Sea Slug Atlas

  • SeaSlugAtlas Logo v1 text.png

Sea Slug Atlas – mapping the distribution of our marine Nudibranch species:

The Sea Slug Atlas aims to map where our Nudibranchs occur. It is geared towards the diving and fishing fraternity and the aim is to obtain records of any Seaslug from anywhere: the deep sea, the nearshore and the coastal and coral reefs.
Simply photograph your Seaslug and upload to iSpot. The more observations we get the better our maps will be. We will be organizing Sea Slugging contests, Dives and Sea Slug Shootouts.

The Sea Slug Atlas is a SeaKeys initiative.

If you are participating in this Atlas, please request a Sea Slug Atlas badge here: Badge Please. You will need to submit 10 observations on iSpot to be eligible.

Please tag your Sea Slug Atlas observations with the tags "SeaKeys" or "Sea Slug Atlas" as you prefer (preferably both: separated with a comma).

If you have any queries, tips or comments, please post them below!

Latest Observations - Sea Slug Atlas:

(see in browse format or send link:

Latest Observations - SeaKeys:



250 observations!!

Scope of the atlas

We need a scope definition. I am assuming that any marine heterobranch molluscs in clades Cephalaspidea, Aplysiomorpha, Sacoglossa, Pleurobranchiomorpha and Nudibranchia are included, and that the geographical range includes South Africa, Namibia and Mozambique.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)

We now have a scope definition!

Well it seems that you have defined it. We now have a scope!

Subject to amendment

It will do for now. May need tweaking at some stage.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)

I don't know

I don't know how that got duplicated.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)

Scope of the atlas

As I am not a scientist but an "enthusiast", and assuming that there are others like me, it would be very helpful if the scope of SeaKeys as well as Sea Slug Atlas and Sea Coral Atlas were defined in terms of the generally used guide to marine life, " Two Oceans " by Branch, Branch, Griffiths and Bechley; i.e. in terms of page 11 headed "Classification System".

Chris Wahlberg
beach walker.


Seakeys: anything from the sea: i.e. anything in 2O (our abbreviation for Two Oceans, usually followed by the publication date, just so we know which edition you are using).

Sea Slug Atlas: any Nudibranch - i.e. member of the Mollusca > Gastropoda > Opisthobranchia
(or see on iSpot ) or pp 172-180 or pl 81-85 of 2O(2007)

Sea Coral Atlas: any Coral - i.e. member of Class Anthozoa - excluding Anemones
(or see )
or pp 16-30 or pl 5-12 of 2O(2007)

But I would strongly recommend that if your enthusiasm extends to the underwater, that you invest in:
King & Fraser. 2014. The Reef Guide. Struik


Thanks. However under Sea Coral Atlas your scope above specifically says excluding Anemones whereas in fact most Anemone ID's include the tag of Sea Coral Atlas. Is this just an error on the part of whoever has done the post?.

Sea Corals

Obviously, some people disagree with me.
But then I am just curator: it is up to the organizers to decide.

I guess one could interpret it to be all species that occur in corals, but that is not what I understood.

If the organizers are happy to include anemones as "very soft" corals, then who am I to disagree.

Sea Coral Atlas scope

To quote the SeaKeys page:

"this will target hard, soft and black corals, seafans, soft corals and even anemones"
I assumed this is official and have been uploading accordingly, although it does stretch the scope of corals beyond what I would consider normal usage.
There are also a few hydroids commonly grouped with sea fans or hard corals.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)

Sea Coral Atlas scope

Peter, thanks for this. Would zoanthids be included as well?.

I would think so

as they are closely related to sea anemones and there is no obvious reason to exclude them. So probably all Anthozoa and the few Hydrozoa that look like corals, such as Stylaster and Solanderia.
This is just my best guess. There is no project coordinator yet that I know of and already 924 observations.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)


988 for Sea Slug Atlas

1117 Sea Fish Atlas


3503 Seakeys observations

Tags for Sea Slug Atlas

In addition to the usual SeaKeys and Sea Slug Atlas tags, please tag with Eggs if there is a sea slug egg ribbon in the photo, and Mating pair if you are fairly certain there is a mating pair in the photo.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)


Thanks! Totally agree!

Sea Slug Shootout!!!

Cape Town Dive Festival 2014

2nd & 3rd May

Seaforth Beach, Simon’s Town

More info at

what species is this?

Did we ever get an ID for the logo?

This - made me think of it.

Any better fits than Chromodoris westraliensis

And why is Chromodoris westraliensis not in our dictionary?

Irididoris hypotheticus

Based on the outline of a chromodorid, but the colours and pattern are loosely based on the SA flag like the Sea Fish Atlas logo.
C. westraliensis is a Western Australian nudibranch not known from this side of the Indian ocean. I have entered a few Australian onservations, as we are supposedly going international some time and I have a quite a lot of identified and geolocated Australian and
s New Zealand photos I took on the Reef Dragon cruise for Reef Life Survey.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)

Blown away

by the diversity!

Occasional Hungarian princess who believes: Indigenous plants have every aspect covered

Some local References

D King & V. Fraser 2014. The Reef Guide (fishes, corals, nudibranchs & other invertebrates) E & S Coasts of s Afr. Struik Nature.
(I guess this is the one with the most comprehensive reference list).

G Zsilavecz 2007. Nudibranchs of the Cape Peninsula and False Bay. SURG.

Gosliner 1987. Nudibranchs of s Afr - a guide to the Ophisthobranch Molluscs of s Afr. Sea Challengers & Jeff Hamann.

2O (well referenced: 2007: pl 81-85.)

There is quite a good reference set to Sea Slugs of the Indo-Pacific (I presume that they are not important or spectacular in the Atlantic).

and electronic:

Thank you for this, Tony.

Thank you for this, Tony.

-- Beetledude

additional resource

Tony has listed the three books that I have found most useful from a South African perspective. The following web site is also good for Reunion Island and the south-western Indian Ocean and yes the Sea Slug Forum has a lot of good info and photos as well. Sadly I think it is defunct now as a discussion forum, but the info is still out there on the web and very useful.

1000 Nudis on iSpot

We have 1000 Nudibranchs on iSpot with

Thanks everyone this is a fantastic achievement with an average of over 250 observations per month, or over 8 per day.

Here is to the next 1000!

Congratulations to the nudes

I love these nudis. But I still have no inkling of who they are or what they do. Or what sizes they are.

Neveryoumindme: keep on posting!

-- Beetledude

What about a key?

There are about 300 nudis in southern Africa.

What about doing a key to them? We have enough examples now to make it worthwhile.


What is will require is someone to code up a matrix of species X characters.
Some characters will be easy and tied to taxonomy (presence (also number of shape) or tentacles, rhinophores, cerata, gills, tails), whereas others will be more variable (rhinophore type) and others will have to be done one by one (colour of: stripes, dots, blotches, rings, margins, reticulated; surface, etc.)

Would be fun though ...

Do you have an example we can refer to?

An example always helps to understand what is required.

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)


data matrix:
character cerata . . . . . . . . . . dots
state . . present absent . huge . none red blue
image xx1 . . . xx2 xx 3

spp1 . . . present . . . . . . . . . . . . . . red
spp2 . . . present . . . . .huge . . . .. . . . . . blue
spp3. . . . . . . . absent . . . . . none

Clear as mud

Sorry, this does not help me. Is there any significance to the number of full stops?

Peter Southwood
Reef surveys and equipment design.
Southern Underwater Research Group (SURG)

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