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Clams

Distribution by Scientific Domains

Life Sciences	50%
Earth and Environmental Science	36%
Chemistry	9%
2 Other Domains	5%

Distribution within Life Sciences

Ecology & Organismal Biology	18%
Conservation Science	6%

Terms modified by Clams

clam shrimp

Selected Abstracts

EFFECTS of SHUCKING METHOD ON OPENING, MEAT YIELD and SELECTED QUALITY PARAMETERS of WEST AFRICAN CLAM, GALATEA PARADOXA (BORN)

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2000
E.O. EKANEM
Samples (n= 100) of freshly harvested clams (Galatea paradoxa Born) from the Cross River, Nigeria, were subjected after 24 h depurations to heat treatment (steam and water at 60, 70, 80, 90, 100C) for 1,6 min to evaluate the effects of level of heat treatment on opening, meat yield, sensory properties, proximate composition, pH and electrical conductivity (EC). Observations were also made on the effects of some chemical shucking aids (NaOH, NaHCO3, Na2CO3, NaCl) in 60C water on these parameters. Results showed that boiling water was most effective in opening the clams, with 100% shucking achieved in 1 min. Steam was least effective, requiring 6 min for 100% opening. Temperature significantly and strongly influenced meat yield (p<0.05;r=-0.92). pH (p<0.01; r=0.97), EC (p<0.05; r =0.65) and sensory properties (p<0.05). In general, shucking aids reduced opening time, significantly p<0.05) raised meat pH and EC, and with the exception of NaCl, insignificantly (P>0.05) improved yield. NaHCO3, and Na2CO3, which cut time for 100% opening from 5 min to 2 min were most effective. There were slight but significant (P <0.05) drops in meat moisture, crude protein and ash contents with increase in temperature (T). the model equations, pH = 4.69 + 0.021 T and % yield = 39.95,0.172 T were found to reliably predict meat pH and yield, with insignificant differences (P>0.05) between predicted and experimental values. [source]

Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft-shell clam, Mya arenaria

ENVIRONMENTAL TOXICOLOGY, Issue 3 2002
C. Blaise
Abstract A spatial and temporal survey of six sites in the Saguenay Fjord and of one adjacent site in the St. Lawrence River estuary (Quebec, Canada) was undertaken to study the possible effects of anthropogenic contaminant input on soft-shell clam (Mya arenaria) populations. Bivalve sampling sites were selected because they reflected a range of areas representative of either no known (or apparent) pollution sources or of areas potentially influenced by different gradients and types of contamination sources. The most upstream site selected in the Saguenay Fjord, nearest to a highly populated and industrialized sector, and the most downstream site, near its mouth with the St. Lawrence River estuary, spanned a distance of some 70 km and encompassed the entire intertidal area suitable for Mya arenaria habitat. To measure effects in collected animals, we used a comprehensive battery of biomarkers composed of metallothionein-like proteins (MT), 7-ethoxyresorufin O-deethylase activity (EROD), DNA damage (DD), lipid peroxidation (LPO), vitellinlike proteins (Vn), phagocytosis (PHAG), nonspecific esterase (NspE) activity, and condition factor (weight-to-length ratio of clams). Vn, PHAG, DD, and NspE biomarkers were assayed in hemolymph (or hemocytes), whereas others (MT, EROD, LPO) were determined in the digestive gland. Whole-tissue metal content was also quantified in clams collected in the spatial survey. The spatial survey conducted in June 1997 showed significant effects at all sites, and principal component analysis indicated in addition that the more important responses were linked to the MT, LPO, and NspE biomarkers. Clams collected from sites closest to the upstream reaches of the fjord generally displayed higher levels of tissue metals (cadmium, manganese), as well as greater responses of NspE activity, MT, LPO, and PHAG. Animals collected from sites influenced by municipal wastewaters had higher levels of Vn, suggesting the presence of environmental estrogens. The results of the temporal survey (six monthly samplings of clams at three sites from May through October, 1997) showed that the bivalve reproductive cycle (vitellogenesis and spawning) can modulate the expression of several biomarkers. Vn levels, for example, were positively correlated with DD and EROD and negatively correlated with MT, suggesting that reproduction can influence the susceptibility of clams to some contaminants. Discrimination analysis over the 6 months of sampling revealed that the mean value of the discriminant function changed significantly over time, suggesting important changes in the relative contribution of each biomarker. In short, this study has provided evidence that clam populations in the Saguenay Fjord are impacted by multiple sources of contamination whose effects can be modulated by reproduction. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 170,186, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10048 [source]

Oxidative stress biomarkers in bivalves transplanted to the Guadalquivir estuary after Aznalcóllar spill

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2003
Antonio Romero-Ruiz
Abstract Biological effects of metals were studied in clams (Scrobicularia plana) transplanted to Guadalquivir estuary (Spain) at several times after the spill of toxic metals from Aznalcóllar pyrite mine (southwest Spain) (April 1998) using biochemical biomarkers responsive to reactive oxygen species. Significant As, Cd, Fe, Mn, Ni, and Pb uptake was found in clams living for seven months at the estuary (from July 1999). Increased activity of antioxidant (catalase, glucose-6-phosphate, and 6-phosphogluconate dehydrogenase) and glutathione-related (glutathione reductase and glyoxalase I and II) enzymes was also found after short exposures; the levels of malondialdehyde and metallothionein increased also, particularly with long exposures. Clams living four weeks at the estuary (from March 2000) but not at a reference site also accumulated metals. The higher malondialdehyde and lower reduced-glutathione levels and the more oxidized glutathione status confirmed the oxidative stress of clams living at the estuary, while no marked increase of antioxidant activities was found this time. Lower metal availability along the second transplant could explain the limited responses in this shorter experiment. Although the status of Guadalquivir estuary has recovered since Aznalcóllar spill, continuous monitoring is needed to confirm its progress and to be alert to possible deterioration after heavy rains. [source]

Variation of metallothionein and metal concentrations in the digestive gland of the clam Ruditapes decussatus: Sex and seasonal effects

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001
Maria A. Serafim
Abstract Metallothionein (MT) and metal (Cd, Cu, and Zn) concentrations were determined in the digestive gland of male and female Ruditapes decussatus. Clams were collected monthly during the period of sexual development, from June to September, at two different sites of a coastal lagoon, the Ria Formosa Lagoon, on the south coast of Portugal. The MT concentrations were determined in the heat-treated cytosolic fraction of the digestive gland of both male and female clams. Total metal (Cd, Cu, and Zn) concentrations in the heat-treated cytosol of the digestive gland were also determined in both sexes. The MT and metal concentrations in the digestive gland were not sex dependent in this species. Therefore, these results suggest that random samples can be used to determine MT and metal concentrations in the digestive gland of R. decussatus. Seasonal and site-specific dependency, however, were detected for MT, Cd, and Cu concentrations. The maximum concentration levels of MT, Cd, and Cu were detected in July and August for both sexes in the same area. Zinc concentrations, however, did not show marked seasonal variations, indicating that this species is able to regulate zinc concentrations. The highest MT concentrations were significantly related to the highest metal concentrations. [source]

Comparison of Development and Larval Growth of Four Venerid Clams

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 2 2005
Young-Baek Hur
The development and larval morphology of four venerid calms, Ruditapes philippinarum, Mactra veneriformis, Cyclina sinensis, and Meretrix lusoria, which cohabit the intertidal zone in western coastal Korea, were compared using laboratory culture techniques. At 87 ,m, the fertilized eggs of C. sinensis and M. lusoria were the largest and at 53 ,m, those of M. veneriformis were the smallest. D-shaped larvae of M. lusoriu were the largest and those of M. veneriformis were the smallest measuring at 135 ,m and 89 ,m, respectively. D-shaped larvae of R. philippinarum and M. lusoria had symmetrical shoulder angles and an elliptical ventral form, in contrast to the asymmetrical shoulder angles and round ventral forms of M. veneriformis and C. sinensis. In general, pediveliger larvae of all species in the study were yellow, but those of M. veneriforks and C sinenis were a more pronounced yellow. In between the early D-shaped and pediveliger stage, 7 and 17 d elapsed for M. lusonia and C. sinensis larvae, respectively. In the early larval stages for all species, the sheU length was longer than the height. However, shell length and height later became approximately the same size in all species except R. philippinarum, which exhibited a flat shape. These results indicate that for these four venerid clams, the different characteristics in larval growth and external morphology provide the evidence necessary for larval identification of natural seed production despite the fact that they spawn concurrently in the intertidal zone. [source]

Foraging behavior of an estuarine predator, the blue crab Callinectes sapidus in a patchy environment

ECOGRAPHY, Issue 1 2000
Mary E. Clark
To define general principles of predator-prey dynamics in an estuarine subtidal environment, we manipulated predator density (the blue crab, Callinectes sapidus) and prey (the clam, Macoma balthica) patch distribution in large field enclosures in the Rhode River subestuary of the central Chesapeake Bay. The primary objectives were to determine whether predators forage in a way that maximizes prey consumption and to assess how their foraging success is affected by density of conspecifics. We developed a novel ultrasonic telemetry system to observe behavior of individual predators with unprecedented detail. Behavior of predators was more indicative of optimal than of opportunistic foraging. Predators appeared responsive to the overall quality of prey in their habitat. Rather than remaining on a prey patch until depletion, predators appeared to vary their patch use with quality of the surrounding environment. When multiple (two) prey patches were available, residence time of predators on a prey patch was shorter than when only a single prey patch was available. Predators seemed to move among the prey patches fairly regularly, dividing their foraging time between the patches and consuming prey from each of them at a similar rate. That predators more than doubled their consumption of prey when we doubled the number of prey (by adding the second patch) is consistent with optimizing behaviors - rather than with an opportunistic increase in prey consumption brought about simply by the addition of more prey. Predators at high density, however, appeared to interfere with each other's foraging success, reflected by their lower rates of prey consumption. Blue crabs appear to forage more successfully (and their prey to experience higher mortality) in prey patches located within 15,20 meters of neighboring patch, than in isolated patches. Our results are likely to apply, at least qualitatively, to other crustacean-bivalve interactions, including those of commercial interest; their quantitative applicability will depend on the mobility of other predators and the scale of patchiness they perceive. [source]

Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft-shell clam, Mya arenaria

Linking environmental warming to the fitness of the invasive clam Corbicula fluminea

GLOBAL CHANGE BIOLOGY, Issue 12 2009
MARKUS WEITERE
Abstract Climate warming is discussed as a factor that can favour the success of invasive species. In the present study, we analysed potential fitness gains of moderate warming (3 °C above field temperature) on the invasive clam Corbicula fluminea during summer and winter. The experiments were conducted under seminatural conditions in a bypass-system of a large river (Rhine, Germany). We showed that warming in late summer results in a significant decrease in the clams' growth rates (body mass and shell length increase) and an increase in mortality rate. The addition of planktonic food dampens the negative effect of warming on the growth rates. This suggests that the reason for the negative growth effect of temperature increase in late summer is a negative energetic balance caused by an enhanced metabolic rate at limited food levels. Warming during early summer revealed contrasting effects with respect of body mass (no warming effect) and shell length (increased shell growth with warming). This differential control of both parameters further enhances the loss of the relative (size-specific) body mass with warming. In contrast, warming in winter had a consistently positive effect on the clams' growth rate as demonstrated in two independent experiments. Furthermore, the reproduction success (as measured by the average number of larvae per clam) during the main breeding period (April) was strongly enhanced by experimental warming during winter, i.e. by eight times during the relatively cold winter 2005/2006 and by 2.6 times during the relatively warm winter 2007/2008. This strong, positive effect of moderate winter warming on the clams' fitness is probably one reason for the recent invasion success of C. fluminea in the northern hemisphere. However, warm summer events might counteract the positive winter warming effect, which could balance out the fitness gains. [source]

Predator size, prey size and threshold food densities of diving ducks: does a common prey base support fewer large animals?

JOURNAL OF ANIMAL ECOLOGY, Issue 5 2009
Samantha E. Richman
Summary 1. Allometry predicts that a given habitat area or common prey biomass supports fewer numbers of larger than smaller predators; however, birds from related taxa or the same feeding guild often deviate from this pattern. In particular, foraging costs of birds may differ among locomotor modes, while intake rates vary with accessibility, handling times and energy content of different-sized prey. Such mechanisms might affect threshold prey densities needed for energy balance, and thus relative numbers of different-sized predators in habitats with varying prey patches. 2. We compared the foraging profitability (energy gain minus cost) of two diving ducks: smaller lesser scaup (Aythya affinis, 450,1090 g) and larger white-winged scoters (Melanitta fusca, 950,1800 g). Calculations were based on past measurements of dive costs with respirometry, and of intake rates of a common bivalve prey ranging in size, energy content and burial depth in sediments. 3. For scaup feeding on small prey <12 mm long, all clams buried deeper than 5 cm were unprofitable at realistic prey densities. For clams buried in the top 5 cm, the profitability threshold decreased from 216 to 34 clams m,2 as energy content increased from 50 to 300 J clam,1. 4. For larger scoters feeding on larger prey 18,24 mm long, foraging was profitable for clams buried deeper than 5 cm, with a threshold density of 147 m,2 for clams containing 380 J clam,1. For clams <5 cm deep, the threshold density decreased from 86 to 36 clams m,2 as energy content increased from 380 to 850 J clam,1. If scoters decreased dive costs by swimming with wings as well as feet (not an option for scaup), threshold prey densities were 11,12% lower. 5. Our results show that threshold densities of total prey numbers for different-sized ducks depend on prey size structure and depth in the sediments. Thus, heterogeneity in disturbance regimes and prey population dynamics can create a mosaic of patches favouring large or small predators. Whether a given area or total prey biomass will support greater numbers of larger or smaller predators will vary with these effects. [source]

Spatially structured genetic variation in a broadcast spawning bivalve: quantitative vs. molecular traits

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2003
P. C. Luttikhuizen
Abstract Understanding the origin, maintenance and significance of phenotypic variation is one of the central issues in evolutionary biology. An ongoing discussion focuses on the relative roles of isolation and selection as being at the heart of genetically based spatial variation. We address this issue in a representative of a taxon group in which isolation is unlikely: a marine broadcast spawning invertebrate. During the free-swimming larval phase, dispersal is potentially very large. For such taxa, small-scale population genetic structuring in neutral molecular markers tends to be limited, conform expectations. Small-scale differentiation of selective traits is expected to be hindered by the putatively high gene flow. We determined the geographical distribution of molecular markers and of variation in a shell shape measure, globosity, for the bivalve Macoma balthica (L.) in the western Dutch Wadden Sea and adjacent North Sea in three subsequent years, and found that shells of this clam are more globose in the Wadden Sea. By rearing clams in a common garden in the laboratory starting from the gamete phase, we show that the ecotypes are genetically different; heritability is estimated at 23%. The proportion of total genetic variation that is between sites is much larger for the morphological additive genetic variation (QST = 0.416) than for allozyme (FST = 0.000,0.022) and mitochondrial DNA cytochrome- c -oxidase-1 sequence variation (,ST = 0.017). Divergent selection must be involved and intraspecific spatial genetic differentiation in marine broadcast spawners is apparently not constrained by low levels of isolation. [source]

Virus-like particles associated with brown muscle disease in Manila clam, Ruditapes philippinarum, in Arcachon Bay (France)

JOURNAL OF FISH DISEASES, Issue 7 2009
C Dang
Abstract Recently, Manila clam, Ruditapes philippinarum, populations have suffered mortalities in Arcachon Bay (SW France). Mortality was associated with extensive lesions of the posterior adductor muscle, which become progressively brown and calcified. Ultrastructural observations by transmission electron microscopy revealed tissue degradation with necrotized muscle fibres and granulocytomas. Unenveloped virus-like particles (VLPs) were detected in muscle, granulocytic, epithelial and rectal cells. VLPs were abundant in the extracellular space, in the cytoplasm (free or enclosed in vesicles) and in the nucleoplasm of granulocytes. Nuclei and mitochondria of granulocytes displayed changes which suggested reactive oxygen species production and apoptosis induction. VLPs exhibited an icosahedral structure with a diameter of 25 to 35 nm. These observations suggest that the VLPs could belong to the family Picornaviridae or the Parvoviridae. [source]

Comparison of Three Culture Methods for the Intensive Culture of Northern Quahog Seed, Mercenaria mercenaria

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2001
Timothy J. Pfeiffer
A number of approaches have been utilized for growing bivalve hatchery seed (1 mm) to a size suitable for field planting (< 8 mm) but few have been directly compared. This study evaluated the growth and survival of northern quahog seed in three different culture systems and two different stocking densities. The three systems were: 1) a stacked-tray unit with downward water flow; 2) traditional upweller culture units with water flowing upward without seed bed expansion; and 3) upweller culture units with water flowing upward at fluidization velocities to provide seed bed expansion. The two stocking densities were 1.0 and 3.0 g whole wet weight clam/cm2 respectively. During each trial period the seed clams were fed a 1% daily ration (% dry weight algae per wet weight clam per day) of the cultured diatom Chaetoceros muelleri. After 14 d of culture at the 1.0 g whole wet weight/cm2 stocking density, seed clams (4.4 ± 0.6 mm initial shell length) under fluidized-flow condition exhibited better growth (0.54/d), and a greater final shell length (5.9 ± 1.0 mm). At the high density stocking conditions, after 28 d of culture, seed clams (4.2 ± 0.6 mm initial shell length) in the fluidized-flow culture conditions again exhibited better growth rate (0.031/d) and a greater final shell length (6.0 ± 1.0 mm). The preliminary evaluation of fluidized-flow for seed clam culture in land-based nurseries indicates its potential as a suitable alternative to raceway, downwelling, or traditional forced-flow culture methods. [source]

A day and a night in the life of a cleft-foot clam: Protovirgularia-Lockeia-Lophoctenium

LETHAIA, Issue 2 2001
Allan A. Ekdale
A remarkable specimen of a compound trace fossil in Pennsylvanian sandstone comprises three very different ichnotaxa in conjunction: Protovirgularia dichotoma, Lockeia siliquaria and Lophoctenium isp. The combined activities represented by these ichnotaxa reflect the locomotion, resting and feeding behavior of a cleft-foot, protobranch clam (bivalve) that burrowed through the sediment, paused five times to deposit-feed, and then burrowed on to a new location, possibly as a reaction to a depositional event. It is estimated that the complete trace fossil was made in 24 hours or less. The three ichnotaxa also provide morphologic details of the bivalve's shell and soft parts (foot and labial palps). [source]

Selective allergy to Venus antiqua clam

ALLERGY, Issue 5 2009
P. Rodriguez-del Rio
No abstract is available for this article. [source]

In Vitro Propagation of Two Perkinsus spp.

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 5 2006
Description of Perkinsus honshuensis n. sp., Parasites from Japanese Manila Clams Venerupis philippinarum
ABSTRACT. Perkinsus species are destructive parasites of commercial Manila clams, Venerupis philippinarum, in Japan, Korea, and Spain. However, in vitro parasite cultures from this important host clam are not available. Tissues of Manila clams collected during April 2002 in Gokasho Bay, Japan harbored Perkinsus sp. parasites at a 97% prevalence (28/29) of moderate- and high-intensity infections. Perkinsus sp. cells in tissue samples were enlarged in alternative Ray's fluid thioglycollate medium, before propagation in DME:Ham's F-12 Perkinsus sp. culture medium. Enlarged parasite hypnospores zoosporulated at high frequencies to release motile zoospores, which gave rise to continuous schizogonic cell lines that also zoosporulated continuously at low frequencies. Four Perkinsus sp. in vitro isolates comprising two distinct morphotypes were cryopreserved, cloned, and archived for public distribution. For three isolates of one morphotype, nucleotide sequences of the ribosomal DNA internal transcribed spacer region, of the large subunit rRNA gene, and of actin genes, were consistent with those reported for P. olseni. Similar sequences from one morphologically unique isolate differed from those of all described Perkinsus species. These results show that at least two Perkinsus spp. infect Japanese Manila clams, and that one represents a new species, Perkinsus honshuensis n. sp. [source]

Biochemical changes during larval development in the short neck clam, Paphia malabarica Chemnitz

AQUACULTURE RESEARCH, Issue 13 2009
Raghavan Gireesh
Abstract Biochemical compositions were determined for eggs, D-shaped larvae, umbo larvae and pediveliger of the short neck clam Paphia malabarica Chemnitz. Spawned eggs were composed of 63.2% protein, 25.4% lipid and 11.4% carbohydrate. After 48 h of embryogenesis, 2.6% of the protein, 11.8% of the lipid and 3.2% of carbohydrate mass had been lost, providing 20.5%, 75.4% and 4.1% of the total energy expenditure of 0.2147 mJ embryo,1. During 48 h of metamorphosis, lipid was utilized first, followed by a heavy consumption of protein; protein, lipid and carbohydrate lost 23.8%, 50.2% and 32.5% of their mass respectively. Protein and lipid supplied a comparable amount of energy for metamorphosis, 34.2% and 55.2%, respectively, whereas, carbohydrate contributed only 10.6% to the 2.733 mJ larva,l metamorphic energy expenditure. [source]

Reproductive performance and offspring quality of Chinese mitten crab Eriocheir sinensis (H. Milne-Edwards) females fed an optimized formulated diet and the razor clam Sinonovacula constricta

AQUACULTURE RESEARCH, Issue 12 2009
Xugan Wu
Abstract After feeding female Eriocheir sinensis on an optimized formulated diet or fresh razor clam Sinonovacula constricta for 7 months, their reproductive performance and offspring quality were compared. To evaluate diet nutrient contents, the proximate, fatty acid and amino acid compositions of the formulated diet and the razor clam were analysed. The nutritional value of the diets was determined by assessing survival, gonadosomatic index (GSI) and hepatosomatic index (HSI) of female crabs from both diet treatments, together with the percentage of females that spawned, total egg production per female and fecundity (number of eggs g,1 female wet weight). Furthermore, the quality of eggs and newly hatched larvae from the two dietary treatments were determined using the following parameters: egg diameter, wet weight and dry weight, hatchability, proximate and fatty acid profile of eggs, larval carapace length, resistant to starvation and osmotic shock, larval survival and development to the zoea II stage. Higher protein, phospholipids (PL) and amino acids (AA) contents were found in the razor clam while the formulated diet contains higher levels of ash, total lipid (TL) and 18:1n-9, 18:2n-6 and 22:6n-3 fatty acids. Although female crabs fed the two different diets showed similar reproductive performances, newly hatched zoea I larvae produced by the crabs fed the formulated diet had significantly longer mean carapace length and shorter development time to the zoea II stage under identical culture condition (P<0.05). Moreover, dietary fatty acid appeared to have more significant effects on the fatty acid composition of the hepatopancreas than it did on mature ovaries or eggs. This suggests that the fatty acid profile of mature ovaries is indicative of the specific fatty acid required for ovarian development in E. sinensis. In conclusion, our results show that the optimized formulated diet developed in this laboratory can totally replace the razor clam, a broodstock food widely used in E. sinensis hatcheries in China. This encouraging result should facilitate more reliable hatchery production of this important aquaculture species. [source]

Developmental stages, larval and post-larval growth of angelwing clam Pholas orientalis

AQUACULTURE RESEARCH, Issue 7 2009
Beewah Ng
Abstract Angelwing clam were induced to spawn by thermal stimulation. Mature eggs measured 50 ,m in diameter. Cell division occurred within 36 min after fertilization. Mobile trochophore larvae were seen after 12 h and larvae developed within 18 h. Reared on a diet of Isochrysis galbana the larvae reached the umbo stage in 6,7 days. On day 10 the foot could be seen and settlement occurred if a suitable substrate was present. The larvae completed metamorphosis into juveniles within 20 days after settling. [source]

Influence of salinity, diurnal rhythm and daylength on feeding in Laternula marilina Reeve

AQUACULTURE RESEARCH, Issue 2 2005
Shuhong Zhuang
Abstract A nature-simulating culture system was used to explore the influence of salinity, the diurnal cycle and daylength on ingestion rate (IR) and assimilation efficiency (AE) of Laternula marilina. The clams used in the experiments were grouped into three sizes: large, medium and small according to shell length and dry fresh weight. The clams in all size groups demonstrated a common response pattern in IR and AE under salinities ranging from 18 to 34 g L,1. The clams achieved the greatest IR within the salinity range 27,30 g L,1. There was a marked reduction in IR outside this range. Of the salinities tested 18 g L,1 was the harshest stress to the feeding of L. marilina. Between the salinities of 24 and 34 g L,1, the AE of the clam responded in an inverse way to that of IR, suggesting that L. marilina is able to compensate for the loss of IR by an increase in AE. Although the differences between clam size groups were not statistically different, those between different salinities were except those between 27 and 34 g L,1 (IR) and 23 and 34 g L,1 (AE). All sizes of clam showed a two-phase diurnal feeding pattern, a high ingestion phase from 00:00 to 08:00 hours and a low ingestion phase from 12:00 to 20:00 hours. The response of feeding (as measured by IR) to daylength comprised high and constant feeding at daylengths from 0 to 16 h and declining and unstable feeding as daylength increased from 16 to 24 h. All sizes of clams demonstrated an inverse adaptation to AE compared with IR, indicating that the clam is able to achieve a stable feeding physiology by compensating for daylength-induced variations in IR by changing AE. [source]

Comparison of Three Culture Methods for the Intensive Culture of Northern Quahog Seed, Mercenaria mercenaria

Impacts of Dreissena invasions on benthic macroinvertebrate communities: a meta-analysis

DIVERSITY AND DISTRIBUTIONS, Issue 2 2007
Jessica M. Ward
ABSTRACT Dreissenid mussels (the zebra mussel Dreissena polymorpha and the quagga mussel Dreissena bugensis) have invaded lakes and rivers throughout North America and Europe, where they have been linked to dramatic changes in benthic invertebrate community diversity and abundance. Through a meta-analysis of published data from 47 sites, we developed statistical models of Dreissena impact on benthic macroinvertebrates across a broad range of habitats and environmental conditions. The introduction of Dreissena was generally associated with increased benthic macroinvertebrate density and taxonomic richness, and with decreased community evenness (of taxa excluding Dreissena). However, the strength of these effects varied with sediment particle size across sites. The effects of Dreissena differed among taxonomic and functional groups of macroinvertebrates, with positive effects on the densities of scrapers and predators, particularly leeches (Hirudinea), flatworms (Turbellaria), and mayflies (Ephemeroptera). Gastropod densities increased in the presence of Dreissena, but large-bodied snail taxa tended to decline. Dreissena was associated with declines in the densities sphaeriid clams and other large filter-feeding taxa, as well as burrowing amphipods (Diporeia spp.), but had strong positive effects on gammarid amphipods. These patterns are robust to variation in the methodology of primary studies. The effects of Dreissena are remarkably concordant with those of ecologically similar species, suggesting universality in the interactions between introduced byssally attached mussels and other macroinvertebrates. [source]

Behavioural interactions between ecosystem engineers control community species richness

ECOLOGY LETTERS, Issue 11 2009
Paul E. Gribben
Abstract Behavioural interactions between ecosystem engineers may strongly influence community structure. We tested whether an invasive ecosystem engineer, the alga Caulerpa taxifolia, indirectly facilitated community diversity by modifying the behaviour of a native ecosystem engineer, the clam Anadara trapezia, in southeastern Australia. In this study, clams in Caulerpa -invaded sediments partially unburied themselves, extending >30% of their shell surface above the sediment, providing rare, hard substrata for colonization. Consequently, clams in Caulerpa had significantly higher diversity and abundance of epibiota compared with clams in unvegetated sediments. To isolate the role of clam burial depth from direct habitat influences or differential predation by habitat, we manipulated clam burial depth, predator exposure and habitat (Caulerpa or unvegetated) in an orthogonal experiment. Burial depth overwhelmingly influenced epibiont species richness and abundance, resulting in a behaviourally mediated facilitation cascade. That Caulerpa controls epibiont communities by altering Anadara burial depths illustrates that even subtle behavioural responses of one ecosystem engineer to another can drive extensive community-wide facilitation. [source]

Immunocompetence of bivalve hemocytes as evaluated by a miniaturized phagocytosis assay

ENVIRONMENTAL TOXICOLOGY, Issue 3 2002
C. Blaise
Abstract Immune function in bivalves can be adversely affected by long-term exposure to environmental contaminants. Investigating alterations in immunity can therefore yield relevant information about the relationship between exposure to environmental contaminants and susceptibility to infectious diseases. We have developed a rapid, cost-effective, and miniaturized immunocompetence assay to evaluate the phagocytic activity, viability, and concentration of hemocytes in freshwater and marine bivalves. Preliminary experiments were performed to optimize various aspects of the assay including 1) the time required for adherence of hemocytes to polystyrene microplate wells, 2) the time required for internalization of fluorescent bacteria, 3) the ratio of hemocytes to fluorescent bacteria in relation to phagocytosis, 4) hemolymph plasma requirements, and 5) the elimination of fluorescence from (noninternalized) bacteria adhering to the external surface of hemocytes. The results of these experiments showed the optimal adherence time for hemocytes in microplate wells to be 1 h, that phagocytosis required at least 2 h of contact with fluorescently labeled E. coli cells, that the number of fluorescent E. coli cells had a positive effect on phagocytic activity, that at least 2.5 million cells/mL were required to measure a significant intake, and that a linear increase in uptake of bacteria (R = 0.91; p < 0.01) could be obtained with concentrations of up to 1.3 × 106 hemocytes/mL. Afterward, the assay was used in two field studies to identify sites having the potential to affect the immunocompetence of bivalves. The first study was conducted on Mya arenaria clams collected at selected contaminated sites in the Saguenay River (Quebec, Canada), and the second examined Elliptio complanata freshwater bivalves that had been exposed to a municipal effluent plume in the St. Lawrence River (Quebec, Canada). In the Saguenay River field study a significant increase in phagocytosis was observed at sites closest to polluted areas. Phagocytotic activity varied over time and was highest during the warmest months (June, July, and August), closely paralleling the spawning period of Mya arenaria clams. In contrast, a drop in phagocytic activity was observed in Elliptio complanata mussels exposed to surface water 4 km downstream of a major municipal effluent plume, with a concomitant increase in the number of hemocytes in the hemolymph. It appears that both immunosuppressive and immunostimulative effects are likely to occur in the field and that responses will be influenced by the type and intensity of contaminants at play. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 160,169, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10047 [source]

Molluscan shellfish biomarker study of the Quebec, Canada, Saguenay Fjord with the soft-shell clam, Mya arenaria

Assessing exposure of sediment biota to organic contaminants by thin-film solid phase extraction

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009
Lizanne M. Meloche
Abstract Differences in bioavailability among sediments are a source of variability and uncertainty in sediment quality assessment. We present three sets of studies designed to test a thin-film solid phase extraction technique for characterizing the bioavailability of organic chemicals in sediments. Laboratory studies with spiked natural sediments reveal highly reproducible thin-film extractions for chemicals with octanol,water partition coefficients between 104.5 and 108.5, with 95% equilibration times between 1 and 600 h. Studies with field-collected sediments illustrate that method detection limits are sufficiently low for field application at contaminated sites. Bioaccumulation studies with clams (Macoma balthica) show excellent correlations between thin-film and animal tissue concentrations. We conclude that thin-film extraction provides an ecologically relevant, fugacity-based measure of chemical exposure that can be expected to improve sediment quality assessments. [source]

The role of biomarkers to assess oil-contaminated sediment quality using toxicity tests with clams and crabs,

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2008
Carmen Morales-Caselles
Abstract A 28-d bioassay was conducted with two invertebrate species with different feeding habits, the clam Ruditapes philippinarum and the shore crab Carcinus maenas. The purpose of the present study was to assess the quality of sediments affected by oil spills in different areas of the Spanish coast. The organisms were exposed to environmental samples of oil-contaminated sediments during four weeks and, after the experiment, a suite of biomarkers of exposure was measured: The phase one detoxification system was assessed by ethoxyresorufin- O -deethylase (EROD) activity; glutathione- S -transferase (GST) is a phase-two detoxification enzyme but also is implicated in oxidative stress events; glutathione peroxidase (GPX), glutathione reductase (GR), and the ferric reducing ability of plasma (FRAP) assay were analyzed to determine the antioxidant activity of the tissues. The biomarker results were correlated with the chemical compounds bound to sediments (polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], Zn, Cd, Pb, Cu, Ni, Co, V) and a principal component analysis was carried out with the purpose of linking all the variables and to detect those contaminated sediments potentially harmful to the biota. Results showed induction of biomarkers in both invertebrate species and significant differences (p < 0.05; p < 0.01) were established among sediments affected by different spills. The use of the selected biomarkers together with the sediment chemical analysis assesses the bioavailability of contaminants and has proven to be a suitable tool to monitor the environmental quality of sediments affected by oil spills. [source]

Oxidative stress biomarkers in bivalves transplanted to the Guadalquivir estuary after Aznalcóllar spill

Variation of metallothionein and metal concentrations in the digestive gland of the clam Ruditapes decussatus: Sex and seasonal effects

Potential multidrug resistance gene POHL: An ecologically relevant indicator in marine sponges

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2001
Anatoli Krasko
Abstract Sponges are sessile filter feeders found in all aquatic habitats from the tropics to the arctic. Against potential environmental hazards, they are provided with efficient defense systems, e.g., protecting chaperones and/or the P-170/multidrug resistance pump system. Here we report on a further multidrug resistance pathway that is related to the pad one homologue (POH1) mechanism recently identified in humans. It is suggested that proteolysis is involved in the inactivation of xenobiotics by the POH1 system. Two cDNAs were cloned, one from the demosponge Geodia cydoniumand a second from the hexactinellid sponge Aphrocallistes vastus. The cDNA from G. cydonium, termed GCPOHL, encodes a deduced polypeptide with a size of 34,591 Da and that from A. vastus, AVPOHL, a protein of a calculated Mr of 34,282. The two sponge cDNAs are highly similar to each other as well as to the known sequences from fungi (Schizosaccharomyces pombe and Saccharomyces cerevisiae) and other Metazoa (from Schistosoma mansoni to humans). Under controlled laboratory conditions, the expression of the potential multidrug resistance gene POHL is, in G. cydonium, strongly upregulated in response to the toxins staurosporin (20 ,M) or taxol (50 ,M); the first detectable transcripts appear after 1 d and reach a maximum after 3 to 5 d of incubation. The relevance of the expression pattern of the G. cydonium gene POHL for the assessment of pollution in the field was determined at differently polluted sites in the area around Rovinj (Croatia; Mediterranean Sea, Adriatic Sea). The load of the selected sites was assessed by measuring the potency of XAD-7 concentrates of water samples taken from those places to induce the level of benzo[a]pyrene monooxygenase (BaPMO) in fish and to impair the multidrug resistance (MDR)/P-170 extrusion pump in clams. These field experiments revealed that the levels of inducible BaPMO activity in fish and of the MDR potential by the water concentrates are highly correlated with the level of expression of the potential multidrug resistance gene POHL in G. cydonium. This report demonstrates that the detoxification POH pathway, here mediated by the G. cydonium GCPOHL gene, is an additional marker for the assessment of the environmental load in a given marine area. [source]

Laboratory to field validation in an integrative assessment of an acid mine drainage,impacted watershed

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000
David J. Soucek
Abstract An integrative assessment was conducted in the Puckett's Creek watershed of southwestern Virginia, USA, to investigate the environmental impacts of acid mine drainage (AMD) inputs. Twenty-one sampling stations were categorized into groups based on five degrees of AMD input: (1) none, (2) intermittent acidic/circum-neutral AMD, (3) continuous acidic AMD, (4) continuous circum-neutral AMD, and (5) receiving system stations with at least two levels of dilution. Bioassessment techniques included water/sediment chemistry, benthic macroinvertebrate sampling, laboratory acute water column toxicity testing, laboratory chronic sediment toxicity testing, and in situ toxicity testing with Asian clams (Corbicula fluminea [Müller]). Group 3 stations had significantly altered water chemistry (low pH, high conductivity, and high water column metals) relative to the other groups and significantly higher sediment iron concentrations. Both group 3 and group 4 stations had significantly decreased ephemeroptera-plecoptera-trichoptera richness and percent ephemeroptera abundance relative to unimpacted stations. Group 3 stations also had decreased total taxon richness. Water column toxicity testing was sensitive to AMD impacts, with samples from group 3 stations being significantly more toxic than those from groups 2 and 4, which in turn were more toxic than those from groups 1 and 5. Similar results were observed for in situ toxicity testing. No differences in sediment toxicity test survival and impairment results were observed among the station groups. Stepwise multiple linear regression and simple bivariate correlation analyses were used to select parameters for use in an ecotoxicologic rating system, which was successful in differentiating between two levels of environmental impact relative to stations receiving no AMD input. [source]