Farms often use tiles as the foundations of their beds, but when given a choice spat seem to prefer oyster shells.

ECONOMIST: A dozen ocean-cleaners and a pint of Guinness, please

Having found one, it grows into a spat, which when seen beneath a microscope already resembles a tiny oyster, with the shape of a shell already visible.

ECONOMIST: A dozen ocean-cleaners and a pint of Guinness, please