Notarchus indicus
Schweigger, 1820

Superfamily: APLYSIOIDEA
Family: Aplysiidae


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.

Authorship details
Rudman, W.B., 2000 (June 27) Notarchus indicus Schweigger, 1820. [In] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Re: Notarchus indicus at Eilat
    From: Binyamin Koretz, February 17, 2006
  2. Notarchus indicus at Eilat
    From: Bill Rudman, March 15, 2005
  3. Re: Notarchus from Hawaii
    From: John Hoover, August 3, 2000
  4. Strange Sea Hare from Hawaii
    From: John Hoover, August 2, 2000
  5. More photos of Notarchus swimming
    From: Jochen Scholtyssek, July 6, 2000
  6. Notarchus indicus swimming
    From: Jochen Scholtyssek, June 28, 2000

Show factsheet and all related messages