Purple sea slug (Hypselodoris apolegma)

by B. N. Sullivan

Isn't this a pretty little critter?  It is  Hypselodoris apolegma, a nudibranch from the family Chromodorididae.  It doesn't have a standard common name, so we just call it the purple sea slug. This attractive nudibranch lives in the western tropical Pacific region.

H. apolegma feeds on sponges. It seems to prefer a dysideid sponge of the genus Euryspongia, but it may feed on other sponges as well.

Like many nudibranchs, the purple sea slug lays its eggs in a ribbon-like mass. The egg mass of H. apolegma is yellow.

The creature's striking coloration makes it an attractive subject for underwater macro photography.  I photographed this one off the northern coast of the Indonesia island of  Sulawesi, in the Celebes Sea.  This specimen was about 3 cm long (about an inch).

The species fact sheet for H. apolegma on the Australian Museum's authoritative Sea Slug Forum describes this creature's coloring as follows:
The background colour is a rich pinkish purple with a white border to the mantle. At the edge of the mantle the border is solid white but inside this is a region of varying width in which the white forms a reticulate pattern gradually merging in to the pinkish purple. The rhinophore stalks and the base of the gills is an intense purple, the rhinophore clubs and the gills are orange yellow.
Yep, that's our purple sea slug!

Visit the Hypselodoris apolegma species page on the Sea Slug Forum for more information and photos, including feeding records, mating, and the egg mass of this species.


  1. What a calming thing of beauty to come home to, after another frightening session of driving practice.

  2. I've missed your shots. I'm hoping to find more time to visit more often. I don't know if I would call it pretty but it's definitely interesting! The nudibranches I've seen are usually such pretty colors!

  3. I never thought that I would say this about a slug, but he's cute.

  4. He is a most vibrant, beautiful color! The things we miss up here on land - thanks for sharing!!

  5. Hello, ladies. Glad you all like the photo of the purple sea slug.


  6. I love the place I live, but I think your sea slugs are much more colorful. :)

  7. do these purple sea slugs eat corals?



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Bobbie & Jerry