I keep trying to get a decent photo of a limpet with its mouth open, scraping algae. This was better than most; the radula inside the mouth is visible, and even some of the internal organs show dimly through the meat of the foot. But what is that other tube around its "neck"?
|1/4 inch long limpet, cleaning the aquarium wall.|
I've spent several hours looking at limpet photos and reading anatomy pages. Nothing resembles that yellow tube that snakes out from the left side of the mantle and reaches out to the surrounding water. One source (beachwatchers.wsu.edu) mentions that keyhole limpets often carry a commensal scaleworm in the mantle groove. But this isn't a keyhole limpet, and that's no scaleworm.
Could it be a ribbon worm?