The common piddock (Pholas dactylus) is a bivalve mollusc that bores into undersea clefts in the soft rocks of the south coast of England. It was farmed in ancient times because of its eating qualities, and two species of piddock were on the menu at a feast given by Caesar in Rome in 70BC.
Pliny the Elder described how the Romans liked to eat these molluscs while bathing in the sea at night, because of the peculiar fact that the piddock is luminous when the flesh is bruised, having the effect of rendering the diners’ faces and fingers glowing, as well as giving them luminous breath, “with the appearance of a real flame”.
Scientists in Plymouth (a husband and wife team) have recently investigated the photoprotein involved, pholasin, and have developed a test that can help predict when an individual may be about to succumb to a serious infection. Pholasin gives off light when it comes into contact with free radicals, large numbers of which are released by white blood cells as a defence mechanism when the body is challenged by infection.
The test is used when an athlete is feeling overly tired, as it can distinguish between over-exertion, in which case a reduced training programme can be prescribed, and the early signs of infection, when drug treatment may be indicated.
The British sailing team at the Beijing Olympics has been issued with the test and trained in its use. A pinprick of blood is mixed with pholasin in a test tube, and the resulting light levels emitted can be measured. The results are sent by e-mail from Beijing and analysed in Plymouth, and the laboratory then advises the team’s coaches as to the most appropriate course of action.
