Parvicardium hauniense, an endemic species to Baltic brackish water, new to the Mediterranean region

Parvicardium hauniense, a small brackish water bivalve living in the Baltic Sea and considered an endemic species for this sea, was recorded in the étang du Thau (Gulf of Lion, S. France). The ecological conditions in this étang are very different from those known from the Baltic Sea. The occurrence of P. hauniense in the Mediterranean basin suggests wide adaptation possibilities to environmental factors. Because of its occurrence in the Mediterranean basin its presence in other brackish water areas of the European coasts, as in the case of Cerastoderma glaucum, cannot be excluded.