The exotic isopod Synidotea in the Netherlands and Europe, a Japanse or American invasion (Pancrustacea: Isopoda)?

Synidotea is an invasive isopod genus in European waters. The identification of introduced populations has given rise to much controversy. Synidotea recently has been recorded from the Westerschelde estuary on the southern North Sea coast. Other records from the north Atlantic were attributed to S. laevidorsalis; the material from the Westerschelde estuary however is identified as S. laticauda.