Science Sunday! The ampullae of Lorenzini are small vesicles and pores that form part of an extensive subcutaneous sensory network system. Each ampulla is a bundle of sensory cells that are enervated by several nerve fibers. These fibers are enclosed in a gel-filled tubule which has a direct opening to the surface through a pore. These vesicles and pores are found around the head of the shark and are visible to the naked eye. They appear as dark spots in the photo of a white shark head below. They detect the electrical impulses generated by the muscle contractions of nearby fish, seals, or other creatures. Recent research suggests that the ampullae may also allow the shark to detect changes in water temperature.