Indo-West Pacific. Reported to have migrated into Mediterranean through Suez Canal.
ROYAL Diving Center, Akaba, Jordan. Red Sea. 15m., April 2000. Upper photo showing Notarchus swimming. Photos: Jochen Scholtyssek.
Notarchus is a genus of Sea Hare in which the parapodia are almost completely fused. There is a small anterior opening to allow an exchange of water to the mantle cavity. They have no shell. They are able to escape from danger by swimming by jet propulsion. A most spectacular if inelegant display which I have described in a message below.
There are two described species, Notarchus punctatus with an armed penis and Notarchus indicus without. N. punctatus is recorded from the Mediterranean, Caribbean and curiously Japan. Notarchus indicus is known from much of the Indo-West Pacific under various names.
See Jochen's photos and my descriptiion of swimming behaviour below.
See second message with further photos.
• Schweigger, A.F. (1820) Handbuch der Naturgeschichte der skelettlosen ungegliederten Thiere. Leipzig.
Rudman, W.B., 2000 (June 27) Notarchus indicus Schweigger, 1820. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/notaindi
Re: Notarchus indicus at Eilat
From: Binyamin Koretz, February 17, 2006
Notarchus indicus at Eilat
From: Bill Rudman, March 15, 2005
Re: Notarchus from Hawaii
From: John Hoover, August 3, 2000
Strange Sea Hare from Hawaii
From: John Hoover, August 2, 2000
More photos of Notarchus swimming
From: Jochen Scholtyssek, July 6, 2000
Notarchus indicus swimming
From: Jochen Scholtyssek, June 28, 2000