|Rolling Cockles: Shell Abrasion and Repair in a Living Bivalve Cerastoderma edule L.
In: Ichnos: an International Journal for Plant and Animal Traces. Harwood Academic Publishers/Taylor & Francis: Reading. ISSN 1042-0940; e-ISSN 1563-5236, meer
Cerastoderma edule (Linnaeus, 1758) [WoRMS]
Shell abrasion; Cockles; Cerastoderma edule; Shell repair; Storm deposition
Live cockles were eroded from a tidal flat by a storm event and naturally transported to a nearbydike and beach. Their fate was observed regularly for two months. Some died from desiccation highon the shore, and some were consumed by oystercatchers. Others were caught by the byssusthreads of mussels inhabiting the intertidal area, while a few tried to reburrow high on the shore.These cockles were supposedly rolled while being transported to the beach and were laterobserved being rolled by the waves just below the high water line. Hence, it was concluded that theshells were subjected to abrasion and that this was the cause of the holes that some individualsdeveloped near the umbo of one or both of their (still articulated) valves. A few had repaired suchholes, supporting the hypothesis that these holes were made during rolling transportation. Similarshell assemblages of articulated cockleshells partly with subumbonal; holes were later foundelsewhere on the Wadden Sea coast of Texel. This “natural” experiment and the repair indicatedthat this abrasion occurred while the cockles were still alive, and not after their death. It may alsohelp to better discriminate between biologically and physically produced traces on shells.