Miriamin, a defensive diterpene from the eggs of a land slug (Arion sp.)

The eggs of the land slug Arion sp. contain a diterpene, miriamin, characte rized as a polyoxygenated geranylgeraniol derivative. In bioassays with a c occinellid beetle, Harmonia axyridis, miriamin was shown to be potently ant ifeedant, indicating that the compound plays a protective role in nature. I t is suggested that mucilaginous soil-inhabiting organisms, given their int ense exposure to pathogens and predators, may be a rich source of chemical defensive agents.