Egg masses; the direction they spiral

March 5, 1998
From: Irina S.Roginskaya

Dear colleagues,
working with sea slugs in the Southern Hemisphere, can anybody inform me about the direction of coiling of spiral egg ribbons or egg strings of your nudibranchs? In the northern Hemisphere they are practically always counterclockwise directed.
Thank you.
Irina S.Roginskaya.
Moscow, Russia

Roginskaya I.S., 1998 (Mar 5) Egg masses; the direction they spiral. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

This is an interesting question as their is some evidence to suggest that some floating siphonophores such as Bluebottles or Portugese man o'war (Physalia) and the related Velella, have their sails angled in the opposite direction in each hemisphere to catch the prevailing winds. However the direction in which the nudibranch egg coil is spiralled is the same throughout the world. One example I have illustrated above, Onchidoris depressa, is a good example as it is a north Atlantic species which has apparently arrived here in the southern hemisphere by hitching a ride on the bottom of a ship. If the position on the earth somehow affected the direction of spiralling you would expect it to change in Onchidoris but it doesn't. If anyone has photos of clockwise spiralling egg masses to prove me wrong please send them in.

Rudman, W.B., 1998 (Mar 5). Comment on Egg masses; the direction they spiral by Irina S.Roginskaya. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Related messages

  1. Egg spiralling
    From: Gilles Matheron, March 16, 2004
  2. Nudibranch eggs - direction of spiral
    From: Asther M. Lau, May 7, 2003
  3. The direction of egg-mass spiralling
    From: Yoshiaki J. Hirano, April 1, 2001
  4. Spiral egg ribbons
    From: Irina Roginskaya, October 21, 2000
  5. Thanks for spirals
    From: Irina Roginskaya, August 5, 1999
  6. New research on egg coiling direction
    From: I.S. Roginskaya & V.A. Grintsov, July 30, 1999
  7. Re: Egg masses; the direction they spiral
    From: Irina S.Roginskaya, March 12, 1998

Show factsheet and all related messages