Freshwater Bivalve Corbicula Fluminea Research Articles

Characterisation of the impact of aqueous industrial waste in mesocosms: biological indicators and pilot streams

The use of exposure biomarkers in measuring the impact of aqueous waste holds out promise because such tools have short response times, are of flexible use and give an indication of the type of pollution. However, their ecological significance has not yet been demonstrated. During field studies focusing on aqueous industrial waste, the correlations obtained between several biocoenotic indicators and biomarkers measured in a fresh-water bivalve (Corbicula fluminea), demonstrate the need for work to be carried out under controlled conditions. Working in partnership with the Adour Garonne Water Board, the ELF company has developed a pilot scheme incorporating such controlled conditions. This pilot is made up of 16 canals 40 m in length supplied by river water. The pilot scheme, which is currently at the validation stage, makes it possible to reconstitute an aquatic ecosystem which, once established, will be exposed to perfectly controlled pollution conditions. The responses provided by all the indicators--biocoenotic and microbiological indicators, biomarkers--will then be correlated in order to attribute an ecological significance to the biomarkers.

Cholinesterases from the marine mussels Mytilus galloprovincialis Lmk. and M. edulis L. and from the freshwater bivalve Corbicula fluminea Müller

In order to improve the molecular basis for the use of bivalve cholinesterases as a reliable biomarker for aquatic pollution, the polymorphism and characterization of these enzymes in Mytilus edulis, Mytilus galloprovincialis and Corbicula fluminea were investigated. All results are consistent with the presence of only one pharmacological form of cholinesterase in each species. The molecular masses were 180 kDa for the two marine mussels and 240 kDa for C. fluminea. The cholinesterases are anchored to the membrane by a glycosyl inositol phosphate like the G a form (type I) described in vertebrates. Surprisingly, these cholinesterases were poorly inhibited by organophosphorous compounds compared to enzymes from other sources. This suggests that these bivalves could be used as a biomarker for acute rather than chronic contaminations by anticholinesterase insecticides.

Extracellular Matrix and Muscle Fibers in the Gills of Freshwater Bivalves

The supportive tissue in the gills of three species of freshwater bivalves (Corbicula fluminea, Dreissena polymorpha, and Toxolasma texasensis) is composed of a similar extracellular matrix with interspersed muscle fibers. These matrices consist of a periodic acid Schiffpositive tissue supported by small collagen fibrils as determined by morphological and biochemical examination. The periodicity observed in fibrils and the electrophoretic migration patterns are consistent with other collagens. The ultrastructure of the muscle fibers associated with the connective tissue corresponds with a known type of smooth muscle. The high degree of similarity between the tissues of these species suggests a similar, conserved function. Additional key words: collagen, smooth muscle, extracellular matrix The bivalve gill is a highly complex organ composed of regionally specialized epithelial tissue attached to a supportive structure of connective tissue containing blood spaces, nerves, and muscles (LePennec et al. 1988; Kays et al. 1990; Gardiner et al. 1991; Eble & Scro 1996; Gros et al. 1996; Medler & Silverman 1997). LePennec et al. (1988) appropriately emphasized the need for detailed descriptions of the anatomy of littoral bivalve gills. The gill is an important organ involved in nutrition, ion transport, and gas exchange (Dietz 1985; Pearse et al. 1987; LePennec et al. 1988; Kays et al. 1990; Eble & Scro 1996), yet there are gaps in our knowledge of the non-epithelial components of the gill. A number of early investigators noted that muscular movements of the gill were important for integrated gill processes (Setna 1930; Elsey 1935; Atkins 1943; Nelson 1960). We have recently studied the functional organization of the gill muscles and their associated connective tissues (Gardiner et al. 1991; Medler & Silverman 1997), but a detailed understanding of the basic composition of these elements does not exist. This comparative study focuses on the composition of the extracellular matrix and muscle fibers in the freshwater bivalve gill. The connective tissue of the bivalve gill has historically been termed chitinous (Ridewood 1903; Yonge 1926; Elsey 1935; Atkins 1943), although more contemporary work recognizes the tissues as being composed primarily of collagen and associated muscle fibers (LePennec et al. 1988; Kays et al. 1990; Eble & a Author for correspondence. E-mail: smedler@ unix 1.sncc.lsu.edu Scro 1996; Gros et al. 1996; Medler & Silverman 1997). Nevertheless, there are no studies that have explicitly examined the nature of the collagen; the evidence that collagen is the fibrous protein supporting the gill has largely been anecdotal or preliminary (Brown 1952; Ruddall 1955; LePennec et al. 1988; Kays et al.1990; Gros et al. 1996; Medler & Silverman 1997). The intrinsic muscles of the bivalve gill were described many years ago (Setna 1930; Elsey 1935; Atkins 1943) but have received little attention until recently (Gardiner et al. 1991; Medler & Silverman 1997). The ultrastructure of these muscle fibers is poorly known and has been explicitly described for only a single species, Dreissena polymorpha (Medler & Silverman 1997). In the present study, we identify the fibrous structural material of the gill and classify the associated muscle fibers according to their comparative ultrastructure. We studied the gills of the freshwater bivalves Corbicula fluminea, Dreissena polymorpha, and Toxolasma texasensis. Corbicula fluminea and D. polymorpha are members of the subclass Heterodonta (Newell 1965) and share a common evolutionary lineage (Nuttall 1990). Toxolasma texasensis is of the subclass Paleoheterodonta (Newell 1965) and is a member of the family Unionidae. Together, these species are representatives from three different bivalve families (Newell 1965) and were selected because they provide a comparative analysis among higher systematic taxa.

Bioaccumulation and metallothionein response in the asiatic clam (Corbicula fluminea) after experimental exposure to cadmium and inorganic mercury

AbstractThe involvement of metallothioneins (MTs) in cadmium (Cd) and inorganic mercury (Hg[II])bioaccumulation by the freshwater bivalve Corbicula fluminea was experimentally investigated after 0, 15, 30, and 45 d of exposure from the water column source. Three levels of contamination were studied for each metal: 0, 5, and 35 μg Cd/L and 0, 1.45, and 5 μg Hg/L, with two replicates per condition. Forty eight experimental units (EUs) were conducted simultaneously. The mollusks were fed twice a week by additions of phytoplanktonic algae. Quantification of MTs was done by Hg‐saturation assay, using cold Hg(II). A partial purification of these proteins was conducted by gel‐filtration chromatography, followed by Cd determinations in the different eluted fractions. Results at the whole organism (soft tissues) and organ or tissue group (gills, mantle, foot, visceral mass) levels show high metal concentrations, with a fourfold greater accumulation of inorganic Hg than Cd after 30 d exposure at the same concentration of 5 μg/L. Gills and visceral mass were the principal storage compartments. A significant increase in MT concentrations was revealed in these two organs after exposure to Cd: ratios between the MT concentrations in contaminated and control mollusks were 2.4 and 2.8, respectively, for 5 and 35 μg Cd/L. Cd burdens in the cytosol and in ≤18‐kDa protein fractions, similar to purified mammal MTs, correspond to 30 and 14% of the total Cd accumulated in the whole organisms. No significant increase in MT biosynthesis was observed after exposure to inorganic Hg, despite the high metal concentrations in the organs.

Accumulation and elimination of pentachlorophenol in the freshwater bivalve Corbicula fluminea.

The La Plata River, which is one of the most important aquatic systems in South America and provides the freshwater supply for Buenos Aires, the capital of Argentina, receives the discharge of a great number of chemicals (Verrengia Guerrero and Kesten 1994).

Acid-Base Balance during Emergence in the Freshwater Bivalve Corbicula fluminea

The Asian freshwater clam, Corbicula fluminea, was emersed at 23°C under three conditions: humid air, N₂ hypoxia, or air with valves clamped or bound shut. Under all conditions, clams became acidotic during emersion. In air, hemolymph pH declined from 790 to 7.14 in 72 h. Hypoxic clams displayed a similar decline in pH, but clams with valves clamped became acidotic more rapidly. Hemolymph CO₂ content (Cco₂) and Pco₂ rose with duration of aerial exposure in all treatment groups. However, hemolymph of bound clams had significantly higher Cco₂ and Pco₂ than that of either air- or N₂-exposed bivalves after 48 h emersion. Although hemolymph Po₂ declined with emersion time in all groups, there was no effect of exposure condition, suggesting that ventilatory behaviors did not affect hemolymph Po₂ or that the effects were masked by rapid utilization of inspired O₂. Hemolymph calcium and osmolality increased with emersion time and were greatest in clams with clamped valves. Presumably, shell calcium carbonate was ...

Ammonia dynamics during and after prolonged emersion in the freshwater clam Corbicula fluminea (Müller) (Bivalvia: Corbiculacea)

Hemolymph ammonia content during emersion and ammonia fluxes on reimmersion were examined in the freshwater bivalve Corbicula fluminea (Müller). Hemolymph ammonia levels remained at pre-emersion levels over a 5-day emersion period at 25 °C, but thereafter levels increased prior to death. On resubmergence after 3 days emersion, the initial rates of ammonia excretion were low and took 15 h to reach maximum levels. Duration of emergence did not affect postemergence ammonia excretion rates in individuals emersed for less than 3–4 days. These results indicate a lack of ammonia accumulation in aerially exposed specimens. Rather, C. fluminea appeared to suppress protein catabolism during emergence and avoided ammonia accumulation. Death on emergence occurred coincidentally with an increase in ammonia accumulation. After reimmersion, the delay in development of ammonia efflux maxima may represent metabolic "switching" from catabolism dominated by nonprotein energy stores to one partially supported by protein. Suppression of protein catabolism in air is an adaptation to the prolonged and unpredictable emergence not previously reported for any freshwater species.

The Effects of Aerial Exposure and Subsequent Reimmersion on Hemolymph Osmolality, Ion Composition, and Ion Flux in the Freshwater Bivalve Corbicula fluminea

Hemolymph osmolality increased twofold after 120 h aerial exposure at 95% relative humidity and 25° C and was correlated with water loss (r = 0.83). Blood sodium and chloride levels remained approximately constant throughout the period ofaerial exposure. Calcium increased threefold over 120 h emersion and was correlated with osmolality (r = 0.86). Unmeasured solute (presumably HCO₃) also increased. On reimmersion, osmolality returned to normal within 6 h. Hemolymph sodium and chloride levels were lower than controls after 3 d exposure and returned to control levels between 2-6h reimmersion. Hemolymph potassium and calcium concentrations dropped to control levels within 6h after return to pond water. Net ion fluxes in thefirst hour ofreimmersion were high and negative. Calcium and chloride initial netfluxes were highest at-41.6± 4.0 (mean ± SEM) and -23.9 ± 3.8 μEq (g dry tissue · h)⁻¹, respectively. Sodium andpotassium net fluxes were -65 ± 2.2 and -0.9 ± 0.2, respectively. Net ion fluxes decreased and by 5-16 h were not different from zero. There was no effect of aerial exposure on unidirectional sodium fluxes. Chloride eflux increased while influx was not affected. Aerial exposure stimulated the excretion of base equivalents on reimmersion. Some sodium and chloride may shift to intracellular space during emersion and return to hemolymph on reimmersion. Calcium and its anion were mobilized, presumably from the shell, for maintenance of body fluid acid-base balance.

The occurrence of inflammatory granulomas in the ctenidial marsupium of Corbicula fluminea (mollusca: Bivalvia): A consequence of larval incubation

A number of tumor-like cysts in the ctenidia of the freshwater bivalve Corbicula fluminea are described. The cysts result from the encapsulation of incubated larvae within the female inner demibranchs which are modified to form a marsupium. Corbicula fluminea is a protandric consecutive hermaphrodite, and larval incubation commences with sex reversal and the release of the first eggs. For some reason a few of the larvae are not released, and their retention and subsequent death results in the mobilization of the innate cellular defensive mechanism of the parent. This process involves, initially, an invasion of epithelioid cells and amoebocytes (granulocytes), resulting in hyperplasia. This is followed by structural changes to the epithelium bordering the interlamellar spaces (within which the larvae are incubated) to form ultimately the cyst wall. The epithelium is surrounded externally by layers of fibrocytes which eventually form a thick capsule. The autolyzed larval tissues are themselves invaded by fibrocytes, epithelioid cells, and amoebocytes and, in one specimen, had formed a three-layered capsule within the surrounding capsule. The amoebocytes probably reabsorb the larval cellular debris. This unusual example of a molluscan cellular defensive mechanism may assist in the diagnosis and separation of hyperplastic injury responses from neoplasmic conditions in invertebrates.