Glaucus in New Zealand

February 25, 1999
From: Ross Armstrong

Dear Bill

The attached image was supplied by my Uncle and Aunty Bill and Lynda West of Opotiki in New Zealand's Bay of Plenty.  (Central east coast of the North Island). In late January they were walking on the beach and encountered some Glaucilla washed up on the shore.  At the time neither had seen these before and did not know what it was.  They took some samples and had it identified
as Glaucilla alanticus. There have been a lot of easterlies blowing things up on the beach.  After getting it identified they went looking for some more.  So far they have
found a total of 27.  They have tried keeping them in a small aquarium but have a fairly high mortality rate.  I believe the photo was taken in the aquarium.  Neither are marine biologists but they have made some interesting observations including seeing a pair mating?  and also suspecting they might
become cannibalistic if there is a shortage of food.  They have been feeding them on jellyfish that have also been washed up.  They sent me a letter explaining what they have done and observed but I left it at home.
I look forward to any information you may be able to provide or questions that you may have.

kind regards

Ross Armstrong

Armstrong, R., 1999 (Feb 25) Glaucus in New Zealand. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks for the great photo of Glaucus atlanticus. Whoever identified it for your Aunt & Uncle as Glaucilla atlanticus got it half right and half wrong. There are two very similar looking species, Glaucus atlanticus and Glaucilla marginata. Both have very similar life styles, floating upside down in the sea, feeding on Physalia and other similar floating cnidarians. Have a look at the pages and pictures I have on these two species.

To comment on your observations. Glaucus is usually found washed up on beaches with the Portugese man o' war, Physalia after days of onshore winds. With little power of independent movement they are at the mercy of the winds and currents. They will, like most nudibranchs confined in small containers, mate at the drop of a hat! Being hermaphrodite, every member of the same species is a potential partner. Other animals your Aunt & Uncle could try feeding their Glaucus with are Porpita and Velella, two little blue animals which also float at the surface. One has an oval shaped transparent disc with a diagonally placed "sail" which gives it the name of "By-the-wind Sailor" and the other has a circular disk and no sail.

It is possible that Glaucus and Glaucilla will eat each other, when starving, as other aeolids are known to do that. One other interesting thing about these slugs is that they lay short egg strings of 10-20 eggs which float at the surface until the larvae hatch. I have some photos somewhere. As soon as I find them I will put one on the page for you.
Best wishes,

Rudman, W.B., 1999 (Feb 25). Comment on Glaucus in New Zealand by Ross Armstrong. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Glaucus atlanticus

Related messages

  1. Glaucus from South Africa
    From: Emil H Niksch, May 3, 2010
  2. Glaucus atlanticus from Florida
    From: Stephanie Armentrout, April 30, 2010
  3. Glaucus atlanticus from nthn New South Wales
    From: Jayson Dyer, April 23, 2010
  4. Re: Glaucus atlanticus from Florida
    From: Douglas Hernandez, April 6, 2010
  5. Glaucus atlanticus from Florida
    From: Emma C., April 5, 2010
  6. Blue Bottles and Nudibranch washed up at Kiama, NSW
    From: Cherie Noon, March 24, 2010
  7. Glaucus atlanticus in Hawaii
    From: Aaron Silva, January 29, 2010
  8. Glaucus atlanticus find in Northern NSW Australia
    From: Matthew Ross, January 20, 2010
  9. Glaucus atlanticus from Hawaii
    From: Enjoli' Hoskins, September 8, 2009
  10. Occurrence of albino Glaucus atlanticus?
    From: Evan Orellana, August 31, 2009
  11. Glaucus atlanticus from Pacific coast of Panama
    From: Clark Misner, May 14, 2009
  12. My Glaucus atlanticus Report
    From: Kenneth Hattersley, May 14, 2009
  13. Glaucus atlanticus in Gulf of Mexico?
    From: Kenneth Hattersley, April 7, 2009
  14. Re: Tiny, elaborate creature at Stradbroke Island, Queensland
    From: Paul Stewart, March 17, 2009
  15. Glaucus atlanticus from Kenya
    From: Debs North, January 8, 2009
  16. Tiny, elaborate creature at Stradbroke Island, Queensland
    From: Ken Thomas, December 3, 2007
  17. Glaucus atlanticus from Pacific coast of Mexico
    From: Joe Weiss, March 7, 2007
  18. Sea Lizard [Glaucus atlanticus] from New South Wales
    From: Lynne T., March 2, 2007
  19. Glaucus atlanticus mating habits
    From: Johanna Schwartz, January 29, 2007
  20. Glaucus atlanticus in Hawaii
    From: Nichol Miura, January 16, 2007
  21. What type of Nudibranch is this?
    From: Adrian Giles, January 15, 2007
  22. Re: Glaucus atlanticus on Gold Coast, Queensland
    From: Rob Alesbury, January 15, 2007
  23. Glaucus atlanticus on Gold Coast, Queensland
    From: John Campbell, December 14, 2006
  24. Glaucus eating Porpita in Hawaii
    From: Anna-Christina Amason, August 17, 2006
  25. Feeding and some trophic interactions of Glaucus atlanticus
    From: Irina Roginskaya, August 2, 2006
  26. About egg masses of Glaucus atlanticus
    From: Irina Roginskaya, May 25, 2006
  27. Unknown creature from Fraser Island, Queensland
    From: Richard Wilsher, May 9, 2006
  28. Some notes about Glaucus atlanticus
    From: Irina Roginskaya, May 9, 2006
  29. Not sure if this IS a sea slug?
    From: Mary Patterson, April 26, 2006
  30. Glaucus at Anna Bay, New South Wales
    From: Jim Doyle, March 31, 2006
  31. Re: Cannibalism in Glaucus?
    From: Peter Whiter, March 30, 2006
  32. Cannibalism in Glaucus?
    From: Peter Whiter, March 28, 2006
  33. What the ?
    From: Eve Whicker, March 23, 2006
  34. What is Filurus dubius?
    From: Gary Rosenberg, February 24, 2006
  35. Glaucus atlanticus - habitat
    From: Brandon Pinkney, February 21, 2006
  36. Is this a sea slug ??
    From: Karen Beal, February 14, 2006
  37. Blue Sea slug
    From: Liliana Alaniz, February 2, 2006
  38. Glaucus atlanticus from the Canary Islands
    From: Kim Boettcher, May 23, 2005
  39. Information on Glaucus atlanticus
    From: Kealy Baker-Clark, April 22, 2005
  40. Blue, lizard-like feather-finned tiny animal
    From: Paiton Meurer, April 14, 2005
  41. Glaucus atlanticus from Reunion Island
    From: Philibert Bidgrain, February 19, 2005
  42. Found some interesting sea slugs in Florida
    From: Sarah McDowell, January 31, 2005
  43. Neon Blue sea slug from Fraser Island?
    From: Neil Rhodes, January 1, 2005
  44. Is this a nudibranch?
    From: Scott Godwin, January 21, 2004
  45. Glaucus atlanticus from Sth Africa
    From: Juleen du Toit, January 21, 2004
  46. Glaucus atlanticus from Queensland
    From: Nick Falconer , December 3, 2003
  47. Glaucus from Wellington Pt, Brisbane
    From: Mimi & Phong, November 17, 2003
  48. Glaucus in Hawaii
    From: Chaunte Ling, May 27, 2003
  49. Mysterious blue and white swirley things
    From: Sally, April 25, 2003
  50. Re: Glaucus in Sydney
    From: Alex & Marcus Dawes, March 19, 2003
  51. Glaucus in Sydney
    From: Alex and Marcus Dawes , March 12, 2003
  52. Glaucus atlanticus from Lord Howe Island
    From: W.B. Rudman, January 24, 2003
  53. Glaucus atlanticus reference
    From: Michael Schroedl, November 14, 2002
  54. Glaucus atlanticus - observations
    From: A. Lovatt., October 21, 2002
  55. Thanks
    From: Amanda Johnson, June 15, 2002
  56. Glaucus atlanticus information
    From: Manda, June 6, 2002
  57. Re: Collaroy 'Blue Dragon' - thanks
    From: Stephen Martin, May 23, 2002
  58. Mass of blue dragon(?) nudibranchs
    From: Stephen Martin, May 20, 2002
  59. Questions about Glaucus
    From: Luke Short, April 25, 2002
  60. Blue plankton in Uruguay
    From: Philip Miller, February 16, 2002
  61. Glaucus from Pensacola, Florida
    From: Elvira Davis, February 4, 2002
  62. Re: Glaucus detecting prey
    From: Belinda Biggam, March 18, 2001
  63. Glaucus detecting prey
    From: Belinda Biggam, March 15, 2001
  64. Re: Glaucus
    From: Lisa, February 20, 2001
  65. Glaucus
    From: Chris Parks, August 24, 2000
  66. Information on Glaucus atlanticus
    From: Angela, August 12, 1999
  67. Eggs of Glaucus and Glaucilla
    From: Bill Rudman, May 16, 1999
  68. Glaucus & Porpita in New Zealand
    From: Ross Armstrong, March 31, 1999
  69. Re: Glaucus in New Zealand
    From: Ross Armstrong, February 26, 1999

Show factsheet and all related messages