Mating behavior and spawning event in Thuridilla moebii

All the photos whose present in this page are taken in a small area of "Trou d'eau lagoon", on a large population in September 2010 by Christophe Cadet and Philibert Bidgrain

Since the begining of September a large population of Thuridilla moebii was observed on the fringing reef of Trou d'eau lagoon. I observed betwwen 20 and 50 specimens during each observation... All these specimens crawl during the day on the substratum, sometimes forming little group (maximum five specimens)

Mating event



24 September 2010. Full moon day,

Christophe Cadet

I saw a dozen of "couples" into this configuration "head to tail", which you can see below the head, the genital papillae

In addition, during each mating or when they are able to reproduce (when the reproductive organ is out), the anterior border of the foot becomes red (b)

The genital papillae (a)


Some specimens are walking alone, genital papillae visible (a)


26 September 2010

Philibert Bidgrain

Only one mating behavior on the 25 specimens observed...

The beginning of the "Parade nuptiale" ?


Spawning event

28 September 2010

Christophe Cadet

I have photograph three spawn with the animal...

The spawn is formed by a thin orange filament arranged in spiral, glued onto the substrate.

3 October 2010. I watched about twenty specimens, but no spawn and no mating, specimens observed continuing to crawl on the substrate.