Soft-shell Clam Mya Arenaria Research Articles

Tissue distribution and excretion of 99mTc-disofenin in three marine species: Pleuronectes americanus (winter flounder), Homarus americanus (lobster), and Mya arenaria (soft-shell clam)

To determine the pharmacokinetics of a small lipophilic molecule in vivo, the distribution and accumulation of 99mTc-radiolabelled disofenin (diisopropylacetanilide iminodiacetic acid) were traced during 1991–1992 by scintigraphy and gamma well counting in winter flounder (Pleuronectes americanus collected from Boston Harbor and Long Island Sound in 1992), lobsters (Homarus americanus collected from Massachusetts Bay in 1991), and soft-shell clams (Mya arenaria purchased in 1991). The agent was distributed throughout the bodies of lobsters within 12 s, throughout flounder within 40 s, and throughout clams within 2 min. It was concentrated most strongly by the liver of flounder, which contained 61.2±7.8% of the injected dose within 1 h of injection, and by the lobster hepatopancreas. Accumulation also occurred in the flounder kidney, lobster antennal glands, and the kidney and pericardial glands of clams. The compound was rapidly excreted from the flounder liver into the gall bladder, and from the lobster hepatopancreas into the stomach. The data suggest its excretion from the lobster antennal glands and clam kidneys. The rate of clearance of disofenin from the body varied among species: 99±2.1% of the initial dose remained in flounder sampled 16 to 24 h after injection, compared to 80.5±7% remaining in the lobster after 15 h, and 87.4±5.9% remaining in clams after 27 h. The clearance rates in flounder and lobster are considered to be minimum values because of the lack of gut activity in unfed individuals. Overall, these in vivo tracer studies establish the utility of scintigraphy for assessing the uptake and excretion of a lipid soluble compound in different taxa, and may be applicable for evaluating disease and/or environmental effects on organ function in marine animals.

Temporal variations in heat dissipation and oxygen uptake of the soft shell clamMya arenarial. (bivalvia)

Abstract Heat dissipation and oxygen uptake of the soft shell clam Mya arenaria were measured during long term experiments. Clams from both intertidal and subtidal habitats all exhibited a conspicuous alternating pattern of either high or very low metabolic activity, with an up to 23-fold difference between the two rates. The heat dissipation of intertidal clams from Loves Cove, Maine was 1–3 µW during low activity, and 11–41 µW at high activity. These clams spent 9-61%of the measured interval at a high heat dissipation. The alternating pattern in heat dissipation of intertidal clams did not demonstrate a distinct relation to the tidal pattern. The oxygen uptake of intertidal clams from Lagten Beach, Denmark during low and high activity was 1–8 µmol O2 g-1 h-1 and 23–28 µmol O2 g-1 h1, respectively, with the active periods lasting 60–81% of the total measured interval. Subtidal clams from Sebbersund, Denmark showed an oxygen uptake during low activity of 8–34 µmol O2 g-1 h-1 , while the oxygen uptake duri...

Settlement and recruitment of Mya arenaria L. in the Wadden Sea

Four stations (B1–B4) on an intertidal sandflat south of the island of Borokum (German Bight) were investigated in 1986 for the settlement of the soft shell clam Mya arenaria. The abundance of larvae in the plankton as well as of early postlarval stages in the benthos was recorded. Settlement of M. arenoria was restricted to those two stations with the lowest tidal elevations (B1, B2). In the upper part of the flat no early benthic stages were found. At that station where most of the larvae settled, recruitment in terms of abundance, growth, mortality and production was analysed using two sampling methods. The results suggest that size-specific peibenthic predation not only caused mortality but also affected growth and production.

High taurine levels in the Solemya velum symbiosis

1. 1. To compare biochemical differences between bivalves with and without endosymbiotic chemoautotrophic bacteria, specimens of Solemya velum, a bivalve species known to contain bacterial endosymbionts, and the symbiont-free soft-shelled clam Mya arenaria, were collected from the same subtidal reducing sediments during October and November 1988. 2. 2. Total and free amino acid compositions were determined for both species. Protein-bound amino acids were calculated as the difference between total and free amino acids. In addition, stable isotope ratios of the total and free amino acids of each species were measured to determine potential sources for these molecules. 3. 3. Both species had similar total hydrolyzable- and protein-bound amino acid compositions; approximately 50% of the protein-bound amino acids were essential amino acids. In S. velum, the small size of the digestive system suggests that these amino acids are probably synthesized by the endosymbiotic bacteria and translocated to the animal tissue. The δ 13C and δ 15N ratios of the amino acids are very similar to the isotope ratios previously found in both the endosymbionts and whole tissues of S. velum. The relative and absolute amounts of free amino acids are very different in the two species. In S. velum, the absolute concentrations of taurine, a sulfur-containing amino acid, were greater than the total free amino acid concentrations found in other bivalves. 4. 4. The δ 34S ratios of the free amino acids of S. velum, which were predominantly composed of taurine, were extremely negative (−17.2ℵ) suggesting that taurine is synthesized using sulfur originally derived from external reduced sulfur sources, such as pore water sulfides. The possible roles for taurine in this animal-bacteria symbiosis are discussed.

Comparative study of phagocytosis in normal and diseased hemocytes of the bivalve mollusc Mya arenaria

Large numbers of the soft-shelled clam Mya arenaria from New Bedford Harbor, Massachusetts, exhibit a blood cell disease referred to as hematopoietic neoplasia (HN). Diseased hemocytes differ morphologically from normal hemocytes by their high nucleocytoplasmic ratio. The phagocytic activity, one of the internal defense mechanisms, was compared in the two populations. Surface receptors, essential for recognition during phagocytosis, were demonstrated for both populations using Con A staining. Adherence and uptake were measured after in vitro incubation with yeast. Examination of hemocytes with scanning electron microscopy showed that yeast cells adhered only to the surface of normal hemocytes, and not to diseased hemocytes. Quantitative analysis of adherence and uptake of yeast by hemocytes showed that diseased hemocytes were unable to adhere and ingest yeast. This is thought to be caused by differences in cytoskeletal organization. Finally, the activity of four lysosomal enzymes was used to evaluate intracellular degradation in normal and diseased hemocytes. Histochemical analyses showed diseased hemocytes to have higher than normal acid phosphatase, nonspecific esterases and β-glucuronidase activity. These results indicate that enzyme activity cannot be directly correlated to intracellular degradation. However, it is possible that stress on the lysosomal system may activate certain enzymes.

The effect of cheliped loss on blue crab Callinectes sapidus Rathbun foraging rate on soft-shell clams Mya arenaria L.

Loss of single chelipeds was common (4–17%) in populations of blue crab Callinectes sapidus Rathbun surveyed in Chesapeake Bay and along the southeastern Atlantic coast and Gulf of Mexico. In contrast, blue crabs missing both chelipeds were relatively rare (0–5%). Laboratory experiments were conducted to determine the effects of cheliped autotomy on blue crab foraging rate on soft-shell clams Mya arenaria L. In replicated aquarium experiments, clams (44–72 mm shell length) were allowed 48 h to burrow in sandy substratum before an intact male crab or one missing one or both chelipeds was introduced. After 48 h, clams were checked for evidence of siphon injury or mortality. Foraging rate (clams consumed/48 h) of crabs missing a single crusher cheliped did not differ significantly from that of intact crabs. Blue crabs compensated for the loss of a crusher by using the cutter cheliped and opposite first walking leg to forage. In contrast, crabs missing both chelipeds experienced a greater feeding handicap; their consumption of clams was significantly lower than that of intact crabs. The low incidence of individuals missing both chelipeds suggests that such injury does little to diminish blue crab predation on M. arenaria populations.

Respiration of sarcoma cells from the soft-shell clam Mya arenaria L. under various conditions

Oxygen consumption of sarcoma cells from the soft-shell clam Mya arenaria L. was studied. Hemolymph of clams in the terminal stage of sarcoma was strongly hypoxic. In early cases of sarcoma, partial pressure of oxygen in the hemolymph did not differ from the control animals but declined as the sarcoma advanced, and finally fell below the detection limit causing death of sarcomatous clams. Mitotic index declined as the sarcoma progressed and was 100 × lower in hypoxic plasma in the terminal stage than in early cases. Oxygen consumption of the sarcoma cells in 15% salinity seawater (18 °C) was 3.9 × 10 −4 μl· h −1·cell −. Respiration rates declined in salinities < 7.5‰ and > 15% . Temperature stress (37 °C) depressed oxygen consumption before mortality could be detected but returning the cells to 18 °C increased oxygen consumption above the initial level.

Commentary: Concluding Remarks on Session I

The papers presented during the first session have provided a useful introduction and a review of several important points that have been established during the past decade. Many carefully studied near shore marine environments and freshwater lakes are polluted with chemicals as indicated primarily by measurements of certain organics and metals in sediments. Fish and shellfish, including bivalve mollusks (clams, mussels, oysters) and crustacean (crabs and shrimp) used as food resources by humans inhabit contaminated aquatic environments. Fish and shellfish, especially bivalve mollusks, concentrate many undesirable organics and metals in their tissues. Fish and shellfish suffer from cancerous diseases. For finfish especially, there are correlations between the occurrence and/or prevalences of cancerous diseases and the degree of chemical contamination in the environment they inhabit. Meyers (1), Wolke (2), and Black (3) all described such a relationship for fish and the aquatic systems they have studied. For bivalve mollusks, the connection between cancerous diseases and chemical contaminants is much less convincing (4). There has been little solid evidence of a link between the two in studies conducted to date. Farley's studies on the sarcomas of softshell clams (Mya arenaria) from Maryland do not suggest a possible chemical causation (5). However, Gardner's interesting studies indicate that the germinomas of M. arenaria from contaminated areas he has studied appear to be associated with certain chemicals in the environment (6). In addressing the central question to be considered during this conference (is there an increased risk due to the consumption of aquatic foods with measurable levels of contaminants?), the following general points and questions, related to the preceding papers, seem pertinent. Which chemicals, or classes of chemicals, are important relative to risk assessments for aquatic resources? How can this be determined? For various reasons, there has been a considerable emphasis on polycyclic aromatic hydrocarbons (PAH) in many studies conducted to date. However, given the uncertainties about oral PAH exposures causing tumors in humans (7) and the rapid metabolism of PAH by fish, it may be more worthwhile to concentrate on other chemicals in the environment. Which compounds bioaccumulate in fish or shellfish? Which compounds bioaccumulate in edible tissues of these organisms? To what extent are they passed on to mammals if consumed? Which aquatic species are important food sources? Several species of fish mentioned during this session would not appear to be particularly important in assessing risk (e.g., carp, brown bullheads) while others are, at least in certain geographical areas

Hematopoietic neoplasia inMya arenaria: Prevalence and indices of physiological condition

A field survey of hematopoietic neoplasia (Hn) in the soft shell clamMya arenaria (L.) was undertaken using an immunoperoxidase diagnostic technique. Monthly collections ofM. arenaria were made at two sites: Little Buttermilk Bay and New Bedford Harbor, both in Buzzards Bay, Massachusetts, USA, from May 1986 to October 1987. Clams were diagnosed for leukemia and analyzed for soft-tissue dry weight, condition index, and carbon and nitrogen content of the soft tissue. Prevalence of leukemia inM. arenaria exhibited a seasonal fluctuation with a maximum prevalence in fall (September to October) and a minimum prevalence in early summer (March to July). A second maximum peak in late winter (January to March) was observed at one site. Leukemia primarily affected clams that were 3 to 4 yr post-settlement. Lower prevalence levels were observed in both younger and older clams. LeukemicM. arenaria with advanced stages of the disease, were in poorer physiological condition based on dry weight of the soft tissue, condition index, and carbon content of the tissue. Nitrogen metabolism appeared to be unimpaired. Significant differences were observed between the two sites with respect to prevalence of Hn and the physiological condition of clams. Differences in disease prevalence between the two sites may be the result of unknown environmental factors that facilitate initiation of the disease or, that compromise the defense mechanisms of the clams.

Cytomorphology of the pedal aperture glands of Mya arenaria L. (Mollusca, Bivalvia)

A glandular cushion, called the pedal aperture gland in this paper, lies adjacent and internal to each of the two mantle margins composing the pedal aperture of the soft-shelled clam Mya arenaria. Two types of glandular cells are found in the glands. The principal type (bacillary mucous cell) manufactures secretory vesicles that contain discrete protein-rich fibers in a matrix of glycoprotein. The second type (mucous goblet cell) produces sulfated and nonsulfated mucosubstances. The glands function in the formation of pseudofeces from particulate material, especially burrow sediments that enter the mantle cavity through the pedal aperture. Their possible phylogenetic relationship to similar glands in other bivalves is discussed briefly.

Environmental limits for survival of sarcoma cells from the soft-shell clam Mya arenaria

L'influence des parametres environnementaux sur la survie des cellules du sarcome dans l'eau de mer a ete etudiee avec differentes salinites, temperatures, concentrations de cuivre et differents pH, afin de tenter d'expliquer les differences epizastiques observees dans des populations naturelles

Induced triploidy in the soft-shelled clam Mya arenaria: energetic implications

Given that triploid adult bivalves reportedly grow larger and faster than their diploid siblings, such differences should be traceable to variation in energy allocation. In one proposed mechanism, retarded gametogenesis found in triploid adults may allow them more energy for somatic growth. Another hypothesis states that triploids are more heterozygous; increased heterozygosity has been positively correlated with enhanced growth. Juvenile soft-shelled clams, Mya arenaria, were treated with cytochalasin B to induce triploidy and examined with respect to components of a balanced energy equation (C=P+R+E). The variables measured were oxygen uptake (Vo2), filtration rate (FR), dry tissue weight, shell length, shell height and shell inflation. Energy budgets were constructed and diploid and triploid groups compared. Few significant differences were found between diploid and triploid juvenile clams with respect to energy budget components. However, at seven loci assayed electrophoretically the triploid individuals were nearly twice as heterozygous as their diploid siblings. Moreover, tripoloid variances were less than diploid variances for every variable measured. Increased heterozygosity has been correlated with the decreased variance of morphological parameters. This study is believed to be the first to show decreased variance of physiological properties as well as morphological characters. Overall the data clearly indicate that energy allocation in juvenile M. arenaria is not related to ploidy.

Trace metal residues in shellfish from Maryland waters, 1976-1980.

Levels of seven heavy metal residues, arsenic, cadmium, chromium, copper, lead, mercury and zinc were monitored in samples of the American oyster (Crassostrea virginica), the soft shell clam (Mya arenaria), the hard shell clam (Mercinaria mercinaria) and the blue crab (Callinectes sapidus). Samples were taken from the Maryland section of the Chesapeake Bay and its tributaries over a five year period (1976-80). This study was undertaken to provide an estimate of a baseline for values of trace heavy metals. Also, the oyster, being a non-mobile filter feeder, provides information regarding the level of metal residues in its environment (water and sediment), because heavy metal uptake is related to the surrounding metal concentrations. Additionally, this type of monitoring program is essential to ensure that shellfish sold for human consumption are within safe limits established for toxic substances by the United States Food and Drug Administration. Results of the study are consistent with data from previous years and no statistically significant year-to-year trends were observed over the period of the investigation.

Epizootic Neoplasia in Soft Shell Clams Collected from New Bedford Harbor

ABSTRACT Soft shell clams (Mya arenaria) were collected from tidal flats in southeastern New England, and their heamolymph analyzed for the presence of neoplastic cells. The prevalence of neoplasia varied from 10-90% with the highest prevalence found in New Bedford Harbor, a site containing high levels of pollutants, including PCBs, heavy metals and industrial wastes. Further analyses showed that quantifiable levels of Aroclors 1242 and 1254, congeners of PCB, could be detected in neoplastic cell extracts derived only from clams collected from New Bedford Harbor. These studies suggest an association between the high prevalence of disease and the location of soft shell clams at or near an industrially contaminated site.

Organochlorine residues in shellfish from Maryland waters, 1976-1980.

Shellfish samples, including the American oyster (Craessostrea virginica), the soft shell clam (Mya arenaria), the hard shell clam (Mercenaria mercenaria) and the blue crab (callinectes sapidus), were taken from the Maryland section of the Chesapeake Bay and its tributaries over a five year period (1976-80) and analyzed to determine residue levels of various organochlorine pesticides. Qualitative and quantitative information was obtained for a variety of polychlorinated hydrocarbons. The purpose of this study includes the establishment of baseline values for levels of shellfish contamination, utilization of the data as an indicator of probable levels of water and sediment contamination in the vicinity of the sampling site and ensurance that shellfish harvested for human consumption are within U.S. Food and Drug Administration guidelines for organochlorine contamination. All mean values and virtually all individual values were within FDA guidelines.

The effects of sediment type on growth rate and shell allometry in the soft shelled clam Mya arenaria L

Hatchery-reared juvenile Mya arenaria L. were grown for 11 wk in replicated gravel, sand, mud, and pearl net treatments under flow-through sea-water conditions in Maine. Analyses of variance showed significant differences between sediment treatments for final shell length, dry meat weight, chondrophore growth increment, and percent shell weight. Growth of juvenile M. arenaria was more rapid in fine sediments than in coarse sediments or nets. Regression slopes of shell length-shell height and shell length-shell depth varied significantly between sediment treatments. Slower-growing clams from nets and gravel were more globose than clams from sand or mud treatments. Clams grown in sand were longer and narrower than those from mud. Differences in growth rates and shell form were attributed primarily to the physical properties of the substrata, and their effects on the scope for growth of M. arenaria.

Growth reduction in the soft-shell clam Mya arenaria from a heavily oiled lagoon in Chedabucto Bay, Nova Scotia

Growth rates were determined in Mya arenaria collected from a heavily oiled lagoon lagoon shortly after the Arrow disaster (Nova Scotia, Canada). The clams, ranging in length from 30 to 50 mm, were compared with a sample collected from the same location 9 years later. Both samples from Janvrin Lagoon were compared with Mya arenaria collected in 1979 from a non-oiled neighbouring lagoon on Potato Island. Annual internal growth bands seen in shell cross-sections rather than shell external annuli were used for age determination. The 1979 Janvrin Lagoon sample, compared with the 1970 sample, suffered growth retardation in tissue and shell growth by 2–5 years.

A severity index to assess and monitor the incidence of pollution-related pathological conditions in marine organisms

A normalised matrix of the occurrences and co-occurrences of n-pathological conditions in a hypothetical population is termed a severity matrix and was used to define a volume in an n-dimensional vector space representing the severity or extent of the spread of the conditions in the population. The changes in this volume resulting from varying the numbers of occurrences and co-occurrences in the severity matrix are described by the varying determinant of the matrix. The natural logarithm of this determinant was shown to be a consistent measure or index of severity for comparing the spread of the same pathological conditions among different populations or among chronological samples from the same population. While the eigenvalues of the severity matrix are used to determine the relative contribution of each pathological condition to the index of severity, the eigenvectors serve to investigate possible associations among the conditions. Actual data from a population of the soft-shell clam Mya arenaria were used to demonstrate the application of this methodology to characterise the incidence of five pathological conditions assumed to be indicators of pollution related stress on the clam population.

The Shellfish Resource in a Polluted Tidal Inlet

In the City of Gloucester, Massachusetts, 30% of the Soft-shell Clam (Mya arenaria) beds in a tidal inlet known as the Annisquam River are not harvestable owing to the discharges of untreated sewage from the surrounding area. A large proportion of the total area of the clam-flats has been closed to clamming because of exceedingly high levels of coliform Bacteria in the clams and in the water. These polluted areas represent a ‘loss’ of resources for the community, and they were surveyed in 1980 to determine the number and value of Clams which could have been harvested if only the sewage discharges had been controlled.In the productive areas of the closed-to-fishing flats, which totaled 25.9 ha, the densities of Clams larger than 2.5 mm were found to be statistically the same on the 9 flats sampled and averaged 122.3 per m2. The average number of legally harvestable Clams (those with shells more than 51 mm in length) was 23.3 per m2, and the total yield that could have been harvested in 1980 was estimated at 6 × 106 Clams. Assuming that only 50–60% of the Clams would actually have been harvested in a year (i.e. 3.2 × 106 animals), the local community lost $332,400 in retail sales alone for lack of adequate sewage treatment facilities. Locally, 70% of the harvest goes into the restaurant trade where a bushel (35.2 1), which contains some 1,600 animals, retails for $210, and 30% is sold fresh at $64 per bushel.

Uptake and excretion of fenitrothion by clams and mussels.

This paper describes the uptake and excretion of fenitrothion by soft-shelled clams (Mya arenaria), mussels (My™ edulis) and freshwater clams (Anodonta cataractae). Fenitrothion has a relatively low uptake and a relatively high excretion rate constant and, consequently, a low accumulation coefficient in these species. The data indicate no danger of shellfish contamination from a normal application of fenitrothion. The fate of organophosphate pesticides in aquatic biota has received little attention. Results of some laboratory studies are summarized in Table I. Only for two cases (BENDER 1969, TAKIMOTO and MIYAMOTO 1976) was it possible to calculate the uptake and excretion rate constants according to the "one compartment model" of BRANSON et al. (1975), for comparison with the values given in this paper.