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.
Halgerda guahan & H. johnsonorum - mating pair
From: Harry Blalock, September 17, 2007
Re: Mating Halgerda guahan from nthn Mariana Islands
From: Harry Blalock, May 23, 2007
Re: Mating Halgerda guahan from nthn Mariana Island
From: Greg Moretti, March 6, 2007
Mating Halgerda guahan from nthn Mariana Islands
From: Yuji Fujie, January 22, 2007
Photos of Halgerda guahan
From: C. Carlson & P.J. Hoff, March 20, 2000