaurosira subsalina (Hustedt) Morales and Staurosirella olden‐burgiana (Hustedt) Morales) are provided. Morphological details of an additional taxon, Staurosira construens var. binodis (Ehrenberg) Hamilton in Hamilton et al. are also presented. The taxonomic affinities of all these taxa, as well as some evolutionary aspects and ecologic characteristics, are discussed in the light of published material.     

Inhibitory effect of the essential oil from <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> on the growth of food-borne pathogens

In this study, the antibacterial activity of essential oil from Chamaecyparis obtusa (Sieb. et Zucc) leaves and twigs was investigated. The test strains were Klebsiella pneumoniae, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, Escherichia coli, Legionella pneumophila, and Methicilline-resistant Staphylococcus aureus. Antibacterial activity was estimated by measuring bacterial growth inhibition. Histopathological examination was also performed. C. obtusa oil distinctly inhibited the growth of all test strains and exhibited the strongest antibacterial activity against L. monocytogenes. It was chromatographically divided into several fractions. The fractions were further tested against antibacterial activity and their chemical compositions were analyzed. The fraction containing terpinen-4-ol (TA) showed high antibacterial activity toward all strains tested. Tests with authentic samples showed that TA played a major role in the antibacterial activity of C. obtusa oil, and in a mice test, the oil actively minimized inflammation by S. aureus.     

The genusDaphnia in Cameroon,West Africa

Three species of the genusDaphnia are recorded from Cameroon.Daphnia obtusa was found in a single lake out of 37 sampled.Daphnia laevis was found in the same lake asD. obtusa and in two other lakes, whileD. rosea was found in three other lakes. All the lakes were at altitudes over 1 000 m. The records can be interpreted either as altitudinal survivals of continually dispersing species, or as relicts in an area whereDaphnia is usually very rare or absent.     

Population genetic structure of three pond-inhabiting Daphnia species on a regional scale (Flanders, Belgium)

1. Only a few studies have compared patterns of genetic variation among populations of different Daphnia species on a regional scale. The present study addresses this gap and examines the relationship between diversity as revealed by allozyme variation and habitat size for populations of Daphnia pulex, D. obtusa and D. curvirostris in Flanders (Belgium). In addition, we examined whether patterns of isolation‐by‐distance could be observed in each of these three Daphnia species. 2. The relationship between genetic diversity and habitat size varied among Daphnia species that occur in the same region. In D. pulex and D. obtusa populations, a positive relationship between local genetic diversity and habitat size was found, whereas the relationship was negative in D. curvirostris populations. 3. Regional genetic diversity was lower than expected from patterns of local genetic diversity in D. pulex and D. obtusa populations in Flanders. This suggests that the subdivision of local Daphnia populations in a region did not obviously increase genetic diversity. 4. Genetic differentiation among populations of these three species in Flanders was moderate and comparable with values observed in other Daphnia species. Patterns of isolation‐by‐distance could be observed, but the scatter was high (D. pulex) or the slope was very low (D. obtusa).     

Evaluation of cleaved amplified polymorphic sequence markers for <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> based on expressed sequence tag information from <Emphasis Type="Italic">Cryptomeria japonica</Emphasis>

We have developed and evaluated sequence-tagged site (STS) primers based on expressed sequence-tag information derived from sugi (Cryptomeria japonica) for use in hinoki (Chamaecyparis obtusa), a species that belongs to a different family (although it appears to be fairly closely related to sugi). Of the 417 C. japonica STS primer pairs we screened, 120 (~30%) were transferable and provided specific PCR amplification products from 16 C. obtusa plus trees. We used haploid megagametophytes to investigate the homology of 80 STS fragments between C. obtusa and C. japonica and to identify orthologous loci. Nearly 90% of the fragments showed high (>70%) degrees of similarity between the species, and 35 STSs indicated homology to entries with the same putative function in a public DNA database. Of the 120 STS fragments amplified, 72 showed restriction fragment length polymorphisms; in addition, the CC2430 primers detected amplicon length polymorphism. We assessed the inheritance pattern of 27 cleaved amplified polymorphic sequence markers, using 20 individuals from the segregation population. All the markers analyzed were consistent with the marker inheritance patterns obtained from the screening panel, and no markers (except CC2716) showed significant (P<0.01) deviation from the expected segregation ratio. In total, 136 polymorphic markers were developed using C. japonica-based STS primers without any sequence modification. In addition, the applicability of STS-based markers developed in one species to other species was found to closely reflect the evolutionary distance between the species, which is roughly concordant with the difference between their rbcL sequences. We plan to use these markers for genetic studies in C. obtusa. Most of the markers should also provide reliable anchor loci for comparative mapping studies of the C. obtusa and C. japonica genomes.     

Population‐level dynamics in experimental mixed infections: evidence for competitive exclusion among bacterial parasites of Paramecium caudatum

Parasites frequently share their host populations with other parasites. However, little is known about how different parasites respond to competition with diverse competitor species in the within‐host and between‐host environments. We explored the repeatability of competition by simultaneously exposing microcosm populations of the ciliate Paramecium caudatum to pairs of parasites from the Holospora species complex (H. undulata, H. caryophila and H. obtusa). We measured how competition affected the persistence and prevalence of each compared to single infections, across three host genotypes. Three weeks post‐inoculation we identified the presence of each parasite using fluorescence in situ hybridisation (FISH). Competitive exclusion (62/72) was more common than co‐existence (10/72) in populations inoculated with two parasites. There was a clear pattern of competitive superiority, with H. caryophila persisting in all doubly inoculated populations (with either H. undulata or H. obtusa), and H. undulata tending to exclude H. obtusa. This mirrored infection success in single infections, with H. caryophila having a higher infection prevalence in single inoculations, followed by H. undulata then H. obtusa. The probability of persistence in co‐inoculations did not change across the different host genotypes, and prevalence was the same as in single infections. Our results are consistent with superinfection models, which assume the competitive exclusion of parasites upon contact within the same host. Furthermore, such non‐random competitive epidemiological dynamics, where one parasite always wins, may be of interest for public health management, especially if the winning parasite is avirulent, as is seemingly the case here.     

The Effects of Seaweed Secondary Metabolites on Biofouling

Antifouling activity is one poorly investigated property of seaweed natural products. To determine, in the field, whether seaweeds contain chemicals able to influence the settlement of fouling organisms, crude organic extracts from Stypopodium zonale, Dictyota menstrualis (Phaeophyceae) and Laurencia obtusa (Rhodophyceae) were incorporated at natural volumetric concentrations, into hard stable gels that served as substrata for fouling in the experiments. Fouling organisms settled at a significantly higher rate on plates treated with S. zonale extracts than on control gels, while settlement was strongly inhibited on gels containing L. obtusa extracts. Fouling on gels treated with the D. menstrualis extract was not significantly different from the fouling found on control gels. The findings suggest that the broad antifouling properties of the crude extract of L. obtusa inhibit the settlement of fouling as well as hinder the development of settled fouling species, thereby reducing the richness of species. The results imply that L. obtusa possibly harbours powerful agents that can be explored for the development of antifouling technology.     

Somatic embryogenesis and plant regeneration from immature zygotic embryos of Hinoki cypress (Chamaecyparis obtusa Sieb. et Zucc.)

We established a plant regeneration system for Hinoki cypress (Chamaecyparis obtusa) via somatic embryogenesis. Embryogenic tissues were successfully induced on three kinds of Smith media from megagametophyte explants containing pre-cotyledonary embryos of C. obtusa plus-trees. Factors affecting somatic embryo maturation were examined. The concentration of polyethylene glycol 4000 in the medium was a critical factor for embryo maturation and its effective concentration was 150 g/l. The addition of 30 g/l maltose to the medium had a positive effect on embryo maturation, but sucrose was ineffective. The mature somatic embryos germinated at a germination frequency of approximately 60%, and the presence of activated charcoal was effective in stimulating plantlet growth. The plantlets acclimatized successfully in a greenhouse. To our knowledge, this is first report describing details of a plant regeneration method for C. obtusa via somatic embryogenesis.Abbreviations ABA Abscisic acid - PEG Polyethylene glycol 4000 - SM1 Smith Standard Embryonic Tissue Capture Medium - SM2 Smith Standard Embryogenesis Medium - SM3 Smith Embryo Develop Medium     

SEA ICE DIATOMS (BACILLARIOPHYCEAE) OF THE CANADIAN ARCTIC. I. THE GENUS STENONEIS1

Ice diatom assemblages in the Canadian Arctic are dominated by the Naviculaceae, a family which includes the genus Stenoneis Cleve. A taxonomic history of S. inconspicua var. baculus (Cleve) Cleve (including type material of Navicula baculus Cleve) is presented with morphological data including the first SEM views of the genus. Stenoneis inconspicua var. baculus was compared with S. obtuserostrata (Hustedt) comb. nov. (basionym: Navicula obtuserostrata Hustedt). In the SEM, external, short, flattened siliceous ridges were revealed beside the proximal parts of the raphe branches and central pores. This may be a significant taxonomic feature of the genus. Valves of S. inconspicua var. baculus ranged from 40–103 μm in length, 7–11 μm in width and had 17–20 striae in 10 μm, whereas valves of S. obtuserostrata were shorter (27–53 μm), narrower (6–7.5 μm) and more finely striated (24–30 in 10 μm). Both taxa have a circumpolar Arctic distribution.     

A New Form of Structural Peptidoglycan in Selenomonas ruminantium: Existence of Polyamine in Peptidoglycan

The chemical constituents of calluses of Thujopsis dolabrata (Hiba), Chamaecyparis obtusa (Hinoki), Chamaecyparis pisifera (Sawara), and Platycladus orientalis (Konotegashiwa), all of which belong to Cupressaceae, were examined by GC analysis. The main components of these calluses were diterpenoids of an abietane-type and sitosterol in common, while the chemical constituents of these parent plants were different from each other.     

NITZSCHIA ALICAE SP. NOV. AND N. PURIFORMIS SP. NOV., NEW DIATOMS FROM EUROPEAN RIVERS AND COMPARISON WITH THE TYPE MATERIAL OF N. SUBLINEARIS AND N. PURA1

Nitzschia sublinearis Hustedt and N. pura Hustedt are common oligosaprobic freshwater diatom species that frequently occur in diatom inventories, thus being important in water quality studies. Both are considered as species with overlapping diagnostic criteria in several floras, which is typical of the whole genus Nitzschia. The type material of Hustedt of N. sublinearis and N. pura was examined using LM and EM in order to document the range of variation within the type populations and to compare it with populations occurring in different European rivers. Detailed observations allowed recognition of two new freshwater diatom species: N. alicae sp. nov., occurring in mesotrophic up to eutrophic conditions, and N. puriformis sp. nov., mostly occurring in oligotrophic habitats, both in rivers and streams at middle and high altitudes. The most reliable taxonomic features that separate both new species from the most similar taxa are the density of fibulae and striae, valve shape, and valve width as well as the shape of areolae. Morphological examination of different populations indicates that N. puriformis is relatively common in European rivers and has been overlooked to date and confounded with N. pura by several researchers. By contrast, N. alicae has, to date, been collected only in Slovakia and Northern Italy, but with a high frequency of occurrence and sometimes in high abundance at sites.     

Historical biogeography and phylogenetic relationships of the genus Chamaecyparis (Cupressaceae) inferred from chloroplast DNA polymorphism

The genus Chamaecyparis comprises five species and one variety native to Taiwan, Japan, Canada, and USA, which demonstrates a classical eastern Asian, western North American, and eastern North American disjunct distributional pattern. The phylogenetic relationships of the species of Chamaecyparis were inferred by comparing 1130 bp of the combined data set of chloroplast trnV intron and petG-trnP intergenic spacer. The phylogenetic tree shows that Chamaecyparis nootkatensis (Cupressus nootkatensis or Xanthocyparis nootkatensis) is clearly diverged from other Chamaecyparis species. For Chamaecyparis species, C. thyoides is sister to C. formosensis and C. pisifera and these together form a monophyletic group. C. lawsoniana is sister to C. obtusa and C. taiwanensis; and these form another monophyletic group. Homogeneity in evolutionary rates was found among species in these two monophyletic groups. Results indicate the divergent evolution of C. taiwanensis and C. formosensis and molecular evidence in this investigation supports C. taiwanensis as a variety of C. obtusa. Utility of cpDNA intergenic spacer petG-trnP in Chamaecyparis is also discussed. Several biogeographical implications were inferred: (1) at least two divergence events have produced the eastern Asian, and both western and eastern North American disjunct distribution in Chamaecyparis; (2) intercontinental sister species pairs are found in Chamaecyparis; (3) cpDNA divergence between two intercontinental sister pairs of C. thyoides and C. pisifera, and C. lawsoniana and C. obtusa is 2.8% and 1.1%, which suggest an estimated divergence time of 14 and 5.5 million years ago during middle and late Miocene, respectively; (4) cpDNA divergence of two Asian Chamaecyparis groups between C. obtusa and C. taiwanensis, and between C. pisifera and C. formosensis is 0.25% and 0.57%, which suggest an estimated divergence time of 1.3 and 2.9 million years ago during Pleistocene and late Pliocene, respectively; these estimated divergence times suggest a relatively recent migration of Chamaecyparis to Taiwan from the Japanese Archipelago; (5) that climatic deterioration caused the disappearance of Chamaecyparis in continental Asia is probable.