Gymnodoris sp.

Photo courtesy of the Webmaster
Animal courtesy of Akiko Miyamoto
May, 2002

Gymnodoris sp. (undescribed species)

This weeks BOW is another spectacular example of the nudibranchs crawling around the reef substrates of the Kerama Islands in Japan. This terrific beast was first featured on the cover of Atsushi Ono's excellent field guide to the opisthobranchs of this region. This is an undescribed species, and a whopper for sure(est. 75-100 mm by Webmaster). Years ago when webmaster Miller and brancher buddy Terry Gosliner came across what later turned out to be Gymnodoris aurita , we thought it reminded us the tyrannical dinosaur, Tyrannosaurus rex, and nick-named the critter Gymnodoris REX. Atsushi's animal here may be a better candidate for that moniker.

Specimens of this white on white beauty reach up to a honking 100 mm in length. It is a member of one of the more voracious genera who feeds on other opisthobranchs and some species are in fact cannibalistic. See Bill Rudman s presentation on Gymnodoris inornata for a few stories and some great photos of a Gymnodorid chowing down on a colorful, brother branch.

This species large white mushroom shaped pustules make it easy to identify and its size make it easy to find. Aside from Atsushi s specimens from Kerama, specimens have been documented from northern Queensland, Australia, Mozambique and Natal, south east Africa, and Enewetak and Kawajalein in the Marshall Islands (see the Sea Slug Forum - Gymnodoris sp. 5).

I can't wait to see next weeks surprise from Mike's trip to Japan.

Dave Behrens
Danville, Calif
Jul., 2002

Webmaster, Akiko, and Jerry at docking area, Zamami Island,Kerama Islands, Okinawa

I have been a diver for 13years, traveled almost all area in Micronesia and used to work as a divemaster in Grand Cayman 1992-96, then came back to home in Japan. Two years ago, when I encountered Mr Ono's branchs guide book unintentionally at the book store's shelf, I didn't expect that my career in diving would reset .Everything became brand new ! Had I missed the wonderful m/m macro world for 13 years?? I found that every dive site I went before there are still unsearched areas to prowl about for nudibranchs.

Frequently I fly to the Kerama islands in Okinawa (only 2hours flight from Tokyo + 45mnt.. by boat), water temperature is as warm as in Florida. To my surprise, in Japan there are many divemasters in the process of learning a lot about specific aquatic life, in order to meet their customer's interests. Quite a few diver's come to Ono's dive shop only to do "the branchs' diving". Most of them have U/W cameras and are well-trained divers. I did my first shopping for a U/W digital camera and purchased a system for around US$540 that included a Olympus C-2020 + a plastic housing +lights and modified the housing and camera only to shoot the m/m branchs. The great fun of digital camera is that during the trip I can ask the name of the branchs in a day not only to the divemaster and also anyone on the web. If someone were to say that the branch I found today was a new spieces, I feel like "I got BINGO !"

It was so fun to join Michael Miller and Jerry Allen and their Japanese friends (Rie Nakano and Nishina Masayoshi ) in May. I was glad in this season in Okinawa has been rather dry compared to the usually sticky rainy season.

Finding the tiny spieces sometimes we flap the bottom of cracked corals, that skill need a good eyesight .In first few dives most of branchs were very tiny ones. When we found the white giant Gymnodoris and a pair of Halgerda calsoni at once, Mike and Jerry seem to say with joy "We have been waiting American size one !"

I favor Okinawan clear water and the energetic corals. Just started the branchs photo to design my web site "Aquatic Gems---Okinawan sea slugs"

I would like to make the site as "Treasure branchs hunting on the web" for the kids, wishing they could be aware of the precious tiny life like m/m branchs.

Akiko Miyamoto
Hiroshima, Japan
Jul., 2002
Send Akiko email at

Webmaster's Notes: Ever fantasize about branchs you might see on any given trip?? I did! The subject of this week's BOW was defintely on my wish list to see for the Okinawa visit! Akiko made this dream come true!! Akiko was a bundle of activity in the water searching everywhere for the elusive sea slugs. Jerry and I kinda of trailed behind in wonderment at the number of branchs the Japanese divers were finding. After they were through,we moved in with our film based cameras but really didn't have much luck with the really small animals. We are in the process of rectifying this deficiency! When Akiko isn't out diving for branchs, she can be found in her spare time working as a volunteer in assisted living for the elderly in Hiroshima. What a lady! Our hats are off to Akiko Miyamoto!!

Mike Miller
The Slug Site
Jul., 2002

Taxonomic information courtesy of:

David W. Behrens

Author: Pacific Coast Nudibranchs
Co-Author Coral Reef Animals of the Indo Pacific
Propriator of Sea Challengers Natural History Books !

Send Dave mail at

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