The common spider crab is a long-legged, slow-moving crustacean that is also called the portly spider crab or the nine-spined spider crab. It hides itself from predators by covering itself in algae and small sticks.
Found on a variety of ocean, bay or harbor bottoms, from shallow water to depths exceeding 150 feet
It lives in the salty and brackish water of the Chesapeake Bay from Washington, D.C., to the western Gulf of Mexico, which stretches from Nova Scotia to the Gulf of Mexico. C. , to the Bays mouth.
The common spider crab’s shell is tan and in the shape of a triangle. It is about four inches wide and four inches tall, and it has a row of nine low spines that make it different from the six-spined spider crab. Its shell is often covered in algae, debris and small invertebrates held in place by hook-like hairs. With its legs spread out, the common spider crab can cover up to a foot of space. Males are bigger than females. The crab has short, white claws that move slowly and aren’t very strong. Its nose is tapered, and its eye stalks are short.
These crabs are sluggish and unaggressive scavengers with poor eyesight. The common spider crab can find food in the water or mud as it walks because it has taste and feeling organs on the tips of its walking legs. It will often feed on large starfish.
Spider crabs are in a group of animals called “decorator crabs.” Their main defense against being eaten is their ability to blend in with algae, debris, small animals, and other plants and animals. When startled, it will wave its pincers over its head as a warning sign.
Spider crabs are fascinating creatures that inhabit coastal waters around the world. With their long, spindly legs and rounded bodies, they almost look alien One of the most intriguing things about spider crabs is their sheer size – some species have leg spans over 10 feet! In this article, we’ll take a closer look at how big these giants of the crab world can get
The Japanese Spider Crab
The largest species of spider crab is the Japanese spider crab, scientific name Macrocheira kaempferi These massive crustaceans are found in the waters around Japan. Their leg span reaches an incredible 12 feet from claw to claw – that’s wider than a car! Their bodies alone can weigh up to 42 pounds.
To give you an idea of just how big the Japanese spider crab is, consider this:
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Their leg span is larger than a great white shark!
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They can be heavier than a medium sized dog.
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Their claw to claw measurement is wider than a Volkswagen Beetle car.
So in terms of crabs, the Japanese spider crab is truly a giant. It’s one of the largest arthropods (creatures with external skeletons) on Earth.
Other Large Spider Crab Species
While the Japanese spider crab takes the cake for sheer size, there are several other spider crab species that get impressively large:
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The Queen crab (Libinia emarginata) has a leg span up to 5 feet. They inhabit waters off the Atlantic coast of North America.
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The Red spider crab (Maja crispata) lives around the British Isles and has a leg span around 3 feet.
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The Giant Pacific spider crab (Pseudocarcinus gigas) reaches just under 3 feet across and is found from Alaska to Mexico.
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The Tasmanian giant crab (Pseudocarcinus gigas) has a leg span up to 2.5 feet wide. They are native to Southern Australia.
So while not as large as the Japanese spider crab, these species still get much bigger than your average crab. To put it in perspective, common edible crab species like blue crabs and Dungeness crabs usually only reach 1 foot across at most.
Why Are Spider Crabs So Big?
There are a few key reasons spider crabs are able to grow so large:
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Their diet is rich in nutrients. Spider crabs are omnivores and get nutrients from both plant matter and smaller animals. This diverse diet provides fuel for growth.
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They have a longer lifespan. Many spider crabs live over 20 years, giving them more time to get big.
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Cold water temperatures. Species like the Japanese spider crab live in deep, cold waters which allows their metabolism to work more efficiently.
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Lack of predators. Not much wants to mess with these intimidating giants! Their formidable size helps protect them from predators.
So while their massive size is an evolutionary advantage, it also results from an ideal habitat and lifestyle. Given the right conditions, spider crabs are able to keep growing larger throughout their long lives.
Measuring Spider Crab Size
When assessing spider crab size, the measurement that gets used is their leg span from claw tip to claw tip. This gives a good representation of their “total width” with legs extended. The carapace or body width is also measured, but leg span better demonstrates their impressive proportions.
Here are some key measurements for the largest species:
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Japanese Spider Crab leg span: 12 feet
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Japanese Spider Crab body width: Up to 16 inches
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Queen Crab leg span: Up to 5 feet
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Red Spider Crab leg span: Around 3 feet
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Giant Pacific Spider Crab leg span: Just under 3 feet
As you can see, the Japanese spider crab is in a league of its own when it comes to massive size. But even the smaller spider crab species have very sizable dimensions compared to your average crab.
Astounding Proportions
When you see photos or videos of spider crabs, their incredible size never fails to amaze. The Japanese spider crab in particular seems otherworldly in its proportions. These creatures are a testament to nature’s ability to grow life to astounding scales. Spider crabs remind us that even in familiar groups like crabs, there are giants lurking in the depths we have yet to fully explore. Their size is a glimpse into the unknown wonders the ocean still holds.
So while we may never see a spider crab the size of a car, these stunning giants of the crab world will continue to capture our imaginations with their larger-than-life spans. Their uncanny proportions are a symbol of both the diversity and mystery of the natural world.
Reproduction and Life Cycle
The common spider crab must molt to grow. When molting, this crab clings to top of eelgrass close to waters surface. In the fall, they shed their skin in big groups called “pods.” During the winter, they hibernate in dense patches, and in the spring, they mate in large groups. Females close to releasing eggs are held behind males and aggressively protected. When the eggs are laid, they are bright orange-red, but they turn brown as they grow. This process takes about 25 days.
- Polluted water and eutrophic, or low-oxygen, environments are fine for spider crabs to live in.
- Like other crabs, they can side-step when they walk, but they usually walk forward.