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Invertebrate of the Week #16 – Peltodoris atromaculata

Peltodoris atromaculata
Peltodoris atromaculata. Source:

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, P. atromaculata is known for its penchant for Petrosia ficiformes sponges.  Once attached, the nudibranch may remain there for a couple days, gradually scraping away areas of the sponges’ surface.

Peltodoris atromaculata.  Photo: MassimoCapodicasa
Peltodoris atromaculata. Photo: MassimoCapodicasa

The striking coloration of P. atromaculata has earned it the nicknames “leopard slug” and “swiss cow”.  Such conspicuous coloration suggests an aposematic approach to predator deterrence and research seems to back up that assumption by demonstrating that P. atromaculata is capable of sequestering toxic compounds derived from the sponge prey.  Couple this with a mantle buttressed by calcareous skin spicules and it’s clear that this little nudibranch is not to be trifled with.

P. atromaculata branchial plume.  Photo: Phillipe Guillaume
P. atromaculata branchial plume. Photo: Phillipe Guillaume

Being dorid nudibranches, P. atromaculata breathe via a “naked gill” plume on their backs.  Known as branchial plumes, these structures are composed of fully retractible gill leaves oriented about a central axis.

Peltodoris atromaculata.  Source:
Peltodoris atromaculata. Source:
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
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