Intersex and sterility in the periwinkle Littorina littorea (Mollusca : Gastropoda) along the Western Scheldt estuary, the Netherlands

In this study we present the results of an intersex survey of Littorina lit torea along the heavily polluted Western Scheldt estuary (the Netherlands), and record for the first time the intersex phenomenon in L. littorea from Dutch waters. Intersex differed significantly between localities and was th e highest in the vicinity of the harbours of Antwerp and Vlissingen, as ref lected by the ISI distribution along the estuary. In contrast, sterility di d not differ significantly between the different sites, but nonetheless, fo llowed the ISI distribution as well, ranging from 0 to 33%. Despite the cur rent ISI levels are high (maximum = 1.26), they are still much lower than t he ISI levels reported for L. littorea in some German harbour areas. (C) 20 01 Elsevier Science Ltd. All rights reserved.