Electric Ray

It varies a lot by species. The small numbfishes and marbled torpedoes produce discharges in the range of about 8 to 45 volts, enough to stun a shrimp or a small fish and to give a person a sharp, unpleasant jolt. The Atlantic torpedo, the largest species, is the powerhouse — it can generate up to roughly 220 volts at high current in short bursts, delivering a shock strong enough to knock a grown adult off their feet or briefly incapacitate a limb. The power comes in a rapid train of pulses that fades quickly as the organs discharge, and the ray needs time to "recharge" before it can deliver another full jolt. Electric rays are not considered deadly to humans, but the shock is genuinely hazardous to a diver in deep water or a person who falls.

With paired electric organs that fill much of the front half of its disc, one on each side of the head. Each organ is a honeycomb of hundreds to thousands of vertical columns, and each column is a stack of flattened, disc-shaped cells called electrocytes — modified muscle cells that have lost the ability to contract but kept the ability to build up a voltage across their membranes. Nerves trigger all the electrocytes in a column to fire almost simultaneously, and because they are stacked in series like batteries in a torch, their small individual voltages add up. The columns are wired in parallel, which boosts the current. The ray can fine-tune the strength and pattern of the discharge for stunning prey versus warning off a predator.

The name comes straight from the ray. "Torpedo" is a Latin word meaning numbness, stiffness, or sluggishness — from torpere, "to be numb" — and it was the Romans' name for the electric ray because handling one left your arm dead and tingling. The English words "torpid" and "torpor" share the same root. When the self-propelled underwater explosive weapon was developed in the 19th century, it was named "torpedo" after the fish, partly by analogy with an earlier sense of the word for a moored naval mine that lay in wait. So the modern military torpedo is named, at two removes, after a flat, slow, shocking ray.

Yes. The therapeutic use of the torpedo ray's shock is one of the oldest recorded forms of what we would now call electrotherapy. The Roman physician Scribonius Largus, writing around 46 AD, recommended placing a live black torpedo on the head to relieve chronic headache and migraine, and standing on one at the seashore to treat gout, with the numbing shock repeated until the affected part went dead. Greek and later Arab physicians described similar treatments for pain and for anal prolapse. The practice continued in folk medicine around the Mediterranean into modern times, and it is sometimes cited as a distant conceptual ancestor of TENS machines and other electrical pain therapies.