Effect of some insecticides on the periodic activity of the fresh-water mussel (Anodonta cygnea L.).

The effect of the insecticides Hungaria L-7, Dimecron-50, Thimet-10 G and Satox 20 WSC containing lindane, phosphamidon, phorate and trichlorfon, respectively, as active ingredient was investigated on the survival and pumping behaviour of the fresh-water mussel Anodonta cygnea L. The shortening of active periods was used as indicator of the sublethal effects. Hungaria L-7, Thimet-10 G and Satox 20 WSC caused significant inhibition of the filtering activity, while Dimecron-50 was less effective. Fifty per cent shortening of active periods required 6 X 10-3 g/l Hungaria L-7, 8 X 10-3 g/l Thimet-10 G and 2 X 10-2 ml/l Satox 20 WSC. Thimet and Satox were lethal at 10-1 g/l and 1 m/l concentrations, respectively. Although the mechanism of the effect can be different with various substances, the results have shown, that monitoring of the activity of mussels can be a suitable test for the biological indications of water pollution.     

The role of abiotic factors and pesticide levels on enzymatic activity in the freshwater mussel Anodonta cygnea at three different exposure sites

Natural variation in abiotic factors, such as temperature and pH, probably influence the activity of enzymes used as potential biomarkers in bivalve mollusks to assess environmental contamination in the field. Changes in levels of an enzymatic biomarker may thus merely reflect natural variation in the annual physiological cycle of a species rather than exposure to contaminants. To investigate this issue, we documented the relationship between pesticide levels in water and three different enzymatic biomarkers over 1 year in enclosed populations of the freshwater unionid mussel Anodonta cygnea at three different sites of exposure. We considered the natural variation in temperature, pH and dissolved oxygen over the year and across the different sites as a potential correlate of enzymatic activity to disentangle the relative contribution of abiotic factors and pesticide levels. Pesticide levels varied among the three sites and over the course of the year. Catalase (CAT) and acetylcholinesterase activity (AChE) varied as a function of abiotic factors but showed no relation to pesticide levels. Glutathione S-transferase (GST) activity was also related to abiotic factors but also decreased with increases in total pesticide levels. The lack of activity induction or inhibition by pesticides and the natural variation in abiotic factors among sites and across time limits the use of CAT and AChE to assess environmental contamination in this species.     

Light and Electron microscopic autoradiography of 3H-dopamine uptake in the ganglia of the freshwater mussel, Anodonta cygnea L

In the central nervous system of the freshwater mussel, Anodonta cygnea, uptake of 3H-dopamine has been investigated by light and electron microscopic autoradiography following in vitro incubation and topical application, respectively. The autoradiographic reaction observed over the ganglia can be taken as a morphological evidence of the existence of a specific uptake mechanism for dopamine. It has been found that labeled dopamine was taken up by the axon profiles and terminals, while perikarya remained free of activity, indicating a basic difference between the perkaryal and axonal membrane in respect of the 3H-dopamine uptake. According to the electron microscopic autoradiography, labeled terminals and axon profiles contained both normal and accentric dense-core vesicles and they proved to be similar to those seen after 3H-serotonin in vitro incubation. Therefore, it seems possible that certain Anodonta central neurons contain both dopamine and serotonin.     

Factors affecting the heart activity and blood pressure of the swan mussel Anodonta cygnea.

1. The rate of heart beat increased with temperature and was three times as high in the active as in the inactive animal. 2. The rate of shell valve movement rose and the rate of heart beat fell when the foot was extended. 3. The rates of heart beat and shell valve movement decreased when the water was saturated with carbon dioxide. This heart response remained when the visceral ganglion was destroyed. 4. Ventricular contraction occurred simultaneously over the shole chamber. The passage of blood into the posterior aorta could be restricted by the protuberances on its wall. 5. Pericardial cavity pressure rose by about 5 cm H2O at shell valve adduction and 0-25--0-6 cm H2O at ventricular diastole. 6. Pulse pressure changes of 0-25--0-6 cm H2O occurred in the auricle and 1--3 cm H2O in the ventricle and anterior aorta.     

Mineral composition variation in the shells of freshwater mussel Anodonta woodiana at different growth stages

The levels of mineral element Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Mo, Al, As, Ag, Cd, and Tl were quantified in the whole shells of the freshwater bivalve Anodonta woodiana at three different growth stages (i.e. J1 juveniles of 1 month old, J2 juveniles of 3.5 months old, and adults of 36 months old). The concentrations of Na and Al were different between different growth stages (p < 0.05). The highest Na concentrations (2715 ± 86 μg/g dry weight) were found in J2 juveniles. The highest Al concentrations (303.9 ± 5.95 μg/g dry weight) were found in J1 juveniles. Manganese concentrations (517.0 ± 47.98 μg/g dry weight) were significantly higher in J2 juveniles than in J1 juveniles (432.3 ± 9.87 μg/g dry weight) (p < 0.05). Copper concentrations (27.32 ± 0.15 μg/g dry weight) were significantly higher in J1 juveniles than in J2 juveniles (26.21 ± 0.86 μg/g dry weight) and adults (24.74 ± 1.43 μg/g dry weight) (p < 0.05). Burdens of Na, Ca, Mn, Fe, Co, Cu, Mo, Ag, and Tl were positively correlated with the shell length (p < 0.05). These findings can possibly contribute to an understanding of elemental requirements for shell growth and, hence, facilitate improvement of survival and growth rates during artificial mussel culture.     

Growth and age structure of the swan mussel Anodonta cygnea (L.) at different depths in lake Mattsee (Salzburg, Austria)

Unionid clams were collected at 1–2 m, 3–4 m and 6–7 m depth in lake Mattsee, a moderately mesotrophic lake, to investigate the effect of depth on clam growth and age structure. No significant differences in age structure of Anodonta cygnea were found (p=0.65). Three and ten years old clams were present at all depths, but in different percentages. Whereas at 1–2 m 13.3% of the collected clams were <4 years old, this percentage was 4.4% at 6–7 m and 7.1% at 3–4 m. A greater percentage (6.7%) of older mussels (9, 10 years) were collected at 6–7 m than at 1–2 m (2.2%). Growth declined with depth. Total length at a given age of clams at 1–2 m and 3–4 m did not differ (p=0.54), whereas differences were significant between clams at 1–2 m and 6–7 m (p<0.05) as well as between 3–4 m and 6–7 m (p<0.05). The Growth constant k was highest at 1–2 m depth.     

Ultrastructural effects of 6-hydroxy-dopamine and 5, 6-dihydroxytryptamine on the central nervous system of fresh-water mussel, Anodonta cygnea L

Ultrastructural effects of 6-hydroxydopamine and 5, 6-dihydroxytryptamine treatments were investigated in the central nervous system of fresh-water mussel. Two days after the treatments, the following characteristic find-structural alterations could be observed in the neuropil of the ganglia: frequent occurrence of multilamellar bodies, lysosomatic structures and elongated tubular forms; shrinking of varicose axon profiles with an enchancement of the density of the axoplasm and clumping of its content; abnormal swelling of certain axons in the neuropil. This degenerative process was accompanied by an intense phagocytosis. The damages evoked by the employed "false transmitters" in the mussel ganglia were, in general, similar to those found in vertebrates. Statistical analysis of the vesicle population of ganglia suggests the intragranular uptake of 6-hydroxydopamine and 5, 6-dihydroxytryptamine and, in addition, the role of dense-core vesicles of different types in the storage of both serotonin and catecholamines. Perikarya composing the cortical layer of the ganglia were not affected by the "false transmitters". This shows that different parts of a mussel neuron are differently sensitive to 6-hydroxydopamine and 5, 6-dihydroxytryptamine.     

Changes in gape frequency, siphon activity and thermal response in the freshwater bivalves Anodonta cygnea and Margaritifera falcata

Physiologically-driven rhythms in bivalve molluscs are predictedto vary as a function of metabolic rate and temperature, incontrast to genetically predisposed biological clocks. Theserhythms can be evaluated using long-term video monitoring techniquesunder controlled conditions in laboratory aquaria. The bivalvesAnodonta cygnea and Margaritifera falcata were used to evaluatethe effect of temperature on rhythms in gape and the formationof siphons at the mantle edge. Frequency and duration of shellclosure vary with temperature in both species, but with differentresponses. Mean duration of intervals of valve closure decreasesas temperature rises in both species, and is consistent withphysiological limitation by increased biological oxygen demand.For A. cygnea, cumulative gape duration peaks at 25°C, withless time spent closed than at any other temperature, but increasingtemperatures correspond to an increase in gape frequency witha strong increase observed at 31°C. In contrast, frequencyof adduction and valve closure peak at 25°C in M. falcata,and continuous gaping is observed above 29.5°C. This physiologicalstress is consistent with evidence from sclerochronologically-calibratedstable isotope studies of shells, where growth breaks in manymarine taxa coincide with maximum temperatures above 31°Cas derived for ¹⁸O_carbonate. The results of this study suggestthat these growth breaks may be due to physiological limitationsin oxygen uptake and metabolic activity, rather than being adirect consequence of elevated temperature alone. (Received 17 March 2008; accepted 3 October 2008)     

An electron microscope study of the formation of the periostracum in the freshwater bivalve, Anodonta cygnea

The periostracum and cells lining the periostracal groove of Anodonta cygnea L. have been studied at the electron microscope level. The cells lining the inner face of the outer fold differ in fine structural details, five cell types being recognized. Along the length of the outer surface of the middle fold, to which the periostracum is closely applied, only two cell types are evident. At the base of the periostracal groove the two epithelia are separated by a bulbous region containing a group of basal cells which initiate the periostracum. The periostracum, which is homogenously electron-lucid, originates in the intercellular space between a basal cell and the first cell of the middle fold. It increases in thickness in the periostracal groove due to the secretory activity of the different outer fold cells. The cells of the middle fold do not appear to be involved in periostracum formation.     

Heart action of the freshwater bivalve Anodonta anatina during activity.

1. Heart action of Anodonta anatina (L.) was investigated by recording the electrocardiogram (ECG), heart impedance, and ventricular and pericardial cavity pressure during different aspects of the normal behaviour. The contribution of mechanical and nervous mechanisms in controlling changes in heart action is discussed. 2. Pressure recordings were generally more reliable than the other methods and it is suggested that pericardial pressure pulses indicate the stroke volume output of the ventricle. 3. During spontaneous periods of prolonged shell closure there was an initial small increase in heart activity followed by a large reduction in both heart rate and systolic pressure, indicating that total heart output was considerably reduced. When the shell reopened, heart rate increased very rapidly with an initial overshoot of the normal level; systolic pressure increased more slowly with no overshoot. 4. These major changes in heart activity appear to be associated with respiratory changes and are controlled largely by the nervous regulatory system, but some minor rhythmic variations in the amplitude of heart beat are probably caused by mechanical factors. 5. Characteristic patterns of change in heart action were recorded during burrowing. These appear to result from haemodynamic changes associated with the muscular movements of the digging cycle. Control of the heart by the nervous regulatory system is apparently of much greater importance in relation to respiratory control than in relation to the haemodynamic functioning of the fluid-muscle system in locomotion.     

Monoamine precursor uptake in ganglia of a mollusc Anodonta cygnea L. (Bivalvia)

Summary In vitro-uptake and localization of ³H-5-hydroxytryptophan and ³H-dihydroxyphenylalanine have been investigated by means of light microscopic autoradiography in the central nervous system of the freshwater mussel, Anodonta cygnea L. Accumulation of the labelled monoamine precursors could be observed both over neuronal perikarya and neuropil in the ganglia. ³H-5-hydroxytryptophan and ³H-dihydroxyphenylalanine were taken up by neurons characterized by a small size (10–20 m), a polygonal form and an intense staining with toluidine blue. Labelled axon branches situated either in the neuropil or between nerve cells in the cortex exhibited only a moderate activity, frequently of a diffuse character.After pretreatment for 24 h with colchicine, silver grains were also seen over the neuronal perikarya and some axon profiles. This shows that local uptake of the monoamine precursors and, presumably, the synthesis of the monoamines takes place both at perikaryal and axonal/terminal level.The nerve cells accumulating the monoamine precursors contain a nucleus with rich chromatin content and a deeply invaginated nuclear envelope. Further ultrastructural characteristics of these neurons are their well-developed rough endoplasmic reticulum system, a great number of mitochondria and glycogen granules, and the presence of dense-cored vesicles of different types. All these features are responsible for the electron-dense appearance of the cytoplasm.     

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

1. Microsomal preparations from the gills of the freshwater mussel anodonta cygnea cellensis show Mg2+ -dependent Na+ - or K+ -stimulated ATPase activity, which is not inhibited by ouabain. 2. Na+ - or Ka+ -ATPase activity is decreased by Ca2+, acetylcholine, choline, and tetramethylammonium, but slightly increased by ethyl alcohol. 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.     

Bioaccumulation and toxicity of aluminium in the pond snail at neutral pH

The low solubility of aluminium (Al) at neutral pH means that it largely exists as colloidal particulates in aquatic systems. However, the pond snail Lymnaea stagnalis accumulates significant amounts of Al following exposure to water containing added Al (up to 500 microg l(-1)) at pH 7. This is accompanied by depression of behavioural activity (locomotion, feeding) which subsequently recovers, suggesting tolerance to the metal. The presence of silica ameliorates behavioural toxicity of Al, but does not prevent uptake of the metal. In vitro studies using the isolated central nervous system demonstrate toxicity at the cellular level. Extracellular application of Al (100 microM) led to membrane depolarisation, bursts of action potentials and action potential broadening. The chemical form in which Al is applied influences the extent of bioaccumulation and toxicity. Detailed knowledge of its solution chemistry is therefore essential.