Accumulation of45Ca in the freshwater unionidsAnodonta anatina andUnio tumidus, as influenced by water hardness, protons, and aluminum
✍ Scribed by Pynnönen, Kirsi
- Book ID
- 102895178
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 1005 KB
- Volume
- 260
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Abstract
Previous studies have revealed that freshwater bivalves subjected to acid stress suffer from severe electrolyte imbalance. A typical initial reaction is a transitory increase in concentration of Ca in the hemolymph during the first few days of exposure to such stress. Although this calcium obviously originates from the CaCO~3~ reserves in the clam, a possible ambient origin has never been ruled out. In the present study the uptake of Ca was studied under both circumneutral and acid conditions: two freshwater unionids, Anodonta anatina and Unio tumidus, were exposed to a bathing medium that contained ^45^Ca for a period of 24 hrs. In order to study the effect of the ambient Ca concentration on the efficiency of uptake of Ca, two media with different Ca concentrations (35 and 3.5 mg Ca/1; 4 × 10^6^ cpm ^45^Ca/1 and 4 × 10^5^ cpm ^45^Ca/1, respectively) were used. The role of the ingested food as a source of Ca was evaluated by feeding the clams with algae labeled with ^45^Ca. After the clams had been exposed for 24 hrs to ^45^Ca, the accumulation of ^45^Ca in the soft parts, including hemolymph, calcium concretions and glochidial larvae, was measured. Low pH (4–4.5) significantly decreased the uptake of ^45^Ca from the medium, whereas the addition of aluminum (900 μg/1) had only a minor effect on the uptake of ^45^Ca. The sites of accumulation of ^45^Ca under acidified conditions did not change: in all cases highest values for ^45^Ca concentration were measured in the gills, where the calcium concretions sequestered a large part of the ^45^Ca. A 90% decrease in the ambient Ca concentration caused a similar decrease in the uptake of ^45^Ca. Clams were able to utilize both dietary and waterborne Ca.