Crabs are a diverse group of crustaceans found in nearly every aquatic environment, from tide pools to ocean trenches. Their wide variety often sparks curiosity about which among them is the largest.
The World’s Largest Crab
The undisputed title for the world’s largest crab belongs to the Japanese Spider Crab (Macrocheira kaempferi). This deep-sea inhabitant has exceptionally long, slender legs that can stretch up to 12 feet (3.7 meters) from claw to claw, making it the arthropod with the greatest leg span. Its body, or carapace, measures up to 16 inches (40 centimeters) wide, and it can weigh up to 44 pounds (20 kilograms).
These crabs live in the cold, deep waters off Japan’s southern coast, primarily at depths between 160 and 1,970 feet (50-600 meters). As omnivorous scavengers, their diet includes dead fish, invertebrates, mollusks, and algae from the seabed. Despite their intimidating appearance, these slow-moving creatures are docile and can live for up to 100 years.
Measuring Crab Size
Determining the “biggest” crab involves different measurement criteria, which can sometimes lead to confusion. The most common metrics include leg span, carapace width, and overall weight. Leg span refers to the distance from the tip of one outstretched leg to another. Carapace width measures the broadest part of the main body shell, and weight provides overall mass.
The Japanese Spider Crab holds the “biggest” title due to its extraordinary leg span, which far surpasses that of any other arthropod. While other crab species might have a heavier body or a wider carapace, their leg spans do not compare. For commercially harvested crabs, carapace width is often the standard measurement.
Other Notable Large Crabs
While the Japanese Spider Crab claims the top spot, other crab species are also impressive. The Alaskan King Crab (Paralithodes camtschaticus) is known for its substantial weight and leg span. Male red king crabs can reach a leg span of 5 feet (1.8 meters) and weigh up to 28 pounds (12.7 kilograms) in the cold North Pacific waters.
The Coconut Crab (Birgus latro) is the largest terrestrial arthropod. These land-dwelling crabs can weigh up to 10 pounds (4.5 kilograms) and have a leg span exceeding 3 feet (1 meter). Found on islands across the Indian and Pacific Oceans, the Coconut Crab is well-adapted to its terrestrial environment, capable of climbing trees and using its powerful claws to crack coconuts. They can live over 60 years.