Carlson & Hoff, 1993
Known only from the original description from Guam.
UPPER: 48mm; Guam, Anae Is; March 1991. leg. Peter Schupp. LOWER: this is either a 32mm specimen from Agat, or a 41mm specimen from Bile Bay; March 1969. PHOTOS: C. Carlson & P.J.Hoff.
See message for futher details.
Translucent white with orange-edged ridges and an opaque white mantle border. There can be orange marks between the ridges. Translucent white gills and rhinophores have large scattered black spots.
• Carlson, C.H. & Hoff, P.J. (1993) Three new Halgerda species (Doridoidea: Nudibranchia: Opisthobranchia) from Guam. The Veliger, 36(1): 16-26.
Rudman, W.B., 2000 (March 14) Halgerda guahan Carlson & Hoff, 1993. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/halgguah
September 17, 2007
From: Harry Blalock
I came across something I have never seen before and wonder just how unique it is. I spotted a Halgerda guahan and a Halgerda johnsonorum mating in the Grotto. I sat and watched them for about 45 minutes, they were not just passing, they were clearly lined up properly and in the process of mating. And I guess the next question is, what do you get when a Halgerda guahan and a Halgerda johnsonorum mate?
Locality: Grotto - a cavern dive, 35', Saipan, Northern Mariana Islands, Pacific Ocean, 16 September 2007, Red algae covered rocks. Length: 2". Photographer: Harry Blalock.
Thanks as always for your time!
email@example.comBlalock, H., 2007 (Sep 17) Halgerda guahan & H. johnsonorum - mating pair. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20736
'What do you get when a Halgerda guahan and a Halgerda johnsonorum mate?' - it sounds like a joke is on the way! By definition animals of different species are not supoosed to mate. I have had some doubts about some of the species of Halgerda described in recent years but these two species seemed quite distinct from one another with little evidence of intermediate colour forms.
All I can say is keep a look out for possible intermediates and for more matings across the apparent species barrier.
July 28, 2007
From: Harry Blalock
Over the weekend we stumbled upon something fairly significant I think. Friday afternoon I noticed a single Halgerda guahan on the rope rock in the Grotto on the island of Saipan, a very unusual spot for one to hang out. The next day, as we were coming in to the Grotto, we found an area that had 7 Halgerda guahan and 1 Halgerda malesso all within a 30' radius. Two of them were very close, but not mating at that point I don't believe. Then when I went back to the rope rock, I noticed 3 Halgerda guahan on the rock. I stayed there taking hundreds of pictures, and before long 3 more Halgerda guahan came out of holes and one more Halgerda malesso came out. I got some great shots of a couple of them obviously mating. Sunday when I went back, it was the same situation, and then I even got to watch a Halgerda guahan laying an egg ribbon on the rope rock as well. How often does this species mate, and do they all do it at once as seemed to be the case this weekend? I posted hundreds of their pictures on my website at www.saipandiver.smugmug.com/Nudibranchs
I'll include a couple pictures of them and the egg sack.
Locality: Grotto, a cavern dive , 20' - 60', Saipan, Northern Marianas Islands, Pacific Ocean, 20, 21 & 22 July 2007, boulders and on hard rock bottom. Length: between 1 inch and 3 inches. Photographer: Harry Blalock.
firstname.lastname@example.orgBlalock, H., 2007 (Jul 28) Halgerda guahan - a weekend of mating. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20305
I suspect we know nothing about the biology of this species, or for that matter, very little about any species of Halgerda. I think the question of whether nudibranchs meet to mate or mate when they meet is still to be answered. I suspect that once they are physically mature they are willing and able to mate whenever they meet, and I suspect much meeting occurs because they are attracted to a particular food. I guess chance meetings and following the mucus trail of a potential partner are other ways they may meet but I can't imagine that is very productive. Again this is another area for research.
May 23, 2007
From: Harry Blalock
Concerning message #19191:
I have also come across some Halgerda guahan and Halgerda malesso [see separate message #19939 ] recently on the island of Saipan. They seem to like the Grotto, as I have seen quite a few of them there now. Here are a few of my pictures.
Locality: Grotto, 50', Saipan, Northern Mariana Islands, Pacific, 18 February 2007, cave with lots of big rocks that fell in from the ceiling years ago. Length: approximately 4". Photographer: Harry Blalock.
email@example.comHarry Blalock, 2007 (May 23) Re: Mating Halgerda guahan from nthn Mariana Islands. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19937
These species seem to be restricted to the tropical NW Pacific so it is good to get some more records of them so we have a better idea of their variability.
March 6, 2007
From: Greg Moretti
Concerning message #19191:
Here's another photo of Halgerda guahan from Saipan, CNMI.
Locality: Grotto, 10m, Saipan, Commonwealth of the Northern Mariana Islands, Pacific, 18 February 2007, Reef. Length: 40mm?. Photographer: Greg Moretti.
firstname.lastname@example.orgMoretti, G.S., 2007 (Mar 6) Re: Mating Halgerda guahan from nthn Mariana Island. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19527
January 22, 2007
From: Yuji Fujie
Here we have two pictures from mating Halgerda guahan in Saipan.
Locality: Grotto, 10m, Saipan, Northern Mariana Islands, Pacific Ocean, 27 May 2006, on the rock in darkness. Length: 30mm. Photographer: Yuji Fujie.
email@example.comYuji Fujie, 2007 (Jan 22) Mating Halgerda guahan from nthn Mariana Islands. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19191
Thanks for this. It is nice to compare it with your photos of the similar lookingH. malesso [#19190] but which differs in having the orange lines absent from the tubercles.
March 20, 2000
From: C. Carlson & P.J. Hoff
The 1969 specimen is one of the first animals we ever photographed. The original slide is not doing too well as well as holding color and holding off the fungus.
UPPER PHOTO: 48mm; Guam, Anae Is; March 1991. leg. Peter Schupp.
LOWER PHOTO: this is either a 32mm specimen from Agat, or a 41mm specimen from Bile Bay; March 1969.
Clay & Patty Jo.
firstname.lastname@example.orgCarlson, C. & Hoff, P.J., 2000 (Mar 20) Photos of Halgerda guahan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2129