River pearl oyster

River pearl oyster (Margaritifera of margaritifera), the sufficiently important representative of fresh-water mollusks, only from the mollusks in Latvia, who is capable to form pearl. (Shell of adult mollusk it has a length of approximately 10 c[m].). In all probability, in 16-18 centuries the valuable pearls, obtained from the Latvia rivers, was supplied to the highest courts of Sweden and Russia. The intensive catching of pearls in the ancient times and the pollution of rivers during our days they became the reason for the extinction of river pearl oyster not only in Latvia, but also in entire Baltic sea. By Wednesday the inhabiting of river pearl oyster are presented special requirements - oligotrophic type small fast flowing rivers with the cold water, the sandy bottom of river without the silt and the algae, and also the covered with forest shore. Are at present in Latvia known only five rivers with the bottom, which is suitable for the cultivation of pearls. In the last 100 years their quantity was reduced five. Latvia is unique fact that river pearl oyster here it was preserved in the plains rivers, while in other places these forms can be revealed only in the clean mountain rivers. This is one additional proof of the fact that the environment of Latvia is less contaminated than in the majority of the countries of Europe. Amphibious The amphibious include frog, toad and the tritons. These essences are conducted in the abundance. Frog concert is in spring almost from each reservoir audible; in summer toad and tritons hunt for the insects and the mollusks, and in the shoal other tritons are heated in the sun. The presence of amphibious also testifies about the quality of environment, since they avoid the contaminated regions.