From paper plates to daily contact lenses to disposable nappies, our lives are full of things that are meant to be used once and then thrown away. Thankfully, penises don’t fall into the list.

The same can’t be said for Chromodoris reticulata, a type of sea slug (or nudibranch) found in Indo-Pacific waters. It looks like a red-and-white baby’s slipper, with two tentacles on its head and a flowery set of gills on its backside. It also has the world’s only known example of a disposable penis, which snaps off every time it finishes mating. But don’t worry! It’s got spares—up to two back-up penises coiled away within its body.

Like almost all nudibranchs, C.reticulata is a hermaphrodite. Every individual is