Cross-species matings - Chelidonura

April 10, 2003
From: Richard Willan

Dear Bill,
Since opisthobranchs are inherently rare in time and space, it follows that, theoretically, there should be more cross-species matings when individuals encounter each other than in relatively commoner molluscs. I have not seen any instances of cross-species matings in opisthobranchs myself, but believe I have documented the result of one such mating, that is a naturally-occurring hybrid individual. In the paper I published with Riccardo Cattaneo-Vietti in 1995 (on page 13), I described and illustrated one specimen of Chelidonura from Palau that seemed to be a hybrid of C. amoena with C. electra because it possesed pigmentation and shape characteristic of both species. Could you widen this page to include possible hybrids between known opisthobranch species like this one as well as records of both cross-species matings?

• Willan, R.C. & R. Cattaneo-Vietti (1995) New data on Chelidonura amoena Bergh, 1905 (Opisthobranchia: Cephalaspidea: Aglajidae). The Beagle, Records of the Museums and Art Galleries of the Northern Territory, 12: 9-18.


Thanks Richard,
I'm happy to add hybrids to the page, although it is one step removed from actually seeing interactions between two species. Unless we actually see the mating and isolate the resulting eggs, saying that a particular animal is the result of a cross-species mating is a pretty risky business. It also raises the question of species definition. If two 'species' are unable to distinguish between each other, is this a comment on our ability to determine what is a species?

In the particular case of these two 'species' of Chelidonura, C. electra was named by me so I might be thought to have an interest in its future - Who would want such a spectacular animal to be lumped with dull, and much older C. amoena? Despite that, if I consistently found animals which were intermediate in colour I would be inclined to consider them to be colour variants of one species rather than hybrids of two. It is certainly something worth looking into. If anyone has further photos of these two species to add to the ones we already have, they would be very welcome.
Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Apr 10). Comment on Cross-species matings - Chelidonura by Richard Willan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Chelidonura amoena

Related messages

  1. Color variation in Chelidonura amoena from Lembeh
    From: Mike Krampf, July 27, 2007
  2. Re: Chelidonura amoena piggyback
    From: Kristin Anderson, July 17, 2007
  3. Chelidonura amoena piggyback
    From: Kristin Anderson, July 12, 2007
  4. Re: Chelidonura amoena from the Philippines
    From: Jose Victor Santos, May 15, 2007
  5. Re: Are Chelidonura electra and C. amoena the same?
    From: Roberto Sozzani, November 24, 2006
  6. Are Chelidonura electra and Chelidonura amoena one species?
    From: Linda Ianniello, November 22, 2006
  7. Chelidonura amoena from Malaysia
    From: Asther M. Lau, August 12, 2006
  8. Chelidonura amoena from Komodo, Indonesia?
    From: Robert Whitton, July 26, 2006
  9. Chelidonura amoena in Taiwan
    From: Alex Tattersall, July 25, 2006
  10. Pre-mating Ritual - Chelidonura amoena
    From: Mike Krampf, June 7, 2006
  11. Chelidonura amoena from Derawan, Indonesia
    From: Gennaro Ciavarella, December 13, 2005
  12. Chelidonura amoena in Malaysia
    From: Asther M. Lau, September 11, 2003
  13. Chelidonura amoena at Pulau Redang
    From: Kheong Sann Chan, September 11, 2003
  14. Chelidonura amoena - shape and colour variation
    From: Atsushi Ono, July 2, 2003
  15. Chelidonura amoena mating
    From: Paul Whitehead, June 21, 2003
  16. Chelidonura amoena population explosion
    From: Todd Garthwaite, May 24, 2003
  17. Re: Chelidonura amoena spawning
    From: Nishina Masayoshi, May 12, 2003
  18. Chelidonura amoena spawning.
    From: Johny Leffelaer, May 9, 2003
  19. Chelidonura amoena from Malaysia
    From: Kelvin Tan, April 24, 2003
  20. Twin Tail Nudibranch from Malaysia
    From: Spencer Huang, October 10, 2002
  21. Chelidonura amoena from Malaysia
    From: Richard Houghton, July 19, 2002
  22. Chelidonura amoena from Malaysia
    From: Maliza Anuar, July 19, 2002
  23. Chelidonura flavolobata? from SE Sulawesi
    From: Lindsay Warren, June 16, 2002
  24. Re: Chelidonura amoena population explosion
    From: Todd Garthwaite , June 10, 2002
  25. Chelidonura amoena from Christmas Island
    From: W.B. Rudman, April 30, 2002
  26. Chelidonura amoena population explosion in Taipei
    From: Todd Garthwaite, April 27, 2002
  27. Chelidonura amoena from Taiwan
    From: Todd Garthwaite, April 1, 2002
  28. Chelidonura amoena - colour variation
    From: Nishina Masayoshi, February 21, 2002
  29. Chelidonura amoena from the Philippines
    From: Mary Jane Adams , June 16, 2001
  30. Chelidonura cf. amoena from SE Sulawesi
    From: Lindsay Warren, March 1, 2000
  31. Chelidonura amoena from the Philippines
    From: Erwin Koehler, May 1, 1999

Show factsheet and all related messages