Tropical and warm temperate Indo-West Pacific.
UPPER: Two animals on Caulerpa filiformis, Shelly Bch, Manly, Sydney, 6m, March 1984. Note enrolled structure of rhinophores clearly visible in smaller animal.
LOWER: Koumac Beach (=Baie de Ouanap), near Koumac, New Caledonia, grass-beds, algae, October 1993, 2 specimens (25 & 31mm long alive), showing colour variation.
PHOTOS: Bill Rudman.
Species of Oxynoe are found feeding on a variety of species of Caulerpa where they are well camouflaged because of their colour. There are a number of different species, but the common one throughout the Indo-West Pacific, Oxynoe viridis, would appear to be somewhat variable in colour even in a single locality. The green can very from dark green to grenish yellow and the blue spots can be range from large blue eyespots all over the body to small blue specks along the parapodial edge. Some variation is illustrated on this page.
Oxynoe has a fragile bubble-shaped shell which is partially enclosed by parapodial flaps. They can produce a sticky white secretion when attacked or disturbed, and in extreme danger they can break off the long muscular foot which continues to wriggle vigorously for some time after it is broken off. In time, a new tail will grow.
• Pease, W.H. (1861). Descriptions of new species of Mollusca from the Pacific Islands. Proceedings of the Zoological Society of London: 242-247.
Rudman, W.B., 1999 (July 12) Oxynoe viridis (Pease, 1861). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/oxynviri
July 28, 2008
From: Takao Urasawa
Concerning message #4946:
Here are two pictures. We haven't as yet seen a juvenile Oxynoe viridis.
The point we took these photos has a rapid current.
Locality: Flemming, 10 m, Tinian, Northern Mariana Islands, Pacific Ocean, 16 April 2008, on the Caulerpaceae before drop-off. Length: 6 mm. Photographer: Takao Urasawa.
Would you tell us your idea, please ?
email@example.comTakao Urasawa, 2008 (Jul 28) Re: A juvenile Oxynoe viridis ? from nthn Mariana Islands. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21590
This is definitely a species of Oxynoe and it's possible the dark spots we can see become blue, as in O. viridis, as it grows. But we still have much to learn about these animals so it is important to get to know your local populations. For example, if this is a juvenile O. viridis then you would be likely to find adult O. viridis on this species of Caulerpa as well. If not, then perhaps there is another species of Oxynoe that is found on it?
Because they are so well camouflaged on their algal food, it is sometimes quite difficult to find more than one or two specimens of Oxynoe at any time, and even harder to find small juveniles, but I am afraid the only way to link juveniles and adults (other than breeding them in aquaria) is try and find them living together on the same algae and to try and find growth stages linking them all together.
November 26, 2007
From: Tom Turk
I am sending you several photos of five sea slug species photographed along the coast of Turkey near the town of Kas. I believe that at least three species are actually Indopacific (lessepsian immigrants) in the Mediterranean Sea. I have tentatively identified three of them, for the other two I have no idea. I appreciate your help in this matter.
Locality: Kas, 25 m, Turkey, Mediterranean, end of October 2007, rocky bottom near or on Caulerpa. Length: 5-10 cm. Photographer: Borut Furlan
firstname.lastname@example.orgTurk, T., 2007 (Nov 26) Sea slug species from Turkey. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21173
September 11, 2006
From: Brian Francisco
Concerning message #17473:
After reading your comments about whether or not the Caulerpa sertularioides algae is "right for the species" of Oxynoe viridis, I went through my photo records and found another occurrence. These photos were taken about two weeks after my original entry and show an O. viridis once again on C. sertularioides, this time having just laid eggs (photos 1 and 2). I also found a record of O. viridis eggs having been laid on C. racemosa, located in the same sandy area (photo 3).
Locality: Tasi Tolu, 12 meters, East Timor, Banda Sea, 28 August 2006, sandy slope. Length: 15 mm. Photographer: Brian Francisco.
I suppose it's possible that O. viridis is feeding on neither of the Caulerpa species, but on some other algae growing on it.
Hurry back from vacation.
Francisco, B., 2006 (Sep 11) Re: Oxynoe viridis from East Timor. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/17790
Sorry if my comment was a bit ambiguous. What I was doubtful about was whether my identification of the Caulerpa as C. sertularioides was correct. The shape of the 'branchlets' or individual 'leaves' didn't look quite right, but it does in your upper photo in this message, so I guess it's just me being overcautious.
I like your photo of an egg ribbbon nestled in the cup-like 'branchlet' of the other Caulerpa. The taxonomy of Caulerpa seem somewhat confused. This is probably one considered a form of C. racemosa (C. racemosa var peltata) or as a distinct species (C. peltata). I find the website Algaebase [http://www.algaebase.org/] to be very useful, but its not a site for a quick browse, and as a 'work in progress' gives useful clues rather than quick answers.
Concerning what Oxynoe viridis feeds on. It seems to specialise on species of Caulerpa but has been recorded on a number of different species.
September 9, 2006
From: Brian Francisco
For your records, here's a photo of Oxynoe viridis feeding.
Locality: Tasi Tolu, 12 meters, East Timor, Banda Sea, 6 August 2006, Sandy Slope. Length: 15 mm. Photographer: Brian Francisco.
email@example.comFrancisco, B., 2006 (Sep 9) Oxynoe viridis from East Timor. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/17473
It's not often you find such a brightly coloured specimen. The algae it is feeding on is a species of Caulerpa, perhaps Caulerpa sertularioides, but it doesn't look quite right for that species and I am no expert.
February 23, 2005
From: Dr. Jacob Dafni
I was given these two pictures taken by a local diver, and I have not the slightest idea what is it. My best guess is a slug, possibly related to Ceratosoma sinuata (where I saw in your site green and speckled specimens). Yet I am not convinced that it is a mollusc at all. Does it ring a bell for you?
Locality: Dekel Beach, Eilat. Israel, Red Sea. Depth: 7-8 m. Length: ca 5 cm. February 19, 2005. among coral rubble. Photographer: Shmulik Shrenkel.
firstname.lastname@example.orgDafni, J., 2005 (Feb 23) Oxynoe from the Red Sea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13195
This is a particularly brightly coloured specimen of the sacoglossan 'bubble-shell' Oxynoe viridis. In the close-up, which I have posted alongside my comments it seem to be trying to eat the end of what looks like a bit of coral rubble. Perhaps there are traces of its algal food there. The parapodial flaps have completely enclosed the shell in Shmulik's photos but often in this species quite a bit of the shell is visible. It is colourless, but the brightly coloured mantle can be seen through the shell.
July 6, 2002
From: Nishina Masayoshi
Date: 2002 April 6
Location: Hachijo Island Japan
Photo by N. Masayoshi
email@example.comMasayoshi, N., 2002 (Jul 6) Egg mass of Oxynoe viridis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6842
Thanks very much. It is very interesting to see the egg masses of these sacoglossans.
May 16, 2002
From: Baki Yokes
Here are some photos of a species that we encountered recently. The blue spots indicate Oxynoe viridis, is it correct? If so, I think this is an other new record for the Mediterranean. We found 2 specimens on a Caulerpa racemosa field. It seemed that one of them was eating an alga other than Caulerpa. Do these animals have a broad range of food or was it only by chance, because the specimen did not leave the alga for a long time until we took it, and it was mowing back-and-forth on the alga as if it was trying to eat it. We observed that, beside C. racemosa, this species also likes C. prolifera and they do not specially prefer one of them when both are present. This species should also be tested to for its potential in controlling the Caulerpa invasion in the Mediterranean.
Upper Right: 29 April 2002, Antalya, Turkey
Divesite: Kucuk Ada, Uc Adalar. Depth: 6m, Size: 3cm. On Caulerpa racemosa.
Lower Left: As above - On an alga other than C. racemosa
Lower Right: 29 April 2002 - Aquarium photo on Caulerpa prolifera.
Yokes, B., 2002 (May 16) Oxynoe viridis? from Turkey. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6935
Although it is unusual to find an animal in the western Pacific so gaudily spotted with blue, specimens I used to find in Dar es Salaam, Tanzania were often this yellowish colour with prominent blue spots. So yes I agree with ypou that this is another lessepsian migrant from the Red Sea.
Concerning its diet, Oxynoe viridis seems to prefer Caulerpa racemosa in the field, but that may be because it is often the dominant species of Caulerpa in many of the localities Oxynoe is found. Obviously it will eat other species of Caulerpa and in Sydney, it is usually found on Caulerpa filiformis which is an introduced species, probably from South Africa. In southern Australia, O. viridis is usually found on Caulerpa cactoides. So it is possible the unknown algae in your lower right photo is being eaten by Oxynoe. Perhaps someone will recognise it for us.
This is another very interesting find.
May 10, 2002
From: Nishina Masayoshi
In your comment on O. kabirensis, you mentioned that "there are usually a few scattered very elongate papillae, which are probably retractile"
This is correct, The papillae are retractile in both O. viridis and O. kabirensis. I have attached images of the same individual of O. viridis, one with papillae extended, the other with papillae retracted.
firstname.lastname@example.orgMasayoshi, N., 2002 (May 10) Retractile papillae in Oxynoe. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6828
Thanks to your photos, I've taken the 'probably' out of my comment
April 30, 2002
From: Nishina Masayoshi
I suspect this is a kind of Oxynoidae, perhaps Oxynoe viridis but I have never seen one look like this. From my experience all of the Oxynoe viridis ever seen has "blue eyespots or blue specks" somewhere on the body. The stuff that looks like parapodial flaps is not a flaps. It is a broken parapodia which usually covers a shell.
Photographed by Moguricyo
Data: Hachijyo Island,
email@example.comMasayoshi, N., 2002 (Apr 30) Oxynoe? from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6667
Absence of a character is the most difficulty thing to interpret. O. viridis usually does have some blue spots sometimes not. Hamatani (1980), in the paper he describes O.kabirensis,
reports that he also found specimens of O. viridis in Japan without blue spots on the body and parapodia, so this is probably a form of O. viridis.
August 17, 2001
From: Nishina Masayoshi
Oxynoe viridis is rare in Sagami Bay but common in Hachijo at the right time of the year. It is a seasonal animal being present between June to October when the green alga is growing.
Date: 29 June, 2001
Place: Sokodo, Hachijo Island, Japan
Photos by Nishina Masayoshi.
Size: UPPER is 50mm which I think is the biggest it grows here. LOWER LEFT - 20mm and LOWER RIGHT - 10mm are within the normal size range here.
Nishina, M., 2001 (Aug 17) Oxynoe viridis from Hachijo Island, Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4946
Thanks very much for these photos. By chance I also have some photos from South Australia which I will also post today for comparison.
August 17, 2001
From: Nigel Holmes
The attached photo of Oxynoe viridis on Caulerpa cactoides is from Spencer Gulf, South Australia, just off Port Pirie, but I, and Karen Gowlett-Holmes, have also seen it elsewhere in South Australia, mostly on C. cactoides on which it seems well camouflaged.
Nigel.Holmes@env.qld.gov.auHolmes, N., 2001 (Aug 17) Oxynoe viridis f rom South Australia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5029
This is certainly a darker green than usual for this widespread species but may reflect the colour of the Caulerpa it feeds on. I am not sure where the skin pigment comes from in these sacoglossan species which do not retain plastids from their food. Another of the many mysteries we still need to investigate.
August 6, 2000
From: Julie Marshall
A photo of a large (25 mm) Oxynoe viridis found on Caulerpa racemosa on the reef flat at Heron Island in April this year. Although it had blue spots on the head, tail and lower sides of the parapodia the usual blue spots on the parapodial margins were very small dots.
Marshall, J., 2000 (Aug 6) Oxynoe viridis from Heron Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2819
Thanks for the photo. Because it was quite a large scan I have been able to prepare close-ups of the mantle edge near the head (lower left photo) to show the large glands along the edge of the mantle just at the mouth of the shell. These glands are part of an armoury of 'repugnatorial glands' which produce a white distasteful secretion when the animal is disturbed. Elsewhere on the skin the glands are much smaller. The lower right photo shows some of the secretion from the posterior foot.
July 21, 1999
From: Grey McNeil
Is this a Juliidae?? I found it at Bare Island, La Perouse, Sydney, N.S.W, Australia, in 8m, Febuary 1997.
GREYMACIND@bigpond.com.auMcNeil, G., 1999 (Jul 21) Is this a Juliidae?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1019
This is Oxynoe viridis (Family Oxynoidae). It has a fragile bubble-shaped shell in the centre of the body which is partially enclosed by parapodial flaps.
The Family Juliidae is another shelled sacoglossan family, but in that remarkable group the shell is bivalved, like a clam or cockle. I have posted a page on Julia exquisita, a typical species of the Juliidae.
Bill Rudman.Rudman, W.B., 1999 (Jul 21). Comment on Is this a Juliidae? by Grey McNeil. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1019
July 13, 1999
From: Karen Gowlett-Holmes
CSIRO Division of Marine Research
GPO Box 1538
Karen.Gowlett-Holmes@marine.csiro.auGowlett-Holmes, K., 1999 (Jul 13) Oxynoe viridis & Lobiger viridis the same?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1058
They are quite different, the most obvious difference being the four enrolled tentacular 'streamers' off the edge of the parapodia in Lobiger. The shell is much more flattened and reduced in that species as well, but it's not a character you can look at in the living animal. You should be able to identify your animal from these photos. If you'd like to send a photo of it on Caulerpa cactoides it would be a nice addition to the story. It is possible you have Roburnella wilsoni which is an endemic species (and genus) to southern Australian waters, but it is not reported to live on Caulerpa cactoides.
Bill Rudman.Rudman, W.B., 1999 (Jul 13). Comment on Oxynoe viridis & Lobiger viridis the same? by Karen Gowlett-Holmes. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1058