It is believed that the softshell or sand gaper Mya arenaria was introduced from America in the 16th or 17th century. There is also evidence that Vikings brought this species to Europe around 1245-1295, intentionally as food or accidentally in bilge water. Because the sand gaper is able to survive in different types of environments, it has a worldwide distribution. It is a large clamp – up to 15 centimetres – which, when abundantly present, can significantly influence the environment. Because of its entrenched way of life (sometimes up to 50 centimetres deep in the soil!) its presence often remains unnoticed.
- VLIZ Alien Species Consortium http://www.marinespecies.org/aphia.php?p=sourcedetails&id=132969