I thought that it was perhaps due to my party’s affection for twinsets and pearls, but I confess that I could not even borrow a Scottish freshwater pearl necklace or brooch for the debate—even the Mrs Carlaws could not oblige.I did not know much about the freshwater pearl mussel—which is also known as Margaritifera margaritifera—when I became species champion, but I was pleased to know that I could have got the narrow-headed ant, which was given to my colleague Jamie McGrigor.Like many people, I thought that the freshwater pearl mussel existed to produce...