rockpools along Lyme Regis beach is the Piddock (left). This shellfish is interesting for a couple of reasons. First, it isn’t satisfied with having its own shell for protection: it also burrows into the rock for additional security! Secondly—and even more bizarrely—it exhibits the phenomenon known as bioluminescence... in other words, it glows in the dark!
Piddock shells were amongst the thousands of edible mollusc shells discovered at the Roman villa at Holcombe, about a mile outside Lyme Regis (this was the site where the Iron Age mirror was found). It’s quite common to find hoards of “used” sea-shells at Roman sites, because eating shellfish was very fashionable in those days. At Holcombe, the piddock shells were found in the vicinity of the bath-house, together with oysters, scallops and edible snails.
I came across the story of the Holcombe piddock shells in an excellent blog post by Ray Girvan, who describes how the Romans (and presumably the Romano-British) used to amuse themselves by eating the glowing shellfish while bathing at night. Pliny the Elder, in Book IX of his seminal encyclopaedia Natural History, makes two oblique references to this practice. The longer of the two, from chapter LXXXVII, is quoted in Ray’s article, while chapter LI also briefly mentions “...piddocks, which shine as if with fire in dark places, even in the mouth of persons eating them.”
We’re doing our best to produce our own photograph of a Piddock glowing in the dark... but hopefully it won’t be inside someone’s mouth!
I’m grateful to Ray Girvan for his original post and for a subsequent e-mail discussion last week, and to Marrina Neophytou (Devon County Council) and Claire Pinder (Dorset County Council) for help with the archaeological records.