- Kingdom: Animalia
- Phylum: Mollusca
- Class: Gastropoda
- Subclass: Heterobranchia
- Order: Nudibranchia
- Suborder: Dexiarchia
- Infraorder: -
- Superfamily: -
- Family: Heroidae
- Scientific name: Hero formosa
- Norwegian: -
I did not recognize this as a slug when the photo above was taken. The maximum body length is 4 cm, but is usually significantly shorter. The very branched, gill-like cerata, give an appearance similar to a small, deceased dead man´s fingers. The body color is translucent white or pale yellow or red. A white line runs along the back, from the head to the tail.
It feeds on hydroids. It probably thrives on a large variety of substrate. The observations range from the subtidal zone and down to 60 meters depth.
This species is only registered along the coasts of the British Isles and Scandinavia, from the west coast of Sweden to Troms, Norway. It seems to have become more abundant over the last decade.
The Heroidae family is currently not assigned to any particular infraorder within the Dexiarchia suborder. Genetic studies will hopefully sort this out for us. In the meantime, seawater.no present the Heroidae species together with Arminoidea species, simply by tradition.