
This week we are highlighting the distinctive nudibranch Peltodoris atromaculata.
A southern European species, this spotted Discodorid sea slug can be found throughout the Mediterranean and select locations off the western coast of Europe, including the Asturias, the Canary islands, Açores, Madeira, and the Strait of Gibraltar.
Inhabiting low-light rocky reef environments, Peltodoris atromaculata has a penchant for chewing on Petrosia ficiformes sponges. Once attached, the nudibranch may remain there for a couple of days, gradually scraping away areas of the sponges’ surface.

The striking coloration of Peltodoris atromaculata has earned it the nicknames “leopard slug” and “swiss cow”. Such conspicuous coloration implies, perhaps, an aposematic approach to predator deterrence and research seems to back up that assumption. Peltodoris atromaculata is capable of sequesters toxic compounds derived from its sponge prey.
Couple that with a mantle buttressed by calcareous skin spicules and it’s clear that this little nudibranch is not to be trifled with.
Being dorid nudibranches, Peltodoris atromaculata breathe via a “naked gill” plume on their backs. Known as branchial plumes, these structures are composed of fully retractible gills oriented about a central axis.


Further Reading
- Gemballa, S., & Schermutzki, F. (2004). Cytotoxic haplosclerid sponges preferred: a field study on the diet of the dotted sea slug Peltodoris atromaculata (Doridoidea: Nudibranchia). Marine Biology, 144(6), 1213-1222.
- Pawlik, J. R., Kernan, M. R., Molinski, T. F., Harper, M. K., & Faulkner, D. J. (1988). Defensive chemicals of the Spanisch dancer nudibranch Hexabranchus sanguineus and its egg ribbons: macrolides derived from a sponge diet. Journal of Experimental Marine Biology and Ecology, 119(2), 99-109.
- Wagele, H., Ballesteros, M. A. N. U. E. L., & Avila, C. O. N. X. I. T. A. (2006). Defensive glandular structures in opisthobranch molluscs-from histology to ecology. Oceanography and Marine Biology, 44, 197.
- Peltodoris atromaculata – by OPK Opithosbranquis