Electric Catfish

The largest species, the African electric catfish Malapterurus electricus, can produce discharges above 350 volts and, in some reports, up to around 450 volts, released in rapid bursts of many pulses. The current is relatively low, so a healthy adult human who is shocked typically gets a sharp, painful jolt and brief loss of muscle control in the affected limb rather than a life-threatening injury, though a strong shock in deep water could be dangerous by causing someone to lose coordination and drown. The shock is more than enough to stun the small fish the catfish eats and to make a would-be predator let go immediately. Fishermen who handle these catfish in nets and traps are shocked regularly and treat them with respect.

Unlike the electric eel and electric ray, where the electric organs are concentrated in the tail or the wings, the electric catfish's organ forms a thin, continuous layer that wraps almost the entire body like a sleeve, sitting just beneath the skin and outside the muscle. It is built from thousands of flattened, disc-shaped electrocytes, cells derived from muscle tissue that have lost the ability to contract but retained the ability to build up a charge across their membranes. Nerve signals make all the electrocytes fire together, and because they are stacked and connected in series their small individual voltages add up to the total discharge. The head end is negative and the tail end positive, the opposite polarity to most other strongly electric fish.

Yes, and it is one of the earliest animals whose electric shock was recorded. Electric catfish appear in Egyptian art from the Old Kingdom, around 5,000 years ago, most famously in a fishing scene in the tomb of Ti at Saqqara, and the fish had its own hieroglyph. Classical authors including Pliny mentioned a Nile fish that numbed the hands, and medieval Arabic medical texts describe applying a live electric catfish to a patient to treat conditions such as epilepsy and pain, paralleling the Greco-Roman use of the Mediterranean torpedo ray. So the phenomenon of a "shocking fish" was known and even used therapeutically for millennia before electricity itself was understood.

They are kept by specialist keepers of large or unusual fish, and they are hardy, but they are a serious commitment and a genuine hazard. An adult needs a very large tank (the biggest species outgrows most home aquariums), a soft substrate and robust hiding place, and a meaty diet, and it must be housed alone because it is highly aggressive to other electric catfish and will eat or shock tankmates. The main issue is the shock — routine maintenance means reaching into a tank containing a fish that can deliver a strong, painful jolt, so keepers use tools, switch off electrical equipment, and take great care, and the fish is not recommended for households with children. Smaller Malapterurus species are more manageable but still shock.