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11 Facts About Japanese Spider Crabs That Will Keep You Up At Night



The fear of spiders is one of the most common phobias in the world, so chances are you know someone who has it. Or maybe you yourself are terrified of long-legged arachnids, which would be unfortunate, because you’re about to learn about a creature that will likely send you running for the hills. It’d called the Japanese spider crab. And while it’s not actually a spider, this crab has long spider-like legs, scuttles across the ocean floor, and can get monstrously huge in size. If this knowledge isn’t enough to give you the chills, then these Japanese spider crab facts and photos will definitely do the trick.

You might think that crabs aren’t really that scary – after all, they taste pretty amazing, right? Well, Japanese spider crabs are in a class of their own. They are not only the largest crab known to exist, but they can live longer than humans – and are carnivorous. They’ve even been known to chop off human fingers with their claws!

Even if you don’t find these big guys terrifying, that doesn’t make them any less fascinating. Read on to learn more about this creepy but very interesting undersea giant.

They Can Grow To Be Over Twelve Feet Long

Photo: Tsarli at English Wikipedia / Wikimedia Commons / CC BY-SA 3.0

Despite it’s spindly, spider-like appearance, the Japanese spider crab is absurdly huge. Scientists and researchers estimate that this crab can weigh up to 44 pounds and can have a leg span of thirteen feet at their largest! Not only does this mean that this crab could actually tower over you if it wanted to, but it also makes it the largest crab in the entire world. It’s important to note, though, that this creature really is mostly legs with its body only reaching about a foot and a half across in size, but that’s what makes their appearance so terrifying.

True, the ones that have been caught tend to be on the smaller side, only a few feet across at the legs, but who knows how big they’re getting out there in the dark depths of the ocean.

They’ll Eat Just About Anything, Including Corpses

Photo: bryce_edwards / flickr / CC-BY 2.0

When you’re the biggest crab in the sea and you only have a few predators out there to worry about, who do you decide to eat? The answer is pretty much anything smaller than you. They’re not exactly hunters, but these crabs have been known to eat algae, kelp, mollusks, slow-moving invertebrates, and the dead bodies of any creatures that happen to be floating around. In fact, this last option seems to be their favorite, as they seem to prefer to scavenge dead flesh rather than kill things themselves.

Ancient mariner legends tell that these crabs used to actually drag sailors overboard and eat them alive in the depths of the ocean. While this is pretty unlikely, it is probably true that these crabs would enjoy the opportunity to pick apart the occasional dead sailor who had washed overboard.

They Don’t Only Live In The Deep Sea

Photo: Castles, Capes & Clones / flickr / CC-BY-NC-ND 2.0

In general, you never have to worry about happening across a Japanese spider crab because they only really live in the depths of the ocean near Japan. They’re usually found at around 150 to 300 meters down, which is nearly a thousand feet, so you have nothing to worry about, right? Well, that’s not entirely true. This crab does like to venture into shallower waters when it gets the urge to mate.

During the breeding season, spider crabs can be found in water as shallow as 50 meters, which is only a little over 150 feet deep, and that’s where their larvae hatch. As they get bigger, they tend to move into deeper water, so the really freaky guys are probably not going to come around to bother you…probably.

They Can Live For Over A Century

The average crab that you find in the supermarket can actually live a pretty long time. Blue crabs can live up to eight years, horseshoe crabs live up to twenty, red crabs can live around thirty years, and hermit crabs can reach well past sixty! However, the Japanese spider crab puts all of them to shame. Not only are there records of spider crab fossils spanning back millions of years, but we now know that spider crabs can live for at least a century, perhaps even longer!

Most terrifying of all is that the older they get, the bigger they get. These crabs molt, shedding their shells and growing new ones as they age – each time getting a little bigger. One of the largest crabs ever caught alive was only forty years old, so who knows how big they can get once they reach 100!

They Start Off Nearly Microscopic In Size

If you’ve ever gone swimming in Japan, you probably brushed past thousands of these crabs and didn’t even know it. The reason for this is that they look nothing like crabs when they first hatch. First off, these crabs lay a lot of eggs – to the tune of well over a million! After the mother crab carries the eggs around, they hatch into tiny, round, plankton-like babies that are so small and primitive you can barely see them.

These plankton crab larva float around and grow slowly over the course of around 70 days before they actually begin to look like anything. In other words, one (or a hundred) of these little buggers could be cuddling up with you while you’re swimming off the coast of Japan and you’d barely feel a tickle.

You’ll Never See Them Coming, Maybe

Photo: guppiecat / flickr / CC-BY-NC-ND 2.0

Even though these crabs are massive, they still have to watch out for the occasional predator, such as the octopus, so they’ve had to get really good at camouflaging their enormous bodies. They are known to be a type of decorator crab, as they like to pick up things from their environment to attach to their backs in order to appear like just another part of the ocean floor.

They do this using sponges, kelp, and other substances. They also have a spotted and bumpy shell that, when nestled into a crack or hole, looks very much like a rock or part of the ocean floor.

Their Claws Can Seriously Injure You

Photo: Matt Tillett / flickr / CC-BY 2.0

Although the legs of the Japanese spider crab are very spindly, they’re also quite muscular. They don’t often hunt their prey, but they can move quickly when needed thanks to their long legs and are able to kill smaller animals with ease. Their claws are also strong and large enough to pry open muscles and clams in order to get at the tasty creature inside.

With this in mind, you can imagine why these crabs could be harmful to humans if the crab were handled incorrectly. When this crab was first discovered, the researcher documenting it noted that it could inflict serious injuries to humans, and had in fact done so while being caught.

Luckily, these crabs don’t tend to be aggressive toward humans – don’t hurt them, and they won’t hurt you.

They Can Survive After Losing Their Legs

Photo: chriggy1 / flickr / CC-BY-NC-ND 2.0

These crabs is that they are crazy resilient. For one, their bodies are heavily armored and it’s difficult to get past their hard shells. However, their legs are pretty vulnerable, and can be broken very easily. About three quarters of these crabs that have been caught were missing a limb, so that must be the way to fend these guys off, right?

Not quite. You see, Japanese spider crabs can quite happily survive while missing up to three of their limbs. That means they can still wander around after an octopus rips off a leg, as if nothing at all had happened. What’s more is that there is evidence these guys can actually regenerate their legs on their own, so even if one goes missing, they’re likely to just shrug it off and regrow a fresh one over the next few years.

People Eat Them As A Delicacy

Photo: Maarten1979 / flickr / CC-BY 2.0

One apex predator that this odd creature has is, unfortunately, us. It’s hard to catch these guys because they live so deep in the ocean, and there’s no real commercial industry for them. However, that being said, there are still some dishes that call for them in parts of Japan and other Asian countries, so they can be a top-dollar seller as a delicacy in restaurants. Fishermen used to try to go after the crabs during breeding season when the large ones would come into shallower water, but regulations against fishing for them in spring have curbed that immensely.

Those who have had th rare opportunity to try the crab describe its being so flavorful that one only needs to eat it with a squeeze of lemon, because the other flavors are so rich.

They Are Gentle Giants

Video: YouTube

All this being said, you might think these crabs are horrifying monster-spider death machines, but that’s really not true. Not only do they prefer being scavengers to being hunters, but they’re actually very gentle creatures. Researchers have found that, with smart handling, they’re easy to work with, and actually do fairly well in captivity. They’re even a popular installment at aquariums, as you can see in the video, and tend not to harass or destroy their tank-mates.

One of the biggest crabs ever caught, appropriately named Crabzilla, was even put on display in an aquarium for people to visit. So, while these creatures are monstrous they might not be monsters.

We Have No Idea How Many Of Them Are Out There

Photo: Gene1138 / flickr / CC-BY-NC-ND 2.0

So, just how many of these creatures are out there? The truthful answer is that we have no idea. It’s impossible for us to get a good idea of how many are scurrying along on the bottom of the sea, and because they’re not commercially fished, we can’t get a decent population estimate that way either.

What we do know is that they lay millions of eggs each spring, though only a small portion of them hatch. We know that they live a long time, and can breed throughout much of their lifespan. We also know that, in recent years, fishermen have been reporting bringing in fewer and fewer of them, meaning that their populations might be in trouble after all. Either way, they could be amassing an army for all we know, or they could be quickly dwindling.

We can also safely say that, while these creatures terrify many with their spider-like appearance, they are still an amazing and fascinating wonder hidden in the deep ocean.

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