Favorinus tsuruganus - egg-laying observations

August 20, 2003
From: Jim Black

Hi Bill
Here is some behavior for you - from Anilao, Batangas, Philippines

I was taking a pic of a nudi laying eggs on a small piece of dead coral. A nice spiral ... I moved the coral to suit a better photo angle ... as I resettled to shoot ...I noticed that the nudi was now laying the eggs across its pattern. I believe that these little guys have a built-in gyro and heading orientation for navigation ... and when this one got messed up-by me - he continued on the original heading for the continued egg laying spiral .... very interesting!!

All the best
Jim Black
Pittsburgh, Pa


Thanks Jim,
It is certainly an observation worth repeating. There is a lot of interest in the direction they spiral [clockwise or anti-clockwise], but I can't think of anyone who has studied the mechanics of maintaining the spiral during an egg-laying.

By the way, your animal is Favorinus tsuruganus, one of a genus of nudibranchs which feed on the eggs of other opisthobranchs. I can't recall seeing an animal with a whitish region below the black tip of each ceras, but it fits in all other respects.
Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Aug 20). Comment on Favorinus tsuruganus - egg-laying observations by Jim Black. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10739

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