What structure do sharks use to detect weak electrical signals from prey?

Sharks use the ampullae of Lorenzini to detect weak electrical signals from prey. These sensory organs are jelly-filled canals, usually visible as small pores around the head and snout.

Muscle contractions and nerve activity create tiny electrical fields in seawater. The ampullae can detect these signals, helping sharks locate animals even when prey is buried in sediment or visibility is poor. They also assist with sensing electrical effects associated with the Earth's magnetic field.

The organs were described by the Italian anatomist Stefano Lorenzini in the seventeenth century. Their sensitivity is possible because seawater conducts electricity and because the canals connect the external pores to specialized receptor cells.

The ampullae are not the same as a shark's lateral line. The lateral line mainly detects water movement and vibration along the body, whereas the ampullae of Lorenzini detect electric fields. Both systems work alongside smell, vision, and hearing to build a detailed sensory picture of the surroundings.