Schelpafwijkingen bij Acanthocardia tuberculata (Linnaeus, 1758) (Bivalvia, Cardiidae) van het strand van Hoek van Holland (Laat-Pleistoceen, Eemien)

Abstract: Extensive collecting of Eemian (Late Pleistocene) specimens of Acanthocardia tuberculata (Linnaeus, 1758) (Bivalvia, Cardiidae) (total number of valves collected: 914) from dredged sediments from the Eurogeul area deposited on the beach of Hoek van Holland (The Netherlands) yielded 8 specimens (0.9%) with substantial growth abnormalities. These abnormalities are: (1) an abnormality of the posterior muscle scar (1 specimen); (2) an abnormal pattern in the ribs (3 specimens); (3) repaired damage to the umbo region (1 specimen); (4) abnormalities in adding new growth rings to the shell (3 specimens). These abnormalities are described and possible causes are considered.