Japanese Spider Crabs Why Not

This crab is eating a mollusc - it was very dainty about it

When I go to esports events I spend a lot of time in arenas and darkened studios focusing on screens and on digital worlds. Matches run long, interviews and transcriptions pepper the day and free time ends up being extra writing time. I want to attend the tournaments, don’t get me wrong, but sometimes you get home and realise you saw nothing of an entire city even though you were there a whole week.

That is why I ended up at the Georgia Aquarium yesterday. I’d paid my dues to the gods of Smite, wrapped up all my Paladins interviews and had hours to kill between checking out and my home flight*. The Japanese Spider Crabs caught my attention. They’re so alien and beautiful, living on the seabeds of the Pacific Ocean around Japan. I’ve been reading up about them. Here are some things I found out:

1. Eavesdropping on a kid’s conversation with aquarium staff I found out that the staff have to put protective boxes around the crabs sometimes. It’s because of how they shed. When crabs grow their rigid exoskeleton can’t expand to accommodate the bigger crab. Instead it must shed its old shell and grow a new one.

I found an account of how shedding actually works over on the National Oceanic and Atmospheric Administration website. The crab reabsorbs some of the calcium carbonate from its old shell before enzymes separate the old shell from the underlying skin. The skin then secretes a new soft shell beneath the old hard one.

“A day before molting, the crab starts to absorb seawater, and begins to swell up like a balloon. This helps to expand the old shell and causes it to come apart at a special seam that runs around the body. The carapace then opens up like a lid. The crab extracts itself from its old shell by pushing and compressing all of its appendages repeatedly. First it backs out, then pulls out its hind legs, then its front legs, and finally comes completely out of the old shell. This process takes about 15 minutes.”

The new shell doesn’t harden for a few days and so the crab is vulnerable. In the wild it is vulnerable to predators but in the tank at the Georgia Aquarium the crab is vulnerable to the other crabs in the tank who can be kind of jerks and poke their tank-mate with their long legs. The box is thus to protect the soft shell from jerks until it stiffens up.

2. The guy at the tank said the crabs can grow to 12 feet across because of their ridiculous supermodel legspan. That is a lot of crab.

The Blackpool Sealife centre apparently houses the world’s biggest crab – a giant Japanese Spider Crab called Big Daddy. There is a professional Dota 2 player called BigDaddy. You can tell the two apart because one is a crab and the other is not a crab. Also the crab is 10.2 feet across. I think BigDaddy is like 5 something.

3. This is about crabs more generally but I learned that the name for the claw legs at the front of the crab is “cheliped”. The claws themselves are also known as chelae so the legs that join them up to the crab are the chelipeds.

4. According to the Georgia Aquarium website:

“This species belongs to the Majidae family, which is known ‘decorator crabs.’ This group of crabs will pick up small anemones, pieces of sponge or other benthic animals and cement them to the top of their carapace (shell). This provides the crab with natural camouflage that protects it from predators.”

I feel like this is a strong look which I want to embrace for 2016. I am not sure how I would best disguise myself at esports events though because sponges and anemones and benthic animals (they’re the ones you find on or in the bottom of a body of water) would probably make me stand out. I mean I guess I could wear jeans and a hoody but I like the idea of just having things placed on my carapace – keyboard keys, cans of Red Bull, light-up dongers and USB sticks full of art assets and press info.

And that is my presentation on Japanese Spider Crabs. The end.

*It was that or I made good on my mission to track down an actual real peach tree rather than a street sign proclaiming Peachtree Boulevard or Parkway or Street. I don’t know what a peach tree looks like if it doesn’t have peaches dangling off it so it’s probably just as well that I opted for the fish.

This article was originally published as part of, and thanks to, the RPS Supporter Program.


  1. Garou says:


  2. Wowbagger says:

    Best article i’ve seen today. Spider crabs are ugly muthas, wash up on the beach all the time. We don’t tend to eat a lot of them in blighty but other places are quite keen.

    • Cropduster says:

      Yeah it’s odd, I was born in the channel islands and the spider crab was very much the crab de jure in the fish markets.

      • All is Well says:

        “Crab de jure” is my new favorite expression.

        • wraithgr says:

          As opposed to the de facto crabs, which really just showed up one day and started being crabs at the fish market, despite people refusing to officially recognize them as such…

  3. Harlander says:

    I’m pretty surprised to learn that you have a carapace.

    • tigerfort says:

      It’s usually disguised as a frog onesie, but the signs are there if you know where to look.

  4. Premium User Badge

    DelrueOfDetroit says:

    I suspect this means Neo Aquarium will be the first game Pip boots up when she gets home.

  5. Premium User Badge

    Bluerps says:

    Man, these creatures. Reading about them, I get the same feelings as when reading about spiders. It’s usually very interesting, but after a while I need to take a break and look at some pictures of cats and/or dogs until I stop feeling queasy.

    Also, I’m pretty sure I, and also the rest of the world, has forgotten how to convert feet into meters, because 10 feet is approximately 3 meters and that is just ridiculous.

    • Viral Frog says:

      As an American, I’m tired of having to convert our idiotic measurements to metric. Why we haven’t switched to the metric system at some point is beyond me. It makes so much more sense to do everything in metric measurements.

      • Niente says:

        As a Briton, I’m tired of having to convert metric into Imperial. I was brought up with both, taught metric at school but at home and in ‘real life’ I was exposed to and preferred Imperial. I’m not a member of UKIP or anything, I just prefer Imperial.

        As for the crabs, they are truly awesome and bit frightening.

        • PancakeWizard says:

          I’m certain this is wholly to blame for the decline of the high street grocers or butchers. We come out of school, confidently striding around with our school bag full of kilos drinking from our millilitres of fizzy pop, spot a good looking salami in the window and go instantly pale when we see it is priced by the pound. Then there’s nothing for it but to dejectedly walk home, metre by sodding metre in litres of rain.

          • PancakeWizard says:

            I read back that last sentence and wish I’d now parodied Blade Runner.

    • thetruegentleman says:

      It isn’t that hard: look at your feet, imagine 10 of them in a line, and think how long that would be in meters. You’ll be pretty much in the right ballpark.

      ..what, you don’t go measuring short distances all the time enough to do that? Psh. Weirdo.

    • Premium User Badge

      Bluerps says:

      Heh. I worded that poorly, last month. What I found ridiculous was the size of the crab, not imperial measurements. I learned how to deal with those a long time ago, when I played pen&paper RPGs written by US Americans and needed to know the range of my wizard’s spells.

    • GWOP says:

      Crabs and spiders are fine. What you should fear is the mantis shrimp. Strikes so fast it heats up the water around it momentarily to 4000⁰C…

      • Premium User Badge

        Bluerps says:

        I mean, yes, on the one hand your are right, mantis shrimp are terrifying – but on the other hand at least they don’t look like spiders that are 3 meters across.

        I guess, marine life is both interesting and terrifying in general.

        • Press X to Gary Busey says:

          The sea is the source of most madness inducing, ancient cosmic horrors.

  6. distantlurker says:

    gz to Blackpool, I guess.

  7. Kreeth says:

    I am a big fan of the in-depth research and painstaking fact-checking displayed in the phrase “I think BigDaddy is like 5 something”

    Yay for great big scary crab bastards.

    • Horg says:

      Since moving from support to playing a core role, BigDaddy N0tail has developed the broadest back in e-sports.

  8. Petethegoat says:

    *thunderous applause*

  9. KDR_11k says:

    Also they’re apparently making their way around Siberia and are invading the North Sea.

  10. nillenille says:

    Must be one hell of a Christmas Party, if you’re still drunk like this…

  11. TheAngriestHobo says:

    Note to self: Never go to the Georgia aquarium after playing Halflife.

  12. teije says:

    I was at that aquarium a couple months ago and those crabs are cool. But the otters were the best of course. Best animals ever.

    And it is a weird and somewhat desolate feeling downtown, Peachtree named roadways everywhere.

  13. Don Reba says:

    I wonder if BigDaddy feels he has not fulfilled his potential. After all, he could have grown 12 feet across.

  14. Malagate says:

    More like this please, marine life is my favourite.

    Also thanks for the tip on Big Daddy, did not know about him, might have to visit Blackpool in 2016 now. Can’t go wrong a world record, unlike in Plymouth where their only record is (maybe was, it’s been a decade since I’ve visited) Europe’s deepest indoor marine tank – that just sounds lame in comparison to a really big crab.

    • Nereus says:

      Since you like marine life, here are a few things you might find interesting:

      Sponges (phylum: porifera) are weird things. If you cut two sponges up and stick the bits in a tank, they will manage to self-differentiate when they regenerate.

      Dolphins (and probably all cetaceans) don’t drink. They get all their water from their food. If you point a hose at a dolphin and have it drink, it will not eat because it processes the two resources through the same mechanism.

      Certain cephalopods (squids, octopuses etc)have a feature known as autotomy. This means they can detach their limbs, and those limbs will continue to act autonomously. This is useful because a squid can attach its legs to an enemy and if they get detached it will keep attacking. Don’t harrass squid, folks. They will never let you forget it.

      Leatherback turtles have rows of what are effectively teeth, lining their throat. Don’t go sticking your arm down a leatherback’s throat next time you’re at the beach. Baby turtles use natural light sources reflecting off the ocean to find the ocean when they hatch and are easily confused by streetlamps and resort lights built near nesting areas.

      Some sharks are warmblooded, just like us! This is why you can find species like the great white in temperate and sub-polar waters, because they heat their bodies internally. Next time you recoil in fear during shark week on the discovery channel, remember you’re not that different :-)

      When whale’s die, and their carcasses eventually sink to the ocean floor, they become known as a ‘whale fall’. Whale falls are important events in the deep sea, being a buffet for various species that live there and are host to bacterial communities that have to date been found nowhere else. We still havn’t figured out how this occurs because they do not happen very frequently nor are they usually in close proximity so where the bacteria comes from is a mystery.

      • GWOP says:

        Thanks a lot for those wonderful tidbits!

      • KDR_11k says:

        Because pearlfishes love to hide in the anus of a sea cucumber and sometimes eat the cucumber’s flesh from in there (not enough to kill it but still inconvenient) some sea cucumbers have developed teeth on their anus. They can’t clench it shut for too long because sea cucumbers breathe through their anus.

        Cephalopods are related to snails and shellfish. Hence creatures like the nautilus that are squid-like but have snail-like shells.

        The biggest sharks are plankton eaters, they just float around and filter water.

        Beware of cookie cutter sharks, they cut fist sized chunks of flesh out of anything soft they encounter (including deep sea cables and radar dampening mats on submarines) and swim off.

        Ocean sunfishes look weird but funny…

        • poliovaccine says:

          Hang on a sec – which end of the sea cucumber is the anus? I ask cus I grew up in the (US) Virgin Islands and I’d often go snorkeling and pick up sea cucumbers, just out of my little-kid instinct to lay my hands on anything I thought interesting.

          But when you do that, especially if you bring it out of the water, the stiff “cucumber” goes limp and starts blasting sandy ropes of feces-looking material from BOTH holes, on either end! Further, I remember some adult on the beach who saw me playing with one telling me how their anus and mouth are interchangeable, or one in the same, or something like that – which would mean they kind of have two of each? Keep in mind that’s only hearsay..

          But yeah, now I’m curious where a sea cucumber’s anus is located (there must be something useful I should be doing right now). I also thought it bore mention, in case anyone into marine life here wants to go Youtubing, that sea cucumbers, once they’ve been harassed, can actually fairly quickly retreat. Once they’ve voided themselves of their digestive contents all across your forearms, and you’ve flung them back in the ocean with a little yelp of deep, primal disgust, they actually CURL UP INTO A DONUT shape and ROLL AWAY LIKE A TIRE across the ocean floor. You can’t make this shit up… (and, in perfect Far-Cry-esque collusion/collision of cohabiting natural entities, the rolling cucumber will sometimes trundle right over a buried flounder, eel, crab or goby, which in turn acts basically like a flailing land mine, causing an eruption of frantic sand-clouds as the poor, blind, warty-penis-shaped sea creature is even further disrupted).

          But my main question remains simply: if this thing can spray me with some kind of sandy fecal product from BOTH ends of its body, WHICH END IS THE ANUS??? The people have a right to know.

      • 2Ben says:

        Congrats, now I’ve spent my whole evening reading about whale falls, marine snow and the different strata of water depending on light, pressure and temperature conditions.
        Bravo sir!

  15. Nereus says:

    They really shouldn’t be that alien to you, they’re in the arthropod taxa as are arachnids. You can think of Decapoda(crabs, shrimp, lobsters/crays etc) as second cousins to Araneae (Spiders).

    Though I read this as if you were narrating it to me, and found your voice adorably filled with child-like wonder at the animal in the tank. Thanks Pip :)

  16. popej says:

    link to toomuchhorrorfiction.blogspot.co.uk

    “Crabs, crabs, crabs. Crabs the size of beach donkeys.”

  17. alms says:

    So basically it’s just like a nekkid person getting out of the same nekkid person. I like spider crabs: they’re yummy. European ones are, but I like brown crabs better.

    Now picture this. American lobsters don’t have the time bomb code in their DNA that makes everybody age and die. So they just get bigger and bigger. And bigger again. If they can. Must play a bit like a game of agar.io.

    • KDR_11k says:

      Turtles don’t have aging mechanisms in some of their organs. I guess lacking that also increases the risk of cancer so it makes sense not to have the whole body ageless.

    • poliovaccine says:

      Oh yeah, that’s a cool thing about some marine life. The whole “goldfish” mechanism of growth. I can only hope similar stuff happens with planet-sized organisms whose medium of “sea” is outer space…!

      But that reminded me of visiting some coastal Oregon touristy site and seeing that this one restaurant on the boardwalk had a pet lobster for a mascot, named Victor, which at that time was just over 28 pounds… he was damn near two feet long, NOT counting antennae! He made regular lobsters look like, well, shrimp… What was cool was that he wasn’t just longer, or fatter, but everything was larger in proportion. The most striking feature under that effect was totally the eyes, the big wet shiny black stalk-eyes, just sticking out at you all glistening and huge like a segment on a ripe blackberry… what is THAT thing’s experience of life, I wonder??