Didymium spongiosum, also known as dog sick slime mold, is a species of true slime mold in the order Physarales. Before reclassification in 2023 it was known as Mucilago crustacea. Due to its visual resemblance to canine vomit, it is known colloquially as the "dog sick slime mould" or "dog sick fungus", albeit that slime moulds are not true fungi.