The piddock bores into the substrate for shelter, and lives in a tubular burrow formed by grinding the material away with hard parts of the shell by rotating on the longitudinal axis. It has been known to bore into the hard metamorphic rock gneiss, though it more often lives in softer rock. It is a filter feeder, using its siphons to reach the water outside the burrow. It was once a highly esteemed food in Europe.[2][1]
Pholas dactylus: 1. Animal in the shell a) foot b) siphons c) inhalant orifice d) exhalant orifice. 2. shell e) accessory valves or plates
It is sensitive to light, retracting into its shell when exposed to it.[3]
Pliny spoke of luminescence in the mouths of people who ate Pholas, the rock-boring shell-fish, and of such importance is this phenomenon that it is even said to have gained the first king of Scotland his throne.[4] Hippolytus of Rome tells us that it was a common pagan trick to use the luminescent property of this clam to create the illusion of burning, "And they accomplish the burning of a house, by daubing it over with the juice of a certain fish called dactylus."[5]
^[1] Author: Field Naturalists' Club of Victoria, Volume: v.21, 1904-1905, Subject: Natural history; Natural history, Publisher: [Melbourne] Field Naturalists Club of Victoria, Year: 1884, Possible copyright status: NOT_IN_COPYRIGHT, page 93
^[2] Author: Hippolytus of Rome, Refutation of All Heresies Book IV, Chapter XXXI.
