Re: Trapania maculata with eggs

February 26, 2009
From: Dominique Horst

Concerning message #22277:

Hi Bill,

Two more pictures to show the visible egg mass from different point of view.
Not sure these help to be sure that the egg ribbon is pre-formed in the slug before laying it down.

Locality: Cannes, 23 m, France, Mediterranean sea, 21 February 2009. Length: 7 mm. Photographer: Dominique Horst.

Kind regards,
Dom.

dominique.horst@wanadoo.fr

Horst, D., 2009 (Feb 26) Re: Trapania maculata with eggs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22287

Dear Dom,

I think these photos clarify the situation quite well. Although from the right side of the animal the eggs do seem to be coiled in an ribbon-like tube, the photo from the left side shows the eggs scattered more randomly. So I think we can say that their apparent arrangement in a coiled egg ribbon is just an illusion. To further explain the position of the ovotestis - which makes the eggs and sperm - have a look at your photos in an earlier message [# 22088]. The dark brown-black organ which fills the back half of the body is the digestive gland, which is unique to molluscs, and as its name suggests, is involved with digesting the food, absorbing the nutrients into the bloodstream, and in excreting the waste products. In most dorids the ovotestis forms a layer over the top half of the digestive gland and in some cases, such as Trapania, also extends into a lump behind the digestive gland. We can see this very clearly in your two photos.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Feb 26). Comment on Re: Trapania maculata with eggs by Dominique Horst. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22287

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