Last Updated on March 24, 2024 by themubbi63
Imagining the size of a crab is always an awkward business. Are you just referring to the height and width and length of the shell? What about when you take all the legs into account? Because the legs and the width of the legspan is an altogether different matter. That’s especially the case with the Japanese spider crab (Macrocheira kaempferi) who is thought to be the world’s largest living crab. And most of that is because of its enormous legspan.
Spider Crab Width
Now, when it comes to width, we usually measure the carapace of the crab. That’s the main body cavity, excluding the legs. This is also quite impressive for this species of marine crab.
The average spider-crab measures around 12 – 16 inches (30 – 40 cm) across at the body. That’s comparable to the largest land crab in the world, the coconut crab. However, the spider crab’s claim to fame is its long long legs – it’s even named for them in Japanese.
| Animal | Inches | Centimeters |
| Spider Crab | 12 – 16 | 30 – 40 |
Spider Crab Weight
The spider-crab isn’t just one of the longest crabs in the world, it’s also quite weighty. In fact, at a weight of 42 lb (19 kg), the Japanese SpiderCrab is second in mass to the American lobster. No other living arthropod can compare.
| Animal | Pounds | Kilograms |
| Spider Crab | 40 – 42 | 18 – 19 |
SpiderCrab Legspan
Known in Japan as taka-ashi-gani which literally translates to “tall legs crab”, the Japanese spider crab has the largest legspan of any crab in the world. The legspan of the spider-crab measures over 12 feet or 3.7 meters from one claw to the other. That’s why this crab qualifies as the largest crab in the world.
Spider Crab Clutch Size
Female spider crabs can lay a very large amount of eggs per season! One individual female spider-crab may lay upto 1.5 million eggs at one go. They carry these fertilized eggs around on the underside of their stomach for 10 days, at which point the eggs hatch into larvae.
Just like all other crabs, there’s no real parenting involved in the growing up of these baby crabs. The larvae go through several stages before they reach adulthood and look very different from the adult crabs during this period.
Young crabs live in the shallower waters where they are born for a time before migrating to the deeper, cooler waters.
Spider Crab Size Comparison to Humans
While it’s quite strange to compare the size of a crab as compared to a human, sometimes the comparison is required to get a rough estimate of how big the creatures are. The average human being stands about 5 feet 7 inches to 5 feet 9 inches off the ground. Meanwhile, the length of a spider-crab is just over 1 foot at 12 – 16 inches.
However, the true point of comparison would be the massive legspan of a spider-crab. Measuring around 12 feet from one clawtip to the other, that would be two tall individuals put together.
Related article: Yellow Garden Spider Size Explained & Compared With Other Spiders
Spider Crab Vs American Lobster Size Comparison
As we have already seen, spider-crabs are heavier than all arthropods but the American lobster. That doesn’t mean that the American lobster is of a very great size (although it is quite long), it just means that they have quite a lot of mass.
The average American lobster is usually anywhere between 8 and 24 inches long as compared to the spider crab’s 12 – 16 inches body length. And while most American lobsters weigh around 1 – 9 lb, they hold the record for being the heaviest crustacean because there are specimens that weigh 44 lb.
| Animal | Length | Weight |
| Spider-Crab | 12 – 16 inches (30 – 40 cm) | 40 – 42 lb (18 – 19 kg) |
| American Lobster | 8 – 24 inches (2 – 61 cm) | 1 – 44 lb (0.45 – 20 kg) |
Spider-Crab Vs Coconut Crab Size Comparison
The largest terrestrial crabs happen to be coconut crabs. The biggest specimens have got a pretty impressive body length that can compare to the length of the spider crab – 16 inches. However, in all other ways, the coconut crab sadly falls short. Land crabs just aren’t as big as their marine cousins.
The spider crab not only outstrips the coconut crab in legspan, being 144 inches to the coconut crab’s 36 inches, it also is far weightier. The average coconut crab only weighs upto 10 lb while most spider-crabs quadruple that amount.
| Animal | Length | Weight | Legspan |
| Spider-Crab | 12 – 16 inches (30 – 40 cm) | 40 – 42 lb (18 – 19 kg) | 144 inches |
| Coconut Crab | 6 – 16 inches (15 – 40 cm) | 10 lb (4.5 kg) | 36 inches |
Spider Crab Vs Red King Crab Comparison
Finally, we’ve got another crab that resides in the cold Pacific waters around the Japanese islands – the red king crab. The red king crab is very popular with fisheries because it’s no small crab itself.
With a carapace length of 7 – 11 inches and a weight of around 28 lb, they’re quite big. However, they still don’t really compare to the immense size of a spider-crab which has a body length of 12 – 16 inches and a weight of 40 – 42 lb.
Related Article: Trapdoor Spider Size Explained & Compared With Other Spiders
The legspan of a red king crab can be upto 5.9 feet or 71 inches. That’s just about half the legspan of the spider crab at 144 inches.
| Animal | Length | Weight | Legspan |
| Spider Crab | 12 – 16 inches (30 – 40 cm) | 40 – 42 lb (18 – 19 kg) | 144 inches |
| Red King Crab | 7 – 11 inches (17 – 28 cm) | 28 lb (12.7 kg) | 71 inches |
Conclusion
The Japanese Spider-Crab is a true marvel of the deep. Its immense size, particularly its record-breaking legspan, sets it apart in the crustacean world. From its impressive weight to its staggering number of eggs, this spider crab continues to amaze scientists and oceanographers alike.
FAQs
How big is a spider crab compared to a human?
While their bodies are similar to a large dinner plate, their legspan stretches far beyond! Imagine two tall people side-by-side – that’s the impressive reach of a spider-crab.
What’s the biggest crab in the world?
The Japanese Spider-Crab (Macrocheira kaempferi) reigns supreme with a legspan reaching over 12 feet (3.7 meters)!