Gills Of Freshwater Mussels Research Articles

Calmodulin‐like calcium‐binding protein identified in calcium‐rich mineral deposits from freshwater mussel gills

AbstractExtracellular calcium concretions found in the gills of freshwater unionids are largely inorganic, containing calcium and phosphate. The organic fraction of the isolated concretions accounts for 25% of their dry weight as determined by ashing. The organic fraction of isolated concretions was examined using SDS‐polyacrylamide electrophoresis. The concretion fraction is separated into 13–14 protein bands. These bands can be further differentiated into EDTA soluble proteins and insoluble core proteins. One of the soluble proteins has a molecular weight of approximately 17,000 daltons (Da) and comigrates with authentic vertebrate calmodulin. The 17,000‐Da concretion protein cross‐reacts with sheep IgG prepared against bovine brain calmodulin as shown by immunoblot. Rabbits and mice, challenged with the entire concretion organic fraction, produce an IgG fraction which always recognizes an epitope of the 17,000‐Da protein as the major antigenic determinant. This same protein is also a calcium binding protein as shown by 45Ca autoradiography even after heat and SDS/mercaptoethanol treatment. To determine that this protein was not bound to the concretions as an artifact of the isolation procedures, immunocytochemical procedures were used to localize the antigenicity to 17,000‐Da and vertebrate calmodulin in situ. Immunocytochemical localization indicates the protein is present on the concretions in situ but documents that the majority of this protein is located in concretion‐forming cells. Electron microscopic immunocytochemistry demonstrates that the protein is found largely in early concretion‐forming cells in protein granules formed before concretion architecture is observed. This may imply that the protein is likely important in the initiation of concretion formation, and is only a residual protein as found on the extracellular concretions.

Maternal calcium contribution to glochidial shells in freshwater mussels (Eulamellibranchia: Unionidae)

AbstractPrevious work has demonstrated that calcium concretions, located in the gills of freshwater mussels, disappear during the reproductive season. While calcium is being mobilized, there is no increase in calcium content in the blood. The current study documents the passage of maternal calcium to glochidia, for the production of calcium carbonate shells while the larvae are brooding in the water channels of the lateral gills; 45Ca was injected into Anodonta grandis 2 mo before the onset of reproduction and the label was distributed through the animal but was concentrated largely in the calcium concretions. Following glochidia development, 45Ca was found incorporated in the shell of the embryos. To determine the extent of the maternal passage of calcium to the embryos, Ligumia subrostrata containing embryos undergoing shell formation were exposed to 45Ca, either by injection into the blood or by inclusion of label in the bathing medium. The amount of label found in the developing glochidia is proportional to the 45Ca content in the blood of the maternal animal. Isolated glochidia directly exposed to label will adsorb 45Ca onto their shells, but there is little addition of label to glochidia in intact maternal gills during the bath exposure experiments. The results indicate that the maternal contribution of 45Ca is over 90%, with direct contribution from the bathing medium accounting for less than 8%. These results indicate that the branchial water channel in which the embryos are developing is isolated from bath 45Ca. This study presents morphological evidence that the physiological isolation of glochidial shells from bath 45Ca is due to a rearrangement of water channel morphology, and that the chamber, in which the embryos develop, has no contact with the bathing medium.

Seasonal Changes in the Lipid Composition of Gill Tissue from the Freshwater Mussel Carunculina texasensis

The lipid composition of gill tissue from the freshwater mussel Carunculina texasensis was determined. Particular attention was paid to the distribution of arachidonic acid, because the arachidonic acid metabolite prostaglandin E2 appears to be involved in the regulation of Na uptake by gills of freshwater mussels. Arachidonic acid is the most abundant fatty acid in the phospholipid fraction of gill tissue, but it is not prevalent in the neutral lipid fractions. In contrast with marine molluscs, in which fatty acids of the n-3 family predominate, fatty acids of the n-6 family predominate in the phospholipid fraction from C. texasensis gills. The effects of season on lipid composition also were investigated. Gill tissue from mussels collected in winter contained higher proportions of polyunsaturates and lower amounts of saturates than did gill tissue from animals collected in summer. The percentage of arachidonic acid, however, was uniformly high throughout the year, suggesting that this fatty acid serves an important function in which precursor stability is required. Seasonal alterations in the proportions of free sterols and triglycerides and in the phosphatide composition were observed. The functional significance of the various changes is not known, but they may be related to some of the aspects of gill function other than ion regulation.

Glucose metabolism in hepatopancreas and gill of Lamellidens marginallis during methyl parathion toxicity

Changes in glucose metabolism were studied in hepatopancreas and gill of freshwater mussel, Lamellidens marginalis, exposed to a sublethal concentration (8 ppm) of methyl parathion. A slight decrease in glycogen and pyruvate and an increase in lactate levels were observed. An increase in phosphorylase and aldolase suggested increased formation of trioses during methyl parathion toxicity. The decrease in lactate dehydrogenase activity and increase in lactate content indicated reduced mobilization of pyruvate into the citric acid cycle. Glucose-6-phosphate dehydrogenase activity was increased, suggesting enhanced oxidation of glucose by the HMP shunt pathway. Citric acid cycle enzymes such as isocitrate, succinate, and malate dehydrogenases were found to be decreased, suggesting abnormality in mitochondrial oxidative metabolism as a consequence of methyl parathion toxicity. The decreased cytochrome c oxidase and Mg 2+-ATPase, apart from citric acid cycle enzymes, indicated impaired energy synthesis as a result of reduced aerobic oxidation of glycose. The increase in acid and alkaline phosphatase activities suggested enhanced breakdown of phosphate to release energy in view of inhibition of the ATPase system during methyl parathion stress. The changes were more pronounced in hepatopancreas as compared to gill of mussel exposed to methyl parathion.

Ion-stimulated ATPase activity and NaCl uptake in the gills of freshwater mussels

Microsomal membranes prepared from gills of the freshwater mussel Carunculina texasensis contain HCO3− ATPase, Cl−–HCO3− ATPase, and Na+–K+ ATPase activity. The HCO3− ATPase activity displays saturation kinetics with a Vmax of approximately 10 μM P/mg protein∙h−1 and an affinity of 5 mM HCO3−. The HCO3− ATPase can be stimulated by the addition of 1 mM Cl−, but it is inhibited by > 3 mM Cl− and by SCN−. The gill tissue ouabain-sensitive Na+–K+ ATPase activity represents approximately 1.5 μM P/mg protein∙h−1, which is low compared with the Mg2+ ATPase activity (12 μM P/mg protein∙h−1). We present preliminary evidence that the gills in freshwater mussels are a major site of Na+ and Cl− accumulation.

ATPase stimulated by Na + or K + in gills of the freshwater mussel Anodonta

1. 1. Microsomal preparations from the gills of the freshwater mussel Anodonta cygnea cellensis show Mg 2+-dependent Na +- or K +-stimulated ATPase activity, which is not inhibited by ouabain. 2. 2. Na +- or K +-ATPase activity is decreased by Ca 2+, acetylcholine, choline, and tetramethylammonium, but slightly increased by ethyl alcohol. 3. 3. It is tentatively suggested that Na +- or K +-ATPase is involved in the mechanism of active monovalent cation uptake through the gills of freshwater mussels.

Histochemical studies on the mucosubstances in the gill of fresh water mussel, Parreysia corrugata var. nagpoorensis (Lea)

The present paper deals with the characterisation and distribution of the mucosubstances elaborated by the gill in fresh water mussel by employing recent well-established histochemical techniques. The results showed that the gill secretes the mucosubstances consisting of neutral mucins, sulfomucins, sialomucins and atypical high pH azurophilic mucosubstances having alcianophilia at pH = 5.6. Hyaluronic acid could not be detected. The importance of these mucins is discussed with reference to feeding.

Ionophore-mediated calcium entry induces mussel gill ciliary arrest.

Lateral cilia of freshwater mussel gills, which normally beat with metachronal rhythm, are arrested pointing frontally by perfusion with 6.25 to 12.5 millimolar calcium and 10(-5) molar A23187, a calcium ionophore. Arrest does not occur in either calcium or ionophore and monovalent cations alone. Activity returns with continued perfusion in potassium chloride or calcium chloride, and more slowly in sodium chloride, after removal of ionophore. These results support the hypothesis that a local rise in internal calcium causes ciliary arrest.

Thermal resistance acclimation of ciliary activity in the gills of fresh water mussels Anodonta anatina and Anodonta cygnea

1. Thermal resistance and thermal resistance acclimation of ciliary activity as well as the effect of acetylcholine, choline and tetramethylammonium on the thermal resistance of ciliary activity was studied in the isolated surviving gills of fresh water mussels Anodonta anatina anatina and Anodonta cygnea cellensis collected from Northern Germany. 2. No thermal resistance acclimation of ciliary activity was found in the gills of A. anatina, but in the gills of A. cygnea it appeared in 1 day when gills were kept at 4 or 24°C. 3. Acetylcholine, choline and tetramethylammonium prolonged the thermal resistance times of ciliary activity in the gills of both species. 4. Atropine added to the acclimation medium reduced the longer resistance times of warm-acclimated gills to the value of colf-acclimated gills in A. cygnea.