West coast of Nth America from Alaska to Santa Barbara, California.
22 mm long, on its ctenostome bryozoan prey, Alcyonidium polyoum. Rocky intertidal at Cape Arago, Oregon, USA, August 1987. Photo: Jeff Goddard.
The background colour ranges from translucent white to grey. The mantle is covered in prominent conical papillae which are tipped with milky yellow. There is a milky yellow border to the mantle. The gills and rhinophores are tipped with a colour which ranges from orange-brown to a dark maroon. Grows to about 35mm in length.
O'Donoghue, C.H. (1921). Nudibranchiate mollusca from the Vancouver Island region. Transactions of the Royal Canadian Institute, Toronto, 13(1): 147-209
Rudman, W.B., 2005 (November 10) Acanthodoris nanaimoensis O'Donoghue 1921. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/acannana
July 31, 2008
From: Susan E. Glarum
Concerning message #15213:
The gray form of Acanthodoris nanaimoensis is fairly common along the northern Oregon coast, USA. My most recent find was of four individuals in the rocky intertidal at Haystack Rock in Cannon Beach, Oregon, USA on 20 April 2008. I do have digital pictures, but am not sure how to send them. I will attempt to upload a photo I took last summer (2007) at Ecola Point, Cannon Beach, Oregon, USA. I apologize for the quality of the photo; my camera is a relatively simple one. Also, I am neither a professional photographer nor a scientist, just an enthusiastic amateur.
Locality: Haystack Rock, Cannon Beach, Exposed at low tide, rocky intertidal, Oregon, USA, Pacific Ocean, 20 April 2008, Intertidal. Length: approximately 1 1/4 inches. Photographer: Susan E Glarum.
Susan E. Glarum
Beachie47@iinet.comGlarum, S. E., 2008 (Jul 31) Re: Grey colour form of Acanthodoris nanaimoensis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21551
It is hard to tell if this is A. nanaimoensis or A. hudsoni, as I don't see any maroon pigment on the gill or rhinophores. In any event, both species can be grey in ground color.
February 12, 2007
From: Pete Naylor
I have seen a number of dorids with all the identifying features of Acanthodoris hudsoni (yellow rhinopore tips and foot margin etc) but a darker mottled base. Often times I see these in the same area as more typical examples of Acanthodoris hudsoni, and they are generally very near or in contact with a second specimen. I am wondering if this coloration is related to reproductive activity or if this is actually a different species that I haven't been able to find in my books.
FWIW, I have also seen similar color variations in the very similar Acanthodoris nanaimoensis - though in those cases I've generally noted a bluish hue to one specimen while the other retained the white base color.
I've attached a photos to illustrate both the observations above. Sorry if this is in fact two separate species - I'm including both photos because I'm just not sure.
Locality: Admiralty Inlet, Puget Sound, 40 feet, Washington, USA, Northeastern Pacific Ocean, 13 January 2007, Submerged rock formation.. Length: 1.5 inches. Photographer: Pete Naylor.
Naylor, P.J., 2007 (Feb 12) Acanthodoris hudsoni color variation?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19229
To answer your question right off, all of these specimens are in fact Acanthodoris nanaimoensis. The important give-away when you see these darker pigmented, mottled specimens, is that the tips of the rhinophores and/or gills have some degree of red wine color, as shown in the close-up alongside.
As you are aware, Acanthodoris hudsoni has a white body with yellow at the tips of the dorsal papillations, rhinophores and gills. But there is never any wine colored pigmentation. Both species have a yellow marginal line.
Photographs of both color phases of A. nanaimoensis can be found in Lamb & Hanby, page 255 top, insert, and my very first edition of Pacific Coast Nudibranchs, (1980, blue cover), page 49.
Some of my colleagues have suggested that if your start with A. pilosa, and move to A. hudsoni, then to A. nanaimoensis and A. rhodoceras, we have a single species with very wide color variation, from white to dark, no color on tips to red then black. Food for thought.
Lamb, A. & B.P. Hanby. (2005) Marine Life of the Pacific Northwest. Harbour Publishing.
Behrens, D.W. (1980) Pacific Coast Nudibranchs. Sea Challengers Publishing.
Thanks for sharing these,
March 6, 2006
From: Jan Kocian
More nudibranch from Whidbey Island. Saturday dive at Keystone Jetty provided me with two very similar looking slugs, Acanthodoris hudsoni [lower] and Acanthodoris nanaimoensis [upper]. The two were just about ten feet apart, in the dark and murky water due to overcast weather looking like the same species.
Locality: Jetty, Whidbey Island, Puget Sound, WAshington, USA. Pacific coast. Depth: 25 feet. Length: 35 mm. 08 October 2005. Photographer: Jan Kocian
firstname.lastname@example.orgKocian J., 2006 (Mar 6) Acanthodoris spp in Puget Sound. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15010
Some photos of A. nanaimoensis seem to indicate its papillae are longer, more flexible and more densely packed than in A. hudsoni, but in these photos the only difference seems to be the paint job.
March 2, 2006
From: Jan Kocian
I just finished looking at photos from a dive two days ago, I found two pairs of Acanthodoris nanaimoensis trailing in two separate parts of the jetty. They were not going anywhere fast, the first pair was very close to the spot I found them thirty five minutes ago at the beginning of my dive. The "nose" of the trailing slug beneath the rear end of the leader.
Locality: Jetty, Washington USA, Puget Sound, NE Pacific Ocean, 24 February 2006, rocky. Length: 20 mm. Photographer: Jan Kocian.
email@example.comKocian J., 2006 (Mar 2) Re: Trailing Dorids. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15967
As usual your cartoon has made my day. Thanks.
Well I have to admit this sure looks like trailing to me, however we usually see the follower with its head above the posterior mantle of the leader, not underneath as in your photos. Maybe this is a new version of this interesting behavior. One thing for sure, this adds to our list of species that apparently trail. This is a first for an Acanthodoris.
November 10, 2005
From: Marli Wakeling
I found many large Acanthodoris nanaimoensis while on my Campbell River excursion. Many were mating, and some were much larger than the size range in my guidebook.
Locality: Steep Island, Campbell River, British Columbia, Canada. Pacific coast. Depth: 40 feet. Length: 35 mm. 08 October 2005. Rocky wall. Photographer: Marli Wakeling
firstname.lastname@example.orgWakeling, M., 2005 (Nov 10) Acanthodoris nanaimoensis from British Columbia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15187
Thanks for the photo. I hadn't realised until I saw your photo close up just how long and plentiful the dorsal papillae are. Size ranges are only as good as the available information. I'll change the Fact Sheet to 35 mm.
November 10, 2005
From: Jan Kocian
I found what I think is dark phase of Acanthodoris nanaimoensis but the rhinophores seem short compared to other pictures on the Forum, also lacking marking on gills.
Locality: Whidbey Island, Puget Sound. Washington, USA. Eastern Pacific Ocean. Depth: 15 feet. Length: 35 mm. 06 November 2005. old wharf. Photographer: Jan Kocian
email@example.comKocian J., 2005 (Nov 10) Grey colour form of Acanthodoris nanaimoensis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15213
I read that there is a grey colour form of this species, so I guess that is what this is. Certainly there are reddish tips to the rhinophores. The lack of colour on the gills is probably and individual variation. But if it is something else I am sure someone will let us know
January 2, 2005
From: Marli Wakeling
Here's a photo of Acanthodoris nanaimoensis, found on the Sunshine Coast of British Columbia, at a dive site called Tzoonie Narrows.
Locality: Tzoonie Narrows, British Columbia, Canada, Pacific Ocean. Depth: 40 feet. Length: 25 mm. 13 November 2004. Current swept channel. Photographer: Marli Wakeling.
firstname.lastname@example.orgWakeling, Marli, 2005 (Jan 2) Acanthodoris nanaimoensis from British Columbia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12869
We certainly are getting a good range of photos showing colour variation in this species.
October 23, 2003
From: Bruce Wight
Johanna and I were up at the Northern end of Vancouver Island the first week of October diving around Port Hardy and Browning Pass, British Columbia. This was our first time diving in Canada.
This was one of two species of Acanthodoris we saw.
email@example.comWight, B., 2003 (Oct 23) Acanthodoris nanaimoensis from British Columbia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11280
April 1, 2002
From: Marli Wakeling
Here is Acanthodoris nanaimoensis, found at Bowyer Island, Howe Sound, British Columbia.
PHOTO: South East Bowyer Island, Howe Sound, British Columbia, Canada
DEPTH: 40 feet
LENGTH: 3 cm.
DATE: Dec.3, 2000
PHOTO BY: Marli Wakeling
firstname.lastname@example.orgWakeling, M., 2002 (Apr 1) Acanthodoris nanaimoensis from British Columbia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6480
It is interesting to see the quite considerable colour range between the gills and rhinophores of your animal and Jeff Goddard's
December 30, 2000
From: Jeff Goddard
Here is a photo for the Forum of Acanthodoris nanaimoensis O'Donoghue 1921, 22 mm long, on its ctenostome bryozoan prey, Alcyonidium polyoum. I found two specimens in the rocky intertidal at Cape Arago, Oregon in August 1987. A. nanaimoensis ranges from Alaska to southern California (Behrens, 1991).
email@example.comGoddard, J., 2000 (Dec 30) Acanthodoris nanaimoensis from Oregon. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3272