Sea slugs don’t just seek out the most delicious meals; they seek out super toxic treats. They can store the toxic compounds from the sponges they eat for their own use, and new research finds that they choose to store one particularly dangerous compound more than any others.

For a study in the journal PLOS ONE, researchers from Australia and Italy collected five types of sea slugs (or nudibranchs) from reefs off the coast of Queensland, Australia, dissected the slugs, and analyzed the chemical compounds found in their bodies. They discovered that rather than storing a host of sea sponge toxins, the sea slugs largely stored Latrunculin A, a toxin that is deadly at even small doses for creatures like brine shrimp. (It’s also quite toxic to cancer cell lines, the researchers found.) There were high concentrations of this chemical in the sea slugs’ mantle, the layer of tissue that covers a mollusk’s back (mollusk shells attach to the mantle, for reference).

While scientists aren’t sure exactly how the sea slugs store these poisonous chemicals without harming themselves, the fact that they do keep a stockpile of deadly chemicals hints that predators might be able to sense this toxicity in some way and know to stay away. Further research will focus on whether the most toxic slugs are the brightest in color, and if sea slugs that aren’t colorful still have high levels of this compound.