May 7, 2003
From: Asther M. Lau
Just wondering which direction do most nudibranchs lay eggs. Clockwise or anti-clockwise?
Asther M. Lau
firstname.lastname@example.orgLau, E.M., 2003 (May 7) Nudibranch eggs - direction of spiral. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9839
Have a look at the egg spiral page. You will find a number of relevant messages there and a number of links to other messages.
Most opisthobranch egg masses seem to spiral in an anticlockwise direction [sinistral] - that is coiling in a anticlockwise direction from the centre. However some such as Melibe australis and Melibe engeli seem to be dextral, coiling clockwise from the centre.
However you will see there is some discussion about whether in the northern hemisphere they spiral anticlockwise and in the southern hemisphere clockwise, but there is not a lot of evidence to support that idea. Another complication is whether the egg ribbon is started at the outside or in the centre. Usually the egg ribbon is started at the centre, but in a few animals the egg ribbon is started at the outside. If a ribbon is started at the outside then it will look the reverse to what it actually is. Nothing is simple I'm afraid.
From: Gilles Matheron, March 16, 2004
The direction of egg-mass spiralling
From: Yoshiaki J. Hirano, April 1, 2001
Spiral egg ribbons
From: Irina Roginskaya, October 21, 2000
Thanks for spirals
From: Irina Roginskaya, August 5, 1999
New research on egg coiling direction
From: I.S. Roginskaya & V.A. Grintsov, July 30, 1999
Re: Egg masses; the direction they spiral
From: Irina S.Roginskaya, March 12, 1998
Egg masses; the direction they spiral
From: Irina S.Roginskaya, March 5, 1998