The Glowing Clams of Great Britain

Where the River Lym flows into the Lyme Regis a Roman villa was discovered with shellfish shells strewn about the floor:  the remnants of a magical midnight snack.

The Pholas dactylus, or common piddok, is a strange little bivalve. The seven-inch creature slowly bores into rock, using ridges on the edge of its shell, and then spends the rest of its eight years of life never leaving its hole except when protruding a double-siphon with which it filters the tides for food particles. There is something else odd about the common piddock. It glows when you eat it.

“…If the flesh is chewed and held in the mouth, the breath becomes luminous and looks like a real flame” reads one account of eating the raw shellfish. Written about by Roman statesman Pliny, the bioluminescent bivalve made for an excellent midnight snack in an age before electricity. Late-night Roman eating raids were all the rage, with men and women covering themselves and each other in the glowing goo and filling up on fresh shellfish. Pliny wrote that the piddock “glitter both in the mouth of persons masticating them and in their hands, and even on the floor and on their clothes when drops fall on them, making it clear beyond all doubt that their juice possesses a property that we should marvel.”

Raphaà Dubois, a 19th-century scientist, did indeed marvel at them and used the piddock along with fireflies to help discover Luciferin and Luciferase, the engine and fuel involved in producing bioluminescence. Curiously, the piddock bioluminescence is now being extracted and used to help predict when people are about to become unwell. The common piddock can be found throughout the south and southwest coast of Great Britain and Ireland, as well as in the Iberian Peninsula, the Mediterranean, Black Sea, and the Atlantic coast of Morocco.

Though no late-night bioluminescent eating parties seem to currently exist, now seems a perfect time as any to start one.