Caviar is the roe(魚卵), or eggs, of various species of sturgeon(チョウザメ)processed as a piquant(ピリッとする)table delicacy(珍味). Due to its high price, it is synonymous in Western culture with luxury and wealth. The best-known caviar comes from the countries on the Black and Caspian seas and the rivers that flow into them. In 2006, however, declines in sturgeon species led to a suspension(停止)of the international trade in nearly all caviar from wild Caspian sturgeon. Caviar is never served with utensils made of what material?