恐怖寄生故事：蟲草花是 Cordyceps Flowers: A Parasitic Horror Have you ever wondered what it would feel like to be so hungry because there are parasites in your body draining all your nutrients? Imagine being so manipulated by a hidden invader that you simply couldn't stop eating, no matter how much food you gobbled down. This is how “cordyceps flowers” (蟲草花) flourish: by controlling their poor little hosts, silkworms. Next time when you are served a comforting bowl of soup with cordyceps flowers, you might want to pause and drum up the courage for the first sip. Cordyceps flowers are Cordyceps militaris, a parasitic fungus that infects silkworms [1, 2]. In a healthy silkworm caterpillar, a 12-carbon sugar called trehalose circulates through its blood. This disaccharide is formed by two glucose molecules, linked through a glycosidic bond that is different from the one in maltose. As the healthy caterpillar munches on leaves, the elevation in the caterpillar’s blood sugar level eventually signals to the brain that it is full and satisfied. However, the case is totally different in an infected silkworm. The parasitic C. militaris expresses its trehalase gene and floods the caterpillar's bloodstream with the enzyme, which acts like molecular scissors to break down the 12-carbon trehalose into two six-carbon glucose molecules. For the fungus, this glucose is a feast, allowing it to flourish inside the host. But by wiping out the trehalose, the fungus completely
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