Lugworm Arenicola Marina Research Articles

Molecular adaptation to an extreme environment: origin of the thermal stability of the pompeii worm collagen

The annelid Alvinella pompejana is probably the most heat-tolerant metazoan organism known. Previous results have shown that the level of thermal stability of its interstitial collagen is significantly greater than that of coastal annelids and of vent organisms, such as the vestimentiferan Riftia pachyptila, living in colder parts of the deep-sea hydrothermal environment. In order to investigate the molecular basis of this thermal behavior, we cloned and sequenced a large cDNA molecule coding the fibrillar collagen of Alvinella, including one half of the helical domain and the entire C-propeptide domain. For comparison, we also cloned the 3′ part of the homologous cDNA from Riftia. Comparison of the corresponding helical domains of these two species, together with that of the previously sequenced domain of the coastal lugworm Arenicola marina, showed that the increase in proline content and in the number of stabilizing triplets correlate with the outstanding thermostability of the interstitial collagen of A. pompejana. Phylogenetic analysis showed that triple helical and the C-propeptide parts of the same collagen molecule evolve at different rates, in favor of an adaptive mechanism at the molecular level.

Can synchronous spawning be predicted from environmental parameters? A case study of the lugworm Arenicola marina

The annual epidemic spawning period of a Scottish population of Arenicola marina (L.) has been recorded over a period of 13 yr. This population spawns between mid-October and mid-November in a discrete spawning event over a period of 4 to 5 d. Endocrine manipulation experiments showed that spawning is induced in females only if sufficient titres of PMH (prostomial maturation hormone) are present in the prostomia. These levels are attained during the 2 to 3 wk prior to the natural spawning date. The East Sands, St. Andrews population always spawns during periods of spring tides regardless of tidal amplitude or whether they are full- or new-moon tides. Meteorological data, including sea-temperature data were collected for each year, and correlation of the environmental data with spawning time was attempted. Correlation of spawning times with weather patterns showed that mean daily air pressures were significantly higher during the spawning period than from September to November as a whole. Evidence also suggests that a reduction in sea temperature is required prior to spawning. A significant moderate negative correlation was found between May to July air temperatures and spawning date, suggesting that higher May to July temperatures may induce early spawning. Daily rainfall and wind speed were also lower during the spawning period, but not significantly so. These results indicate that air pressure (or changes therein) may act as a final spawning cue, and the advantages of this are discussed in relation to fertilization success. A model of the interplay between environmental parameters and the endocrine mechanisms controlling the induction of spawning is proposed. Higher than average summer temperatures may advance gametogenesis to bring the population into a state of maturity (full-size oocytes, well-developed sperm morulae), and may also advance spawning time. Once the population has completed gametogenesis, a drop in sea temperature is then required to trigger an increase in endocrine titres within the prostomium, without which spawning cannot be induced by prostomial injection. The population spawns on spring tides; however a lack of clement weather coinciding with the spring tide will result in population-wide spawning being aborted, as in 1996. Clement weather (high pressure, low rainfall and wind speed) in conjunction with spring tides permits spawning to proceed to completion.

Contrasting interference functions and foraging dispersion in two species of shorebird (Charadrii)

Summary 1. Above a threshold density of ≈ 100 birds ha‐1, strong interference occurred between redshank Tringa totanus (Linnaeus) feeding by sight on the amphipod crustacean Corophium volutator (Pallas). No aggressive interactions occurred between the birds and the probable cause was prey depression. 2. Redshank fed in a square metre of mud that had recently been exploited by another redshank much less often than would be expected by chance. By avoiding areas where prey would have been recently exploited, the feeding rate of redshank was up to three times faster than it would have been had they not avoided other foraging redshank. 3. Bar‐tailed godwit fed in a square metre of mud that had been recently exploited by another godwit much more often than would be expected by chance in randomly moving birds. They tended to flock while foraging and showed no tendency to avoid areas where prey would have been recently exploited. 4. There was no evidence that interference occurred between bar‐tailed godwit Limosa lapponica (Linnaeus) feeding on the polychaete lugworm Arenicola marina (Linnaeus) at densities below 300 birds ha‐1, even though aggressive interactions occurred between birds.

The effect of colliery waste on the feeding of the lugworm Arenicola marina

Sandy shores in northeast England that are heavily contaminated by colliery waste (essentially coal particles) have lower species richnesses and diversities than less contaminated shores. Analyses of the sediment utilised putatively as food, the gut contents, and the faecal casts of lugworms Arenicola marina (L.) (Annelida: Polychaeta) from a heavily contaminated site (Newbiggin) and a site lightly contaminated (Seahouses) were performed to determine the effect of colliery waste on the feeding of this deposit-feeder, which has been reported to decline in abundance at contaminated sites. Colliery-waste content of sediment was 10 to 18 times greater at Newbiggin than at Seahouses. At Newbiggin the sediment contained significantly higher levels of colliery waste than did the gut contents or faeces, which were not significantly different from each other. At Seahouses the colliery-waste contents of sediment, gut, and faeces were not significantly different. Particle-size distributions in sediment, gut, and faeces from lugworms at Seahouses were similar, while at Newbiggin the sediment contained a greater proportion of larger particles (>250 μm) than did the gut contents or the faeces. These results suggest that lugworms at heavily contaminated sites are selective feeders, rejecting coal particles perhaps on the basis of particle size. We did not detect selectivity in animals at the less contaminated site. Lugworms from Seahouses, however, avoided burrowing into sediment containing colliery waste both when the waste was on the surface and buried. Lugworms from Newbiggin avoided burrowing into colliery waste only when it was buried. These data suggest a chemosensory response to colliery waste.

Juvenile-adult distribution of the bivalve Mya arenaria on intertidal flats in the Wadden Sea: why are there so few year classes?

Patchy distribution is frequently observed in benthic marine invertebrates. In order to indentify factors causing spatial patterns in the bivalve Mya arenaria, abundances of juveniles and adults, as well as death assemblages, were recorded on a 20-km scale in the intertidal zone of the Sylt-Romo Bight. Both adults and juveniles exhibited pronounced patchiness. Shell length of juveniles rarely exceeded 2 mm in 1995, which was most likely a consequence of epibenthic predators truncating the size spectrum. Only a few yearclasses dominated the adult population. While the northern part of the Bight was colonized mainly by a 1993-cohort, most M. arenaria in the southern part were from the mid-1980s. It is hypothesized that epibenthic predation is a major cause of the lack of dense M. arenaria beds from other years. However, examination of the length–frequency distribution of death assemblages revealed that other unidentified causes of mortality exist. High abundances of adults were found in the mid and lower intertidal zone but not in the high intertidal zone. There was no indication that dispersal of M. arenaria spat in a landward or seaward direction contributed significantly to the observed distribution pattern, since spat occurred abundantly at all tidal levels except in the high intertidal zone. There was no evidence of negative adult-juvenile interaction. M. arenaria was not attracted by seagrass or projecting shell beds – the latter indicating erosion of the sediment – as abundances of adults and juveniles were generally low in these habitats. The effects of sediment type and of the bioturbating lugworm Arenicola marina were inconsistent. While adults were more abundant on muddy sand than on sand, recruitment was independent of sediment type. At all high density sites of adults (>50 ind m–2), lugworm densities were below 5 ind m–2, which may indicate a negative interaction. However, lugworm densities >30 ind m–2 did not prevent relatively high M. arenaria recruitment of >500 ind m–2.

Effect of macrofaunal bioturbation on bacterial distribution in marine sandy sediments, with special reference to sulphur-oxidising bacteria

We have studied the impact of the bioturbating macrofauna, in particular the lugworm Arenicola marina and the bivalve Cerastoderma edule, on abundances and distribution patterns of total bacteria and of bacteria of selected functional groups in sandy intertidal sediments. The selected groups comprised the colourless sulphur-oxidising bacteria and the anoxygenic phototrophic bacteria, which are expected to occupy small zones at the oxygen–sulphide interface in stable (non-bioturbated) sediments. The presence of a wooden wreck buried in the sediment at 10 cm depth within a large area of intertidal sand flat colonised by lugworms provided a unique opportunity to confront field observations with laboratory simulations. The site with the wooden wreck, which was used as control site, was devoid of both A. marina and C. edule, while the composition of the rest of the zoobenthic community was rather similar to that of the surrounding area. In the field, the density of total bacteria was approximately one order of magnitude higher in the control site than in the natural (bioturbated) site. This can be explained by the higher contents of silt and clay particles (higher surface-area/volume ratio) and higher total organic-carbon contents found at the control site. It appears that the presence of macrofauna affects sedimentation processes, which indirectly influence bacterial dynamics. Samples from the control site have been incubated in the laboratory with A. marina and C. edule added (bioturbated core), while an unamended core served as a control. The laboratory experiments contrasted with the field observations, because it was found that total bacteria were actually higher in the deeper layers of the bioturbated core. Moreover, the populations were more homogeneous (less stratified) and colourless sulphur bacteria were on average less numerous in the bioturbated core. In general, laboratory incubations resulted in a decrease of total bacteria with a concomitant increase of colourless and phototrophic sulphur-oxidising bacteria and thus in modifications of the bacterial community structure. Hence, our results demonstrate that care must be taken in extrapolating results from laboratory experiments (e.g. mesocosm research) to field situations.

Excretion of thiosulphate, the main detoxification product of sulphide, by the lugworm arenicola marina L

Thiosulphate, the main sulphide detoxification product, is accumulated in the body fluids of the lugworm Arenicola marina. The aim of this study was to elucidate the fate of thiosulphate. Electrophysiological measurements revealed that the transepithelial resistance of body wall sections was 76+/-34 capomega cm2 (mean +/- s.d., N=14), indicating that the body wall of the lugworm is a leaky tissue in which mainly paracellular transport along cell junctions takes place. The body wall was equally permeable from both sides to thiosulphate, the permeability coefficient of which was 1. 31x10(-)3+/-0.37x10(-)3 cm h-1 (mean +/- s.d., N=30). No evidence was found for a significant contribution of the gills or the nephridia to thiosulphate permeation. Thiosulphate flux followed the concentration gradient, showing a linear correlation (r=0.997) between permeated and supplied (10-100 mmol l-1) thiosulphate. The permeability of thiosulphate was not sensitive to the presence of various metabolic inhibitors, implicating a permeation process independent of membrane proteins and showing that the lugworm does not need to use energy to dispose of the sulphide detoxification product. The present data suggest a passive permeation of thiosulphate across the body wall of A. marina. In live lugworms, thiosulphate levels in the coelomic fluid and body wall tissue decreased slowly and at similar rates during recovery from sulphide exposure. The decline in thiosulphate levels followed a decreasing double-exponential function. Thiosulphate was not further oxidized to sulphite or sulphate but was excreted into the sea water.

Sexual Satellites, Moonlight and the Nuptial Dances of Worms: The Influence of the Moon on the Reproduction of Marine Animals

The evidence that the moon has a profound effect on the timing of reproductive activities of marine animals is compelling. Some moon phase related spawning events are revealed by the constant phase relationship between the timing of “once per year” spawning events and the lunar phase as in the highly synchronised breeding of the palolo worm Palola viridis and the Japanese crinoid Comanthus japonicus In other cases there is a repeated lunar cycle of reproductive activity and again the marine worms provide many good examples. The breeding of the palolo worm involves the highly synchronised release of what are in effect detached sexual satellites and the timing of this has annual (solar year), lunar, daily and tidal rhythm components. In a similar way, the onset of sexual maturation and participation in the nuptial dance of Platynereis dumerilli has strong lunar components. Sexual reproduction is the culmination of a process of sexual maturation that takes many months for completion and the mechanisms by which moon phase relationships are imposed on this process must have been selected for by mechanisms relating to reproductive success. The polychaetes provide excellent models for investigation of both the selective advantage and the physiological processes involved in reproductive synchrony. We have recently shown that the spawning of the lugworm Arenicola marina has lunar components and we conclude that an interaction between solar and lunar signals is widespread in the timing of reproduction in marine animals. Carl Hauenschild was the first to demonstrate the existence of a free-running circa-lunar rhythm in marine animals using captive populations of Platynereis dumerilli His experiments also provided clear evidence for the influence of moonlight (light at night) as the zeitgeber for this rhythm. This implies a high level of sensitivity to light, and the operation of appropriate endogenous biological rhythms. Using Nereis virens we have demonstrated a high level of sensitivity to low intensity solar light signals in relation to rhythmic processes with the properties similar to the circadian and photoperiodic mechanisms of terrestrial organisms. The spawning of N. virens is also believed to have lunar components reflecting the complex influences of the sun and the moon in the marine domain, where influences of the moon and sun are more equal. We suggest that evolution of biological rhythmicity that can be entrained to either lunar or solar systems arose in the marine domain. Recent advances in understanding the molecular components of the circadian clock system suggest that a search for a common molecular mechanism for both lunar and solar related biological rhythms in marine organisms might be very fruitful.

Factors affecting PAH residues in the lugworm Arenicola marina, a sediment feeding polychaete

Being a sediment feeder, the lugworm Arenicola marina could be a suitable candidate organism for the biomonitoring of sediment-bound contaminants in intertidal areas. Since lugworms are only rarely used in environmental monitoring, little is known about the natural variation in their body residue levels. In this study, we assessed the importance of seasonal fluctuations, spatial variation and sexual development to polycyclic aromatic hydrocarbon (PAH) residues in lugworms. Over a period of 15 months, lugworms were sampled along a contamination gradient in the Western Scheldt estuary in the Netherlands. A clear seasonal pattern in the body residue levels of PAH was observed, with lowest levels in March and highest levels just prior to the spawning season in September. During the spawning season the body residue levels showed a marked decrease. Although this seasonal pattern is apparently related to the reproductive cycle of the lugworm, no clear differences in body residue levels were found between animals with or without developed gonads. The contamination gradient, present in the estuary, was clearly reflected in the body residue levels of PAH. The expected gradient of internal concentrations was, however, absent in October, when the spawning period was not yet finished. The variation in lugworm body residue levels was smaller than the fluctuations in sediment PAH levels. It can be concluded that the lugworm is a suitable organism for the biomonitoring of sediment-bound contaminants, provided that attention is paid to its reproductive cycle.

A new pressure sensory mechanism for prey detection in birds: the use of principles of seabed dynamics?

We demonstrate a novel mechanism for prey detection in birds. Red knots (Calidris canutus), sandpipers that occur worldwide in coastal intertidal areas, are able to detect their favourite hard-shelled prey even when buried in sand beyond the reach of their bills. In operant conditioning experiments designed to find out whether the birds could tell buckets containing only wet sand from buckets containing hard objects in wet sand, we show that they detect the presence not only of deeply buried live bivalves but also of stones. The latter finding virtually excludes, under experimental conditions, prey-detection mechanisms based on vision, acoustics, smell, taste, vibrational signals emitted by prey, temperature gradients and electromagnetic fields. A failure to discriminate between food and non-food trays with dry sand indicates that pore water is involved. Based on the presence of large arrays of Herbst corpuscles (sensory organs that can measure the acceleration due to changes in pressure), the specifics of foraging technique and the characteristics of sediments on which red knots feed, we deduce that the sensory mechanism involves the perception of pressure gradients that are formed when bills probe in soft sediments in which inanimate objects block pore water flow. To our knowledge, this mechanism has not been described before. It is argued that repeated probing in soft, wet sediments allows red knots to induce a residual pressure build-up of sufficient strength to detect the pressure disturbance caused by a nearby object. The cyclic process of shaking loosely packed sand grains followed by gravitational settling into a closer packing, leads, owing to insufficient drainage of the sediment, to a locally increased pressure disturbance that is 'pumped up' at each shake.

Macrofauna on flood delta shoals in the Wadden Sea with an underground association between the lugwormArenicola marina and the amphipodUrothoe poseidonis

Living conditions for macrofauna on flood delta shoals are determined by surf, strong currents and sediment mobility. Thus, a unique assemblage of invertebrate species colonize these far off-shore, low intertidal flats. We here describe the macrobenthic fauna of emerging shoals in the Wadden Sea between the islands of Römö and Sylt. Besides ubiquitous macroinvertebrates of the intertidal zone and species which attain their main distribution in the subtidal zone, the flood delta shoals are characterized by organisms adapted to live in these highly unstable sediments, like the polychaetesSpio martinensis, Streptosyllis websteri, Magelona mirabilis, Psammodrilus balanoglossoides, the pericarid crustaceansCumopsis goodsiri, Tanaissus lilljeborgi, Bathyporeia sarsi and a few others. Average abundance (1440 m−2 of ind >1 mm) and biomass (12.9 g AFDW m−2) were low compared to other intertidal habitats in the Wadden Sea. Biomass was dominated by largesized individuals of the lugwormArenicola marina. The U-shaped burrows of these polychaetes were inhabited by high numbers ofUrothoe poseidonis. Maximum densities of these amphipods occurred in the deepest parts of the burrows. Sampling at approximately montly intervals revealed no apparent seasonality ofU. poseidonis abundance. Together with smallCapitella capitata, these amphipods constitute a deep-dwelling component of the macrofauna associated with lugworms, which is separated from all other macrofauna living at the sediment surface. As a response to rising sea level and increasing tidal ranges, we expect the unstable sandy shoals, inhabited by numerousSpio martinensis andUrothoe poseidonis, to expand within the Wadden Sea at the cost of stable sandy flats with abundant macrofauna.

Action of CMF (coelomic maturation factor) on oocytes of the polychaeteArenicola marina (L.)

Oocyte maturation in the lugworm Arenicola marina is controlled by two hormonal steps: a prostomial maturation hormone and a coelomic maturation factor (CMF). Oocyte maturation and spawning follows release of the maturation hormone from the prostomium and the appearance of CMF activity within the coelomic fluid. In this study, injection of female prostomial homogenate into gravid females induced the production of CMF after approximately 1 to 2 h. Once induced, CMF activity remained for 1 to 4 h. Titres of CMF assayed in vitro between females also varied. CMF in some females induced 100% of oocytes to mature, whereas CMF removed from others induced only about 30% maturation. Oocytes required an exposure time of approximately 20 min to CMF before maturation is able to proceed independently. Optimal CMF activity in vitro was observed at temperatures at or below 10°C. CMF has already been shown to be thermolabile and have a molecular mass greater than 10 kDa. CMF is shown here to be trypsin sensitive and to have a molecular mass of greater than 30 kDa, suggesting a proteinaceous nature. J. Exp. Zool. 281:65–71, 1998. © 1998 Wiley-Liss, Inc.

Action of CMF (coelomic maturation factor) on oocytes of the polychaete Arenicola marina (L.)

Oocyte maturation in the lugworm Arenicola marina is controlled by two hormonal steps: a prostomial maturation hormone and a coelomic maturation factor (CMF). Oocyte maturation and spawning follows release of the maturation hormone from the prostomium and the appearance of CMF activity within the coelomic fluid. In this study, injection of female prostomial homogenate into gravid females induced the production of CMF after approximately 1 to 2 h. Once induced, CMF activity remained for 1 to 4 h. Titres of CMF assayed in vitro between females also varied. CMF in some females induced 100% of oocytes to mature, whereas CMF removed from others induced only about 30% maturation. Oocytes required an exposure time of approximately 20 min to CMF before maturation is able to proceed independently. Optimal CMF activity in vitro was observed at temperatures at or below 10°C. CMF has already been shown to be thermolabile and have a molecular mass greater than 10 kDa. CMF is shown here to be trypsin sensitive and to have a molecular mass of greater than 30 kDa, suggesting a proteinaceous nature. J. Exp. Zool. 281:65–71, 1998. © 1998 Wiley-Liss, Inc.

Role of cold resistance and burial for winter survival and spring initiation of an Ulva spp. (Chlorophyta) bloom in a eutrophic lagoon (Veerse Meer lagoon, The Netherlands)

In the eutrophic Veerse Meer lagoon (The Netherlands) large amounts of free-floating thalli from Ulva spp. are present from May to October. In winter however, no algae seem to occur in the lagoon. Sexual reproduction appears to be negligible, as spore formation and germling growth are observed only sporadically. Results of a field survey showed that in winter, viable Ulva biomass is present buried in the sediment of the shallow parts of the lagoon. Freezing experiments demonstrated that the algae are able to survive temperatures of −5 °C for 2 weeks when kept in darkness. In spring, the buried Ulva thalli are liberated out of the sediment to initiate a bloom. A field experiment indicates that bioturbation by the lugworm Arenicola marina does not stimulate the release of the thalli. Burial and winter survival can explain the rapid increase in Ulva biomass in spring and suggest that the initial spring biomass is one of the major factors determining the maximal biomass in summer.

Ecotoxicity of contaminated sediments, a matter of bioavailability

Marine and freshwater mesocosm-scale experiments with contaminated sediments have shown that there is a direct relationship between the accumulated contaminant levels and the feeding habits of the organisms used. The highest levels of PAHs and PCBs were found in the sediment feeding lugworm Arenicola marina and in Tubifex worms. The levels of contaminants in the suspension feeding mussels Mytilus edulis and the zebra mussels, Dreissena polymorpha, were not influenced by the contaminant content of the sediments, but were related instead to the level of contaminants in the sea water above. Intermediate levels were found in the baltic tellin, Macoma balthica, which is a filter feeder as well as a deposit feeder, depending on the availability of food. These results show that there is no simple relationship between contaminant concentration in the sediments and bioavailability. Higher levels of contaminants do not necessarily lead to higher levels of these contaminants in Arenicola, due to differences in the sediment structure and the ageing of the contamination. On the other hand, toxic effects are related to the internal concentrations of certain chemicals. The internal concentrations observed in Arenicola may provide a good estimation of the true bioavailability of sedimentary contaminants and can also be used as an indicator for potential environmental effects.

Effects of bioturbation by the lugworm Arenicola marina on cadmium uptake and distribution in sandy sediments

The effect of bloturbation by the lugworni Arenicola marina on uptake and distribution of cadnxum in sediment was assessed using laboratory sediment cores. Carner-free was added to the water phase each day. Bioturbation (irrigation) was measured using bromide (Br-) as a tracer for water movement. In cores without lugworms all Cd was found in the surface sediment where it continued to build up over 16 d of exposure. In cores containing lugworms a distinct peak of Cd was found both at the sediment surface and, after a few days, at the feeding pocket of the worm (10 to 15 cm depth). During the 16 d of exposure this subsurface: peak broadened and eventually Cd was found in all depths from top to feeding depth of the indiv~dual worm. Compared to sediment cores without worms, the presence of lugxeorms more than doubled the rate of removal of Cd from water to sediment. Thls was attributed to an ~ncreased turnover of sediment (due to feeding activity), an increased sediment surface area (due to fecal casts, head shaft, tube and irrigation of the whole burrow) and an increased contact of Cd-labelled water with potential binding sites in the sediment due to irrigation Exposure to 1 ppm Cd reduced the fract~onal ratcl at which lugworms removed Cd from the water (as 'F of Cd in the water). The total Cd flux to the sediment, however, was much greater due to the h g h e r Cd concentrations in the water Water fluxes estimated using Bras a solute tracer revealed a 10to 20fold increase in water exchange of the sediments when lugworms were present. This enhanced water flux was not affected by exposure of lugworms to 1 ppm Cd. The results indicate that the presence of bioturbating infauna influences both the uptake rates of trace metals in near-shore sediments and the distribution of those metals.

Oocyte maturation and post-fertilization development of Arenicola marina (L.) (Annelida: Polychaeta)

Summary Oocyte maturation in the lugworm Arenicola marina takes place in the coelomic fluid and is induced by a coelomic maturation factor (CMF) (Watson and Bentley, 1997). CMF production itself results from the action of a prostomial maturation hormone. A recently described in vitro assay for oocyte maturation in A. marina has been adopted, distinguishing immature (full sized, prophase I) from mature (full sized, metaphase I) oocytes and enabling the action and nature of CMF to be investigated (Watson and Bentley, 1997). In this study, immunocytochemical techniques were used to characterize microtubule structures during oocyte maturation and post-fertilization development. Prior to the discovery of CMF, mature oocytes could be obtained only by collecting eggs from females that had spawned spontaneously in the laboratory or following the injection of homogenized prostomia thereby inducing maturation and spawning of the oocytes. Mature oocytes can now be obtained by the in vitro incubation of oocytes in coelomic fluid containing CMF. These three methods of maturation were employed and compared with respect to meiotic spindle morphology and post-fertilization development. Oocytes matured in vitro have a meiotic spindle identical to those matured in vivo. Post-fertilization development in in vitro matured oocytes is, however, retarded by approximately one mitotic cycle after 5h incubation at 10°C. These results suggest that oocytes matured in vivo differ in some way from those matured in vitro. The modification of development time in spawned vs. in vitro matured oocytes is discussed.

Ecotoxicity of contaminated sediments, a matter of bioavailability

Marine and freshwater mesocosm-scale experiments with contaminated sediments have shown that there is a direct relationship between the accumulated contaminant levels and the feeding habits of the organisms used. The highest levels of PAHs and PCBs were found in the sediment feeding lugworm Arenicola marina and in Tubifex worms. The levels of contaminants in the suspension feeding mussels Mytilus edulis and the zebra mussels, Dreissena polymorpha, were not influenced by the contaminant content of the sediments, but were related instead to the level of contaminants in the sea water above. Intermediate levels were found in the baltic tellin, Macoma balthica, which is a filter feeder as well as a deposit feeder, depending on the availability of food.These results show that there is no simple relationship between contaminant concentration in the sediments and bioavailability. Higher levels of contaminants do not necessarily lead to higher levels of these contaminants in Arenicola, due to differences in the sediment structure and the ageing of the contamination. On the other hand, toxic effects are related to the internal concentrations of certain chemicals. The internal concentrations observed in Arenicola may provide a good estimation of the true bioavailability of sedimentary contaminants and can also be used as an indicator for potential environmental effects.

Acute toxicity of ivermectin to the lugworm Arenicola marina

Ivermectin (22,23-dihydroavermectin B1a and B1b), as the commercial Premix for Pigs, was found to be acutely toxic to the marine sediment-dwelling polychaete Arenicola marina (10-day LC50 0.023 mg/kg dry weight of sediment, confidence limits 0.018 and 0.027 mg/kg). At all concentrations tested (i.e., 0.006 mg/kg dry weight and above), ivermectin reduced the rate of cast production. Prior exposure to 0.010 mg/kg or more reduced the rate at which A. marina was able to rebury in clean sediment. The results indicate that there is a clear case for targeted field studies at marine salmon farming sites where permission may be given to use ivermectin to control ectoparasitic sea lice infections.

Oxygen consumption and sulfide detoxification in the lugworm Arenicola marina (L.) at different ambient oxygen partial pressures and sulfide concentrations

The lugworm Arenicola marina is a typical inhabitant of intertidal flats. In its L-shaped burrow the animal is exposed to varying concentrations of O2 and toxic sulfide depending on the tides. The lugworm is able to detoxify sulfide through its oxidation to thiosulfate. When exposed to declining O2 tensions Arenicola marina reacted as an oxyconformer. In the presence of 25 μmol · l−1 sulfide the respiration was not affected. In contrast, the lugworm consumed significantly less O2 at any Po2 in the presence of 200 μmol · l−1 sulfide. Without sulfide anaerobic metabolism started at a Po2 of approximatedly 10 kPa. Even at high O2 tensions animals exposed to sulfide produced significantly more anaerobic metabolites compared with the controls. Accordingly the critical value PcM, the ambient Po2 below which anaerobic metabolism starts, was shifted towards normoxia. Since O2 supply was sufficient for aerobic metabolism, anaerobiosis was induced by sulfide. An influx of sulfide was observed at 25 as well as at 200 μmol · l−1 sulfide. The main product of sulfide detoxification in the lugworm was thiosulfate. Its synthesis increased with ambient Po2 and depended on the sulfide concentration. Sulfide and thiosulfate were detected in the coelomic fluid, the blood, and the body wall of Arenicola marina. Only about 2% of the ambient O2 was used for sulfide detoxification at 25 μmol · l−1 sulfide and about 50% at 200 μmol · l−1 sulfide, respectively. Even at the low sulfide concentration Arenicola marina's capacity to detoxify sulfide was too low to maintain a complete aerobic metabolism.