Risbecia imperialis
(Pease, 1860)

Photographed by: Pauline Bosserelle
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Subclass: | Opisthobranchia |
| Order: | Nudibranchia |
| Suborder: | Doridina |
| Family: | Chromodorididae |
| Species: | Risbecia imperialis |
Comment from Richard Willan on photo #4615
At present this individual would have to be classified as Risbecia godeffroyana simply because it does not come from Hawaii. However, in lacking a strong pink suffusion over the central area of the mantle, in having dark blue-black ‘tongues’ laterally and in having only a few orange spots inside these ‘tongues’ it would qualify as Risbecia godeffroyana on its appearance. So in my opinion, this animal (and plenty of other intermediates like it) shows there is insufficient colour differences to separate Risbecia imperialis and Risbecia godeffroyana, and they should be synonymised. In that case, the name Risbecia imperialis must apply because it is the older name.Comment from Richard Willan on photo #1682
I would have identified this nudibranch as Risbecia godeffroyana too if I didn’t know where it was from. But because it comes from Hawaii and because nobody has studied the comparative anatomy of that species and compared it with specimens from the western Pacific Ocean (presently called godeffroyana) and hence concluded they are separate or different species, then we are obliged to call it R. imperialis for now. In fact, if they are the same species, then it will have to take the name R. imperialis anyway because imperialis was published in 1860 and godeffroyana in 1877.Locality:
- USA
- Oahu, Hawaii (5) May, Jun, Dec
- Maui, Hawaii (1) Sep
- Kenya
- Malindi (3) Aug, Sep
- Kilifi Creek (2) Aug, Sep
- French Polynesia
- Taha'a (1) Mar
Pictures of Risbecia imperialis
Similar Species
Author: Richard Willan
I would have identified this nudibranch as Risbecia godeffroyana too if I didn’t know where it was from. But because it comes from Hawaii and because nobody has studied the comparative anatomy of that species and compared it with specimens from the western Pacific Ocean (presently called Risbecia godeffroyana) and hence concluded they are separate or different species, then we are obliged to call it Risbecia imperialis for now. In fact, if they are the same species, then it will have to take the name Risbecia imperialis anyway because imperialis was published in 1860 and Risbecia godeffroyana in 1877.