Zilvermeeuwen dragen muiltjes naar de dijk

Among the large mussels dropped by herring gulls upon the pavement along the Wadden Sea dike (Island of Texel), I observed in October-November 2002 several slipper limpets which were apparently dropped together with the mussels to which they were attached. Those slipper limpets dislodged during dropping were consumed by the gulls. Sometimes a chain of slipper limpets attached to a living mussel was dropped, of which only the lower limpet was dislodged and eaten, the others were still alive. Barnacles settled on top of the second slipper limpet made formation of a ‘classic’ slipper limpet chain (on average 7 specimens) somewhat difficult. Moreover, small Pacific oysters ( Crassostrea gigas) had settled on top of the barnacles (Fig. 1) and slipper limpets. If such ‘symbioses’ had remained in the Wadden Sea, the oysters might have overgrown all their hosts.