Antioxidant responses of microalgal species to pyrene

The antioxidant response of four freshwater microalgal species, Chlorella vulgaris Beij., Scenedesmus platydiscus (G. M. Smith) Chod., Scenedesmus quadricauda(Turp.) Bréb., and Selenastrum capricornutum Printz without pyrene addition (control) and at two pyrene concentrations (0.1 and 1.0 mgL⁻¹) were investigated. Under the control condition, the values of the antioxidant parameters differed significantly among species and the difference was seemed not to be related to their susceptibility to pyrene. The antioxidant response to pyrene treatments also varied from species to species. Pyrene led to a significant increase in total glutathione (GSH) content in all species except C. vulgaris, a species did not exhibit any ability to metabolize pyrene. The glutathione-S-transferase (GST) activities also remained unchanged in pyrene treated C. vulgaris, increased greatly in S. platydiscus and Se. capricornutum (the two species with higher pyrene metabolism ability), but inhibited remarkably in S. quadricauda (the only species sensitive to pyrene toxicity). On the other hand, the glutathione reductase (GR) activities increased in C. vulgaris but remained at a similar level as the control in the other three species. The malondialdehyde (MDA) content, an indicator of lipid peroxidation, declined in S. quadricauda but showed no significant change in the other three species. The activities of glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT) in pyrene treated cells remained almost the same as the controls for all microalgal species. Results suggested that the alterations of antioxidant systems in microalgae might not be useful indicators of pyrene exposure but pyrene-enhanced GSH metabolism might be important in pyrene biotransformation.     

Monoclonal Antibodies againstAntigens of Hydra vulgaris and Hydra oligactis

The goal of the study was to obtain a panel of monoclonal antibodies (MAb) against antigens of freshwater polyps of the genus Hydra. Hybrid mice F₁(Balb/c × SJL/J) were immunized with cell membrane fraction of H. vulgaris and three months later their splenocytes were fused with cultured mouse myeloma cells 653A. Testing of culture fluids in ELISA with immobilized H. vulgaris cells, 82 hybridomas producing MAb were revealed. Study of MAb specificity in ELISA with H. vulgaris and H. oligactis cells indicated that 22% of them recognized only H. vulgaris antigens. About 50% of MAb recognized equally antigens of the both species. The rest of MAb reacted with H. vulgaris and H. oligactis antigens to different degree. Eight hybridomas producing MAb of all three above groups were adapted for growth as ascitic tumors. The distribution of antigens binding these MAb was studied in indirect immunofluorescence on fixed polyps, living or fixed cells, and on paraffin- embedded sections. Among the best studied MAb, of the greatest interest were the following reagents. One of them (1A10) revealed an antigen on surface membranes of ectodermal epithelial cells of H. vulgaris. The second one (1G10) was specific of the antigen located in mesoglea and basal cytoplasmic areas of ectodermal and entodermal epithelial cells of the both hydra species. The MAb 4G3 interacted with cytoplasmic antigen of ectodermal epithelia-muscular cells of the both hydra species. MAb 4H1 revealed nematocytes in H. vulgaris and H. oligactis. The data obtained indicate that in two species of hydra the epitopes binding the same MAb might be located in cells of different types.     

水陆生境和氮沉降对香菇草(Hydrocotyle vulgaris)入侵湿地植物群落的影响

大气氮沉降对湿地外来植物入侵的影响已成为生态学研究的热点之一。选用梭鱼草(Pontederia cordata)、水菖蒲(Acorus calamus)、黄花鸢尾(Iris wilsonii)和粉绿狐尾藻(Myriophyllum aquaticum)模拟湿地植物群落,设置有无香菇草入侵、水生和陆生生境(水位分别为15 cm和0 cm)及有无氮沉降处理(15 g N m~(-2)a(-1)和0)交叉组成的8种处理组合,进行为期70d的温室控制实验,以分析水陆生境及氮沉降对香菇草入侵湿地植物群落的影响。结果表明:(1)水生生境下,香菇草的总生物量、叶生物量、叶片数和节点数与陆生生境相比显著降低;水生生境下氮沉降处理对香菇草各指标无显著影响,陆生生境下氮沉降处理的香菇草叶片数、节点数显著多于无氮沉降处理。(2)实验周期内氮沉降和香菇草入侵没有对群落的多样性指数及群落内4种湿地植物的生物量产生显著影响;水生生境下植物群落的总生物量及梭鱼草和粉绿狐尾藻的生物量与陆生生境相比显著提高。(3)水生生境下香菇草的相对优势度相比陆生生境下显著下降;氮沉降只在陆生生境下显著提高了香菇草的相对优势度。因此,香菇草向水生生境扩散和入侵的能力不强,其入侵在短时间内对湿地植物群落影响较小。研究结果可以为入侵植物生态学研究提供案例借鉴。     

Diversity of nodule-endophytic agrobacteria-like strains associated with different grain legumes in Tunisia

This study represents the first report describing the genetic diversity of nodule-endophytic agrobacteria isolated from diverse legumes and their phylogenetic relationships with the valid species of agrobacteria, as well as the non-recognized genomospecies of the former Agrobacterium tumefaciens (Rhizobium radiobacter). The genetic diversity of a collection of 18 non-nodulating agrobacteria-like strains, previously isolated from root nodules of Vicia faba, Cicer arietinum and Phaseolus vulgaris from different geographical regions of Tunisia, was studied by REP-PCR and PCR-RFLP of the 16S-23S rDNA IGS, as well as by sequence analysis of the 16S rDNA and the housekeeping genes recA and atpD. The aim of the work was to study the genetic diversity of the different isolates and to check for any host-specificity. The results from the different techniques were congruent and suggested a specific interaction for P. vulgaris, whereas no specific endophytic interaction was observed for V. faba and C. arietinum. The phylogenetic analysis clearly indicated that some isolates were affiliated to R. radiobacter or to its non-recognized genomic species (genomovars G2, G4 and G9). However, the other isolates probably constitute new species within Rhizobium (Agrobacterium) and Shinella.     

Microsatellite loci for the Siberian flying squirrel,Pteromys volans

We report the isolation and characterization of polymorphic microsatellite loci for the Siberian flying squirrel Pteromys volans. The seven most useful loci had between six and 11 alleles and expected heterozygosities ranging from 0.477 to 0.866. We also tested the utility of these loci in other squirrel species, northern flying squirrels (Glaucomys sabrinus and G. volans) and the common red squirrel (Sciurus vulgaris). Three of the Siberian flying squirrel loci were polymorphic in other squirrel species, suggesting a limited potential for cross‐species use.     

Genetic diversity and relationships between nine species of bamboo in Sri Lanka, using Random Amplified Polymorphic DNA

Random Amplified Polymorphic DNA (RAPD) showed a high degree of polymorphism in nine species of bamboo, Dendrocalamus giganteus Wall ex Munro, D. asper Becker ex K. Heyn, D. longispathus (Kurz) Kurz, Bambusa vulgaris `Striata', B. ventricosa, B. bambos (L.) A. Voss, B. atra Lindley, Gigantochloa atroviolacea Wdjaja and Arundinaria hindsii, in Sri Lanka. The lowest mean genetic distance of 0.143 was between B. vulgaris and B. ventricosa. They could however be distinguished morphologically. The genetic distances separating D. longispathus from D. giganteus and D. asper were both greater than that between the latter two species, which had a value of 0.313. Although the genetic distances between Bambusa vulgaris, B. ventricosa and B. bambos were relatively small, B. atra separated from them at greater distances. The smaller genetic distances between G. atroviolacea and B. vulgaris, B. ventricosa and B. bambos indicated that G. atroviolacea had a closer affinity to these three Bambusa species than B. atra. A. hindsii with the greatest genetic distances from all other species in the study, was not related to any of them. RAPD analysis was useful in determining the genetic diversity and relationships and in detecting problematic generic assignments.     

Temporal and host-related variation in frequencies of genes that enable Phyllotreta nemorum to utilize a novel host plant, Barbarea vulgaris

The flea beetle, Phyllotreta nemorum L. (Coleoptera: Chrysomelidae), is an intermediate specialist feeding on a small number of plants within the family Brassicaceae. The most commonly used host plant is Sinapis arvensis L., whereas the species is found more rarely on Cardaria draba (L.) Desv., Barbarea vulgaris R.Br., and cultivated radish (Raphanus sativus L.). The interaction between flea beetles and Barbarea vulgaris ssp. arcuata (Opiz.) Simkovics seems to offer a good opportunity for experimental studies of coevolution. The plant is polymorphic, as it contains one type (the P‐type) that is susceptible to all flea beetle genotypes, and another type (the G‐type) that is resistant to some genotypes. At the same time, the flea beetle is also polymorphic, as some genotypes can utilize the G‐type whereas others cannot. The ability to utilize the G‐type of B. vulgaris ssp. arcuata is controlled by major dominant genes (R‐genes). The present investigation measured the frequencies of flea beetles with R‐genes in populations living on different host plants in 2 years (1999 and 2003). Frequencies of beetles with R‐genes were high in populations living on the G‐type of B. vulgaris ssp. arcuata in both years. Frequencies of beetles with R‐genes were lower in populations living on other host plants, and declining frequencies were observed in five out of six populations living on S. arvensis. Selection in favour of R‐genes in populations living on B. vulgaris is the most likely mechanism to account for the observed differences in the relative abundance of R‐genes in flea beetle populations utilizing different host plants. A geographic mosaic with differential levels of interactions between flea beetles and their host plants was demonstrated.     

Predator-prey behavior and its effect on rotifer survival in associations of Mesocyclops edax,Asplanchna girodi,Polyarthra vulgaris,and Keratella cochlearis

Summary The predatory copepod Mesocyclops edax preys effectively on the rotifers Asplanchna girodi and Polyarthra vulgaris but not on the rotifer Keratella cochlearis. It readily captures individuals of this latter species but usually releases them unharmed, being unable to remove the soft parts within their loricae. The predatory A. girodi regularly eats K. cochlearis but cannot catch P. vulgaris. When P. vulgaris is contacted by the corona of A. girodi, it immediately escapes by elevating its paddles and jumping away a distance up to about ten times its own body length. In experimental communities of these predator and prey species the survival of Polyarthra and Keratella is significantly affected by the species of predator present and by predator-prey interaction between the two predators when both are present.Supported by National Science Foundation research grant DEB 76-09768 and Public Health Service career development award KO4-GM 70557 to J.J.G.     

Genetic diversity and similarity in the Barbarea vulgaris complex (Brassicaceae)

Two subspecies of Barbarea vulgaris are taxonomically recognized as ssp. vulgaris and ssp. arcuata. In addition, two types of Barbarea vulgaris ssp. arcuata occurs in Denmark. The G‐type is resistant to an herbivorous flea beetle (Phyllotreta nemorum) whereas the P‐type is susceptible. A previous study suggested that the P‐type evolved by a loss of resistance from a resistant progenitor. We analyzed the genetic relatedness among eight Barbarea taxa: B. vulgaris spp. vulgaris, B. vulgaris ssp. arcuata G‐ and P‐types, hybrids between the types, B. verna, B. intermedia, B. stricta, B. orthoceras and B. australis, using AFLP and SSR markers. A clear distinction between the G‐ and P‐types was revealed. Both were distinct from B. vulgaris ssp. vulgaris, the G‐type less so than the P‐type. Barbarea verna and B. intermedia formed unambiguous clusters, whereas the remaining taxa produced less discrete groupings. Possible evolutionary scenarios for flea‐beetle resistance and susceptibility are discussed, including lineage sorting from a polymorphic ancestral population, and de novo loss of resistance in the P‐type of B. vulgaris ssp. arcuata.     

DIEL RHYTHM OF ALGAL PHOSPHATE UPTAKE RATES IN P‐LIMITED CYCLOSTATS AND SIMULATION OF ITS EFFECT ON GROWTH AND COMPETITION1

Oscillations in the phosphate (P_i) uptake rates for three species of green algae were examined in a P‐limited cyclostat. For Ankistrodesmus convolutus Corda and Chlorella vulgaris Beyerinck, the P_i uptake rates increased during the daytime and decreased at night. In contrast, Chlamydomonas sp. exhibited the opposite uptake pattern. Cell densities also oscillated under a light:dark cycle, dividing at a species‐specific timing rather than continuously. In general, the cell densities exhibited an inverse relationship with the P_i uptake rates. A competition experiment between A. convolutus and C. vulgaris in a P‐limited cyclostat resulted in the dominance of C. vulgaris, regardless of the relative initial cell concentrations. Chlorella vulgaris also dominated in a mixed culture with Chlamydomonas sp., irrespective of the initial seeding ratio and dilution rate. However, Chlamydomonas sp. and A. convolutus coexisted in the competition experiment with gradual decrease of Chlamydomonas sp. when equally inoculated. Mathematical expressions of the oscillations in the P_i uptake rate and species‐specific cell division gate were used to develop a simulation model based on the Droop equation. The simulation results for each of the species conformed reasonably well to the experimental data. The results of the competition experiments also matched the competition simulation predictions quite well, although the experimental competition was generally more delayed than the simulations. In conclusion, the model simulation that incorporated the effect of diel rhythms in nutrient uptake clearly demonstrated that species diversity could be enhanced by different oscillation patterns in resource uptake, even under the condition of limitation by the same resource.     

FLORAL PIGMENTATION STUDIES IN THE GENUS GOSSYPIUM II CHEMOTAXONOMIC ANALYSIS OF DIPLOID GOSSYPIUM SPECIES

The chromatographic pigment arrays of nine diploid species (G. arboreum, G. anomalum, G. herbaceum, G. stocksii, G. sturtii, G. thurberi, G. gossypioides, G. raimondii and G. klotzschianum) were studied. Among the Old World cottons, G. sturtii of Australia was very different from the species analyzed. The two species of the Herbacea section (G. herbaceum and G. arboreum) were found to have very similar pigment arrays. Both G. anomalum and G. stocksii were more like the Herbacea species than any other species in the genus, but both G. anomalum and G. stocksii had unique pigment characteristics. Although the evidence obtained so far from pigmentation patterns suggests that some pairs of species are closely related, the pigment arrays do not support the classification of the New World diploids into more than one section. From analysis of pigments of interspecific hybrids and their parents, it was found that with a hybrid and one parent species the pigment array of the other parent species could be predicted. Using this approach, the pigment arrays of three New World diploid species were predicted.     

Establishment and metabolic analysis of a model microbial community for understanding trophic and electron accepting interactions of subsurface anaerobic environments

Background  

Communities of microorganisms control the rates of key biogeochemical cycles, and are important for biotechnology, bioremediation, and industrial microbiological processes. For this reason, we constructed a model microbial community comprised of three species dependent on trophic interactions. The three species microbial community was comprised of Clostridium cellulolyticum, Desulfovibrio vulgaris Hildenborough, and Geobacter sulfurreducens and was grown under continuous culture conditions. Cellobiose served as the carbon and energy source for C. cellulolyticum, whereas D. vulgaris and G. sulfurreducens derived carbon and energy from the metabolic products of cellobiose fermentation and were provided with sulfate and fumarate respectively as electron acceptors.     

Estimating plant competition coefficients and predicting community dynamics from non-destructive pin-point data: a case study with Calluna?vulgaris and Deschampsia?flexuosa

A method is proposed for estimating plant competition coefficients and predicting the dynamics of herb and grassland plant communities from non-destructive pin-point measurements. The method is applied to inter-specific competition in a natural heathland community with relatively few interacting species. The study shows that the dynamics of the heathland plant community may be thought of as essentially a two-species system of Calluna vulgaris and Deschampsia flexuosa. There were significant competitive interactions between C. vulgaris and D. flexuosa. D. flexuosa affected both the cover and compactness of C. vulgaris individuals as a function of the compactness the previous year, whereas C. vulgaris significantly affected only the compactness of D. flexuosa. There was a significant negative effect of drought on the compactness of both C. vulgaris and D. flexuosa individuals, whereas night warming had no significant effects on either species. The predicted long-term outcome of the competitive interaction between C. vulgaris and D. flexuosa was that of unstable equilibrium, where the more dominant of the two will outcompete the other. However, when both species are found at relatively high plant covers the two species are predicted to co-exist for a long time period relatively to the time scale of the ageing process of C. vulgaris. Direct analyses of the inter-specific competitive interactions in natural plant communities with non-destructive measurements can provide important new insight into the processes that determine the composition of plant communities.     

Selection for improved nitrogen fixation inGlycine max (L.) Merr. andPhaseolus vulgaris L.

Summary While symbiotic nitrogen (N₂) fixation byG. max andP. vulgaris reduces their need for combined N, N₂ fixation under field conditions is rarely maximized. This paper reviews constraints to N₂ fixation in these species, then examines the genetic variability recorded for traits affecting N₂ fixation and the further work needed in this area. It considers emerging programs for the improvement of N₂ fixation inG. max andP. vulgaris and pays particular attention to methodological considerations.Scientific Journal Series, Minnesota Agri. Exp. Station. No 14190.     

Cryptic speciation among intestinal parasites (Trematoda: Digenea) infecting sympatric host fishes (Sparidae)

In the north‐western (NW) Mediterranean, the teleosts Diplodus sargus, D. vulgaris and D. annularis coexist in infralittoral habitats. These fishes are infected by two species of the Digenea (Platyhelminthes, Trematoda): Macvicaria crassigula (Opecoelidae) and Monorchis parvus (Monorchiidae) for which we obtained Internal Transcribed Spacer rDNA sequences. Each parasite species represents a complex of two cryptic species, one restricted to D. annularis, and the other shared by D. sargus and D. vulgaris. Cytochrome b mtDNA sequences were used to infer host phylogenetic relationships which showed that the distribution of parasites in Diplodus hosts is not a consequence of coevolutionary interactions. We used diet analyses available for the fish hosts to assess the degree of overlap in the use of food among the three species. The feeding overlap was significant only between D. sargus and D. vulgaris, but not for the other fish pairs. The possible mechanisms involved in the speciation of the digenean fauna of Diplodus fishes are discussed.     

Experimental manipulation of succession in heathland ecosystems

An experiment was carried out in two heathland ecosystems, one dominated by Calluna vulgaris and the other by Molinia caerulea, to analyse the effects of soil organic matter accumulation and nutrient mineralization on plant species dynamics during succession. The experiment included one treatment that received nutrient solution and two treatments where the rate of soil organic matter accumulation was reduced by removing litter or accelerated by adding litter. In a fourth treatment the C. vulgaris litter produced in the C. vulgaris-dominated plots was replaced by litter of M. caerulea and vice versa. Treatments were applied over 8 years. Addition of nutrient solution caused C. vulgaris to decline, and grass species to increase sharply, compared to the control plots. Addition of litter enhanced both N mineralization and the biomass of M. caerulea and Deschampsia flexuosa but reduced the biomass of C. vulgaris. The effects of replacing C. vulgaris litter by M. caerulea litter, or vice versa, on N mineralization and species dynamics could not be attributed to differences between the decomposability of the different litter materials that were transferred. The results confirm the hypothesis that increased litter inputs accelerate the rate of species replacement during succession.     

GENETIC DIVERSITY,INTROGRESSION, AND INDEPENDENT DOMESTICATION OF OLD WORLD CULTIVATED COTTONS

Gossypium arboreum L. and G. herbaceum L. are the diploid species of cultivated cotton. Little is known regarding the time and place of domestication of either species. Because G. arboreum is known only as a cultigen, others have proposed that it arose from domesticated G. herbaceum during the more than 5,000-year history of Old World cotton cultivation, with wild G. herbaceum subsp. africanum (Watt) Mauer as the putative ancestor of both species. An alternative hypothesis is that the two species have independent origins from progenitors that diverged prior to domestication. The relative merits of these opposing hypotheses were evaluated using data derived from starch gel electrophoresis of enzymes. One hundred and three accessions of G. arboreum and 31 accessions of G. herbaceum were examined for allelic variation at 40 allozyme loci. All measures of genetic variability demonstrated that G. arboreum contains greater diversity than G. herbaceum, although both species have relatively low levels of allozyme variation. In contrast to expectations based on morphology and other chemical data sets, the two species are highly differentiated with respect to allozyme composition. Gossypium arboreum and G. herbaceum each contain a large number of unique alleles and are fixed or nearly fixed for alternate alleles at 8 loci. Five allozyme loci have alleles that are rare in one of the two species but common in the other. Based on restricted occurrence of these alleles to areas with a long history of sympatric cultivation and the geographic distribution of a null allele, we suggest that a significant portion of the allelic diversity in both species results from historical, bidirectional interspecific introgression. The interspecific genetic identity estimate (0.74) is markedly lower than for documented progenitor-derivative and crop-ancestor species pairs. Based on these data, as well as previous cytogenetic data and the observation of F₂ breakdown in interspecific crosses, we suggest that cultivated G. arboreum and G. herbaceum were independently domesticated from divergent ancestors.     

Morphological assessment of the Octopus vulgaris species complex evaluated in light of molecular‐based phylogenetic inferences

Cryptic species are common in the ocean, particularly among marine invertebrates such as octopuses. Delineating cryptic species is particularly problematic in octopus taxonomy where the plasticity recorded among taxonomic characters often results in low resolution at the species level. This study investigated the morphological relationships among seven phylogenetic clades (identified using cytochrome c oxidase subunit I) of the broadly distributed Octopus vulgaris species complex and close relatives. Morphological analyses in this study were successful in delimiting O. sinensis, Brazilian O. vulgaris and O. vulgaris sensu stricto, which was congruent with the molecular findings of this study. Analyses based on male morphology were successful in distinguishing 14 of 15 total pairwise comparisons and proved to be a more reliable indicator of species‐level relationships in comparison with female morphology. The majority of characters with the greatest discriminatory power were male sexual traits. Significant morphological differences were also recorded among sampling localities of conspecifics, with phenotype showing correlation with local environmental data. The findings of this study support the hypothesis that multiple O. vulgaris‐like species are currently being incorrectly treated under a single species name, O. vulgaris. Octopuses being exported globally under the name O. vulgaris are of extremely high fisheries market value and profile. Our findings have potentially significant implications for the naming and conservation of commercially harvested members of this species complex throughout their ranges.     

A STUDY OF TRIPLOID AND 3 X – 1 ANEUPLOID PLANTS IN THE GENUS GOSSYPIUM

Cytological comparisons were made of triploid and 3x – 1 plants of Gossypium hirsutum (haplo 17 and 18) X G. aridum, G. armourianum, G. harknessii, and G. raimondii. Tests and observations led to these conclusions: (1) Chromosome conjugation varied significantly from plant to plant and date to date within plants. (2) The D genome chromosomes of G. hirsutum are closer in homology to G. raimondii than to the other species tested. (3) The chromosomes of G. aridum, have closer homology to the A genome of G. hirsutum than do the chromosomes of the other D species tested. (4) The D genome of G. hirsutum has a small translocation as compared to the genomes of the four D species studied.