Automatic recording of the radular activity of dogwhelks (Nucella lapillus) drilling mussels (Mytilus edulis)

The radular activity of dogwhelks, Nucella lapillus, drilling mussels, Myti lus edulis, was monitored by piezoelectric transducers and recorded by an a utomatic digital system. In this way, for the first time, the drilling beha viour of dogwhelks was analysed in detail. Radular activity was similar to that previously recorded for limpets, each radular stroke (rasp) being form ed by a sequence of 1-8 unit events, each probably corresponding to the app lication of one row of radular teeth on the substratum. During drilling, ra dular rasping followed a consistent pattern, each bout of radular rasping ( lasting about 6-8 min) being followed by a period of radular inactivity (la sting about 35 min), when chemical dissolution is probably applied. The per iodicity with which rasping was applied decreased during the drilling seque nce (from about 25 min in the first quarter of the drilling process to abou t 40 min in the last quarter), together with a decrease in the rasping rate , i.e. number of radular rasps per min (from about 12 to about five rasps p er min). Accordingly the total number of radular rasps recorded during the first quarter of the drilling time was higher than during the other quarter s (from about 3000 to about 500 rasps). The role of the radula in shell pen etration was therefore rather extensive, accounting, during the first quart er of the process, for about 34% of drilling time. The results are discusse d in relation to studies of chemical dissolution and mussel shell ultrastru cture.