Side-gilled slugs are often hard to notice . They tend to be nocturnal and hide under rocks, in the sand or in side crevices during the day. Some of them also look a LOT like sponges, lie flat and inconspicuous until disturbed, and generally have a rubbery texture. Their gills are, as their name suggests, found on the left side of their body, but the plumage is concealed between the mantle and the foot. Their most identifiable feature is their rolled rhinophores that appear tube-like. It’s often possible to see a small shell through their mantles as well as some internal organs. Thus far, we have only found six different species — one rolling about and swimming off the bottom (Euselenops luniceps) and the other five at the edge of rocky reefs, lagoons or protected surge zones.
