The very idea of an electric fish seems like some outrageous science fiction creature dreamed up by... well, an author like myself. Even its scientific name sounds like science fiction: Electrophorus electricus. But, I assure you, this creature is real.
What the heck is an Electric Eel?
Well, for starters, it isn't an eel at all. The electric eel is actually a type of knifefish, which means it's more closely related to catfish than to eels. They live in dark, murky rivers in South America, including the Amazon.
These fish use their electrical superpowers in several fascinating ways, mostly for locating and then subduing their prey, typically smaller fish.
Electric eels are large fish, typically growing over six feet (2 m) long and weighing 44 pounds (20 kg). Like catfish, electric eels do not have scales.
Amazing Facts about Electric Eels
Obviously, we need to explore this whole electric thing, right? There's a lot here to consider, so I'll try to organize it logically.
First, how in the heck do these fish generate a voltage? Basically, the electric eel has an amazing nervous system. Its nervous system can synchronize the activity of a series of specialized, disc-shaped cells that produce electricity. These cells are contained within a specialized electric organ. Actually, there are three pairs of these organs, and the organs can make up to 80% of the animal's body!
The disc-shaped cells are called electrocytes, and they are lined up within the organs so that a current of ions can flow through them. When the fish's brain decides to generate a shock, it sends a signal through its nervous system to the organs. Without getting too technical, I'll just say that this signal causes a sudden switch in the organ's polarity, thus generating an electrical current. Think of the organ as a battery, which has a series of stacked discs that produce a current in a similar way.
You see, the eel must activate all the electrocytes at once for this to work. The problem is, these cells are at different distances from the brain. That's where the fish's amazing nervous system comes in... the system has a complex array of nerves that makes sure all the cells activate at the exact same time, no matter how far out they are! Mind boggling, if you ask me.
How powerful is the shock? An electric eel can generate up to 860 volts and up to 1 amp of current. Is that enough voltage to kill a person? Probably not, but it would be painful, and it could incapacitate a person long enough for them to drown. Such drownings have occurred, although they are rare.
To give you an idea of what the shock might be like, consider this story from Philip Stoddard, a zoologist at Florida International University in Miami. Philip had a five-foot-long electric eel as a pet in an aquarium. The eel's name was Sparky. One day Philip decided he wanted to reach into the aquarium and pet Sparky. Philip knew the risk, but he figured the fish was comfortable around him and wouldn't feel threatened (hmm... ).
So, he reached in and stroked the fish's back. You can guess what happened, right? The fish zapped him with 500 volts of electricity, more than four times the shock he would get by sticking his finger into a typical North American household socket (for various reasons, here in the US we use 110-volt outlets—actually they are closer to 120 volts these days—whereas many other countries use 220). Anyway, Philip got a powerful shock. His entire arm hurt for about an hour.
Check out this video about how electric eels can defend themselves with electricity.
Now that we've talked about HOW they produce electricity, let's explore WHY they do this.
Obviously, one reason is for defense against predators. An electric eel can actually kill an attacking caiman that is trying to eat it. Even if the predator isn't killed, it will immediately realize it has made a mistake and will back off. Or, it will be incapacitated long enough for the eel to escape (you might find this a little disturbing, but here is a video recorded by a fisherman who catches an electric eel, then a caiman tries to attack the eel as the guy is reeling it in... the caiman appears to be killed).
But the eel's use of electricity is much more complex than just predator defense. They use their electricity in multiple ways.
They use low voltages to sense their surroundings, kind of like an electrical version of sonar. Remember, these fish live in muddy, murky water, and they have poor eyesight, so this low-voltage sensory ability comes in handy.
They use high voltages in several ways.
High-voltage use #1: To detect prey. The eel can emit pairs of high-voltage pulses, 500 of these pulses per second. These pulses cause their hidden prey to involuntarily twitch. The eel can sense these twitches (remember that low voltage use described above?), allowing it to locate the prey animal.
High-voltage use #2: To stun or kill prey. Once the eel locates the prey, it emits even higher-voltage pulses at 400 pulses per second. This stuns the prey fish, and the eel can approach it and suck it into its mouth with one gulp.
One more interesting morsel about electric eels. An electric eel at the Tennessee Aquarium has its own Twitter account. Yes, you read that right. The fish's name is Miguel Wattson. The fish's tank is set up to constantly monitor its electrical output. Whenever Miguel Wattson gets excited and generates enough electricity, this activates a connected computer to send out a pre-written tweet, many of which are clever and fun. Here's an example:
You can follow Miguel's tweets here.
Here's an older one:
So, the Electric Eel deserves a place in the S.A.H.O.F.
(Stellar Animal Hall of Fame).
FUN FACT: The word stellar originated in the 1650s, as an adjective meaning "pertaining to stars or star-like." Beginning in 1883, it was used in a theatrical sense of the word star (as in the star of a play). In this sense, stellar meant "outstanding, leading." Eventually, people started broadening its use to refer to anything that was outstanding, such as, "The company thrived, due to stellar management."
So, stellar is another way to say awesome!
Hmm... usually I explain why I chose the particular animal as the Awesome Animal. This time, the reason is pretty silly. I saw a photo of a Shoebill, and I thought, look at that crazy bill! That's it. Sometimes my reasons are not particularly intellectual.
What the heck is a Shoebill?
This bird is sometimes called the shoe-billed stork, or the whalehead. Figuring out exactly what the shoebill is has been an ongoing challenge. For years it used to be classified as one of the storks. However, anatomical studies (looking at the structure) suggest it is more closely related to pelicans. But then, molecular studies have convinced many scientists that it is actually more closely related to herons. I guess the jury is still out on that. Because of all this confusion, the bird has been placed in its own special family (called Balaenicipitidae... just try to pronounce that one).
Apparently, the shoebill's closest living relative is another odd-looking bird called the hamerkop. Anyway, they're a big, impressive-looking bird. Shoebills are taller than a mailbox, sometimes standing five feet (152 cm) tall, with an 8-foot wingspan!
Shoebills live in central and eastern Africa, and they eat an impressive variety of prey.
Amazing Facts about Shoebills
First, we need to talk about that bill. The bill is sturdy, heavy, and perfectly adapted for the bird's methods of catching prey. Here's why it's so heavy and sturdy: The shoebill hunts by standing still or walking slowly and carefully, watching for anything that moves that it can swallow (and shoebills can swallow a lot!). When it spots an animal, the bird throws itself forward with every ounce of strength it has, and its bill crashes into the water at full speed.
Here is a brief video that shows a shoebill hunting.
Often, when a shoebill grabs a prey animal like this, it also gets a mouthful of water plants and mud. No problem, though. The bird is skilled at shifting its jaws back and forth to discard the salad and keep the meat.
I mentioned above that shoebills eat an impressive list of prey. They are particularly fond of lungfish (see above photo), but they will eat pretty much any creature they can swallow whole. This includes not only surprisingly large lungfish, but also eels, catfish, and frogs. As if that weren't impressive enough, they do not hesitate to eat monitor lizards, snakes, and even young crocodiles. Yep, this is a bird that eats crocodiles.
So, it grabs a mouthful of stuff, shakes out everything else except for the prey animal, then it often maneuvers the animal around until it can decapitate it with its sharp-edged bill. Easier to swallow that way, I suppose. And swallow it does—whole. All at once. Down the hatch. Gulp.
But wait! Even though the bird has eaten its prey, it isn't quite finished with it yet. Sorry, but this part is a little disgusting. Shoebills live in hot places, and to help cool themselves down, they poop on their legs. That's right. How does it work? Well, bird poop is mostly liquid, and when the poop evaporates, it cools the blood circulating through the shoebill's legs, and that cooled blood cools the rest of the bird's body. Isn't that cool?
Um, is it me, or does the shoebill look a little like the long-lost dodo bird?
Hey, why do they call them shoebills? What kind of shoe looks like that? A Dutch wooden clog, of course, and that's how they got their name.
Remember when I said shoebills often hunt by standing still and waiting? I wasn't kidding. You wouldn't want to get into a staring contest with one of these birds because they are capable of standing in one place and staring at the water for hours at a time. They could teach us all a thing or two about the virtues of patience.
Shoebills have large, gold-colored eyes, and when they look directly at you, their stare is rather intimidating. It makes you feel like they are sizing you up, deciding if you are small enough to swallow whole.
Here's a random thought. To me, the shoebill looks very dinosaur-like. Its scientific name is Balaeniceps rex. In other words, it is named B. rex. If you've seen the Jurassic Park movies, you know what a T. rex's death stare looks like. Well, here's the B. rex's death stare:
Don't get me wrong. I'm not implying that shoebills are ill-tempered or dangerous to people. They actually seem quite tolerant of people (although you have to admit... that stare!). Shoebills in zoos seem to like it when approaching people mimic their movements, including bowing to the bird.
Check out this video of these behaviors in a shoebill in captivity.
If you watch videos of a shoebill, you will see and hear it clacking its bill loudly (you can see this in the above video). This is a common form of communication between the birds. They seem to do it most when they are around their nests, although the specific purpose of the sound is uncertain.
One more item of interest. Adult shoebills are certainly strange-looking birds. You must be wondering what baby shoebills look like. In 2009 the Lowry Park Zoo in Tampa, Florida was only the second zoo in the world to successfully hatch a baby shoebill. As it turns out, newly-hatched shoebills look... well, kind of normal (although maybe a little goofy).
So, the Shoebill deserves a place in the B.A.H.O.F.
(Bumper Animal Hall of Fame).
FUN FACT: The word bumper has numerous meanings. As a noun, it refers to the protective guard on the front of a vehicle, or any other kind of rim, pad, or projection that protects something. It even refers to a glass full to the brim (particularly with beer). In Australia it's a slang word for a cigarette butt. However, when used as an adjective, bumper can mean unusually abundant (such as a bumper crop), but it can also mean unusually large and/or fine. And that, folks, is why I think bumper, particularly when referring to the shoebill, is another way to say awesome!
Yesterday I was writing one of the chapters of the third Across Horizons book, and I decided the scene needed a really strange creature. I dug around for ideas and decided on a velvet worm. I then read a few articles on velvet worms, and I was blown away by these creatures. Who knew they were so awesome? I decided velvet worms deserved to be featured in this post, and here they are.
What the heck is a velvet worm?
This question is not so easy to answer. In spite of the name, they aren't really worms. They look a little like a caterpillar, but caterpillars are insects. They look a little like a slug, but slugs are mollusks. They actually belong in their own phylum, Onychophora.
We know of about 200 species, mostly living in the tropics. However, they are extremely secretive, living in dark places in leaf litter on the ground and are only active at night. It is almost certain that many more species exist that we have not yet discovered.
Velvet worms are predators, feeding on almost any creatures their own size or smaller. They average about three inches (7.6 cm) long, but some are less than an inch, and some get as long as eight inches (20.3 cm).
One of the most amazing things about velvet worms is the way they catch and eat their prey! Let's get into the details.
Amazing Facts about Velvet Worms
First let's look at why these critters make such interesting predators. They may be called velvet worms, but I think a better name might be spider-man worms. Why? Because they trap their prey by spraying out two jets of sticky goo from their slime cannons. A two-inch velvet worm can shoot this slime out as far as two feet (61 cm). The slime hits the prey animals and immediately begins to harden like sticky glue.
With the prey creature now immobilized, the velvet worm can take its time and safely approach its meal. It has a specialized knife-like tooth hidden in its mouth, which it slides out and uses to cut through the prey animal's skin or exoskeleton. Once a hole is made, the velvet worm injects saliva, which is deadly to the prey animal. Not only does the saliva kill the animal, it also starts to digest the animal's insides. The velvet worm waits patiently as the saliva does its job, keeping itself busy by re-ingesting and thus recycling the goo it had already squirted. Finally, it goes back to the opening it made in the prey animal and starts slurping up the creature's digested insides. Yum!
Check out this video about the velvet worm's slime cannons.
Notice the jets of goo squirting from this velvet worm:
Let's break this amazing predation process down into steps. First, velvet worms have very poor eyesight, so how do they even locate their prey? Those short, squishy-looking legs allow them to move around on the forest floor without being heard. Also, because their legs do not vibrate the surfaces much, their prey cannot feel them approaching. The velvet worms themselves are extremely sensitive to vibrations and changes in air pressure from movement, so they can detect other creatures moving around nearby. They sneak up on their prey very stealthily, and they get so close that they can touch the prey with their finger-like antennae. Their antennae are highly sensitive, and velvet worms very lightly touch the prey animal to determine if it would be suitable as a meal. Often they spend a full ten seconds touching the animal without scaring it off!
Check out the antennae on the blue velvet worm below:
Once the velvet worm decides the prey is suitable and worth using up some of its precious slime, it squirts the slime through its two slime nozzles.
But where does the slime come from, and what is it? The velvet worm has two huge slime glands inside its body that run most of its entire length, allowing it to produce an impressive amount of the goo.
The slime itself is amazing stuff. Its main ingredient is a special type of protein that, when the protein molecules join together, they quickly form a solid structure. But inside the velvet worm's body, and while the slime is being squirted, the proteins are coated with water molecules that keep the proteins separate. In fact, 90% of the slime is water that is there to keep the proteins from interacting with each other. But... when the slime hits the prey animal, it spreads out, covering the animal, and the water quickly evaporates. Guess what happens when the water is gone. That's right, the proteins join together and form a biological glue.
The cool thing is, no other animals in the world use biological glue that works like this.
As I stated above, once the prey is immobilized, the velvet worm casually approaches and cuts a hole in the prey's body to inject saliva that digests the animal from the inside. The saliva contains hydrolytic enzymes, which use water molecules to break the chemical bonds of the prey animals' internal organs. Once that's done, all the velvet worm has to do is suck up all that digested stuff. It's like sucking the water out of a coconut through a straw.
I know... kind of gross, but you have to admit it's also awesome!
Here's an animated GIF of the velvet worm's specialized mouth. I like to think of it as the SSSIPSO (Shell Slicing, Saliva Injecting, Prey Slurping Orifice).
Okay, one more fascinating thing about velvet worms. Most of the velvet worm species live and hunt alone, but at least a few species live in groups with complex social structures, and they even hunt cooperatively. Velvet worms in the genus Euperipatoides live together in groups of up to fifteen. Each group will make a home together, usually somewhere like inside a rotting log, and the members of the group are really aggressive to velvet worms from other logs.
Each group has one dominant member, usually a female. The group leaves the log at night to hunt as a pack, making it easier to capture prey (15 velvet worms... that's a lot of slime). When they make a kill, the dominant female always feeds first. Next, the other females feed, then the males. Finally, the young feed last (assuming there is anything left to eat!).
The social hierarchy is determined by aggression and submission. The biggest, meanest individuals are more dominant. Interestingly, to avoid getting into a fight with a larger individual, velvet worms carefully measure each other by feeling with their antennae from one end of the body to the other. If the opponent is too big, it's safer to simply become submissive.
So, Velvet Worms deserve a place in the F.L.A.H.O.F.
(Front-Line Animal Hall of Fame).
FUN FACT: The phrase frontline originated in 1842 as a military term to refer to the location of the most advanced combat units. In about 1910, the hyphenated form (front-line) originated as an adjective, meaning "highly experienced or proficient in the performance of one's duties." In other words, "first-rate," as in She is a front-line performer. So, front-line is another way to say awesome!
Everyone needs a creative outlet. That's why I write.