New Zealand opisthobranchs

Related messages

Re: Phyllidia? from New Zealand

September 18, 2001
From: Bernard Picton

Hi Bill,
I'm sure you are right - I think Chris Irvine's mystery is a sponge of the family Polymastiidae which typically grow partly covered by sand and have papillae with osculae at the tips as can be seen here.

Picton, B.E., 2001 (Sep 18) Re: Phyllidia? from New Zealand. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Bernard,
Bill Rudman

Phyllidia? from New Zealand

September 15, 2001
From: Chris Irvine

Dear Bill,
Can you ID this please. It was photographed at Alderman Islands - Bay of Plenty - New Zealand. Size 80 - 100mm. On rocky reef, April 2000.

I had no idea what I was looking at but now assume it is a nudibranch


Irvine, C., 2001 (Sep 15) Phyllidia? from New Zealand. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Chris,
I'm afraid not every weird shape is a nudibranch. I suspect this is a sponge colony. The pale band around the base, which looks like a foot, is probably part of the colony which was previously covered by sand. In future if you come across a strange object take a photo then give it a gentle prod to see if its attached. If it is not attached then by turning it over you may see some clues to what it is. Of course you should turn it back afterwards.

Any further mysteries - or non mysteries for that matter - from New Zealand are always welcome.
Bill Rudman

Rudm,an, W.B., 2001 (Sep 15). Comment on Phyllidia? from New Zealand by Chris Irvine. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Opisthobranchs in NZ & Global Warming

August 19, 2001
From: Wade Doak

Dear Bill
To accompany my message about Aplysia extraordinaria from New Zealand, here is some more information on opisthobrachs from the Poor Knights Islands, northeastern new Zealand. A local diver, Janine Collet sighted Roboastra arika at the Poor Knights on 31 January, 2001 at the Northern Arch. Her companion took a photo. I hope it may be sent to you. As you would know, this is our second Roboastra.

I have been diving the Poor Knights since 1963 and have written about its marine life in 4 books . Reading the discussion you had with Richard Willan, I suggest that the dramatic increase in nudibranch species at the Poor Knights is not just the result of increased diver effort. I am seeing a corresponding increase in exotic species right across the board: fishes , echinoderms crustaceans etc. I suggest it is more likely to be partly the result of climate change.

We were pretty good at distinguishing new species back in the early seventies - a team of red hot young diving marine biologists were with me in those days who now have positions in many leading Australian scientific institutions.

For example,the green Tambja sp. is pretty hard to see on its green Bugula food source. I think I was the first to notice it, while decompressing on the top of Landing Bay Pinnacle, and I published it in my book Beneath NZ Seas in 1971. If we were distinguishing nudibranchs like that I cannot believe we would have overlooked some of the gaudy species turning up in the last few years.

Wade Doak

Doak, W., 2001 (Aug 19) Opisthobranchs in NZ & Global Warming. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Wade,
I hope Janine Collet can organise for the photo of Roboastra arika to be sent to the Forum. For that matter any records are of interest.

Concerning my discussion with Richard Willan. I was not suggesting that divers in the past had poorer observational skills than they have today. The problem is we have no systematically collected baseline data so we do not know if the apparent 'first appearances' of these tropical animals are in fact 'first appearances'. Many nudibranchs are notoriousy patchy in their distribution in both space and time. That is you can never rely on them being present at a certain place or at a particular time of the year. Most opisthobranch enthusiasts who have favourite places are always finding 'new animals' at their collecting spots even after years of visiting. You may be right in saying that more 'tropical' animals seem to be occurring at the Poor Knights now than 20 years ago, but unfortunately we have no way of knowing if this is really so. And even if it were so, we would have to ask whether the fauna 20 years ago was 'normal' or whether the present faunal composition is 'normal'? To know that, we would need baseline data from 50 or 60 years ago. It is interesting that records of tropical shelled molluscs from New Zealand in the 1800s were later dismissed as mislocalised specimens etc, but it is possible that in fact they were recording an earlier warm period.

The other point is that there are many more eyes out there and many more cameras recording things than ever before. While you and the hot young marine biologists were looking 20 or 30 years ago, most other divers then were only interested in what they could shoot with a spear gun, or collect and eat (paua, crayfish, sea urchins etc). As many nudibranchs have very short life cycles, sometimes only a few weeks, I am sure many visitations by transient tropical species could have occurred between visits by interested divers. From what I gather now, the Poor Knights would have diving parties visiting during much of the year, which must greatly increase the chances of animals being seen.

Unfortunately the lack of baseline data is a worldwide problem. Until we begin collecting faunal census data on a systematic and regular basis we will never be able to say with any scientiific certainty just what is happening to our fauna.

Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Aug 19). Comment on Opisthobranchs in NZ & Global Warming by Wade Doak . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Re: Need info on New Zealand sea slugs

June 2, 2001
From: Cynthia Trowbridge

Dear Bill and Katherine,

There is a 106 page paperback book available from the Leigh Marine Laboratory:
• Willan, R. & Morton, J. (1984) Marine Molluscs. Part 2. Opisthobranchia. Leigh Marine Laboratory, University of Auckland, New Zealand.

When I worked in New Zealand, I found this book to be very useful to learn the slug fauna and to access the primary literature. Also, another book that may be helpful is the recent book by Graham J. Edgar, Univ. Tasmania. 1997. Australian Marine Life, The Plants and Animals of Temperate Waters. Reed Books, Victoria.

Perhaps, Bill, you could share with the rest of us, to what is the degree of overlap in opisthobranch species between New Zealand and SE Australia? Are most New Zealand opisthobranchs also in Australia? I assume that those with planktotrophic larvae probably are. I would be keen to hear your thoughts on this.

Trowbridge, C., 2001 (Jun 2) Re: Need info on New Zealand sea slugs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Cynthia,
To answer your question about the relationship between the NZ and SE Australian faunas. I used a recent checklist of NZ molluscs (Spence & Willan, 1996) where there are 138 opisthobranch species (excluding the pteropods) reported from New Zealand. After removing a couple of subantarctic animals and a couple of taxonomic anomalies I divided the remaining 134 species into 3 categories. Those endemic to New Zealand (NZ) those found in both NZ and southern Australia (Aust), and those found in NZ but having a broad distribution in the Indo-West Pacific (IWP).

You will see from the table alongside that there is a characteristic endemic NZ opisthobranch fauna, especially amongst the bubble shells and nudibranchs. There are species common to NZ and southeastern Australia, a phenomenon also evident in other marine molluscs, and a much larger element of species with a wide distribution in the Indo-West Pacific.

New Zealand has a rich endemic fauna of marine molluscs which to a large extent have evolved independently from the Australian fauna since the breakup of Gondwana. At present the prevailing currents in the Tasman Sea are from west to east which explains the occurrence of southeastern Australian elements in the NZ marine fauna. The widespread IWP elements in the fauna have probably been introduced both from Australia and from the large cyclic oceanic water movements which occur in the South Pacific from time to time (El Nino etc).

Thanks for mentioning Willan & Morton's handbook. It is certainly a good introduction, giving biological information on the species covered, but it is by no means comprehensive, dealing only with species that have been recorded from the vicinity of the marine station at Leigh. The other excellent book you mention, by Graham Edgar, includes a broad coverage of the temperate Australian marine fauna and flora, but as I explain above, the NZ fauna and flora is quite distinct.

• Spence, H.G. & Willan, R.C. (1996) The Marine Fauna of New Zealand: Index to the Fauna 3. Mollusca. New Zealand Oceanographic Institute Memoir, 105 (for 1995): [Opisthobranchs on pp 32-37]

Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jun 2). Comment on Re: Need info on New Zealand sea slugs by Cynthia Trowbridge. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Need info on New Zealand sea slugs

May 31, 2001
From: Katherine

Could someone please help me out. I'm on a mission to help my friend and it includes finding out as much as I can about the types of sea slugs that live in New Zealand.
So if anyone has any info I would be greatly appreciative.


Katherine, 2001 (May 31) Need info on New Zealand sea slugs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Katherine,
I'm afraid the New Zealand sea slug fauna is not big enough to justify its own book but if you are really serious the place to look would be:
Powell, A.W.B. (1979) New Zealand Mollusca: Marine, Land & Freshwater Shells. Collins: Auckland. 500pp.

Powell was an expert on New Zealand shells so he did not have a personal knowledge of the sea slugs. The opisthobranch section of the book was based on published information up until that date, and with discussions he had with experts in the field. It certainly will give you a good idea of the New Zealand fauna but I think it is now out of print so you would need to find a library which has it.

For photos, have a look in the Forum. If you go to the SEARCH facility and type in new zealand you will get a list of specific records to sea slugs from New Zealand on the Forum. Another place to look is Ian Skipworth's 'Skip's Underwater Image Gallery' which has some beautiful images of New Zealand Nudibranchs plus several other pages of underwater fauna, lots of links to other related sites - images, diving & equipment.

If you have photos to identify, or specific questions, they are very welcome at the Forum.

Best wishes,
Bill Rudman

Rudman, W.B., 2001 (May 31). Comment on Need info on New Zealand sea slugs by Katherine. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Are nudibranchs indicators of global warming?

May 13, 2001
From: Richard Willan

Dear Bill,
I read your recent message recording Hypselodoris kaname from the Poor Knights Islands, northern New Zealand, with interest. This tropical Indo-Pacific nudibranch represents the third species to have been recorded from the Poor Knights, as this group of islands is popularly known, this year (the others are Cadlinella ornatissima and Protaeolidiella juliae)(see Protaeolidiella reference below), all three of them were recorded between September 1999 and April 2001. It has been known for a century that tropical Indo-Pacific animals reach the north of New Zealand as larvae drifting on the east Australian current, that they arrive during the years the water temperatures are hottest and that they settle at the Poor Knights if they are going to settle anywhere. The Poor Knights seem to be a "stepping stone" to the New Zealand mainland. Shelled molluscs have been some of the animals that have been used as demonstrations of this pattern because their taxonomy is relatively well known and people frequently collect them. Nowadays nudibranchs are noticed just as frequently as shells used to be collected. Divers have been visiting the Poor Knights regularly since the early 1970's, so these nudibranchs would probably have been mentioned if they had turned up previously.

Perhaps nudibranchs, like corals, are bioindicators for global warning? But unlike corals that are long-lived and respond to global warming by "bleaching" the zooxanthellae out of their tissues, nudibranchs are short-lived and so they would seem potentially even more sensitive bioindicators of global warming when populations of Indo-Pacific species become established in marginal areas where they never existed before. It would be interesting to know if other people have noted expansions of range, like the cases cited above, in recent times. Furthermore, I would encourage divers in northern New Zealand to see if such tropical nudibranchs form permanent populations. If three tropical species have been recorded already, one can bet there will be more.
Incidently, I agree with you that Ian Skipworth's chromodorid is Hypselodoris kaname and that H. koumacensis is a junior synonym. For your information, this species also occurs in eastern Australia; in 1985 Carol Buchanan photographed a specimen that was found on a fish trap that had been set in 100 metres off Coffs Harbour. It is typical of H. kaname in every way, but it could not be named at the time because the specimen was not preserved.

• Willan, R.C. (2001) First record of the aeolid nudibranch Protaeolidiella juliae (Burn, 1966) in New Zealand. Poirieria, Journal of the Auckland Museum Conchology Section, 27: 31-33.


Willan, R., 2001 (May 13) Are nudibranchs indicators of global warming?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Richard,
Perhaps you could see if the divers who found these other two species would be willing to post their photos on the Forum so we have a visual record of their interesting find.

Your comments about global warming are interesting. The biggest problem with finding biological evidence of global warming is the lack of any baseline data. Divers have certainly been visiting the Poor Knights for some years but I suspect in earlier times most of them were more interested in hunting fish and collecting shells etc than in photographing nudibranchs, so we can't really say whether thse recent tropical finds are evidence of global warming or part of a fluctuating cycle which sometimes allows tropical larvae to reach northern NZ and survive.

You are familiar with Long Reef in northern Sydney. It is a relatively short reef but it sticks out from a headland that juts out into the sea, like an arm waiting to 'catch larvae floating past. I ran a search on the species of the cowry genus Cypraea which we had in our collection from Long Reef. In total there are 25 species represented, 24 of which are tropical in distribution. Anyone seeing the list would think that Long Reef was a shell-collecting paradise in the tropics. But no, it is a fairly rich temperate water reef with a smattering of temporary tropical species. At any time you might find one species of tropical Cypraea, but usually there would be none. The list is based on over 120 years or more of collecting, but without a scientific sampling program over the same period we have no way of knowing whether
Long Reef is becoming more tropical or not. I had thought of comparing the collection dates of all the specimens but I that would reflect the relative activity of collectors over time rather than give us any information on when cowry species were actually present. It is certainly an interesting topic.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (May 13). Comment on Are nudibranchs indicators of global warming? by Richard Willan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Re: Help me identify NZ nudibranchs please.

January 30, 2001
From: Jane McLeish

Thanks so much, these are exactly the ones I saw. Its nice to know exactly what they are.

Thanks again for your help.

McLeish, J., 2001 (Jan 30) Re: Help me identify NZ nudibranchs please.. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Help me identify NZ nudibranchs please.

January 29, 2001
From: Jane McLeish

I was diving in New Zealand over Christmas and need help in identifying some nudibranchs. I've just started taking an interest in these strange, but beautiful creatures, so please excuse my ignorance.

One was white in colour with orange patches on it, and the other was black, with bright blue patches on it. I saw them while I was diving the Poor Knights Islands.

Sorry, I can't say much more, but any help would be excellent
Thanks so much.


McLeish, J., 2001 (Jan 29) Help me identify NZ nudibranchs please.. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jane,
The most likely species you saw were Ceratosoma amoena for the orange-spotted one, and Tambja morosa for the black one with blue spots.

Have a look at the photos at the top of each species page, and at the messages below them for more information about these two.

However, you haven't given me an awful lot to go on so there is a possibility that I've got it wrong.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jan 29). Comment on Help me identify NZ nudibranchs please. by Jane McLeish. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

photos from New Zealand

December 12, 1998
From: Ross Armstrong

Dear Bill,

Here are some photos of the following nudibranchs from New Zealand:
Ceratosoma amoena
Dendrodoris citrina
Dendrodoris gemmacea
Jason mirabilis
Plocamopherus imperialis 
Tambja verconis
Tritonia incerta

Please note that Diane and I both try to take 'pretty' pictures rather than ID pictures so they may be of limited use.   We do get a reasonable number of ID photos but don't bother getting these scanned.  We have a lot of nudibranch slides and a few sea hare shots also. Other nudibranchs include Tambja morosa, Tambja affinis, Tambja morosa and Archidoris wellingtonensis.

We also have slides showing mating nudibranchs and nudibranchs with egg ribbons.  We could get some of these scanned if you wanted them.  There is also another photographer in Whangarei (Dave Stallworthy) who is particularly interested in nudibranchs.  He even went on a couple of trips with Richard Willan to the Three Kings.  Dave is not taking photos at present but should have a lot more nudibranchs.

The Ceratosoma and Tritonia images were taken on the Tutukaka coast of Northland.  All the other photos were taken at the Poor Knights.  Hopefully I have spelled the names correctly.



Ross Armstrong

Armstrong, R., 1998 (Dec 12) photos from New Zealand. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ross,
Thanks very much for the photos which I will post on the site in the next few days.

I am interested in photos of any species from New Zealand, even things I already have photos of from Australia or elsewhere. The aim of the Forum is to provide not just an identification photo but evidence of a species' geographic range and its biology. So any of the animals you listed would be
great to have as they considerably extend the range of what are tropical or at least "Australian" species. Sea hares, side-gilled slugs (pleurobranchs), bubble-shells etc are all of interest as well as the true nudibranchs.

Your mention of photos with egg masses and mating are of interest as are photos of animals feeding etc so we can get some more information on what they feed on. If you can interest other divers in sending stuff it would be very welcome. If we get a bit of stuff I can set up a New Zealand index page so all the NZ stuff on the site could be readily found.

Concerning "pretty" versus "id" pics. I love pretty pics - unfortunately sometimes an id pic is needed as well to clarify things.

Thanks again,
Bill Rudman.

Rudman, W.B., 1998 (Dec 12). Comment on photos from New Zealand by Ross Armstrong. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from