Ecology of a North Sea pockmark with an active methane seep

ABSTRACT: At a large North Sea pockmark, with active methane seeps, surface sediments were found to have higher insoluble sulphide concentrations than sedlments from the surrounding area. The fauna of the pockmark was characterized by 2 species which have not pi-evlously been reported from the Fladen Ground in the northern North Sea. These species were a b~valve, Thyasira sarsi (which is known to contain endosymbiotic sulphur-oxidising bacteria) and a mouthless and gutless nematode, Astomonerna sp., which also contains endosymbiotic bacteria The nematode was the dominant meiofauna species in the pockmark sediments. Both macro-lnfauna and total nematodes were in low abundance in samples taken from the base of the pockmark. Sediment samples from the pockmark contained numerous otoliths, implying that substantial winnowing of the sediment had taken place. This was supported by studies on the sulphide concentrations in the sediment which showed multiple layering of the sediments on the sides of the pockmark, suggesting displacement. The carbon isotope compositions (6I3c) of the tissues of benthic animals from in and around the pockmark were generally in the range -16 to -2O%, indicating that little methane-derived carbon was contributing to their nutrition. T sarsi had the most 13c-depleted tissues, -31.4 to -35.1 L, confirming the nutritional dependence of this species on chemoautotrophic bacteria that utilize reduced sulphur.

The Nematode-Copepod Ratio And Its Use In Pollution Ecology

The nematode/copepod ratio is critically examined with a view to adding some precision to its proposed use in pollution ecology. At two unpolluted intertidal sites, differing markedly in sediment grade, the metabolic requirements of copepods are shown to be equivalent to the requirements of that fraction of the nematode population which feeds in the same way. The partitioning of this total energy requirement among individuals depends on the distribution of individual metabolic body sizes and the relative rates of metabolism. The distribution of body sizes is constrained by the sediment granulometry, which affects nematodes and copepods differently. These considerations enable precise predictions of the nematode/copepod ratios expected in unpolluted situations, against which observed ratios can be compared.

The Influence Of Temperature And Salinity On Energy Partitioning In The Marine Nematode Diplolaimelloides-Bruciei

Measurements of population growth, generation time, fecundity and respiration in laboratory culture have been made, in relation to temperature and salinity, for the nematode Diplolaimelloides bruciei Hopper, a species normally associated with decayed material of the marsh grass Spartina. The intrinsic rate of increase (r) is high: it is related to temperature between 5° and 25°C by a sigmoid function which is steepest between 10° and 15°C, and is maximum at 26‰ salinity. Generation time is related to temperature by a power function and is shortest at 26‰ salinity. The effect of temperature on generation time is consistent with other data for marine nematodes, and the steep slope of r against temperature is largely due to the marked effect of temperature on fecundity. A sex ratio of 2:1 in favour of males is maintained regardless of culture conditions or population density. Respiration increases exponentially with temperature between 5° and 25°C, with a very high Q10 (3.94), but is not affected by salinity. At 30°C respiration is no higher than at 25°C. A high and relatively stable production efficiency (P/A) is maintained between 10 and 30°C with a maximum of 87% at 15°C; there is a stable reproductive effort (Pr/A) of about 10%. At 5°C both these ratios are zero. Data for the harpacticoid copepod Tachidius discipes, derived from the literature, show that this too has a high and stable production efficiency, which may be a characteristic of meiofaunal species in general, but in this species efficiency is relatively high at 5°C. Many features of the energy balance in D. bruciei can be related to an opportunistic mode of life.

Pattern of benthic biomass size spectra from shallow waters in the East China Seas

Benthic biomass size spectra (BSS) and normalized biomass size spectra were constructed, and benthic secondary production was estimated by a size spectrum equation in the shallow waters in the East China Sea, ranging latitudinally from 40A degrees N to 29A degrees N. The BSS patterns were bimodal, two biomass peaks corresponding to meiofauna and macrofauna, respectively, separated by a trough of low biomass at 8-256 mu g individual dry weight which varied in position with median sediment particle size. The BSS also displayed bimodality within meiofauna size ranges, which in most stations was due to the relative proportions of nematodes and other meiofauna taxa. Re-analysis of data from sites in the UK, South Africa, and Antarctic showed a similar bimodality in the adult species body size distribution within the meiofauna size range. Macrofaunal production estimated by the size spectrum equation was very similar to the results of Brey90 empirical equation. However, these production values were much lower than those calculated by Brey01. Different individual dry-to-wet conversion ratios, temperature deviation, and macrofauna taxonomic composition might be responsible for the between-model differences. The macrofaunal P/B ratios calculated by this equation ranged from 0.3 to 3.4 which were in accordance with values from Northern Hemisphere mid-latitudes. Meiofaunal production estimates will need further empirical support.

Interactions between multiple large macrofauna species and nematode communities — Mechanisms for indirect impacts of trawling disturbance

Highlights •We exposed meiofauna to 7 different large macrofauna species at high and low densities. •Macrofauna presence altered nematode community structure and reduced their abundance. •Macrofauna species had similar effects by reducing the few dominant nematode species. •Meio–macrofauna resource competition and spatial segregation are the main drivers. •Trawling effects on macrofauna affect nematode communities indirectly. Diverse assemblages of infauna in sediments provide important physical and biogeochemical services, but are under increasing pressure by anthropogenic activities, such as benthic trawling. It is known that trawling disturbance has a substantial effect on the larger benthic fauna, with reductions in density and diversity, and changes in community structure, benthic biomass, production, and bioturbation and biogeochemical processes. Largely unknown, however, are the mechanisms by which the trawling impacts on the large benthic macro- and megafauna may influence the smaller meiofauna. To investigate this, a mesocosm experiment was conducted whereby benthic nematode communities from a non-trawled area were exposed to three different densities (absent, low, normal) of 7 large (> 10 mm) naturally co-occurring, bioturbating species which are potentially vulnerable to trawling disturbance. The results showed that total abundances of nematodes were lower if these large macrofauna species were present, but no clear nematode abundance effects could be assigned to the macrofauna density differences. Nematode community structure changed in response to macrofauna presence and density, mainly as a result of the reduced abundance of a few dominant nematode species. Any detectable effects seemed similar for nearly all macrofauna species treatments, supporting the idea that there may be a general indirect, macrofauna-mediated trawling impact on nematode communities. Explanations for these results may be, firstly, competition for food resources, resulting in spatial segregation of the meio- and macrobenthic components. Secondly, different densities of large macrofauna organisms may affect the nematode community structure through different intensities of bioturbatory disturbance or resource competition. These results suggest that removal or reduced densities of larger macrofauna species as a result of trawling disturbance may lead to increased nematode abundance and hints at the validity of interference competition between large macrofauna organisms and the smaller meiofauna, and the energy equivalence hypothesis, where a trade-off is observed between groups of organisms that are dependent on a common source of energy.

Microsporidia-nematode associations in methane seeps reveal basal fungal parasitism in the deep sea

The deep sea is Earth’s largest habitat but little is known about the nature of deep-sea parasitism. In contrast to a few characterized cases of bacterial and protistan parasites, the existence and biological significance of deep-sea parasitic fungi is yet to be understood. Here we report the discovery of a fungus-related parasitic microsporidium, Nematocenator marisprofundi n. gen. n. sp. that infects benthic nematodes at Pacific Ocean methane seeps on the Pacific Ocean floor. This infection is species-specific and has been temporally and spatially stable over two years of sampling, indicating an ecologically consistent host-parasite interaction. A high distribution of spores in the reproductive tracts of infected males and females and their absence from host nematodes’ intestines suggests a sexual transmission strategy in contrast to the fecal-oral transmission of most microsporidia. N. marisprofundi targets the host’s body wall muscles causing cell lysis, and in severe infection even muscle filament degradation. Phylogenetic analyses placed N. marisprofundi in a novel and basal clade not closely related to any described microsporidia clade, suggesting either that microsporidia-nematode parasitism occurred early in microsporidia evolution or that host specialization occurred late in an ancient deep-sea microsporidian lineage. Our findings reveal that methane seeps support complex ecosystems involving interkingdom interactions between bacteria, nematodes, and parasitic fungi and that microsporidia parasitism exists also in the deep sea biosphere.

Effects of elevated CO2 and temperature on an intertidal meiobenthic community

In the near future, the marine environment is likely to be subjected to simultaneous increases in temperature and decreased pH. The potential effects of these changes on intertidal, meiofaunal assemblages were investigated using a mesocosm experiment. Artificial Substrate Units containing meiofauna from the extreme low intertidal zone were exposed for 60 days to eight experimental treatments (four replicates for each treatment) comprising four pH levels: 8.0 (ambient control), 7.7 & 7.3 (predicted changes associated with ocean acidification), and 6.7 (CO2 point-source leakage from geological storage), crossed with two temperatures: 12 °C (ambient control) and 16 °C (predicted). Community structure, measured using major meiofauna taxa was significantly affected by pH and temperature. Copepods and copepodites showed the greatest decline in abundance in response to low pH and elevated temperature. Nematodes increased in abundance in response to low pH and temperature rise, possibly caused by decreased predation and competition for food owing to the declining macrofauna density. Nematode species composition changed significantly between the different treatments, and was affected by both seawater acidification and warming. Estimated nematode species diversity, species evenness, and the maturity index, were substantially lower at 16 °C, whereas trophic diversity was slightly higher at 16 °C except at pH 6.7. This study has demonstrated that the combination of elevated levels of CO2 and ocean warming may have substantial effects on structural and functional characteristics of meiofaunal and nematode communities, and that single stressor experiments are unlikely to encompass the complexity of abiotic and biotic interactions. At the same time, ecological interactions may lead to complex community responses to pH and temperature changes in the interstitial environment

Polychaete burrows harbour distinct microbial communities in oil-contaminated coastal sediments

Previous studies have shown that the bioturbating polychaete Hediste (Nereis) diversicolor can affect the composition of bacterial communities in oil-contaminated sediments, but have not considered diversity specifically within bioturbator burrows or the impact on microbial eukaryotes. We tested the hypothesis that H. diversicolor burrows harbour different eukaryotic and bacterial communities compared with un-bioturbated sediment, and that bioturbation stimulates oil degradation. Oil-contaminated sediment was incubated with or without H. diversicolor for 30 days, after which sediment un-affected by H. diversicolor and burrow DNA/RNA samples were analysed using quantitative reverse transcription PCR (Q-RT-PCR) and high-throughput sequencing. Fungi dominated both burrow and un-bioturbated sediment sequence libraries; however, there was significant enrichment of bacterivorous protists and nematodes in the burrows. There were also significant differences between the bacterial communities in burrows compared with un-bioturbated sediment. Increased activity and relative abundance of aerobic hydrocarbon-degrading bacteria in the burrows coincided with the significant reduction in hydrocarbon concentration in the bioturbated sediment. This study represents the first detailed assessment of the effect of bioturbation on total microbial communities in oil-contaminated sediments. In addition, it further shows that bioturbation is a significant factor in determining microbial diversity within polluted sediments and plays an important role in stimulating bioremediation.

Evaluation of the antidiabetic activity of DPP IV resistant N-terminally modified versus mid-chain acylated analogues of glucose-dependent insulinotropic polypeptide

Glucose dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone with therapeutic potential for type 2 diabetes due to its insulin-releasing and antihyperglycaemic actions. However, development of GIP-based therapies is limited by N-terminal degradation by DPP IV resulting in a very short circulating half-life. Numerous GIP analogues have now been generated exhibiting DPP IV resistance and extended bioactivity profiles. In this study, we report a direct comparison of the long-term antidiabetic actions of three such GIP molecules, N-AcGIP, GIP(LyS(37)PAL) and N-AcGIP(LyS(37)PAL) in obese diabetic (ob/ob) mice. An extended duration of action of each GIP analogue was demonstrated prior to examining the effects of once daily injections (25 nmol kg(-1) body weight) over a 14-day period. Administration of either N-AcGIP, GIP(LyS(37)PAL) or N-AcGIP(LyS37PAL) significantly decreased non-fasting plasma glucose and improved glucose tolerance compared to saline treated controls. All three analogues significantly enhanced glucose and nutrient-induced insulin release, and improved insulin sensitivity. The metabolic and insulin secretory responses to native GIP were also enhanced in 14-day analogue treated mice, revealing no evidence of GIP-receptor desensitization. These effects were accompanied by significantly enhanced pancreatic insulin following N-AcGIP(Lys(37)PAL) and increased islet number and islet size in all three groups. Body weight, food intake and circulating glucagon were unchanged. These data demonstrate the therapeutic potential of once daily injection of enzyme resistant GIP analogues and indicate that N-AcGIP is equally as effective as related palmitate derivatised analogues of GIP. (c) 2006 Elsevier Inc. All rights reserved.

A novel, long-acting agonist of glucose-dependent insulinotropic polypeptide suitable for once-daily administration in type 2 diabetes

Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone with a potentially therapeutic role in type 2 diabetes. Rapid degradation by dipeptidylpeptidase IV has prompted the development of enzyme-resistant N-terminally modified analogs, but renal clearance still limits in vivo bioactivity. In this study, we report long-term antidiabetic effects of a novel, N-terminally protected, fatty acid-derivatized analog of GIP, N-AcGIP(LysPAL(37)), in obese diabetic (ob/ob) mice. Once-daily injections of N-AcGIP(LysPAL(37)) over a 14-day period significantly decreased plasma glucose, glycated hemoglobin, and improved glucose tolerance compared with ob/ob mice treated with saline or native GIP. Plasma insulin and pancreatic insulin content were significantly increased by N-AcGIP(LysPAL(37)). This was accompanied by a significant enhancement in the insulin response to glucose together with a notable improvement of insulin sensitivity. No evidence was found for GIP receptor desensitization and the metabolic effects of NAcGIP(LysPAL(37)) were independent of any change in feeding or body weight. Similar daily injections of native GIP did not affect any of the parameters measured. These data demonstrate the ability of once-daily injections of N-terminally modified, fatty acid-derivatized analogs of GIP, such as N-AcGIP(LysPAL(37)), to improve diabetes control and to offer a new class of agents for the treatment of type 2 diabetes.

Triclabendazole-resistant Fasciola hepatica: β-tubulin and response to in vitro treatment with triclabendazole

Resistance in Fasciola hepatica to triclabendazole (Fasinex) has emerged in several countries. Benzimidazole resistance in parasitic nematodes has been linked to a single amino acid substitution (phenylalanine to tyrosine) at position 200 on the [beta]-tubulin molecule. Sequencing of [beta]-tubulin cDNAs from triclabendazole-susceptible and triclabendazole-resistant flukes revealed no amino acid differences between their respective primary amino acid sequences. In order to investigate the mechanism of triclabendazole resistance, triclabendazole-susceptible and triclabendazole-resistant flukes were incubated in vitro with triclabendazole sulphoxide (50 [mu]g/ml). Scanning and transmission electron microscopy revealed extensive damage to the tegument of triclabendazole-susceptible F. hepatica, whereas triclabendazole-resistant flukes showed only localized and relatively minor disruption of the tegument covering the spines. Immunocytochemical studies, using an anti-tubulin antibody, showed that tubulin organization was disrupted in the tegument of triclabendazole-susceptible flukes. No such disruption was evident in triclabendazole-resistant F. hepatica. The significance of these findings is discussed with regard to the mechanism of triclabendazole resistance in F. hepatica.

A possible model of benzimidazole binding to beta-tubulin disclosed by invoking an inter-domain movement.

Although it is well established that benzimidazole (BZMs) compounds exert their therapeutic effects through binding to helminth beta-tubulin and thus disrupting microtubule-based processes in the parasites, the precise location of the benzimidazole-binding site on the beta-tubulin molecule has yet to be determined. In the present study, we have used previous experimental data as cues to help identify this site. Firstly, benzimidazole resistance has been correlated with a phenylalanine-to-tyrosine substitution at position 200 of Haemonchus contortus beta-tubulin isotype-I. Secondly, site-directed mutagenesis studies, using fungi, have shown that other residues in this region of the protein can influence the interaction of benzimidazoles with beta-tubulin. However, the atomic structure of the alphabeta-tubulin dimer shows that residue 200 and the other implicated residues are buried within the protein. This poses the question: how might benzimidazoles interact with these apparently inaccessible residues? In the present study, we present a mechanism by which those residues generally believed to interact with benzimidazoles may become accessible to the drugs. Furthermore, by docking albendazole-sulphoxide into a modelled H. contortus beta-tubulin molecule we offer a structural explanation for how the mutation conferring benzimidazole resistance in nematodes may act, as well as a possible explanation for the species-specificity of benzimidazole anthelmintics.

A 6-month open-label study of the effectiveness and tolerability of galantamine in patients with Alzheimer's disease

The objective of this study was to assess the effectiveness and tolerability of galantamine in patients with mild-to-moderate Alzheimer's disease (AD) in everyday clinical practice. Patient selection was made on 36 sequential patients attending Belfast City Hospital Memory Clinic between December 2000 and June 2001. Patients were treated with galantamine for 6 months, starting from 4 mg twice daily increasing to 8 mg twice daily and then to 12 mg twice daily at 4-weekly intervals. Patients (25 females, 11 males), mean age 78 years (59-90), were diagnosed with probable AD and had a mini-mental state examination (MMSE) score of 10-26. Efficacy was assessed using the MMSE, neuropsychiatric inventory (NPI), neuropsychiatric inventory caregiver distress (NPI-D) scale and the Bristol activities of daily living (B-ADL) scale at baseline and after 3 and 6 months of treatment. Mean improvements were noted on all four measures of efficacy at 3 and 6 months; improvements were significant on the MMSE, NPI and NPI-D at 3 months and on the NPI-D at 6 months. Galantamine was overall well tolerated. The most common adverse events were gastrointestinal, particularly nausea. Four patients stopped treatment due to adverse events, and seven were stabilised on 8 mg twice daily as they were unable to tolerate the target dose. This naturalistic study confirms clinical trial data, which shows galantamine improves cognition and behavioural symptoms and is overall well tolerated. © 2004 Blackwell Publishing Ltd.

A Multicenter, Randomised Open Study of Early Corticosteroid Treatment (OSECT) in Preterm Infants With Respiratory Illness: Comparison of Early and Late Treatment and of Dexamethasone and Inhaled Budesonide

AIM: To compare early (15 days) steroid therapy and dexamethasone with inhaled budesonide in very preterm infants at risk of developing chronic lung disease. METHODS: Five hundred seventy infants from 47 neonatal intensive care units were enrolled. Criteria for enrollment included gestational age 30%. Infants were randomly allocated to 1 of 4 treatment groups in a factorial design: early (15 days) dexamethasone, and delayed selective budesonide. Dexamethasone was given in a tapering course beginning with 0.50 mg/kg/day in 2 divided doses for 3 days reducing by half until 12 days of therapy had elapsed. Budesonide was administered by metered dose inhaler and a spacing chamber in a dose of 400 microg/kg twice daily for 12 days. Delayed selective treatment was started if infants needed mechanical ventilation and >30% oxygen for >15 days. The factorial design allowed 2 major comparisons: early versus late treatment and systemic dexamethasone versus inhaled budesonide. The primary outcome was death or oxygen dependency at 36 weeks and analysis was on an intention-to-treat basis. Secondary outcome measures included death or major cerebral abnormality, duration of oxygen treatment, and complications of prematurity. Adverse effects were also monitored daily. RESULTS: There were no significant differences among the groups for the primary outcome. Early steroid treatment was associated with a lower primary outcome rate (odds ratio [OR]: 0.85; 95% confidence interval [CI]: 0.61,1.18) but even after adjustment for confounding variables the difference remained nonsignificant. Dexamethasone-treated infants also had a lower primary outcome rate (OR: 0.86; 95% CI: 0.62,1.20) but again this difference remained not significant after adjustment. For death before discharge, dexamethasone and early treatment had worse outcomes than budesonide and delayed selective treatment (OR: 1.42; 95% CI: 0.93,2.16; OR: 1.51; 95% CI: 0.99,2.30 after adjustment, respectively) with the results not quite reaching significance. Duration of supplementary oxygen was shorter in the early dexamethasone group (median: 31 days vs 40-44 days). Early dexamethasone was also associated with increased weight loss during the first 12 days of treatment (52 g vs 3 g) compared with early budesonide, but over 30 days there was no difference. In the early dexamethasone group, there was a reduced incidence of persistent ductus arteriosus (34% vs 52%-59%) and an increased risk of hyperglycemia (55% vs 29%-34%) compared with the other 3 groups. Dexamethasone was associated with an increased risk of hypertension and gastrointestinal problems compared with budesonide but only the former attained significance. CONCLUSIONS: Infants given early treatment and dexamethasone therapy had improved survival without chronic lung disease at 36 weeks compared with those given delayed selective treatment and inhaled budesonide, respectively, but results for survival to discharge were in the opposite direction; however, none of these findings attained statistical significance. Early dexamethasone treatment reduced the risk of persistent ductus arteriosus. Inhaled budesonide may be safer than dexamethasone, but there is no clear evidence that it is more or less effective