Egg eater from Japan

July 30, 2001
From: Nishina Masayoshi

Dear Dr.Rudman,
This I do not find often, so I guess this is
not that common here.

Date: 30 Sep, 2000
Place: Nazumado, Hachijo Island, Japan
Depth: 6m
Size: 10mm

Best Regards,
Nishina Masayoshi

Nishina, M., 2001 (Jul 30) Egg eater from Japan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Nishina,
This is Favorinus tsuruganus, which was first described from Japan, but is now known to be widespread, at least in the western Pacific. Most species of Favorinus appear to be uncommon, but I think it is a question of finding the egg masses they feed on. I don't know whether each species of Favorinus prefers the egg masses of particular species, but Favorinus japonicus, is often very common when Sea Hares are breeding, feeding on their egg masses.

Many nudibranchs, and other sea slugs, appear to be rare until we know something about their natural history - their food, their breeding cycle, etc., Then we know where to look for them.
Thanks for these interesting photos. It is possibly the egg mass of Hexabranchus. If that could be confirmed, it would be interesting, because in an earlier message Stuart Hutchison reported F. tsuruganus feeding on their eggs.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Jul 30). Comment on Egg eater from Japan by Nishina Masayoshi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Re: Colour forms of Favorinus tsuruganus
    From: Colin Ogden, June 27, 2007
  2. Colour forms of Favorinus tsuruganus ?
    From: Richard Swann, May 23, 2007
  3. Favorinus tsuruganus from Sydney Harbour
    From: Nicholas Missenden, May 27, 2005
  4. Favorinus tsuruganus in the Red Sea
    From: Jacob Dafni, April 25, 2005
  5. Favorinus tsuruganus from Reunion Island
    From: Philibert Bidgrain, February 22, 2005
  6. Favorinus tsuruganus on Goniodoris felis eggs
    From: Dong Bum Koh, February 7, 2005
  7. Favorinus tsuruganus from Sth Korea
    From: Dong Bum Koh, December 19, 2003
  8. Favorinus tsuruganus eating Hexabranchus eggs
    From: Yves Coze, December 1, 2003
  9. Favorinus tsuruganus from Korea
    From: Dong Bum Koh, November 15, 2003
  10. Favorinus tsuruganus - egg-laying observations
    From: Jim Black, August 20, 2003
  11. Nembrotha rutilans & Favorinus tsuruganus
    From: Mark Burnett, December 30, 2002
  12. Favorinus tsuruganus - feeding on eggs
    From: Dave Harasti, December 8, 2002
  13. Favorinus tsuruganus from Indonesia
    From: Ginette Allard, November 27, 2002
  14. Favorinus tsuruganus - new record from N.Z.
    From: Gareth Jones, February 14, 2002
  15. Re: Egg eater from Japan
    From: Nishina Masayoshi, August 5, 2001
  16. Re: Colour of Favorinus tsuruganus
    From: Stuart Hutchison, June 4, 2001
  17. Favorinus tsuruganus from Indonesia
    From: Stuart Hutchison, June 3, 2001
  18. Photo of Favorinus tsuruganus
    From: Lindsay Warren, March 19, 1999

Show factsheet and all related messages