MACROCHEIRA KAEMPFERI

When you think of the worlds largest spider you will normally envisage the Tarantula, with a leg span of eight or nine inches, but technically speaking the worlds largest spider is the  Taka-ashi-gani or Japanese Spider Crab, Macrocheira Kaempferi.

One specimen had a twelve foot leg span and weighed forty one pounds! If you bashed it with a broom, you would just have made it mad!...and its not what you would want to find crawling across your living room floor as this picture below illustrates, although I can safely say that this particular one is dead and has been propped up, otherwise there would be a house for sale!

Luckily they are not found too far inland to be much cause for concern, but its amazing that something can grow to this size and those pincers  have a sharp row of teeth for shearing and crushing anything unlucky enough to get corned by it.

<-------------------------twelve foot----------------------->

...with legs extended.  The Japanese spider crab has eight legs and two big feeding arms, and generally lives under water but has been found on land.  Many years ago when one of these was initially found inland, in the Jungles of Japan, they naturally caused quite a stir in the local community.

Below is a drawing of the spider crab standing next to a young woman for scale of its actual size. Imagine finding a spider like this in your bathtub!

The Giant Japanese spider crab can generally be found in the Pacific Ocean around Japan and they can live at depths of a thousand feet.

They generally have a dark orange body, with white spots on their legs.  In male specimens, the limbs on which the claws are located, become more extended than its legs.

The spider crabs eyes are situated directly on the front, and two thorns stick out between them. Younger specimens of the spider crab feature hair and thorns on the body, and their frontal horns are longer, but these get shorter as they grow older.

The giant spider crab is one of the largest arthropods know to man. They measure up to twelve feet from the tip of one claw to another.  The width of their body usually grows to about fifteen inches and they are covered with little nodules called tubercles, most of their size is taken up by their long legs.

Not quite the nicest thing to see crawling up your wall at home though.  Below a twelve  foot one has been made into an interesting mural!

Giant spider crabs are omnivorous and scavenge for food.  They can eat algae, plants, molluscs and small fish, catching and tearing up the meat in their powerful pincers. Their long legs enable them to move quite quickly and stalk their prey.

They move along the Ocean floor very slowly, and are consequently easy targets for hungry predators, that are big enough to attack it.  As some form of protection, they attach sponges and smaller animals to their shells to divert predators.

The spider crab tends to live in Ocean vents or holes that are big enough to take it.  They are now hunted by fisherman as their meat is apparently quiet delicious. The spider crab  is caught using trawling nets, and is often eaten salted and steamed. They are caught in the Sagami, Tosa and Suruga bays  and also around the Izu Islands.

During the spring when the crab lays its eggs, hunting them is prohibited and most fishermen thankfully obey these rules and the spider crab will not be served as a nice dish, allowing it to propagate so that it wont become and endangered species.

Below a guy is suitably impressed...if his expression is anything to go by, standing next to a dead spider crab.  This one is not a fully grown one either !

" I'm coming to get ya ! "

I for one won't be swimming inshore in Japanese waters, unless I have one of the bigger varieties of harpoon-gun with me! Or a big pair of rubber gloves, to hold a baby one, like this guy....

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Is it a spider or is it a crab?

Your Replies.

An ecology student has recently indicated via E-mail that it is indeed from the crab family as it has ten legs, Decapoda (dec as in ten). The feeding arms presumably have been included in this number, but it doesn't use these 'arms' for walking//crawling on, so the original count of eight legs still holds. As I said in my reply " If I was to crawl on all fours would my arms be counted as legs? "

 

Mr. Robert Aaron Grigsby writes:

"Just wanted to point out that the last picture you have on the spider crab page is not at all a spider crab but an Alaskan King Crab, Paralithodes camtschaticus.  You know this by the shorter heftier legs and the short "feeder" legs."

Mr. J. Harker writes:

"As a recent student in the zoology of invertebrates: The Japanese Giant Spider Crab is indeed a crab. Spiders are characterised by poisonous fangs (chelicerates) and spinnerets for silk weaving. They also have what are called 'book gills' (folds of tracheae for respiration) and their epicuticle has become waxy.

Crabs, however have aquatic gills and even land crabs have to keep these moist to keep breathing. They also require water to breed. Crabs also have a larval stage, whereas spiders do not. The taka-ashi-gani fits more criteria for decapoda ( crabs) than the arachnidan. Furthermore, the DNA sequence for the giant spider crab is distinctly Crustacean."

Mr. Mathew Allen Bhar points out in a recent E-mail...

"Actually, there really is no dispute about whether the spider crab is a spider or a crab.  Your defense for the first message you received about crabs actually having ten legs and not six like you had said, is that the forelimbs don't count as legs.  Well referring to something as X legged is generally referring to limbs that originated as a means of locomotion along the land.

All mammals have four "legs".  Based upon your defence, it sounds as if you feel we aren't mammals.  And furthermore, by saying the pinchers "don't count", you aren't only saying that spider crabs aren't crabs, you're also saying all crabs aren't crabs.  The "spider" part of a spider crabs name comes from the spindly legged appearance.  After all, how many spiders have pinchers and lack chelicerae?  "

Another e-mail explains the spider is a crab as Mr. Mike Rutherford writes:

 "I liked the photos you have in the Natural World section of your website but there are a few mistakes in some of the text.

Giant Japanese 'Spider' Crabs are definitely, one hundred percent crabs and nothing to do with spiders at all - no debate it's just a fact. Scorpions are arachnids but Arachnida is not a class of insect.

Both these animals are in the Arthropoda phylum, scorpions are in the subphylum Chelicerate and the class Arachnida, giant spider crabs are in the subphylum Crustacea and the class Malacostraca. Insects are in the subphylum Hexapoda and the class Insecta.

I love that you have taken the time and effort to make a great website and you obviously have a love for some weird and wonderful animals but I just wanted to help you get the correct information out there so that if people find your site they don't get confused. Cheers "

Mike Rutherford, Curator of Invertebrates, Culture and Sport, Glasgow.

 

                                    

Page created May 12th 2002.   Updated November 1st 2012