Effect of biodegradable chelators on induced phytoextraction of uranium- and cadmium- contaminated soil by Zebrina pendula Schnizl.

This study investigated the effect of ethylenediamine-N,N'-disuccinic acid (EDDS), oxalic acid (OA), and citric acid (CA) on phytoextraction of U- and Cd-contaminated soil by Z. pendula. In this study, the biomass of tested plant inhibited significantly following treatment with the high concentration (7.5 mmol·kg-1) EDDS treatment. Maximum U and Cd concentration in the single plant was observed with the 5 mmol·kg-1 CA and 7.5 mmol·kg-1 EDDS treatment, respectively, whereas OA treatments had the lowest U and Cd uptake. The translocation factors of U and Cd reached the maximum in the 5 mmol·kg-1 EDDS. The maximum bioaccumulation of U and Cd in the single plants was 1032.14 µg and 816.87 µg following treatment with 5 mmol·kg-1 CA treatment, which was 6.60- and 1.72-fold of the control groups, respectively. Furthermore, the resultant rank order for available U and Cd content in the soil was CA > EDDS > OA (U) and EDDS > CA > OA (Cd). These results suggested that CA could greater improve the capacity of phytoextraction using Z. pendula in U- and Cd- contaminated soils.

Effects of acetaminophen in oxidative stress and neurotoxicity biomarkers of the gastropod Phorcus lineatus.

The growing use of pharmaceutical drugs has become a major environmental issue considering that these substances (or their metabolites) end up inevitably in sewage waters after excretion. In the wild, these chemicals may affect non-target organisms, and their potential toxicity is not sufficiently studied, a reality that is particularly true for marine organisms. Acetaminophen (also known as paracetamol) is known to be toxic in high dosages, namely, by triggering oxidative effects. These effects may be potentiated in marine organisms subjected to contamination resulting from large human settlements along coastal areas. In order to assess how different exposure regimes (acute vs. chronic) may affect aquatic wildlife, individuals of the gastropod species Phorcus lineatus were acutely (96 h) and chronically (28 days) exposed to ecologically relevant concentrations of acetaminophen. The effects were evaluated through the quantification of selected biomarkers-catalase (CAT), glutathione-S-transferase (GST), and cholinesterase (ChE) activities. The results from acute exposure showed no significant effects in all three biomarkers, but chronically exposed organisms showed significant increases in the activities of CAT and ChEs. The data show that P. lineatus triggered a defensive biological response in the presence of acetaminophen, and also show that realistically low levels of acetaminophen can exert adaptive changes with unknown consequences.

Gastropods and Insects Prefer Different Solanum dulcamara Chemotypes.

Solanum dulcamara (Bittersweet nightshade) shows significant intraspecific variation in glycoalkaloid (GA) composition and concentration. We previously showed that constitutive differences in overall GA levels are correlated with feeding preference of the grey field slug (GFS; Deroceras reticulatum). One particularly preferred accession, ZD11, contained low GA levels, but high levels of previously unknown structurally related uronic acid conjugated compounds (UACs). Here we test whether different slug species as well as insect herbivores show similar feeding preferences among six S. dulcamara accessions with different GA chemotypes. In addition, we investigate whether slug feeding can lead to induced changes in the chemical composition and affect later arriving herbivores. A leaf disc assay using greenhouse-grown plants showed that three slug species similarly preferred accessions with low GA levels. Untargeted metabolomic analyses showed that previous slug feeding consistently increased the levels of N-caffeoyl-putrescine and a structurally related metabolite, but not the levels of GAs and UACs. Slug-induced responses only affected slug preference in one accession. A common garden experiment using the same six accessions revealed that ZD11 received the highest natural gastropod feeding damage, but suffered the lowest damage by specialist flea beetles. The latter preferred to feed on accessions with high GA levels. Our study indicates that different selection pressures imposed by generalist gastropods and specialist insects may explain part of the observed chemical diversity in S. dulcamara.

Comparative evaluation of antibacterial activity of foot muscle extracts from genus Physa and genus Ceciloides (Mollusca: Gastropoda).

The aim of this study is to explore the presence of antimicrobial bioactive agents in the foot muscle extracts of snails belonging to genus Physa and Ceciloides. Antibacterial activity of foot extracts belonging to species named as P. fontinalis, P. gyrina, P. acuta, C. acicula, C. eulima, C. petitiana, was checked and compared against three bacterial strains i.e. E.coli, P. auroginosa, S. aureus by using disc diffusion method. The results were highly significant with maximum zone of inhibition of 20.10 mm in the P. fontinalis acetone extract and the least was 12.97 mm of C. eulima diethyl ether extract. The microdilution method was employed to observe MIC to evaluate antimicrobial resistance pattern of snails foot muscle extract against three mentioned strains. MIC of foot extracts was ranging from 0.03µ/ml-5 µg/ml for six species. TLC was carried out for profiling of extracts with positive results. Foot extracts from species of both genera eluted in different fractions of compounds with a good resolution in 100% n-hexane and ethyl acetate each. The plates developed in solvent system showed purple and yellow spots indicating the presence proteins and organic compounds showing it a promising canditadate for the therapeutic purposes.

[Study on correlation of oxygen consumption rate and suffocation point of Whitmania pigra and Bellamya purificata and optimum way of feeding Whitmania pigra].

The oxygen consumption, oxygen consumption rate and suffocation point of different quality Whitmania pigra and Bellamya purificata were determined by hydrostatic breathing room method. The effects of feeding modes on growth of W.pigra were determined by biomass. The results showed that the oxygen consumption correlated positively with the weight of W.pigra and B. purificata（P<0.05）, suffocation point increased with the increases of the weight（P<0.05）.Oxygen consumption correlated negatively with the weight of W. pigra, the oxygen consumption rate of B.purificata first increased and then decreased with the increasing of the weight. Feeding modes had no significant effects on the finial weight, SGR, WGR, death rates of W. pigra. Feeding modes had significant effects on eating ratio. It suggested that the optimum feeding frequency of W. pigra was once every three days. Scientific and reasonable feeding amount of B. purificata should be calculated based on oxygen consumption and suffocation point of W.pigra and B.purificata at every period. Meanwhile, stocking density, water area and water exchanging frequency should be taken into consideration.

Insight of EDX analysis and EFTEM: are spherocrystals located in Strombidae digestive gland implied in detoxification of trace metals?

Digestive tubules of Strombidae are composed by three cell types: digestive cells, vacuolated cells, and crypt cells. The last one is characterized by the presence of intracellular granules identified as spherocrystals. Such structures are known to occur in basophilic cells of gastropod digestive gland, where they are supposed to be involved in the regulation of some minerals and in detoxification. In this study, energy-dispersive X-ray analysis (EDX) and energy filtered transmission electron microscopy (EFTEM) were used to determine the elemental content of spherocrystals in two Strombidae, Strombus gigas and Strombus pugilis. In freshly collected individuals of both species, the following elements were detected: Ca, Fe, Mg, P, and Zn. Aluminum and Mn were also detected in S. gigas. Their presence in spherocrystals indicates that, in Strombidae, spherocrystals are involved in the regulation of minerals and essential trace metals. In order to answer the question "are spherocrystals involved in nonessential trace metals scavenging?," artificial cadmium and lead exposure by both waterborne and dietary pathways was applied to S. pugilis. No evidence of cadmium (Cd(NO(3))(2)) or lead (Pb(NO(3))(2)) provided by food was found in spherocrystals. Cadmium provided in water (Cd(NO(3))(2) and CdCl(2)) causes structural modifications of the digestive gland; however, this element was not trapped in spherocrystals. These results suggest that spherocrystals are not involved in detoxification of such nonessential trace metals.

Molecular cloning and characterization of prohormone convertase 1 gene in abalone (Haliotis diversicolor supertexta).

Prohormone convertases (PCs) are calcium-dependent serine endoproteases of the subtilisin family that play a key role in the posttranslational processing of precursors for bioactive peptides. In this study, the cDNA of PC1 from abalone (Haliotis diversicolor supertexta) was cloned and sequenced. The PC1 cDNA consisted of 2216 bp with an open reading frame of 2010 bp encoding a 670 amino acid peptide. Comparative structural analysis revealed that abalone PC1 shared high similarity and identity with most PC counterparts. The profile of deduced peptide of PC1 was composed of an N-terminal signal peptide, a prosegment domain, a catalytic domain and a P domain, which were common in many species. Sequence analysis indicated that the abalone PC1 was highly conserved in catalytic domain, including three conserved serine catalytic signatures that comprised a catalytic triad active center. Also conserved were the potential cleavage site for release of the mature peptide, a cognate integrin binding site RGD in P domain, and four cysteine residues involved in forming an intrachain disulfide bridge. To further investigate the functions of PC1 in abalone, real-time quantitative PCR was performed to determine the expression level of this gene at three different reproduction stages (i.e. pre-, during- and post-breeding). Results indicated that PC1 was expressed throughout the three stages but the expression levels varied with the timepoints and different tissues in abalone. The expression levels of PC1 in digestive gland were much higher than those of the gonad. In female abalone, the expression of PC1 was higher at pre-breeding and during-breeding stages (P<0.05), and the expression declined at the subsequent stage. Whereas, the level of PC1 in male individual did not exhibit a significant difference in various reproduction stages. Also, the natural enzyme activity of PC1 partially exhibited a similar tendency with the mRNA expression. According to the results, it can be concluded that PC1 gene is involved in the abalone reproduction process (e.g. spawning or sperming). PC1 is a potential prohormone processing enzyme and it may play a critical role in abalone physiological processes related to reproduction.

Variety is the spice of life histories: comparison of intraspecific variability in marine invertebrates.

Life-history characteristics of marine invertebrates exhibit broad diversity across taxa as well as considerable variation within species. Although such variation is widely recognized, comparisons of the magnitude of variability as an outcome of evolutionary processes are relatively rare. Theory predicts, for example, that patterns of variability within and between clutches can arise as a consequence of population genetic structure, environmental variability, and the uncertainty of future ecological conditions. We review the strengths and weaknesses of several statistical methods for comparing variability across distributions, including Levene's test, use of the coefficient of variation in F-tests, and analysis of covariance. We then use four case studies from our own work and from the literature to illustrate adaptive patterns of variability related to metamorphosis, habitat differentiation, physiological stress, and life-history mode. These examples demonstrate the value of comparing variability for a range of questions associated with reproductive ecology, life-history biology, and genotype-by-environment interactions. We encourage researchers studying larval ecology and life-history evolution to explicitly consider the causes and consequences of variances in traits along with their means in models, experimental designs, analyses, and interpretations.

Factors promoting marine invasions: a chemoecological approach.

The Mediterranean Sea is losing its biological distinctiveness, and the same phenomenon is occurring in other seas. It gives urgency to a better understanding of the factors that affect marine biological invasions. A chemoecological approach is proposed here to define biotic conditions that promote biological invasions in terms of enemy escape and resource opportunities. Research has focused on the secondary metabolite composition of three exotic sea slugs found in Greece that have most probably entered the Mediterranean basin by Lessepsian migration, an exchange that contributes significantly to Mediterranean biodiversity. We have found toxic compounds with significant activity as feeding deterrents both in the cephalaspidean Haminoea cyanomarginata and in the nudibranch Melibe viridis. These findings led us to propose aposematism in the former and dietary autonomy in producing defensive metabolites in the latter case, as predisposing factors to the migration. In the third mollusk investigated, the anaspidean Syphonota geographica, the topic of marine invasions has been approached through a study of its feeding biology. The identification of the same compounds from both the viscera of each individual, separately analyzed, and their food, the seagrass Halophila stipulacea, implies a dietary dependency. The survival of S. geographica in the Mediterranean seems to be related to the presence of H. stipulacea. The initial invasion of this exotic pest would seem to have paved the way for the subsequent invasion of a trophic specialist that takes advantage of niche opportunities.

Gastropod grazers and nutrients, but not light, interact in determining periphytic algal diversity.

The potential interactions of grazing, nutrients and light in influencing autotroph species diversity have not previously been considered. Earlier studies have shown that grazing and nutrients interact in determining autotroph species diversity, since grazing decreases species diversity when nutrients (i.e. N or P) limit autotroph growth, but increases it when nutrients are replete. We hypothesized that increased light intensities would intensify the interactions between grazing and nutrients on algal species diversity, resulting in even stronger reductions in algal species diversity through grazing under nutrient-poor conditions, and to even stronger increases of algal species diversity through grazing under nutrient-rich conditions. We studied the effects of grazing (absent, present), nutrients (ambient, N + P enriched) and light (low light, high light) on benthic algal diversity and periphyton C:nutrient ratios (which can indicate algal nutrient limitation) in a factorial laboratory experiment, using the gastropod grazer Viviparus viviparus. Grazing decreased algal biomass and algal diversity, but increased C:P and N:P ratios of periphyton. Grazing also affected periphyton species composition, by decreasing the proportion of Spirogyra sp. and increasing the proportion of species in the Chaetophorales. Grazing effects on diversity as well as on periphyton N:P ratios were weakened when nutrients were added (interaction between grazing and nutrients). Chlorophyll a (Chl a) per area increased with nutrient addition and decreased with high light intensities. Light did not increase the strength of the interaction between grazing and nutrients on periphytic algal diversity. This study shows that nutrient addition substantially reduced the negative effects of grazing on periphytic algal diversity, whereas light did not interact with grazing or nutrient enrichment in determining periphytic algal diversity.