G. nigricolor on the goby Amblyeleotris steinitzi (Klausewitz). 6 to 8mm long, found 22m depth. Kerama Island, near Okinawa, Japan. PHOTO: Atsushi Ono
This species has only been recorded from the Ryukyu Archipelago. It has a remarkable association with a number of species of gobies, apparently living permanently on their fins, and feeding on the skin between the fin rays. Osumi & Yamasu (1994) suggest that the association is nearer to parasitism than symbiosis.
•Baba,K (1960): The genera Gymnodoris and Nembrotha from Japan (Nudibranchia - Polyceridae). Publications of the Seto Marine Biological Laboratory 8(1): 71-74.
•Williams, E.H. & Williams, L.B. (1986) The first association of an adult mollusk (Nudibranchia: Doridae) and a fish (Perciformes: Gobiidae). Venus, The Japanese Journal of Malacology, 45(3): 210-211
• Mulliner, D.K. (1991) Contact Association between the nudibranch Gymnodoris nigricolor Baba, 1960 (Gymnodorididae) and the Datehaze Goby (Perciformes: Gobiidae). Western Society of Malacologists Annual Report 23: 17.
• Osumi, D. & Yamasu, T. (1994) The nudibranch Gymnodoris nigricolor Baba, parasitic with marine Gobies. Zoological Science, 11 (Supplement: Proceedings of the 65th Annual Meeting of the Zoological Society of Japan): 54.
Bob Bolland has a series of photos of this remarkable association between a nudibranch (Gymnodoris nigricolor) and fish (gobies).Authorship details
Rudman, W.B., 2000 (March 20) Gymnodoris nigricolor [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/gymnnigr
December 22, 2001
From: Mary Jane Adams
Since Gymnodoris nigricolor has only been reported from the Ryukyu Archipelago in southern Japan, I was very surprised to find it in Morovo Lagoon, Solomon Islands. I had already made a dozen dives at this site before spotting the two slugs on the goby's fins. They seemed to be very securely attached to the fin rays. The slug on the
dorsal fin was tossed from side to side every time the goby flicked it's fin. The one on the pelvic fin was dragged across the sand whenever the goby changed position. When disturbed, the goby seemed to bolt into it's burrow as rapidly as any other.
Location: Wickum Island, New Georgia group, Solomon Islands. Depth: 13 meters, 16 November 2001
Goby: Amblyeleotris steinitzi
Shrimp: Alpheus djeddensis
email@example.comAdams, M.J., 2001 (Dec 22) Full house - goby, shrimp & Gymnodoris. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/5867
Dear Mary Jane,
This is indeed a wonderful Christmas present. Not only does it show that G. nigricolor may be widespread in the Indo-West Pacific, but your description and excellent close-up photos help us to understand the nature of the relationship between nudibranch and fish.
Although it has been suggested that they feed on the fin tissue, I could find no sign of damage on any of the fish I have examined. From your photos it seems that the the Gymnodoris, for some reason, firmly attach to the fish by grasping the fins with their buccal apparatus. In your photo you can clearly see the buccal bulb extended out enveloping one or more fin rays. My feeling is that rather than eating the fins, these Gymnodoris are using the fins as a relatively easy part of the body to attach to. This doesn't of course answe the question of what they eat.
I can offer no suggestion about why they have evolved such a relationship and guess we will only properly understand it when we determine just what the Gymnodoris feed on. It is a fascinating relationship.
May 1, 2001
From: Bob Bolland
Here are two ova scans of Gymnodoris nigricolor. One is of the animal laying eggs (rfb2388-B) at the air-water interface of a small glass sorting bowl; the second is of an egg rosette on the glass side of an aquarium (rfb2383) . . . this egg mass measured 8x13mm. Unfortunately the size of the two animals was not recorded, but the animals were collected in June of 1990, from Seragaki, Okinawa. I can't recall ever seeing ova being deposited at the water's surface before, perhaps the 'branch didn't like the glass walls of the sorting bowl?
firstname.lastname@example.orgBolland, R.F., 2001 (May 1) Eggs of Gymnodoris nigricolor. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4247
March 21, 2000
From: Atsushi Ono
This dorid is a parasite on some species of gobies. I am pretty sure this is Gymnodoris nigricolor Baba,1960. This goby is Amblyeleotris steinitzi (Klausewitz).
I have never seen G. nigricolor crawling, it is always parasitic on gobies.
They are about 6 to 8mm long, found 22m depth.
email@example.comOno, A., 2000 (Mar 21) Fish parasite? Gymnodoris nigricolor. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/2131
Thanks for the wonderful photos. Bob Bolland has a series of photos of this remarkable association between a nudibranch (Gymnodoris nigricolor) and fish (gobies).
I remember when I first saw an article on this association, I thought perhaps the Gymnodoris had got 'spiked' on the fish after collection. It is a remarkable relationship which is now considered to be a parasitic rather than symbiotic relationship.