"Things You Wouldn't Know If We Didn't Blog Intermittently."
Yes, a leaf. Sure, that is exactly what it resembles. First thing to come to mind. Nothing else.
The vein pattern is, if I understood correctly what I read, the intestinal tract branching into the body. The cells lining the tract (enterocytes) practise kleptoplasty, that is: they "steal" chloroplasts from the eaten algae and keep them as their own symbionts.At first it was thought that plasts could not survive very long in an animal cell, but it has been discovered that the slug genome does provide the proteins needed for maintaining the plast function!