Among the electric fishes, the South American, electric eel is unique in its ability to generate electric discharges large enough to potentially hurt.
Quick pulses shock its prey into muscle spasms, momentarily rendering the smaller fish defenseless for the electric eel.
If the first shock doesn’t wear out its prey, South American eels can twist around and trap its prey and release a volley of electric charges.
The volley causes a series of uncontrolled contractions in the prey, preventing it from escaping.
Out of all the predation strategies for immobilizing prey, the South American eel absolutely has one of the most unique.
Be sure to know when American Eel spawn.
Table of Contents
- South American, Electric Eel Voltage Levels
- South American Electric Eel
- How Does a South American Eel Produce Voltage?
- Why do Electric Eels Produce Voltage?
- How The South American Eel Hunts With Voltage
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South American, Electric Eel Voltage Levels
Weak electric discharge for navigation and communication are typically less than 1 V.
But, for the purposes of predation, electric discharges can range from 10 to 600 V.
Some reports even show that voltages can get as high as 800 V.
- For navigation/communication: < 1 V
- For predation/defense: 10–800 V
For South American eels, these surges are usually very quick.
They’re not maintained for long enough to actually cause any serious damage to a healthy adult.
For small fish, however, the voltages are more than enough to send it into involuntary muscle contractions.
South American Electric Eel
The South American eel isn’t actually an eel at all.
Also known as the electric eel (Electrophorus electricus), the South American electric fish is actually a knifefish.
They live in the murky freshwater of the Amazon and Orinoco River basins.
Areas where South American eels can be found:
- Coastal plains
South American eels are extremely unique, even among electric fish, for their three electric organs.
While many electric fish have the low-voltage producing Sach’s organ, which is useful for navigating murky floodplains and swamps, the South American eel is the only one to reach voltages large enough to stun.
The ability to generate such large voltages makes the South American eel so unique that it has gone through a couple of different taxonomic reclassifications.
Originally recognized as a knifefish, it was later believed to be so unique that it needed its own genus (Electrophorus) and then eventually its own family.
Only later was it moved back into Gymnotidae with other electric fish.
Male South American eels grow to be larger than females. During the dry season, males make nests for female eels to lay their eggs. From each nest, a few thousand eggs may hatch. Once hatched, larvae often feed on other eggs and embryos.
How Does a South American Eel Produce Voltage?
South American eels have three electric organs: the main organ, Hunter’s organ, and Sach’s organ.
The main organ and Hunter’s organ generate voltages high enough to stun prey, while the Sach’s organ discharges low voltages that are associated with electrolocation.
The electric organs have cells that produce electricity (electrogenic).
For each of these cells, there’s a difference of about 100 millivolts between the outside and inside of the cell.
Once these cells receive a signal from the eel’s neurons, charged ions move across the cell’s membrane to generate the electric charge.
In the South American eel, there are three electric organs. In each of these organs, electrogenic cells are laid out much like small batteries laid in series.
When all the cells are signaled together, the thousands of electrogenic cells can together produce voltages large enough to kill or at the least stun their prey.
Since they are also inside the strong electric field, South American eels have layers of fat and connective tissue to help insulate their vital organs from their own discharge.
The electric current produced usually takes the path of least resistance and will flow through the insulating layers, instead of directly shocking the eel’s vitals.
Why do Electric Eels Produce Voltage?
The weak electric discharges from the electric eel’s Sach’s organ is used to navigate and communicate in the murky freshwater of South America’s tropics.
This is a trait common to all South American knifefish.
By using weak electrical discharges, electric fish can pick up on even the smallest change in their environment, regardless of how little light there may be.
It’s also believed these small electrical fields can be used to send out messages to other nearby electric fish.
What makes the South American eel special from other electric fish is the high voltage electric fields that it can use for attack and defense.
Voltages from the electric eel can reach up to 600 V and 1 A of current.
Uses for the South American eel’s voltages:
- Shocking prey out of hiding spots
- Immobilizing and exhausting prey
- If large enough, electrocution
When hunting prey that’s hiding, South American eels can use these large electric organ discharges to shock muscle contractions to give away their prey’s location away.
Once caught in its electric field, the prey’s muscles will lock up much like a person stunned by a stun gun.
Despite its ability to produce lethal voltages, the South American eel does not usually kill immediately with just electricity.
It’s more typical for the eels to eat immobilized prey before they have a chance to move, or to wear down prey with a volley of electrical charges.
How The South American Eel Hunts With Voltage
The high-voltage electric fields produced by South American eels are undoubtedly one of the most unique and interesting predation strategies out in nature.
However, South American eels don’t usually use their gift for electrocution.
While voltages produced by South American eels can be large enough to kill, in most cases the eels use these electric fields more to stun and immobilize their prey.
Typical steps of a South American eel’s hunt:
- Shock prey out of hiding
- If it’s still struggling, bite onto it and bring the tail around and against the prey
- Keep stunning the prey with a volley of electrical pulses until its exhausted
- Eat the prey
An initial shock can be sent out to stun any prey from its hiding spot.
In many cases, the South American eel can then swoop in and eat the momentarily stunned fish before it can so much as struggle.
For a prey that can still put up a fight, the South American eel will usually twist around it.
This is an extremely interesting attack method since the South American eel has what is essentially its positive electric pole in its head and its negative pole in its tail.
With prey caught in its jaw, the South American eel will bring its tail up to the other side of the fish, trapping it in a concentrated electric field.
It can then send out high-voltage volleys, exhausting the prey with repeated muscle spasms.
The South American eel can then, like any good predator, chow away on its exhausted prey.
Altogether, this method of mobilizing prey is another way for nature to demonstrate just how impressive it can be.
Can the shock from a South American eel kill you?
The shock of a South American eel is unlikely to kill a healthy adult. The electric pulses they generate are generally quick enough that it would be more painful than harmful.
Can South American eels generate electricity indefinitely?
South American eels will eventually tire after generating electricity for an extended period of time. When people have a need to catch South American eels, one strategy is to wait for the eel to exhaust itself before catching it to avoid any painful shocks.
Are South American eels the only electric fish that can use electricity to stun?
Other electric fish can only generate electric fields large enough to help them navigate murky water. The South American eel is unique among electric fish in its ability to produce hundreds of volts.
Be sure to check out what I wrote about how to hook American Eel on a line.