Re: Onchidiid from Thailand

April 28, 2003
From: Kevin J. Caley

We have been calling this animal Onchidium verrucosa, which is uncommon to common in Hong Kong. However, not much work has been done here on this group, so we ARE fumbling in the dark a bit!
Kevin J. Caley

Dear Kevin,
The lack of a shell and the often poor descriptions of living animals, means the onchidiids are in a taxonomic mess. Fortunately, internal anatomy seems to be quite distinctive so it should be possible to sort them out although it may mean consigning many older names to an 'unidentifiable' list. There are similar problems with another 'slug' group -the lamellariid section of the velutinids, but in that case many species were described from the reduced internal shell alone so now it is a question of matching shells with living bodies.

Returning to Onchidium. Onchidium verruculatum is a large Indian Ocean species with secondary gills on its back. I agree that the literature is sparse but Cuvier's original description makes it pretty certain that this large species with seondary gills on the mantle is quite identifiable. Unfortunately later authors have incorrectly identified other species from both the Pacific and the Indian Ocean as O. verruculatum and O. verrucosa [See photo below]. I am not sure that this species is the same - it is certainly large enough, but I can see no sign of the secondary gills.
Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Apr 28). Comment on Re: Onchidiid from Thailand by Kevin J. Caley. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Limpet-like slug from New South Wales
    From: Sam Rodely, February 22, 2010
  2. Re: Onchidella celtica from Channel Ids
    From: Frans Janssens, July 22, 2008
  3. Re: Onchidella celtica from Channel Ids
    From: Jean-Yves Monnat, September 22, 2007
  4. Pulmonate slugs from the Caribbean
    From: Phillip Gillette, July 4, 2007
  5. Marine pulmonate slug from India
    From: Doug Eernisse, April 4, 2007
  6. Onchidium from the Arabian Sea
    From: Bhavik Patel, November 16, 2006
  7. Korean slug in intertidal zone
    From: William Churchill, September 6, 2006
  8. Sea slug from Tioman Island, Malaysia
    From: Andrew Lee, February 16, 2004
  9. Dendrodoris? from Siladen, Indonesia
    From: Ginette Allard, December 3, 2002
  10. Re: Onchidella celtica from Channel Ids
    From: Yves Muller, February 18, 2002
  11. Re: Onchidella 'eggs'
    From: Peter Wirtz, February 17, 2002
  12. Onchidella celtica from Channel Ids
    From: Nick Jouault, February 11, 2002
  13. Giant Onchidium from South Africa
    From: Valda Fraser, May 8, 2001
  14. Pulmonate slug? from Maldives
    From: Erwin Koehler, May 4, 2001
  15. Onchidiid from Thailand
    From: Sylvain Le Bris, March 17, 2001
  16. Pulmonate Slugs from Philippines
    From: Erwin Koehler, January 13, 1999
  17. Photo of Onchidium
    From: Stephanie A. Clark, January 13, 1999

Show factsheet and all related messages