New species of myxosporidians (Myxosporea: Cnidosporidia) from the oilfishes (Comephorus spp.) of Baĭkal lake

Two new species of Myxosporidia, Henneguya bayerii sp. n. and Myxobolus korjakovii sp. n. from the kidney of the Comephorus baicalensis (Pallas, 1776) and C. dybowskii Korotneff, 1905 from the Baikal lake are described.     

Interspecific variability of telomeric DNA length in some Siberian and endemic Baĭkal planarians (Plathelminthes, Tricladida)

The length of the telomeric DNA in nine species of planarians inhabiting Lake Baikal and one Siberian species from Baikal rivers was determined using Southern hybridization. According to preliminary estimations, it varied in the range of 25-30 kb (Rimacephalus arecepta, Rimacephalus pulvinar, Sorocelis hepatizon, Sorocelis nigrofasciata, Protocotylus sp., Baikalobia guttata, Bdellocephala baikalensis, Phagocata sibirica) and 50 kb (Baikaloplana valida, Baikalobia copulatrix). It is the first estimation of the values of telomeric region lengths for Baikal free-living flat worms.     

The new eubacterium Roseomonas baikalica sp. nov. isolated from core samples collected by deep-hole drilling of the bottom of Lake Baĭkal

Microbiological analysis of samples of sedimentary rocks from various eras of the geological history of the Baikal rift has enabled us to isolate a large number of microorganisms that can be classified into new, previously undescribed species. The present work deals with the identification and study of the morphological, biochemical, and physiological properties of one such strain, Che 82, isolated from sample C-29 of 3.4-3.5 Ma-old sedimentary rocks taken at a drilling depth of 146.74 m. As a result of our investigations, strain Che 82 is described as a new bacterial species, Roseomonas baikalica sp. nov., belonging to the genus Roseomonas within the family Methylobacteriaceae, class Alphaproteobacteria.     

Spatial and seasonal distribution of the ichthyofauna of Lake Nokoué, Bénin,west Africa

The fish biodiversity of Lake Nokoué, a lagoon in Bénin, was monitored for one year from August 2000 to July 2001 by means of samples from the artisanal fishery collected once a month at three stations. A total of 5 933 fish weighing 95 322g (mean individual weight 16.0g) belonging to 51 species, 47 genera and 34 families were sampled. An abundance of juveniles was observed, confirming the importance of the lake as nursery grounds, rich in exploitable habitats like other tropical estuaries and lagoons. The fish fauna comprised three main components: i) an estuarine component (strict, freshwater and marine origins) which is the basis of the lagoon fauna community and which is stable in space and time; ii) a marine component containing fishes which appeared in the lagoon during the dry season where the salinity remains high (>20‰) and iii) a freshwater component with fishes coming into the lagoon from the river during the flood period. The magnitude of the spatial and seasonal fluctuations of the last two components varies depending on the area: marine (Zogbo), freshwater (Vêki) or intermediate (Ganvié). The global species richness and the relative abundances of fish vary between stations and from month to month. November, with 20 species on average, and January, with 6 species on average, are significantly different as regards species richness.     

Spatial heterogeneity of the species composition of a clavarioid fungi’s compex in the Eurasian Arctic

Using the example of a model group of macromycete (clavarioid fungi), a large-scale investigation into the mycological complex of the Eurasian Arctic is conducted. The species composition of clavarioid fungi’s complex is revealed in all longitudinal sectors and latitudinal subzones, and a comparative analysis is carried out. It has been determined that, among groups of aphyllophoroid fungi, the clavarioid life form is the most adapted to the extremally psychrophilic conditions of the Arctic. It is shown that the near-oceanic sectors are the richest, whereas the continental sectors are much poorer. The distribution of the species composition of fungi conforms to the similar distribution of flowering plants, especially hemicryptophytes. The average annual quantity of atmospheric precipitation is the leading climatic factor. The differences make it possible to subdivide the Eurasian Arctic into four mycogeographical regions: Atlantic (European), Siberian, Chukotian (Beringian), and High Arctic.     

Spatial variation in species diversity and composition of flea assemblages in small mammalian hosts: geographical distance or faunal similarity?

Aim Spatial variation in the diversity of fleas parasitic on small mammals was examined to answer three questions. (1) Is the diversity of flea assemblages repeatable among populations of the same host species? (2) Does similarity in the composition of flea assemblages among populations of the same host species decay with geographical distance, with decreasing similarity in the composition of local host faunas, or with both? (3) Does the diversity of flea assemblages correlate with climatic variables? Location The study used previously published data on 69 species of small mammals and their fleas from 24 different regions of the Holarctic. Methods The diversity of flea assemblages was measured as both species richness and the average taxonomic distinctness of their component species. Similarity between flea assemblages was measured using both the Jaccard and Morisita–Horn indices, whereas similarity in the composition of host faunas between regions (host ‘faunal’ distance) was quantified using the Jaccard index. Where appropriate, a correction was made for the potentially confounding influence of phylogeny using the independent contrasts method. Results Flea species richness varied less within than among host species, and is thus a repeatable host species character; the same was not true of the taxonomic distinctness of flea assemblages. In almost all host species found in at least five regions, similarity in flea assemblages decreased with increases in either or both geographical and faunal distance. In most host species, the diversity of flea assemblages correlated with one or more climatic variable, in particular mean winter temperature. Main conclusions Spatial variation in flea diversity among populations of the same mammal species is constrained by the fact that it appears to be a species character, but is also driven by local climatic conditions. The results highlight how ecological processes interact with co‐evolutionary history to determine local parasite biodiversity.     

Spatial–temporal patterns of methane dynamics in Lake Taihu

Many European lakes are monitored according to the EU Water Framework Directive (WFD), with focus on phytoplankton biomass and species composition. However, the low-frequency WFD monitoring may miss short-term phytoplankton changes. This is an important issue because short-term extreme meteorological events (heat waves and heavy rain) are predicted to increase in frequency and intensity with climate change. We used records from Lake Mondsee (Austria) from 2009 to 2015 to test if a reduction from monthly to seasonal sampling affected the average annual phytoplankton biovolume. Furthermore, we combined inverted light microscopy, FlowCAM and flow cytometry to estimate the effect of sampling during extreme events on average phytoplankton biovolume. Relative to monthly sampling, seasonal sampling significantly overestimated phytoplankton biomass. A heat wave in 2015 and two episodes of heavy rain in 2015 and 2016 caused species-specific changes; biovolumes of chlorophytes and the filamentous cyanobacterium Planktothrix rubescens (De Candolle ex Gomont) Anagnostidis & Komárek increased significantly during the heat wave. Using live material with FlowCAM and flow cytometry, we detected small and fragile cells and colonies that were either ignored or underrepresented by analysing fixed samples with light microscopy. We suggest a modified sampling and analysis strategy to capture short-term changes within the phytoplankton community.     

Are species of bacteria unclassifiable?

Summary Every one of eleven different strains randomly selected from 10 different randomly selected genera have shown the same high frequency of occurrence of colony mutants as did almost all strains ofAcetobacter (previously considered outstanding in this respect). Correlation of other properties with such mutant colony forms was not specifically studied, but in 4 strains correlation was noticed, suggesting its presence in the others, as was so often found inAcetobacter. It is suggested from this, that a similar study of strains of other genera might reveal a similarly high frequency of occurrence of mutants, most so-called pure cultures being thus probably mixtures of different cells with different properties. Also the proportion of each cell-type in the culture may vary from predominance to extinction according to the biochemical and other tests applied for the purpose of the ‘characterization’ of the species for taxonomic purposes. If the classification of such varying mixtures is considered of doubtful use, then it seems to follow that ‘species’ of bacteria are virtually unclassifiable, and that even the conception of a genus should be on a broader basis than is often the case at present.     

Occurrence,succession and distribution of chroöcoccal Cyanobacteria in Lake Maarsseveen I

Four species of chroöcoccal Cyanobacteria were dominant in Lake Maarsseveen I in 1987:Gomphosphaeria lacustris, Chroöcoccus sp.,Aphanocapsa sp. andMicrocystis aeruginosa. The first two were dominant in the water column, the latter two in the sediment. In the water columnAphanocapsa, Microcystis andGomphosphaeria appeared and showed highest abundance at the same time, whileChroöcoccus filled the gaps between the peaks of the others. The distribution in the sediment was related to its texture.     

Spatial–temporal patterns of flowering asynchrony and pollinator fidelity in hybridizing species of Narcissus

Speciation requires the evolution of reproductive barriers to achieve isolation between species. In this paper, we examine the role of two major pre-zygotic barriers in reducing the chance of F₁ hybrid formation between two pairs of Narcissus species. Field experiments were performed over 5?years in eight natural populations to determine whether flowering phenology and pollinator fidelity could act as reproductive isolation barriers in Narcissus. Our results show that reproductive isolation due to flowering phenology is highly variable and asymmetric. In some populations, pollinator fidelity was so strong that the quantification of reproductive isolation was complete and a strong negative correlation was found between the strength of this barrier and the abundance of hybrids. Nevertheless, the degree of pollinator fidelity was quite variable among populations indicating that reproductive isolation varies geographically but very consistent across years indicating that plant-pollinator interactions are well established. In fact, the finding that hybrid formation between these species occurs only in sites where pollinator fidelity is incomplete suggests that hybrid formation also varies geographically and that divergent evolutionary outcomes may occur in different sympatric populations of Narcissus.     

Spatial distribution and speciation of copper in root tips of cucumber revealed by μ-XRF and μ-XANES

The localization, biotransformation, and chemical speciation of copper in root tips of cucumber (Cucumis sativus) were investigated using synchrotron-based micro X-ray fluorescence (μ-XRF) and micro X-ray absorption near edge structure (μ-XANES). The highest content of Cu was found in root cap and meristematic zone whereas low Cu content in elongation and maturation zone. There was a dramatic increase of Cu content in root cap and meristematic zone after treatment with 100 μM CuSO₄ for 72 h. The μ-XANES analysis revealed that most of Cu in root tip was bound with alginate, citrate, and cysteine-like ligands whereas rarely deposited in form of CuO. From root cap to maturation zone, the proportion of Cu bound with alginate-like ligands increased whereas that bound with citrate-like ligands decreased. The proportion of Cu bound with cysteine-like ligands increased from root cap to elongation zone but sharply declined in maturation zone. The results suggested that Cu was chelated by S ligands in the cell walls which protect protoplasm against possible damage caused by Cu excess.     

Diversity and distribution of alkaliphilic psychrotolerant bacteria in the Qinghai–Tibet Plateau permafrost region

The Qinghai–Tibet Plateau represents a unique permafrost environment, being a result of high elevation caused by land uplift. And the urgency was that plateau permafrost was degrading rapidly under the current predicted climatic warming scenarios. Hence, the permafrost there was sampled to recover alkaliphilic bacteria populations. The viable bacteria on modified PYGV agar were varied between 10² and 10⁵ CFU/g of dry soil. Forty-eight strains were gained from 18 samples. Through amplified ribosomal DNA restriction analysis (ARDRA) and phylogenetic analyses, these isolates fell into three categories: high G + C gram positive bacteria (82.3%), low G + C gram positive bacteria (7.2%), and gram negative α-proteobacteria (10.5%). The strains could grow at pH values ranging from 6.5 to 10.5 with optimum pH in the range of 9–9.5. Their growth temperatures were below 37°C and the optima ranging from 10 to 15°C. All strains grew well when NaCl concentration was below 15%. These results indicate that there are populations of nonhalophilic alkaliphilic psychrotolerant bacteria within the permafrost of the Qinhai-Tibet plateau. The abilities of many of the strains to produce extracellular protease, amylase and cellulase suggest that they might be of potential value for biotechnological exploitation.     

The spring development of phytoplankton in Lake Erken: species composition,biomass, primary production and nutrient conditions — a review

Relative abundance and within-lake distributions of three fishes, northern redbelly dace (Phoxinus eos), finescale dace (Phoxinus neogaeus), and central mudminnow (Umbra limi), were examined using minnow traps in Tuesday Lake, a small bog lake in the Upper Peninsula, Michigan. For these species, catches in minnow traps placed at the perimeter of the lake were 21 to 52 times higher than catches in midlake traps. Variance: mean ratios of perimeter trap catches indicated that both dace species were highly aggregated while the distribution of mudminnows was less aggregated or random. Over an 11 day period during which all fish caught were removed from the lake, catch per unit effort (CPUE) of both dace species declined in response to fish removal. In contrast, CPUE for mudminnows was low initially, increased to an asymptote and then declined only in the last 5 days of the fish removal. The patterns of CPUE for mudminnows indicated that mudminnow trapability and/or activity was reduced in the presence of high densities of dace. The low abundance of dace in traps with many mudminnows suggested mudminnows avoided traps already containing dace. Throughout the removal period, CPUE provided an accurate index of dace abundance, whereas this was true for mudmnnows only after dace populations had been reduced drastically. Therefore, in any use of minnow traps to estimate populations, both spatial distributions and relative species abundance of small fishes must be taken into account.     

Spatial pattern of size distribution of four fish species on Réunion coral reef flats

A comparative study of the size distribution of four fish species was performed on three geomorphological zones (back reef, inner reef flat and outer reef flat) on two comparable fringing reef areas (disturbed and non-disturbed) of Reunion Island, S. W. Indian Ocean. The species chosen Chaetodon trifasciatus, Dascyllus aruanus, Stethojulis albovittata and Ctenochaetus striatus were selected both for their abundance and their diverse diets. The method used is based on the estimation of fish size directly underwater by comparison to a graduated table, i.e. photographs of the species for which different size-classes were previously determined. For the two areas, the size of fishes increases from the back reef zone to the outer reef flat, except for D. aruanus which is not present in sufficient numbers on the outer reef flat to allow a statistical analysis. This suggests the existence of a nursery zone in the back reef from which these species might colonize the reef flat. On the back reef zone and the inner reef flat, there is a significant difference in the size distribution of fishes between the disturbed and non-disturbed areas, except for S. albovittata. The number of juveniles is significantly lower in the disturbed area, probably due to environmental perturbations.

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Résumé Une étude de la distribution des tailles de quatre espéces de poissons coralliens a été réalisée sur trois zones géomorphologiques (arriére récif, platier interne et platier externe) de deux secteurs récifaux comparables (dégradé et non dégradé) de l'île de la Réunion, océan Indien occidental. Les espéces étudiées, Chaetodon trisfaciatus, Dascyllus aruanus, Stethojulis albovittata et Ctenochaetus striatus ont été choisies pour leur abondance et leur diversité de régime alimentaire. La technique utilisée consiste á estimer la longueur du poisson directement sous l'eau á l'aide d'une tablette graduée. Des photographies de poissons de différentes tailles, préalablement définies, y ont été fixées, et ceci pour les quatre espéces. Pour les deux secteurs, une augmentation réguliére de la taille des poissons depuis l'arriére récif jusqu' au platier externe est apparue, sauf pour D. Aruanus ui n'est apas suffisamment abondante sur le platier externe pour permettre une analyse statistique. Ces observations suggérent l'existence d'une nurserie dans l'arriére récif á partir duquel pourrait s' opérer la colonisation du platier récifal. Dans les zones d' arriére récif et de platier interne, il y a par ailleurs une différence significative dans la distribution des tailles des poissons entre le secteur dégradé et le secteur non dégradé, sauf pour S. albovittata. Le nombre des juvéniles est significativement plus faible dans le secteur dégradé, ce qui pourrait être dû aux dégradations de l'environment corallien.

     

Taxonomic composition and species diversity of insect assemblages in grass–shrub cover of peat bogs in Belarus

The species composition and diversity of insect assemblages in the grass–shrub cover has been studied. A total of 374 species from 10 orders have been revealed. Coleoptera, Diptera, Heteroptera, and Auchenorryncha prevailed. Each order was dominated by two to eight species. These species are Cixius similis Kirschbaum, 1868; Neophilaenus lineatus (Linnaeus, 1758); Lepyronia coleoptrata (Linnaeus, 1758) (Auchenorryncha); Lygus pratensis (Linnaeus, 1758); Kleidocerys resedae (Panzer, 1797); Stictopleurus crassicornis (Linnaeus, 1758) (Heteroptera); Lochmaea suturalis (Thomson, 1866); Cyphon padi (Linnaeus, 1758); Plateumaris discolor (Herbst, 1795) (Coleoptera); etc. The assemblages were characterized by low species diversity and distribution of species abundance. The most similar entomocomplexes were those in biotopes dominated by herbs, on the one hand, and dwarf shrubs, on the other. The regression analysis has shown a significant relation between the species richness and diversity of insects and the species composition of plants and their projective cover. The multivariate analysis with various methods (CCA and PCA) demonstrated the influence of these factors on the spatial distribution of certain species and their preferences to particular habitats.     

Community composition and spatial variation of bacteria in the sediments of a eutrophic fresh water urban lake， East Lake， Wuhan， China北大核心CSCD

［Objective］ Sediment bacteria are the important biological factors for remediating of eutrophic environments. To enrich our understanding of the bacteria communities in eutrophic urban lake sediments for better environment protection and pollution control in urban lake eco-systems, we resolved the composition of bacteria communities and their spatial variation in the sediments of a middle-size eutrophic urban lake, East Lake. ［Methods］We used 16S rRNA gene RFLP and sequencing methods to generate the phylogeny information of the bacteria community, used principal coordinates analysis （PCoA） and canonical correspondence analysis （CCA） methods to resolve the relationship between East Lake and other lakes, and the relationship between environmental factors and the bacteria communities. ［Results］ Sediments inhabited 13 phyla and 2 unclassified clusters. PCoA further revealed that the bacteria communities in three sub-lakes of East Lake sediments were closely related to the communities in similar eutropic lake environments, and divergent from the hypereutrophic sub-lake Miao Lake, which was also found to inhabit a relative abundant amount of Thermogymnomonas-type archaea. CCA further revealed that the distribution of bacteria was closely correlated with the carbon, nitrogen and phosphate contents in the sediments. ［Conclusion］The environment factors regulated the bacteria community composition and distribution. The results of this study providereference to the research, protection and pollution control on urban lake eco-systems.     

The vascular epiphytes of a lowland forest in Panama—species composition and spatial structure

We conducted a comprehensive census of the vascular epiphytes in a lowland forest in Panama by means of a canopy crane. In 0.4 ha of ca. 40-m tall forest, 103 species of vascular epiphytes with 13,099 individuals were found. The orchids were the most important family both in species and individual numbers, accounting alone for >40% of all species and >50% of all individuals. There was a clear vertical segregation of species with a concentration at intermediate heights: more than 50% of all individuals were found between 15 m and 25 m above ground. Tree species identity, tree size and the position of a tree in the forest (“space”) all influenced species composition. However, none of the two environmental variables nor space alone explained more than 10% of the total variation in epiphyte assemblages in several canonical correspondence analyses. By far the largest proportion of the observed variation remained unexplained and is arguably due to mere chance. In the future, our results will be used as a baseline data-set for the direct observation of the long-term dynamics in a diverse epiphyte community.