Throughout the tropical and subtropical Indo-West Pacific.
Upper: White juvenile animal without symbiotic zooxanthellae and larger brown animal in which symbiotic zooxanthellae are nurtured in ducts of the digestive gland both in the cerata and the body wall. Lower: Adult Pteraeolidia feeding on the solitary hydroid Ralpharia which is its preferred adult food. Coffs Harbour Region, New South Wales, Australia, December 1990. Photos: Bill Rudman.
Pteraeolidia ianthina, commonly known as the 'Blue Dragon' by divers in eastern Australia, is one of a group of remarkable aeolid nudibranchs which are way ahead of man in harnessing solar energy. Pteraeolidia has evolved a method of capturing and farming microscopic plants (zooxanthellae) in its own body. The plants flourish in this protected environment and as they convert the sun's energy into sugars, they pass a significant proportion on to the nudibranch for its own use. The white animal is a juvenile which as not yet developed its crop of zooxanthellae. If this species is similar to others that have been studied then it must obtain its first "injection" of zooxanthellae by feeding on a hydroid with symbiotic zooxanthellae. White juveniles are usually found in lush growths of short "turfing" hydroids, but until now no sign of zooxanthellae has been found in the hydroids. Adults can last some time without feeding, presumably obtaining sufficient nourishment from their zooxanthellae gardens. The large solitary hydroid is the preferred adult food.
• See Yoshi Hirano's message about egg-laying.
Angas, G.F. (1864). Description d'espèces nouvelles appartenant à plusieurs genres de Mollusques Nudibranches des environs de Port-Jackson (Nouvelles-Galles du Sud), accompagnée de dessins faits d'après nature. Journal de Conchyliologie, 12: 43-70.
Rudman, W.B., 1998 (October 11) Pteraeolidia ianthina (Angas,1864). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/pteriant
November 23, 2009
From: Mirjam Broos
I can't find this slug in my identification books.To me it looks like Phyllodesmium.
Locality: Sipadan, Hanging garden, Sabah, Malaysia, 25 september 2009. Photographer: Geert Prast.
Can you help me out please.
email@example.comBroos, M., 2009 (Nov 23) Juvenile Pteraeolidia from Sabah, Malysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22829
This is a juvenile Pteraeolidia ianthina. As we can see from Sully Bachel's message [#22228] adults show considerable variation in colour with some having tha very white colour form as in her message while others are shades of brown and purple. The brown ones all contain specialised branches of the digestive gland which contain microscopic brown algae [see Solar powered slugs] which they apparently obtain from their food hydroids. However juveniles lack these brown plant cells and so are white.
November 23, 2009
From: Sully Bachel
Concerning message #13227:
here is another white form color of Pteraeolidia ianthina found on an sandy edge in the spot "Cap La Houssaye" at St Paul
Locality: Cap la Houssaye, 8 m, Reunion Island, Indian Ocean, 27 September 2008. Length: 150 mm. Photographer: Sully Bachel.
firstname.lastname@example.orgBachel, S., 2009 (Nov 23) Pteraeolidia ianthina from Reunion Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22228
October 29, 2008
From: Ann Clear
We have just returned from diving in the wonderful Lembeh Strait. I saw this nudibranch on my ascent, he was quite large and was moving very swiftly across the sandy bottom of a reef. I think it is of the Flabellinidae family, but have been unable to identify him. He was really lovely.
Locality: Lembeh Strait, 10 - 12 meters, Indonesia, Molucca Sea, 11 October 2006, Sandy Bottom. Length: 5 - 7 cms. Photographer: Ann Clear.
email@example.comClear, A, 2008 (Oct 29) Colour form of Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/18970
From the gemeral shape and colour of the head, this is clearly Pteraeolidia ianthina, but I must say I have never seen such a pale orange colour form like this before. As you will see from the Fact Sheet, adults usually have brown zooxanthellae in their bodies which gives them a dark brown colouration. Perhaps this one has lost its zooxanthellae?
October 3, 2008
From: Eva Fontaine
Concerning message #21884:
I found four specimens of this seaslug during my holidays in Mayotte island.
I think that it could be a particular form of Pteraeolidia ianthina with longitidinal blue stripes on the cerata.
Locality: M'titi, 2 m, Mayotte Island, Indian Ocean, July 2008. Length: 30 mm. Photographer: Eva Fontaine.
What's your opinion about this identification?
firstname.lastname@example.orgFontaine, E., 2008 (Oct 3) Pteraeolidia ianthina from Mayotte island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21920
Thanks for these photos. This colour form, with fine bluish lines, is not very common, but Chikako's photo in Nishina Masayoshi's message [#4966] from Japan shows that this colour pattern is widespread.
September 23, 2008
From: Leanne & David Atkinson
Concerning message #21780:
With all the discussion of Pteraeolidia ianthina recently we thought you might like to add some mature individuals from Vanuatu. These were both taken at the same dive site but on different days.
Locality: Gotham City, Mele Reef, Hideaway Island, 14metres, Vanuatu, Pacific, 15 April 2008 & 20 April 2008, Coral Reef. Length: 110 mm. Photographer: Leanne & David Atkinson.
As always thanks for your work on the Sea Slug Forum.
Leanne & David Atkinson
email@example.comAtkinson, L. & D., 2008 (Sep 23) Pteraeolidia ianthina from Vanuatu. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21903
Thanks Leanne & David,
September 19, 2008
From: Jeffrey C. de Guzman
Here is a photo of Pteraeolidia ianthina.
Locality: Maiinit Anilao Batangas, 60 feet, Philippines, Philippines, 07 July 2007, Submerge Bamboo pole. Length: 5 inches. Photographer: Jeffrey C. de Guzman.
Jeffrey C. de Guzman.
firstname.lastname@example.orgMr., 2008 (Sep 19) Pteraeolidia ianthina from the Philippines. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20870
The one in the upper photos looks like it may be eating the hydroids which are arranged in rows on the root-like stolons running over the bamboo.
September 18, 2008
From: Marcel Tanke
Concerning message #21739:
Just to share this Pteraeolidia ianthina from Tonga, wrapped around some sponge-covered rock, for your Forum.
15 m, Tonga, 17 October 2007. Length: 15 cm. Photographer: Marcel Tanke.
email@example.comTanke, M.A., 2008 (Sep 18) Pteraeolidia ianthina from Tonga. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21780
September 18, 2008
From: Marcel Tanke
Concerning message #21739:
Just to share this large (12? cm) Pteraeolidia ianthina from Fiji for your Forum.
10 m, Fiji, Koro Sea, 29 April 2005. Length: about 12 cm. Photographer: Marcel Tanke.
firstname.lastname@example.orgTanke, M.A., 2008 (Sep 18) Pteraeolidia ianthina from Fiji. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21779
September 16, 2008
From: Nicholas Missenden
Just in relation to Erwin Kodiats' message on the rhinophores of the Pteraeolidia ianthina [#15742 ]. I have enclosed a picture that shows a very good head shot if you need one for your aeolid head Fact Sheet.
Locality: Bare Island, La Perouse, unknown, NSW, Australia, Botany Bay, 2005, Broken reef, sandy bottom. Length: unknown. Photographer: Nicholas Missenden
Bill RudmanRudman, W.B., 2008 (Sep 16). Comment on Re: head of Pteraeolidia ianthina by Nicholas Missenden. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15778
September 16, 2008
From: Sukhdev Singh
I just thought you might like to see my 'Blue Dragon' pics.
The first is one a friend emailed to me & I believe he took it in the Philippines. The second one I took at Lankayan Island, North Borneo.
The last was taken at Sipadan Island, Borneo. It's a still from the video I had made.
Locality: Island, 15 metres, Borneo, South China Sea, 13 June 2007, Reef wall. Length: 4 inches. Photographer: Sukhdev Singh.
email@example.comSingh,S., 2008 (Sep 16) Photos of Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21884
Thanks for these photos. When I see photos like this of one animal with short cerata and the other with long ones, it makes me think there must be more than one species. But I have looked at the anatomy of a whole series of animals from all parts of the world and can find no obvious differences. Perhaps DNA studies will suggest there is more than one species, but then again maybe the differences are physiological - perhaps to do with the symbiotic zooxanthellae they harbour. I have a few more messages on this species to post. I will do it today or sometime soon.
August 13, 2008
From: Roland Bircher
Recently on a dive at Bare Island I photographed what I think is a Pteraeolidia ianthina. Between the upper and lower photos it looks like the nudibranch is everting something. Is this the oral tube as you mention in an earlier answer or am I completely wrong?
Locality: Bare Island, La Perouse, Sydney, 10 m, Australia, Botany Bay, 19 July 2008, Bay, overgrown rock. Length: 10 cm. Photographer: Roland Bircher.
Bircher, R., 2008 (Aug 13) Pteraeolidia ianthina: looks like something everted. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21777
As you will see from the species Fact Sheet, Pteraeolidia is a solar powered species relying on the energy produced by the microscopic plants it 'farms' in its body. The brown spotting and branching you can see in the two close-ups of the head, are clusters of these plants [zooxanthellae] in branches of the digestive system. For some reason, your animal lacks these branches of the digestive system on the left side of its face and foot, and in its left rhinophore. This could be a developmental fault or it could be that this part of the body has been damaged - perhaps bitten off - and has regrown without the digestive gland ducts.
Now that I have 'set the scene' I hope I can answer your anatomical question. The mouth is situated between the two large oral tentacles. It is a bit further back than the m I have added to the photo but if the oral tube was everted it would be over the top of the 'm'. I have put an 'f ' where something seems to be being everted. This is in fact the left side of the anterior foot. Because it is bright white, it seems to be sticking out more than on the other side, which still has the brown of the digestive system. I hope that makes sense.
July 28, 2008
From: Carrie Lo
Could this be one of the Phyllodesmium serratum? I cannot match it to your gallery.
Locality: Malapascua, Gato Island, 20 m, Philippines, 29 Dec 2006. Length: 2 cm. Photographer: Carrie Lo.
firstname.lastname@example.orgLo, C., 2008 (Jul 28) Pteraeolidia ianthina from the Philippines. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21739
September 20, 2007
From: Natasja Vandeperre
My closest guess to this one is Pteraeolidia ianthina. But I'm not convinced. On the second picture you can see eggs. Are these from this species?
Locality: Tofo, Mozambique, Indian Ocean, 22 July 2007. Length: 100mm. Photographer: Natasja Vandeperre.
email@example.comVandeperre, N., 2007 (Sep 20) Pteraeolidia ianthina (?) from Mozambique. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20580
Firstly I couldn't see any eggs in your second photo so I have included a close-up showing the front half of the animal a bit more clearly. This certainly falls into the group I am calling Pteraeolidia ianthina. I am not entirely convinced that all the animals you can see in the Forum messages are one species, but many years ago when I was first interested in solar powered species I dissected a whole range of different coloured animals, some with relatively short cerata like your animal and others with longer cerata, but could find no consistent differences in anatomy or radular morphology. There are names that have been given to different body shapes but there seems little point in using them unless we can define which is which.
January 16, 2007
From: Stephen J. Reynolds
Concerning message #19105:
Thanks for the Hypselodoris saintvincentius ID.
I have another one for you, a Flabellina sp. from Port Noarlunga reef in 2006.
Locality: Port Noarlunga reef, SA, Ocean, 18 June 2006. Photographer: Paul Macdonald.
firstname.lastname@example.orgReynolds, S.J., 2007 (Jan 16) Pteraeolidia ianthina from Port Noarlunga, SA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19208
December 5, 2006
From: Bruce Wilkie
Concerning message #18378:
Thought you may be interested in these photo`s of Pteraeolidia ianthina feeding on a hydroid (possibly the sea fir Solanderia fusca). I watched this animal for about 10 mins, it must have been rather hungry because it attacked the sea fir with great ferocity.
Locality: Flat Rock North Stradbroke Island, 8 metres, Queensland Australia, Pacific ocean, 02 November 2006, rocky reef with sponges, hard & soft corals . Length: long. Photographer: Bruce Wilkie.
Wilkie, B., 2006 (Dec 5) New feeding record for Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/18844
I am definitely very interested in what this amazing solar-powered sea slug feeds on. As you will know from the Fact Sheet, the only hydroid we know Pteraeolidia feeds on is the solitary tubularian hydroid Ralpharia. However since Ralpharia doesn't have zooxanthellae its been a mystery as to where the aeolid gets its zooxanthellae from. Pteraeolidia also seems to have at least two 'forms' this very elongate form with compact ceratal groups and a shorter form with much longer cerata. So any new information on its biology is very welcome.
This hydroid certainly looks like a species of Solanderia but as far as I know Solanderia does not have symbiotic zooxanthellae in its tissues. Mind you, the very pale colour of the Pteraeolidia suggests it may be lacking zooxanthellae as well. You have added another piece to the puzzle - I can't say it has solved anything but I hope it reignites some enthusiasm for us all to try and find more about its biology.
July 21, 2006
From: Charles Rowe
This is the fourth of a series of nudis from my trip to Sipadan which I would like you to identify and comment on. This nudi was tiny and we had problems focussing on it but I think I did quite a good job.
Locality: Sipadan Island, 15metres, Malaysia, 29 April 2006, reef. Length: 8 mm. Photographer: Charles Rowe.
email@example.comRowe, C., 2006 (Jul 21) Pteraeolidia ianthina from Sipadan trip. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16850
This is a solar-powered nudibranch, Pteraeolidia ianthina. You may be more familiar with it in its dark brown colour phase, but the white phase is an indication that its 'battery is flat'. If you look at the solar-powered Fact Sheet you will see that these nudibranchs store live single-celled plants [zooxanthellae] in their bodies - which gives them their brown colour - but we are not sure where they get the plants from in the first place. All juveniles are white like this, and they stay white until they start to grow zooxanthellae in their bodies.
July 13, 2006
From: Kevin Lee
And, what might this critter be?
Locality: Ahmed, approx 20 feet, Bali, Indoneisa, Indo Pacific (Java Sea), 06 June 2006, rocky/sandy bottom. Length: approx. 2+ inches. Photographer: Kevin Lee.
firstname.lastname@example.orgLee, K., 2006 (Jul 13) Pteraeolidia ianthina from Bali. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16929
This is one of my favourite solar-powered nudibranchs, Pteraeolidia ianthina. Have a look at the Fact Sheet, and earlier messages, for lots of information on this fascinating species
June 3, 2006
From: Carol Yin
Concerning message #15742:
Does this Pteraeolidia ianthina have four rhinophores??
Locality: Hairball, 30 ft, N. Sulawesi, Indonesia, N. Sulawesi. Length: 7 inches. Photographer: Carol Yin.
Thank you :).
Yin, C., 2006 (Jun 3) Re: Closer look at Pteraeolidia ianthina's head. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16758
It does indeed. Sometimes if the animal sustains an injury, then mistakes can occur during regrowth, but it looks to me that something went wrong during its development. I'll add it to the page on abnormal development.
One other interesting thing is the very pale uniform colour of this animal. Pteraeolidia keeps microscopic plants alive in its body [see solar powered sea slugs] and usually they give the animal a darker colour than this. In the close up of some of the cerata I can see no sign of the plants, which appear as small brown specks, so it is possible its pale colour is because it has lost its symbiotic plants.
February 7, 2006
From: Erwin Kodiat
Just took a closer head shot of Pteraeolidia ianthina, it made me realize that the rhinophores are actually the brown one and not the bright one which I guess it is its radula, please correct me if I'm wrong.
Locality: Seraya, Bali, Indonesia, Lombok Strait. Depth: 17 meters. Length: 15 cm. 29 January 2006. Sandy bottom. Photographer: Erwin Kodiat
email@example.comKodiat, E., 2006 (Feb 7) Closer look at Pteraeolidia ianthina's head. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15742
When I get a moment I'll do an aeolid head Fact Sheet to match the Dorid head Fact Sheet. In the meantime I have numbered the 'tentacles' in your photo.
1. rhinophores - chemosensory ['smelling' organs]
2. oral tentacles - tactile [touching] organs which are perhaps also chemosensory.
3. anterior foot corner - the anterior edge of the foot is sometimes rounded and sometimes has angular corners. Sometimes these corners are relatively long and tentacular, as in Pteraeolidia.
The radula is essentially an internal organ which is soemtimes partly everted like a rasping tongue during feeding. If anything is everted during feeding, it is the oral tube and part of the buccal bulb, which is the muscular structire just inside the mouth which contains the radula -see photo of Geitodoris planata [#5126] with partly everted buccal bulb.
February 2, 2006
From: Aisha. E
I'm new and never have been to this site. I'm doing a class project on the blue dragon (nudibranch). Does anybody have any information, pictures, websites, etc. Anything that you may think that might help me I would greatly appreciate.
(This animal doesn't seem to have a lot of infomation from what I've found)Aisha. E
firstname.lastname@example.orgAisha. E, 2006 (Feb 2) Nudibranch - The Blue Dragon. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15682
Have a look at my answer to an earlier question [#6999]. One problem is that common names like 'blue dragon' aren't used very widely, and even when they are they can meam different things to different people. In future use the Forum search facility. Check out the two species I mention in my earlier answer, there is quite a lot of information on both species - dont forget to look at the related messages attached at the bottom of each Fact Sheet
December 13, 2005
From: Makiko Yorifuji
I'm a graduate student working on the life history of Pteraeolidia ianthina under Dr. Yoshiaki Hirano. Please give Yoshi my regards. I've just read the message about P. ianthina dated Oct. 4, 2005 [#14917 ] and I'd like to share some of my findings on this sea slug with you.
First, I've seen P. ianthina crawling or staying on/near Myrionema amboinense in the field (Okinawa, Japan). I've confirmed that P. ianthina eats M. amboinense in the laboratory. Second, I found many kinds of nematocysts probably derived from many hydroids in the cnidosacs of the slug. Prey hydroids of this slug I've confirmed so far include Tubularia, Eudendrium spp., Halocordyle disticha, in addition to M. amboinense. This slug may even eat some other cnidarians. When I gave a species of swimming anemone to hungry slugs of P. ianthina (those kept without food for about 3 months) on trial, some of them ate the sea anemone. Also I've seen a slug of P. ianthina biting a stauromedusa (Stenoscyphus inabai) in a small container in which a student was keeping these two animals together for a few hours after collecting. So, I think P. ianthina has a wide spectrum of food as an adult. Moreover, as they can survive for about a half year only with light (no prey), they may not eat Myrionema so frequently.
Besides, I'm cautious about selling and/or buying sea slugs for a personal hobby. I don't think using P. ianthina to get rid of Myrionema hydroids is a good idea.
email@example.comYorifuji, M, 2005 (Dec 13) Re: I need Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15453
Thanks for this interesting information. I remember Dr Hirano mentioning he had a graduate student studying Pteraeolidia. Certainly in northern New South Wales, adult Pteraeolidia are associated with the solitary tubularian hydroid Ralpharia, but that is not to say in more tropical waters, as you have discovered, that it can potentially feed on a wider variety of cnidarians. What greatly interests me is where it gets its zooxanthellae from? At some early stage in its life cycle it must feed on a cnidarian with zooxanthellae. Have you found a potential source of zooxanthellae?
I also am uncomfortable with the idea of catching and selling Pteraeolidia as possible biological control agents in aquaria.
October 6, 2005
From: Albert Jeffers
Re: message #14917: That's horrible news. Do you have any idea if there is an animal that eats this stuff?
firstname.lastname@example.orgJeffers, A., 2005 (Oct 6) Re: I need Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14929
October 4, 2005
From: Albert B Jeffers
I have a problem with Myrionema hydroids in my reef tank. I have succcesfully controlled other organisms with the use of certain slugs, through the kind advice of you guys on this forum. I need to purchase Pteraeolidia ianthina from somewhere, I don't care where and have no problem with money when it comes to saving my extensive collection of corals.
I fully understand the hazards of keeping zooxanthellate bearing slugs in a coral tank and I am willing to pick them out after the job is done and pass them on to fellow aquarists with the same problem.
If my only option is to get them from a research facility or school, I will be glad to furnish pictures and written observation of my attempt.
Albert Jeffers (squeezix on reefcentral)
Vero Beach, Florida, USA
email@example.comJeffers, A.B., 2005 (Oct 4) I need Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14917
I'm afraid you seem to have missed the point that most nudirbranchs have very specialised diets. Those with zooxanthellae symbiosis certainly don't eat all cnidarians with zooxanthellae, they eat only one or a few closely related species. Most zooxanthellae zymbionts get their zooxanthellae not from hard corals, but from either soft corals or sea anemones. Pteraeolidia, as you'll see from the Fact Sheet, is an exception./ It eats hydroids as an adult, but only some solitary hydroids related to Tubularia which don't have zooxanthellae. They apparently get their zooxanthellae from some unknown small hydroid as juveniles. The point I am trying to make is that there is no evidence that they eat Myrionema.
This is the reason that keeping nudibranchs in aquaria is a bad idea. Most have very specialised diets. Just because you hear that dorid nudibranchs eat sponges, it doesn't mean you can throw in any sponge and think any dorid will eat it. Similarly Pteraeolidia is so fussy we don't even know what it eats as a juvenile and as an adult it certainly doesn't eat Myrionema.
September 10, 2005
From: Umut Tural
Dr. Bill Rudman
This photo was taken last year during our dive trip to Sipadan Kapalai. Among the many beautiful & interesting creatures, the only one we did very curious about it, very long worm or nudibranch, we couldnt figure out What it is. What do you think , Could be a nudibranch ? We would be very glad if you help us identification of this creature.
Locality: Sipadan Kapalai, Malaysia. Depth: 12 m. 24 January 2004. Photographer: Aydin K1_1nbay
firstname.lastname@example.orgTural, U,, 2005 (Sep 10) Pteraeolidia ianthina from Malaysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14693
This spectacular worm-like animal is a nudibranch. It is the solar-powered aeolid Pteraeolidia ianthina. Whether there is more than one species needs further study. I have examined animals from throughout the Indo-West Pacific and can find no anatomical difference or difference in the shape of their teeth. The only difference is that some animals are very long like this and others are much shorter, although even the relatively short ones can greatly extend in length when crawling. I must say it's a major problem when trying to post a photo of the whole animal.
Pteraeolidia ianthina is one of a variety of nudibranchs and sacoglossans which can be called 'solar-powered' because they keep plant cells, or plant organelles, alive in their tissues to photosynthesise. Have a look at the relevant Fact Sheets for more information.
June 2, 2005
From: Ho Wei Kwok Alvin
Here is another slug, Pteraeolidia ianthina, found at Dayang Jetty, Pulau Dayang.
Locality: Dayang Jetty, Pulau Dayang, West Malaysia. South China Sea. Depth: 5 m. Length: 20-30 mm. 2 May 2005. Sand Bottom, Rubble. Photographer: Alvin Ho.
Hobgood, N., 2005 (Jun 2) Pteraeolidia ianthina from West Malaysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13765
I guess you have read about this solar powered nudibranch.
March 1, 2005
From: Philibert Bidgrain
Reunion Island sea slugs.
We have this specimen, observed by Maurice Jay, a white color form of Pteraeolidia ianthina, found in "La Saline" lagoon, under a rock. Reunion Island, Indian ocean. Photographer: Maurice Jay
email@example.comBidgrain, P., 2005 (Mar 1) Pteraeolidia ianthina from Reunion Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13227
February 23, 2005
From: Rainer Mau
Another one I have recently seen in Balinese waters. I suspect it's a Pteraeolidia, but.....
I assume you can help me
Locality: Alam Anda, Bali, Indonesia, Java sea. Depth: 7 m. Length: 9 cm. 20.December 2004. below huge rock, close to shorerline. Photographer: Rainer Mau
firstname.lastname@example.orgMau, R., 2005 (Feb 23) Pteraeolidia ianthina from Bali. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13109
Yes this is Pteraeolidia ianthina. It's a shame that because the animal is so long it is hard to post a big enough photo to show its beauty, which is in the detail. I have included a close-up alongside of the head to show some of the spectacular colouration and the way the cerata are arranged on large plate-like, rounded bases
December 31, 2004
From: Toshiko Tani
Dear Dr Bill Rudman,
Thank you very much for answering my question about a creature we saw in the Beqa Lagoon, Fiji [#12851] - which you told us was Pteraeolidia ianthina! I read all of the related messages on Pteraeolidia ianthina you cited and your answer to each of the messages. Yes, they do indeed seem to vary in colors and sizes. Also thank you for educating us for how the adult forms feed themselves by hosting many microscopic plants in their bodies!! Such an interesting creature!!!
It is wonderful that such a forum on sea slugs is available on-line to gather/share the information where even an non-academic sea creature lover like myself can learn so much.
Thank you again for your kind reply to my question and I thank Australian Museum, too, for running such a good website.
P.S. I am still such a beginner diver and not relaxed enough to handle a camera in the water. The photo of the Pteraeolidia ianthina was taken by my friend Yoko who loves sea creatures, too.
email@example.comToshiko, T., 2004 (Dec 31) Thank you. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12850
As you will see on the Forum, there are many beautiful and interesting sea slugs in Japan, and a whole group of divers interested in them. I hope this is only the first of many messages from you
December 30, 2004
From: Toshiko Tani
My friend and I saw a creature in the attached photo when we were diving near Beqa Island, Fiji, in the middle of December 2004. We went through pages of sea slug information available on the Net to identify what it was but have not had any luck. Could someone in this forum kindly tell us what this is. It may not even be a sea slug but something else...
Locality: 30 minutes by a boat toward the northwest of Beqa Island, Fiji. Depth: 15 metres. Length: 150mm. December 18, 2004. Photo: Yoko Morimoto.
firstname.lastname@example.orgToshiko, T., 2004 (Dec 30) Sea Slug or Centipede?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12851
This is indeed a sea slug. It is the nudibranch Pteraeolidia ianthina. As you will see on the species' Fact Sheet it is one of a very interesting group of nudibranchs which we have called solar-powered because they have many microscopic plants living in their bodies which provide them with sugars and other nutrition. Pteraeolidia is often found like this extended out in the sunlight so the plants in its body can use the sun's energy to photosynthesise. Have a look at Matthias Huerlimann's message [#12820 ] for a photo of a juvenile.
It certainly looks like a centipede, and one of the early names for this species was Flabellina scolopendrella because the French scientist who found it thought it looked like a centipede, [scolopendre = centipede in French]. Have a look at the many other messages on the page. Some of the photos will give you a good idea of the size and shape of this animal.
December 30, 2004
From: Matthias Huerlimann
I found this little nudibranch 2 weeks ago on the Philipines and I was looking for hours now in the internet, but I am not sure if this is a juvenile Pteraeolidia ianthina. Maybe you can help me?
Locality: Pandan Island (occ. Mindoro), Philippines, South China Sea
Depth: ca. 10 m. Length: ca. 10 mm. 6 December 2004
Photographer: Matthias Huerlimann
p.s. your site is just great!
email@example.comHuerlimann, M., 2004 (Dec 30) Juvenile Pteraeolidia ianthina from Philippines. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12820
Yes this is Pteraeolidia ianthina. Juveniles are white like this because they have not as yet, obtained the zooxanthellae which give them the brown colour of adults. See the Fact Sheets on solar-powered animals to see how they use the zooxanthellae.
February 21, 2004
From: Riaan Marx
I photographed this animal at Sodwana, [KwaZulu-Natal] South Africa.
Could you help me identify it please?
firstname.lastname@example.orgMarx, R., 2004 (Feb 21) Pteraeolidia ianthina from Sth Africa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12263
This is Pteraeolidia ianthina. Have a look at the species Fact Sheet to learn something about this remarkable 'solar powered' slug.
February 1, 2004
From: Frank Weber
Could you please tell me what this is. I took the photo at Merimbula, southern New South Wales, [Australia] in 15 m of water in September 2003.
It was about 3 cm long. Any help would be gratefully accepted.
email@example.comWeber, F., 2004 (Feb 1) Juvenile Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12061
This is a young Pteraeolidia ianthina. Have a look at the species' Fact Sheet where I explain how they change from white to brown as they begin to nurture single-celled plants in their bodies.
January 30, 2004
From: Dana Africa
Dear SeaSlug Forum
While scuba diving between Komodo Island and Alor Island in the Indonesian chain, I came across this nudibranch twice. Have never seen it before and cannot find it in my ID books. It is about 20 cm long. I enclose two photos - one of the whole body and one of the head.
AfriDiver@aol.comAfrica, D., 2004 (Jan 30) Pteraeolidia ianthina from Indonesia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12056
December 20, 2003
From: Dave Harasti
On Dec 18th 2003 I found Pteraeolidia ianthina laying eggs on a yellow-lined ascidian. This was at Fly Point - Nelson Bay, NSW, Australia. depth was about 12 metres.
firstname.lastname@example.orgHarasti, D., 2003 (Dec 20) Pteraeolidia ianthina laying eggs - Nelson Bay. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11718
Pteraeolidia has a habit of staying near its eggs. Whether this is just coincidence or a genuine brooding behaviour is not known, but if you are back at the spot in the next week or so it might be worth checking
May 24, 2003
From: Asther M. Lau
Had found tonnes of this seaslug in East Coast of Malaysia. is it a Blue Dragon? Realised that this species likes to hang-out on wrecks and boulders. Also, it comes in brown, blue, black and even silver colors!
This pic was taken recently during my trip to Tenggol Is.
Date: 25th April 2003
Location: Moon Raker, Tenggol Is. Malaysia
Asther M. Lau
email@example.comLau, A.M., 2003 (May 24) Pteraeolidia ianthina from Malaysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9822
Yes this is Pteraeolidia ianthina, often called the 'Blue Dragon'. It is one of the few examples of a common name which seems to be quite common. I don't know if you have looked at the Fact Sheet for this species. If you do you will see that it is one of the the solar-powered species which rely on sunlight to keep the plants in its body healthy.
April 5, 2003
From: Leanne & David Atkinson
After seeing Mary Jane Adams shots of Pteraeolidia ianthina mating we checked out the rest of the Pteraeolidia ianthina pages on the site. In your message with Akos' photo with eggs you talked about them laying on boulders and guarding the eggs. We recently photographed this one with eggs on a common plant/algae. Sorry about the quality of the photo, it was surgy with a sandy bottom and poor viz. The plant was swaying badly even when held. We tried hard not to disturb her/him. It was well wrapped around the eggs and difficult to get a clear shot.
Fly Point, Port Stephens, NSW, Australia
Depth: 8 meters. 11 January 2003
Time: 15.23, high tide 1.22m
Temp: 21 degrees C.
Leanne & David Atkinson
Atkinson, L & D., 2003 (Apr 5) Pteraeolidia ianthina with eggs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9504
Thanks Leanne & David,
I've included 3 versions of your photo to show the egg ribbon in detail and the rather unusual flattened looking cerata. This species seems to be quite variable both in shape and length of the cerata.
March 25, 2003
From: Mary Jane Adams
I photographed these two Pteraeolidia ianthina mating in the Similan Islands, Andaman Sea, Thailand on March 2, 2003. The divesite is called Elephant Head Rock. The depth was 5 meters. There were numerous P.ianthina on the vertical faces of several house-size boulders on this divesite. I saw them from the intertidal region to about 10 meters. They were all the same lavender color which appears purple underwater. The smaller ones were pale pastel and the larger ones deeper shades.
firstname.lastname@example.orgAdams, M.J., 2003 (Mar 25) Pteraeolidia ianthina mating. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9405
Thanks Mary Jane,
They are spectacular animals.
October 13, 2002
From: Marli Wakeling
Here are two photos of Pteraeolidia ianthina from Lembeh Straight, from two different sites. There were lots of these around, often in tangled groups.
Location: Photo 1: Police pier, Photo 2: Hairball, Lembeh Straight, Sulawesi, Indonesia
Date: July 2002
Depth: 45 feet
Length: 15 - 20 cm.
Photographs: Marli Wakeling
email@example.comWakeling, M., 2002 (Oct 13) Pteraeolidia ianthina from North Sulawesi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8129
These are fascinating animals. They have been observed in New South Wales, clustering in groups, and apparently 'guarding' their egg masses. They were certainly make an interesting Ph D thesis or two.
September 27, 2002
From: Michael Mrutzek
Here is a photo of another slug from the Red Sea for use in the Forum.
Data: Stone Beach, Hurghada, Red Sea coast of Egypt, August, 2002, 20 meters. Photo: Copyright Michael Mrutzek
Mrutzek@meeresaquaristik.deMrutzek, M., 2002 (Sep 27) Pteraeolida ianthina from Red Sea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8034
This is Pteraeolidia ianthina. It is an extremely interesting aeolid because it stores microscopic plants in its body. See the Solar powered slugs page for further information.
July 31, 2002
From: Maliza Anuar
This photo was taken at Tioman Island, off the east coast of Malaysia. Dive Site: Labas, 24 June 2002, 11:13am
Depth: 15-18m, Size: 5-7cm
This gorgeous little thing sure looks like a juvenile Pteraeolidia ianthina.
firstname.lastname@example.orgAnuar, M., 2002 (Jul 31) Juvenile Pteraeolidia ianthina? from Tioman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7519
It is indeed a juvenile Pteraeolidia ianthina.
July 30, 2002
From: Maliza Anuar
This photo was taken at Tioman Island, off the east coast of west Malaysia.
Dive Site: Soyak Island, 23 June 2002, 4:40pm
Size: my husband swears it was at least 10cm
I've browsed around the species list and this guys looks like a Pteraeolidia ianthina. We saw quite a few of these (abt 3 per dive) in Tioman. I thought the brown coloring was kind of "boring" but after reading on how these guys are solar powered, I'll definitely be taking a closer look next time.
email@example.comAnuar, M., 2002 (Jul 30) Pteraeolidia ianthina? from Tioman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7517
Yes this is Pteraeolidia ianthina. And I am sure 10 cm was not an exaggeration.
July 16, 2002
From: Maliza Anuar
Could you help ID this little guy? Photo was taken by my husband on our recent diving trip to Tioman Island off the east coast of Malaysia.
Dive Site: Soyak Island, 4:30pm
firstname.lastname@example.orgAnuar, M., 2002 (Jul 16) Pteraeolidia from Tioman, Malaysia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7473
This is Pteraeolidia ianthina. Have a look at the Fact Sheet on this species for more information on its 'solar-powered' lifestyle.
June 2, 2002
From: Stewart L. Sy
These photos were taken in Puerto Galera, on the island of Mindoro in the Philippines. The dive site is called Sinandigan Wall. Depth of 60 feet and the animals are about 2 inches in length.
I wasn't sure what species this is, but from my very limited knowledge, I assumed it to be some form of Flabellina.
email@example.comSy, S.L., 2002 (Jun 2) Pteraeolidia ianthina from Philippines. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7052
This is Pteraeolidia ianthina, which you will see from the two pages of messages is quite variable in shape and colour and is found throughout the tropical and subtropical Indo-West Pacific.
October 10, 2001
From: Marli Wakeling
This is a difficult one for me to figure out. This seems to possibly be some sort of Bornella, but it blended in so well with its' surroundings.
Perhaps you can help solve the mystery!
Location: Nusa Blowholes, Kavieng, Papua New Guinea
Depth: 10 metres
Length: 6 cm.
Photograph: Marli Wakeling
firstname.lastname@example.orgWakeling, M., 2001 (Oct 10) Pteraeolidia from Papua New Guinea. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5370
This part of the 'complex' we call Pteraeolidia ianthina. Have a look at the many messages and photos we have on this 'species'. The difference in size of cerata varies considerably and you can find all variants together. The shapes and colour forms seem to intergrade and I suspect individuals can change the shape of the cerata. I can't find any anatomical or radula differences.
September 22, 2001
From: Jim Anderson
Dear Dr. Rudman,
Another from Sulawesi, Indonesia.
Found this Pteraeolidia ianthina at 7 m on Banks Island dive site Tanjung Sepia on 25 June. It was approx 30 mm long.
email@example.comAnderson, J., 2001 (Sep 22) Pteraeolidia ianthina from NE Sulawesi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5012
August 23, 2001
From: Nishina Masayoshi
I often find Pteraeolidia ianthina here but this is big animal for me.
Date: 14 July 2001
Place: Enoura Beach, Sagami Bay, Japan
Comment: Common here
Photo by Nishina Chikako.
firstname.lastname@example.orgNishina, M., 2001 (Aug 23) Pteraeolidia ianthina from Sagami Bay. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4966
Thanks to you and Chikako for these photos of the marvellous 'Solar-powered Sea Slug' Pteraeolidia. I have included an inset showing the lines of little brown specks in the cerata, which are the single-celled plants (zooxanthellae) which live in special ducts in the body wall and photosynthesise to provide nourishment for the nudibranch as well as the plants.
December 24, 2000
This is one of the species (Pteraeolidia ianthina) I found in Karang Lebar Atoll, Thousand Islands, Indonesia. This species is quite common found in that area. It is found at depth of 40-80 feets, crawling either on sponge or sandy substrate.
email@example.comYasman, Y., 2000 (Dec 24) Pteraeolidia ianthina from Indonesia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3329
Thanks for the record. It seems you have both extremes in sahpe and colour, the upper photo being a brownish animal with relatively short cerata and the lower one more bluish, with relatively long cerata. I was beginning to think the only animals you found were species of the Phyllidiidae.
June 2, 2000
From: Akos Lumnitzer
Hi Bill .... again!
I may be blind, but there don't seem to be any Pteraeolidia ianthina on the Forum. Have they been renamed?
I believe there could be two distinct species; one, the bluey purple colour form, with very evenly spread out cerata and the dull, brown-grey ones with bunched cerata. Could that be a possibility?
Here are three photos from around Sydney [New South Wales, Australia] for you.
UPPER RIGHT: Shark Pt, Clovelly in 16m.
LOWER LEFT: Kurnell in 12 m of water.
LOWER RIGHT: North Head, Port Jackson in 20m water. Animal is about 10cm long
Lumnitzer, A., 2000 (Jun 2) Pteraeolidia - brooding eggs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2489
Far be it for to comment on your sight but there are two pages for Pteraeolidia ianthina on the Forum. Now that the Species List is getting so large a good way to find species is to use the SEARCH button at the top and bottom of every page.
The different shapes and colours found in Pteraeolidia certainly suggest the possibility of more than one species but I have looked at material from all around the Indo-West Pacific and can't find even one consistent anatomical character to separate them. One reason for the colour differences, and perhaps the length of the cerata, relates to their symbiosis with photosynthetic plant cells (zooxanthellae) which is described on Page 1 and on the Solar powered nudibranch Page. Also look at the messages on those pages and below yours on this page.
One particularly interesting phenomenon you have captured in the upper right photo is the habit of this species to cluster in groups around a collection of egg masses which I have arrowed and enlarged in the inset. All observers who have seen this phenomenon in New South Wales find them on the exposed tops of large submerged boulders in 10-15 meters. The boulders are usually covered in encrusting coralline algae (which shows there is enough light for photosynthesis) and the group of Pteraeolidia usually stay with the egg masses for at least 2-3 weeks. At this size they are feeding on the large solitary hydroid Ralpharia sp. so they must either leave the egg masses at night to feed some distance away, starve, or else rely on the products of photosynthesis.
Thanks for the interesting photos. The bottom left photo shows an intermediate sized animal by a colony of colonial hydroids on which it is possibly feeding.
March 10, 2000
From: Valda Fraser
I have not been able to identify this nudibranch. Can you help!
Locality: South Coast KwaZulu-Natal, South Africa. Pumula - near Port Shepstone - 18m
Date: March 1999
firstname.lastname@example.orgFraser, V., 2000 (Mar 10) White Pteraeolidia ianthina from South Africa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2052
This is the white form of Pteraeolidia ianthina. You will see from my comments above that this is one of the Solar-powered nudibranchs which 'farm' one-celled plants in their bodies. However they have to obtain these brownish plant cells (zooxanthellae) after they have settled out of the plankton. Before they find them they are this translucent white colour. Usually they find zooxanthellae by the tine they reach about 10-15mm in length so your animal is apparently having difficulty finding a supply of zooxanthellae.
December 22, 1999
From: Anne Dupont
Regarding your forum discussion about the forms of Pteraeolidia ianthina, here are a couple of blue forms I photographed in Hawaii.
email@example.comDupont, A., 1999 (Dec 22) Pteraeolidia ianthina from Hawaii. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1701
We are certainly getting a large collection of colour forms.
Best wishes, and thanks for all your photos,
December 10, 1999
From: C. Carlson & P.J. Hoff
Have you seen a Pteraeolidia ianthina of this color form? I found quite a number in Yap --usually a bit larger than the 'normal' colored forms in the same area.
Details: 65mm; Yap, Goofnuw, 12m; 1 June 1994
The white forms were found on the walls of Goofnuw channel on the north-east coast of Yap. 'Normal' colored forms were in the same area, though generally slightly smaller.
Clay & Patty Jo
firstname.lastname@example.orgCarlson, C. & Hoff, P.J., 1999 (Dec 10) Forms of Pteraeolidia ianthina. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1649
Dear Clay & Patty Jo,
I have a theory that the colour forms with a lot of opaque white are usually associated with white coral sand or rock. If this is so, I also think that camouflage is not the sole reason for the colour pattern. I think that as with Plakobranchus ocellatus, the white pigmentation cuts down the intensity of the sunlight reaching the endosymbiotic zooxanthellae so that their plastids are not 'burnt-out' by too much sunlight and so continue to photosynthesise. It's just my pet theory and I think it would be a good little hypothesis for a physiologist to test experimentally.
I assume the white in your animals is a skin pigment which masks the brown of the zooxanthellae, while the white of juvenile animals is caused by the absence of skin pigmentation and the absence of zooxanthellae.
One problem with the theory is that if the pigmentation is genetically controlled how do the larvae choose the right colour background when they settle? Or perhaps larvae don't travel very far and populations of white animals have gradually built up in 'white environments' - or perhaps it's all a load of rubbish!
November 21, 1999
From: Vinka Stenhouse
Can you identify these photos from Espiritu Santo Is., Vanuatu (1997) please? They were all found on a sea mount that is prone to currents. 13m depth.
UPPER RIGHT: 10mm long (V.Stenhouse)
LOWER LEFT: 20mm long (J.Stenhouse)
LOWER RIGHT: 18mm long (J.Stenhouse)
Stenhouse, V., 1999 (Nov 21) Feeding? Pteraeolidia from Vanuatu. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1558
These are all juvenile forms of Pteraeolidia ianthina. The upper photo is particularly interesting as it may be a clue to what juveniles are eating. There is a photo of an adult feeding on its preferred food, the solitary gymnoblastic tubularian hydroid Ralpharia, but despite considerable searching I have been unable to confirm what the juveniles feed on. They are often found in areas with dense growths of colonial calyptoblastic hydroids but it would make sense if they fed on gymnoblastic species. There is a special reason why it would be interesting to know what the juveniles are eating. if you look at the page on solar-powered nudibranchs you will see that adult Pteraeolidia nurtures and breeds single-celled plants (zooxanthellae) in its body, and benefits by taking some of the sugars they produce for its own nutrition. What we don't know is where it gets its first zooxanthellae from. The reason all your juveniles are white or bluish-white is that they have not yet obtained zooxanthellae. Once they do they quickly gain a brown background colour. I suspect that, like other nudibranchs with zooxanthellae, they obtain the first injection of zooxanthellae from eating a hydroid with zooxanthellae. As the large Ralpharia don't have zooxanthellae, they must get them from their juvenile food. to prove my theory I need to find the juvenile food.
Lets hope your interesting photo will lead someone to finding the answer to this puzzle.
November 20, 1999
From: Valda Fraser
This one has amazing elastic properties. One photo shows it relaxed and going about its own business. The other shows it disturbed. I hope you will be able to identify it. It is common in our area.
Locality: South Coast KwaZulu/Natal, SOUTH AFRICA. Scottburgh, Rocky reef, 24m, November 1999. Size: 780mm
This is Pteraeolidia iathina which as well as being 'elastic' is also 'solar powered', keeping single-celled zooxanthellae alive in its body where they photosynthesise and provide sugars for the nudibranch. There is some variation in shape and colour throughout the the Indo-West Pacific but I am unable to find any anatomical differences to separate them into more than one species.
Bill Rudman.Rudman, W.B., 1999 (Nov 20). Comment on An 'elastic' aeolid from South Africa by Valda Fraser. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1548
August 18, 1999
From: Max Gillies
Just read your post 'Pteraeolidia from Sydney' on Bill's sea slug page. great shots! I've seen this guy at Fly Point in Port Stephens (best night dive in Australia for slugs I think!) as well but didn't have a camera handy. I was interested that he was at 30m as I found mine in 8m wandering over soft coral.
I could have watched it for hours (except it was turning into a drift dive as the tide had turned).
From memory he appears in 'Sea Slugs of Western Australia' with a small amount of information. I'll bring the book in tomorrow and scan the relevant sections if you're interested.
email@example.comGillies, M., 1999 (Aug 18) Re: Pteraeolidia from Sydney. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1206
They are quite often found on the greyish soft-coral, Parerythropodium which forms a leathery layer over sublittoral rocks. Adult Pteraeolidia feed on the large solitary hydroid Ralpharia which is found embedded in the soft-coral colonies. There is a photo of the hydroid at the Top of the Page.
Bill RudmanRudman, W.B., 1999 (Aug 18). Comment on Re: Pteraeolidia from Sydney by Max Gillies. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1206
August 18, 1999
From: Betsey Hansen
Thanks for the message. I found all of Sydney great for Sea Slugs. Unfortunately, I only spent two weeks there. I found more Sea Slugs diving there in two weeks than I have here in New York diving for ten years. I've been trying to get a transfer To Sydney to no avail.
Elizabeth.P.Hansen@chase.comHansen, E.P., 1999 (Aug 18) Re: Pteraeolidia from Sydney. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1207
August 8, 1999
From: Betsey Hansen
I've search you're entire slug site and can't find this one. Don't feel bad that I went through the entire slug site without finding it, though. I thoroughly enjoy going through all the slug sites and I even learn something on occasion. I promise not to call every sea slug a nudibranch anymore. I don't know if this habit is from scuba divers or Americans, but I will try to correct my friends.
This sea slug is from your part of the world. It was taken in October 1996 on the twin anchors wreck in Manly. [Sydney, New South Wales, Australia] The depth was about 30 meters and I found it crawling across the top of the wreck. It is quite beautiful, but you don't seem to have anything close to it.
Elizabeth.P.Hansen@chase.comHansen, E.P., 1999 (Aug 8) Pteraeolidia from Sydney. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1152
It is a colour form of Pteraeolidia ianthina. Local divers call it the 'Blue Dragon' because of its likeness to the sinuous shape of tradiitonal Chinese dragons.
Pteraeolidia inathina is either quite variable in shape and colour or there are a number of similar species. Your photos are of a form which I felt was a distinct species, but after looking at the anatomy and radula of about 100 specimens from around the Indo-West Pacific, I can find no distinguishing anatomical features. It differs externally in the manner in which it holds the cerata in flattened hand-like clusters and the large whitish crescent shape mark on the base of each ceratal cluster.
February 24, 1999
From: Erwin Koehler
Is this a juvenile Pteraeolidia ianthina? or Flabellina sp.? or something else? Red Sea, Egypt, divesite "Shark Reef ", Sept. '97, size 15mm.
E.Koehler@deutschepost.deKoehler, E., 1999 (Feb 24) Pteraeolidia juvenile?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/607
Thanks for the question. It made be realise I had never added this species into the index, although you could get to it through the Solar Power page.
Yes, I'm pretty sure its a juvenile Pteraeolidia ianthina. The purple bands on the oral tentacles are fairly distinctive.