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Electricity isn’t just something we use to power our TVs and laptops. It’s a naturally occurring phenomenon and is something that many animals are able to produce. In fish, this is surprisingly common and in this shocking guide, we’ll introduce you to some of the marine environment’s most powerful electric producers!
How Did Electric Fish Evolve?
Electric fish use their powers as a form of communication, often to alert other members of the same species and determine their gender as well as helping them to recognize one another.
But what’s fascinating is that all fish have the capacity to become electric but only a handful have actually harnessed this power. It’s all to do with evolution.
You see, all fish have more than one version of a particular gene that they use to produce sodium channels. But electric fish have literally turned off the power to one of these duplicates and turned that same gene on in other cells. It’s as a result of this that they have evolved electrical organs. Fish that are capable of generating electricity are known as electrogenic fish.
This is, for all intents and purposes, a minute change within the fish’s genes, but scientists at the University of Texas are super excited about how this small change means a big difference in the creature’s abilities.
What’s more, these same researchers are looking at how similar processes in the human body could help to combat disease. Since humans also have these replica genes that produce sodium channels, it’s thought that ‘switching one off’ could result in disease. Of course, there’s a lot more research that needs to be done.
How Do Electric Fish Generate Electricty?
There are currently around 400 known species of electric fish, but each of these species produces different levels of electrical currents. There are two types of electric fish; weakly electric fish and strongly electric fish, but in any case, they produce their current using electric organ discharge, known as EOD.
Different fish have their electric organs in different parts of the body. For example, some species, such as the elephant fish, have electric organs in their tails, whereas others, like the stargazer, have an electric organ in the head.
The electric organ in these fish is made up of a combination of specially modified nerves and muscles which were formed through the process of evolution that we discussed earlier. Amazingly, there are some species that can emit up to 860 volts and these electrical currents are often used as a way of stunning their prey.
On the other hand, there are weakly electric fish species that emit a far lower current of less than a single volt. These creatures largely use their electrical pulses to help them navigate the world.
While the electrical organs of most fish work in a similar way, the output can be different. For example, some species will emit short pulses, whereas others will emit a continuous wave of electricity. The former are known as pulse-type EOD fish, while the latter are called wave-type EOD fish.
Why Do Some Fish Produce Electricity?
Many electric fish species will use their currents to navigate the world around them. These creatures often live in the depths of murky waters, which makes it difficult to see. However, they’ll emit small electrical frequencies which bounce off their bodies by as much as a few inches and onto nearby objects. This then allows the fish to determine where there may be a rock, vegetation, a predator or simply another fish.
Some fish use their electricity to communicate with other members of the same species. This is often the case with weakly electric fish. They aren’t able to use very strong signals because this would alert electroreceptive predators, so instead, they use weak signals when it comes to finding a mate. They’ll also use these same signals to seek out rival fish.
What’s really amazing is that some species, like the elephant-nosed fish, will detect if there is another member of the species hunting nearby and will alter its electrical signal so that the two do not clash.
Where communication is concerned, some electric fish will use their pulses to create a kind of mating song when trying to attract a female.
While a lot of fish will use their powers to seek out prey, some will even use it to stun their next meal. They’ll use their strong electrical current to shock prey before they consume it; the catfish is a prime example of this.
What’s more, fish with this kind of high voltage can use their electricity to deter predators; nobody wants a meal that’s going to deliver a nasty shock!
Types of Weakly-Electric Fish
Weakly electric fish largely use their electrical signals for things like communication and navigation. Their ‘shocks’ certainly wouldn’t be enough to stun or even kill prey since they are only able to generate up to one volt.
These fish are, however, able to generate two types of EODs, including wave and pulse types. The wave-type fish generate long, continuous electrical signals, while the pulse-type fish emit a series of shorter electrical signals in succession.
While there are almost 400 types of electric fish, most of them fall into the weakly electrical category. They’re common in murky freshwater where the environment would be difficult to navigate without their electrical abilities.
1. Black Ghost Knifefish (Apteronotus albifrons)
The black ghost knifefish is a stunning creature with a deep, slender black body and stripes of white around its narrow tail. The body is shaped similarly to a knife blade, hence the name, and these tropical fish can grow up to 20 inches (50 cm) in length.
This is a nocturnal species that uses its electrical signals for communication and navigation. The black ghost knifefish is not only able to produce electrical signals but can also receive them which further helps in getting around, especially since these fish do not have excellent vision.
Black ghost knifefish are largely found in the Amazon river and use an electrical organ located in their tails to produce their signals. They use a pulse-type signal and can produce up to 2000 pulses per second!
These fish are popular aquarium pets and, when given the right care, they could live up to 15 years. However, their lifespan may be considerably shorter in the wild.
2. Cornish Jack (Mormyrops anguilloides)
In quiet waters throughout sub-Saharan Africa, you’ll find a weakly electric fish called the Cornish jack. While humans hunt this species owing to its tasty meat, these fish are adept hunters themselves, using their electrical pulses to locate prey.
Typically found in warm tropical bodies of water such as the White Nile, these long fish can get pretty big, with the largest measuring around 5 feet (1.5 meters)!
Amazingly, the Cornish jack is very intelligent and uses its electrical pulses to recognize other members of the species. The fish will produce these signals in varying lengths and will adjust their output so that there is no electrical interference with other Cornish jacks.
During the breeding season, females may carry as many as 25,000 eggs, and this is an abundant species. What’s more, they’re known to live as long as eight years in the wild.
3. Elephantnose Fish (Gnathonemus petersii)
This curious-looking fish has an incredibly small brain with no cortex but still manages to switch between visual and electrical navigation as required. They use an electrical signal produced by an organ in the tail to determine the location of objects within the environment. However, in studies, these fish were shown to come to recognize familiar items within an aquarium using only their visual sense.
These fish, that hail from Africa, feed mainly on mosquito larvae which they find by using their electrical pulses. Amazingly, they’re able to detect, using only their electrical abilities, whether the larvae are alive or dead and even determine whether it’s mosquito larvae or another species. They’ll pretty much leave anything else alone.
Elephantnose fish take their name from the protrusion on the tip of their face which is not a nose but something called the Schnauzenorgen. They use this for electroreception for things like self-defense and communication.
4. Eastern Bottlenosed Mormyrid (Mormyrus longirostris)
The eastern bottlenose mormyrid prefers caved environments and muddy waters. It’s no surprise then, that they require an electrical ability to navigate the dark waters which they inhabit. They’re found in waters around Africa, including the Zambezi River and Lake Malawi, where they feed primarily on insects and weeds.
These ray-finned species can grow up to 20 lbs (9 kg) and as long as 12 inches (30 cm). While they may not be the largest species on this list, humans still hunt them for food, and the population is significant, with females producing as many as 70,000 eggs during breeding season.
Eastern bottlenose mormyrids use their weak electrical signals for both hunting and self-defense. The shock they deliver is very weak but is usually enough to warn off hopeful predators.
5. Glass Knifefish (Eigenmannia virescens)
The glass knifefish has an organ in the tail that allows it to produce a mild electrical current and like many other fish within the same family, uses this for things like hunting, communication, and navigation.
Glass knifefish have a very unique appearance in that they’re often described as being translucent, hence their name. This makes them a popular choice of aquarium fish although it is possible for these fish to grow as large as 55 inches (140 cm), so you’d better have a big aquarium. That said, in captivity, they usually don’t get much bigger than 18 inches (45 cm).
These fish are found in the tropical waters of South America and are known for swimming to much greater depths than other similar species. In some cases, they’ll dive down to 66 feet (20 meters) and have even been seen swimming vertically!
Types of Strongly-Electric Fish
While there are fewer strongly electric fish species, there are still a good number and these include things like catfish, eels, and rays. Where weakly electric fish only normally use their signals for communication, navigation, and hunting, strongly electric fish can produce much higher voltages to stun prey and protect themselves against predators.
1. Electric Eel (Electrophorus electricus)
The name electric eel is a little misleading since these animals are actually more closely related to the catfish and knifefish. Moreover, while scientists thought that there was only one species of electric eel, they’ve recently discovered that there are three. The electrophorus electricus was once thought to be the most powerful of the electric eels, emitting up to 600 volts but in 2012, the Volta’s electric eel was discovered and is far more powerful. But we’ll look at that species in the next section.
Back to the eclectic eel and here we have a creature that uses both high and low-voltage EODs. While the high-voltage EODs can reach up to 600 volts, the fish is also able to produce just 10 volts on the lower end of the scale.
When using those high voltage signals, the electric eel is able to ‘remote control’ its prey by zapping it, determining its location, and preventing it from getting away. And while they were long thought to be solitary hunters, recent research has uncovered that the electric eel will often hunt in groups.
On the other hand, these eels will use their low voltage to navigate the murky waters of the Amazon and Orinoco rivers where they live owing to the fact that their vision is very poor.
So how does the electric eel produce these currents? Well, it does so using a series of organs throughout its body: the main organ, the Sachs organ, and Hunter’s organ. Each of these organs is made from electrolytes and the eel needs all three to create the varying voltages it’s capable of. It’s in fact the Sachs organ that is responsible for generating the lower frequencies which the fish uses for location and hunting. When it locates its prey, the other two organs kick in to produce a higher voltage to stun the victim.
2. Volta’s Electric Eel (Electrophorus voltai)
The Volta’s electric eel is a more recently discovered type of eel that lives in the Amazon river and its tributaries. Where scientists thought that the electric eel was powerful, this creature is able to produce up to 860 volts; that’s more than any other eclectic animal on the planet! It’s aptly named after the inventor of the battery, Alessandro Volta.
These eels, found in South American waters came as something of a surprise to researchers since it was previously thought that there was only one type of electric eel. But now we know that there are, in fact, three.
Growing up to eight feet (2 meters) in length, the Volta’s electric eel uses a similar system to the Electrophorus electricus eel to generate pulses. For navigation, the fish will emit low voltage electricity, but it’ll amp things up when it comes time to stun its prey. Their shocks are so powerful that they’re said to be able to stun an animal as big as a horse!
3. Electric Catfish (Malapterurus electricus)
There are 21 species of electric catfish, and some of the most powerful are able to generate up to 350 volts of electricity. They mainly use this ability to stun their prey since most species are carnivores and are largely found in the Nile River and other tropical African waters. However, the catfish will also deliver a shock in self-defense to warn off predators.
These fish generate their electric signals from the pectoral muscle which surrounds most of the animal’s body.
Electric catfish typically grow to just over 3 feet (1 meter) in length and are very chunky fish that can often be found lurking in rocky areas. The fish are sometimes attractive to aquarium owners, but throughout history the species have played a more interesting role for humans. In ancient Egypt, people would use the shock from an electric catfish to quell arthritic pain.
4. Northern Stargazer (Astroscopus guttatus)
The northern stargazer is a master of disguise that buries itself in the sediment, patiently waiting for prey to pass by. It has a large mouth that acts like a vacuum and sucks in unsuspecting crustaceans and small fish.
However, this notoriously ugly-looking fish is also able to produce an electrical current, which it does thanks to a pouch behind the eyes containing a special electric organ containing more than 200 layers of electric tissues. But unlike some strongly electric fish, the northern stargazer only produces up to around 50 volts; that’s still more than enough to stun prey!
Where hunting is concerned, this fish is also specially adapted with eyes on top of the head. When it buries into the sand, the eyes and large mouth stick out the top so the fish has a good view of any incoming meals.
5. Atlantic Torpedo (Torpedo nobiliana)
Adult Atlantic torpedoes can grow up to 5 feet (1.5 meters). These disc-like rays spend a lot of time on the ocean floor up to depths of 1,150 feet (350 meters), where they will feed on bottom-dwelling fish. The most common location for the Atlantic torpedo is around the coast of Great Britain and Ireland, as well as Canada, but they very rarely come into contact with humans.
These animals have two kidney-shaped organs located under the pectoral fins which produce a powerful enough shock to either stun or kill the prey. The shock can be up to 220 volts which would be enough to incapacitate a human should you ever be unlucky enough to meet one.
6. Marbled Electric Ray (Torpedo marmorata)
Another ray species with the power to produce a shock is the marbled electric ray. It is a reef species found from the eastern Atlantic right down into South African waters.
Compared to the electric ray discussed above, these fish are a lot smaller and don’t typically grow much bigger than 24 inches (60 cm). It’s also easy to tell the two apart as the marbled ray, as its name suggests, has a marbled appearance and is more brownish in color compared to the grayish hue of the Atlantic torpedo.
These fish can produce up to 70 volts in a single shock, although there is a suggestion that the maximum potential could be around 200 volts. They use this power to stun their prey and produce the voltage from a pair of electrical organs that feature jelly-plates which act in a similar way to a battery.
While their shock might pack a punch, it’s rarely enough to fatally harm a human. The worst you’ll feel is some pain, and in the past, humans have even used the shock to cure ailments like headaches and this was common practice in ancient Greece.
7. Pacific Electric Ray (Tetronarce californica)
The Pacific electric ray is another reef dwelling ray species that generally lives at depths up to 650 feet (200 meters). It’s found all the way from Baja up to British Columbia in Canada and will grow up to 4.6 feet (1.4 meters).
They’re very bold creatures that have been known to approach human divers, and it’s no wonder when you consider that they wield a powerful electric shock that’s often used in self-defense. Moreover, they’ll use their electricity to shock and stun their prey when hunting.
The kidney-shaped electrical organs sit on either side of the ray’s head and can produce up to 50 volts in a single charge. However, these fish also have a smaller organ which they use to emit lower voltages and this aids them in communication.
Why Don’t Electric Fish Shock Themselves?
I’m pretty sure that if I was wandering around with an electric current, I’d manage to shock myself. So, it might baffle the mind as to why these strongly electric fish are able to avoid shocking themselves.
In electric eels, there are, in fact, many examples of these fish killing themselves and nearby eels accidentally. This happens when the electrical current travels from its source in the tail, through the body, and hits the vital organs. Just like you or I, an eel will die if it receives a big enough shock to the heart.
It’s also been noted that these animals will accidentally kill one another during a fight. They might not mean to, but it’s common. Fortunately, they do have a tactic to reduce the chances of this happening as well as avoiding shocking themselves, and it all comes down to the shape of their body.
Electric eels will hold their bodies in a specific shape that stops the electrical current form traveling to the heart. This may either be in a straight line as they charge or a U shape. But when they take on the U shape, they have to be very careful not to let their head touch their tail or it’s lights out!
But for the most part, scientists are yet to really figure out why most strongly electric fish can go about their day without zapping themselves. It’s thought that it may be a result of how quickly the current leaves their bodies or it could be to do with protein-based insulators around their organs. There’s no clear-cut answer and we can only assume.