Chromodoris orientalis from Sth Korea

April 2, 2007
From: Kevin Lee

Hi Doc,

Recently, I was in South Korea on a business trip and, afterwards, took off a few days to meet and dive with Dr. Dong-Bum Koh, off Jeju Island. All this thanks to connecting with him via the Sea Slug Forum!

Diving Jeju (my first time) was great and I was surprised by the semi-tropical nature of the fauna there. On my first dive, I photographed five species of slugs.

Locality: Mun-Som Islet, 30 feet, Jeju Island, South China Sea/Yellow Sea, 19 March 2007, algae covered rocky substrate. Length: approx. 1.5 inches. Photographer: Kevin Lee.

Curious if the two slugs shown here are both Chromodoris orientalis, as one has round, evenly distributed black spots, whereas the other looks very similar but is covered with a lot of black streaks and blotches, in addition to the round spots. Also, I include an associated, perhaps mimic, flatworm [lower photo ].

Again, thanks for a great forum thru which I've made a nice connection and friend.


Kevin Lee, 2007 (Apr 2) Chromodoris orientalis from Sth Korea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Kevin,

I am glad the Forum has been a way to make new friends as well as see new slugs. I think this is the first time I have seen an example of C. orientalis with such a streaky black pattern. We don't know that much about this species, so its a useful bit of new information. When looking at similarly coloured animals like this, I tend to look for some other feature of the colour pattern to link them or separate them. For example, in both your specimens the translucent white gills have an orange-yellow line along the outer edge and a black one along the inner edge. This is a very unusual colour pattern which suggests to me that the two are the same species. If you look at other photos of this species on the Forum you will see that the black lines are sometimes brown, and sometimes absent. It's one of those characters whose presence can give you a positive identfication, but whose absence can't really be used.

I would very much like to get photos of this animal laying eggs. As I mention earlier [message #5172], there are reports that it lays a flat egg-ribbon, but on the Forum we have photos of it with a ribbon apparently attached along one edge. It would be valuable to clarify this. It would also be nice to know what type of sponges it feeds on as well. 

Thanks also for the flatworm photo. There are a lot of flatworms which look remarkably like particular nudibranchs, but as you suggest, we can't always be sure they are real mimics

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Apr 2). Comment on Chromodoris orientalis from Sth Korea by Kevin Lee. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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