I am continuing with feeding trials of the 2 captive slugs, Megapallifera mutabilis. Here is one of them right after I interrupted its feeding on a piece of algae-covered beech.
The enlargement of the area in front of the slug's tail shows the teeth marks at the edge of the feeding track.
I still haven't figured out how exactly they create those marks, because I still haven't observed them feeding. As soon as I turn a light on, start opening lids and moving things around, the slugs stop feeding. The best I have done so far is the following shot. It shows the front of one slug's head. The mouth is right below the lower tentacles; it was, however, raised above the green crust of cyanobacteria.
I'll get lucky one of these nights.