Comparative growth and propagule production byHydrilla verticillata grown from axillary turions or subterranean turions

Hydrilla verticillata (L.f.) Royle produces two types of vegetative propagules, subterranean turions and axillary turions. After 8 or 12 weeks growth under similar conditions, plants grown from subterranean turions weighed 1.7 to 2 times as much as plants grown from axillary turions. Subterranean turion-derived plants produced more propagules (by weight and number) per plant than plants from axillary turions. Characteristics of weight frequency distributions (median, minimum, maximum, and coefficient of variation) for new subterranean turions were also influenced by the type of propagule from which the parent plant was derived. The number of root crowns per plant which reflects the plant's ability to expand horizontally was significantly greater for subterranean turion-derived plants (by 2 times) than for plants from axillary turions. These results support the hypothesis that following colonization of an area the impact ofHydrilla on resident species changes over time.     

Consequences of inbreeding for the cowpea seed beetle, Callosobruchus maculatus (F.)(Coleoptera: Bruchidae)

Inbreeding is said to reduce vigour and fitness. It may also determine how a population responds to selection. Local populations of Callosobruchus maculatus , the cowpea seed beetle, are established annually from small numbers of founders and the species has been distributed to many parts of the world where isolated populations may have been founded by very small numbers of individuals. After more than 20 generations of inbreeding, inbred lines have been shown to diverge from a common ancestral stock in similar directions with respect of some variables such as developmental speed, but haphazardly in respect of other parameters such as male weight. The respective roles of drift and of selection as effective evolutionary forces in inbred lines are discussed in the light of these results. It is argued that some intraspecific differences in C. maculatus may be explained as a product of periodic inbreeding, but that the process does not impair the ability to adapt to local conditions so contributing to the status of the species as a pest of international importance.     

Structures of Azaspiracid Analogs,Azaspiracid-4 and Azaspiracid-5, Causative Toxins of Azaspiracid Poisoning in Europe

Two new analogs of azaspiracid, azaspiracid-4 and azaspiracid-5, isolated from the mussel Mytilus edulis, involved in a newly emerged shellfish poisoning in Europe were determined to be 3-hydroxy-22-demethylazaspiracid and 23-hydroxy-22-demethylazaspiracid, respectively.     

Inter-relationships between standing crop, biodiversity and trait attributes of hydrophytic vegetation in artificial waterways

1. The extensive British canal system potentially provides a favourable habitat for aquatic plants and, because of its uniformity, it is ideal for studying relationships between disturbance intensity (largely from boat traffic) and communities of aquatic macrophytes. 2. The standing crop and species composition of aquatic plants were measured in summer at 396 sites distributed randomly over the canal network. We also quantified the number of rare species and ‘attribute groups’ (groups of species sharing similar suites of biological traits). These data were analysed in relation to standing crop, assumed to indicate a disturbance gradient. 3. Consistent with unimodal models and the Intermediate Disturbance Hypothesis, maximum hydrophyte species richness occurred at an intermediate biomass (50–200 g DWm^?2). This corresponded to a low frequency of low magnitude disturbance (light boat traffic) on navigable sections, or occasional high magnitude disturbance (the post‐interventionist phase) on sections currently unnavigable and subject to active vegetation management. The frequency of rare species was also the greatest under these conditions, reflecting the availability of regeneration niches. 4. Sorting of species into attribute groups revealed that the overall relationship between species richness and standing crop comprised of closely overlapping unimodal responses of nine attribute groups, superimposed on a core vegetation of Potamogeton pectinatus, together with greater representation of filamentous algae, lemnids and elodeids with increasing standing crop (i.e. assumed low disturbance). High species richness was associated with the overlap of functionally different groups of species, rather than with disturbance‐mediated coexistence of functionally similar plants. 5. The analysis of a matrix of sites and the representation of plant traits weighted by the biomass of species that displayed them, in relation to different aspects of disturbance, highlighted a shift from traits associated with resilience (turions, unanchored floating or submerged leaves, low body flexibility, budding, small body size), or competitiveness (entire leaves, low reproductive output, high biomass density, large body size) at high standing crop, through to attributes more associated with resistance to disturbance (rhizomes, tubers, streamlining of foliage, low biomass density) at low standing crop. 6. Comparison with a stochastic null model of change in species number along a constrained gradient, after correction for variation in sampling effort, indicated that sites towards the tails of the gradient (excluding those with extremely low biomass) supported more species than might be expected from chance alone, while the most species‐rich sites in mid‐gradient generally supported many fewer species than expected. 7. We suggest that a disturbance regime that maintains intermediate standing crops would be appropriate for the conservation of species‐rich aquatic vegetation. Precise definition of this regime, under a range of circumstances, requires the study of temporal change at representative sites.     

Analysis of factors controlling responses of an aquatic microcosm to organic loading

The changes in the numbers of individuals of the constituent species and ammonia concentrations in 6 subsystems (Bacteria, bacteria-Cyclidium, bacteria-Aeolosoma, bacteria-Chlorella, bacteria-Cyclidium-Chlorella, bacteria-Aeolosoma-Chlorella) of an aquatic microcosm were examined after the addition of organic substance (peptone) at both the young and mature stages of succession. Organic loading led to decreases in the numbers of bacteria and Aeolosoma after temporary increases in their numbers and an oscillation in the numbers of Cyclidium but the densities of these populations were maintained at constant values in the presence of Chlorella. When organic substance was added at a young stage where the photosynthetic activities of algae were high, invertebrates, especially Aeolosoma, were damaged by unionized ammonia which was formed as the pH value increased. In contrast, organic loading at the mature stage enhanced the population densities and biomasses of all constituent species.     

Selenium Impacts on Fish: An Insidious Time Bomb

A selenium time bomb situation is developing in the United States and elsewhere that may result in substantial impacts on fish populations. The selenium time bomb has three components: (1) high food-chain bioaccumulation, (2) steep toxic response curve for fish, and (3) insidious mode of toxicity. If the threshold for selenium toxicity is exceeded, the time bomb explodes and a cascade of events is set into motion that will result in major ecosystem disruption. Several human-related factors are emerging that are capable of igniting the fuse of the time bomb by increasing waterborne concentrations of selenium and providing conditions favorable for bioaccumulation. Some of these factors are (1) mobilization of selenium due to open-pit phosphate mining, (2) use of constructed wetlands to treat selenium-laden wastewater from oil refineries and agricultural irrigation, (3) landfill disposal of seleniferous fly ash from coal-fired power plants, and (4) mobilization of selenium from animal feedlot wastes. Collectively, these threats may be sufficient to cause widespread, unanticipated toxic effects in fish populations. Only environmentally sound risk assessments followed by prudent management actions can defuse the selenium time bomb — once it explodes, it is too late to avoid significant impacts.     

Investigation of anti-inflammatory and toxicity effects of mangrove-derived Streptomyces rochei strain VITGAP173

Mangrove ecosystems generate the major biodiversity hotspots of actinobacteria. Among the actinobacteria, Streptomyces species are the prolific producers of bioactive natural products. In this study, with research efforts to discover biopotential compounds from marine actinobacteria, 41 actinobacterial strains were isolated from sediment soil sample of Indian mangrove regions. The phylogeny prediction using the 16S rRNA gene sequences revealed that the isolates were related to Streptomyces. Isolates were further screened based on a two-step process wherein the first step, around nine strains, unveiled the presence of type 1 polyketide synthase gene and dTDP-glucose 4,6-dehydratase gene through polymerase chain reaction. As the second step of the screening process, cell viability assay was performed in RAW264.7 cells to assess the toxicity of extracts. Among all the isolates, Streptomyces rochei strain VITGAP173 was subjected to further analysis. To explore the bioactivities, the organic solvent extraction method was utilized to extract the broth culture of VITGAP173. Inhibition of nitric oxide and cyclooxygenase enzymes upon lipopolysaccharide-induced inflammation were utilized to evaluate the anti-inflammatory efficacy, and the results showed the potency of VITGAP173 in a dose-dependent manner. The extract significantly suppressed the messenger RNA levels of the inflammatory mediators such as tumor necrosis factor-α and interleukin-6 induced by lipopolysaccharide in RAW264.7 macrophages. The presence of several chemical constituents was identified through gas chromatography-mass spectrometry analysis of VITGAP173 extract. To achieve the toxicity analysis, oral administration of VITGAP173 extract in Wistar albino rats was carried out to investigate the biochemical parameters, histopathology which revealed its nontoxic nature.     

Eutrophication of Lake Geneva indicated by the oligochaete communities of the profundal

Primary production rates and total phosphorus concentrations indicated that Lake Geneva (Switzerland) was meso-eutrophic from 1970 to 1983. Worm communities of the profundal (50–309 m deep) were very similar in 1978 and 1983. Species numerically dominant in eutrophic lakes — such as Potamothrix hammoniensis, P. heuscheri and Tubifex tubifex — constituted the bulk (75%) of the communities. Species numerically dominant in mesotrophic lakes (mostly Potamothrix vejdovskyi) or in oligotrophic lakes (mostly Stylodrilus heringianus) constituted respectively 18% and 7% of the worm communities. The dominance of eutrophic species increased with depth in the whole lake; it increased also in the eastern region of the lake which is directly exposed to the heavy organic inputs of the Rhône River. Oligotrophic and mesotrophic species decreased along the same gradients. Species dominant in oligotrophic lakes were absent in 1978 and 1983 from the deepest area of Lake Geneva (300–309 m) whereas they constituted therein 25% of worm communities in 1967. Data based on worm species groups — i.e. species with similar resistance to eutrophication pooled together — were more easy to analyse statistically than those based on the isolated species. Thus, the relative abundance of three species groups, expressed in several ways, can indicate precisely the trophic state of a lake.     

Abscisic acid inhibits shoot elongation of Scirpus mucronatus

The relationships between free ABA levels and shoot elongation were investigated in shoots of Scirpus mucronatus L. Under submergence, shoot elongation increased but free ABA levels decreased. The extent of the increase in length and the decrease in free ABA in submerged shoots increased with the increase of water depth. When the shoots were transferred to air after 12 days of submergence, they ceased to elongate and the free ABA levels recovered to the values of air-grown shoots. ABA, at concentrations from 1 μ M to 1 m M , inhibited the submergence-induced shoot elongation. In ambient air, fluridone, an inhibitor of ABA biosynthesis, at 7 μ M decreased the free ABA levels in shoots but increased shoot elongation. The effects could be reversed by 10 μ M ABA. These results indicate that ABA is an internal inhibitor of shoot growth in Scirpus .     

Kinos of Eucalyptus species and their acid degradation products

The kinos of Eucalyptus astringens, E. lehmannii and E. platypus contain mainly polymerized leucocyanidin, appreciable amounts of dihydrokaempferol 3-rhamnoside and trace amounts of other components, The acid degradation products of different kinos contained components not present in the products from wood and bark. These include phloroglucinol and two other components whose properties are described.