The ocean contains an astonishing variety of life, and the sheer size of some marine arthropods often captures human fascination. When searching for the largest crab in the world, the metric used for measurement becomes a determining factor for the final answer. Based on the widest possible reach, the title belongs to a creature known for its startlingly long limbs, the Japanese Spider Crab (Macrocheira kaempferi). This species holds the undisputed record for the greatest leg span of any arthropod on Earth.
Identifying the Record Holder
The Japanese Spider Crab is the definitive answer to the question of the world’s largest crab by sheer length. Adult specimens can achieve a maximum leg span reaching up to 12 to 13 feet (3.7 to 4 meters) from the tip of one claw to the tip of the opposite claw. This immense size is primarily a function of its extraordinarily long, slender legs, which dwarf its body. The creature’s carapace, or body shell, is comparatively modest, measuring up to 16 inches (41 centimeters) in width.
The crab also possesses a substantial mass, with the largest individuals weighing up to 42 pounds (19 to 20 kilograms). The impressive reach is due to the male’s chelipeds, the legs bearing the claws, which are significantly longer than the walking legs. This combination of vast horizontal reach and considerable weight firmly establishes the Japanese Spider Crab as the largest crab species by overall dimension.
Deep-Sea Life and Unique Anatomy
This species is found in the deep waters surrounding the Pacific coast of Japan, primarily at depths ranging from 344 to 984 feet (105 to 300 meters), though they have been observed as deep as 1,640 feet (500 meters). This deep-sea habitat is characterized by low temperatures and high pressure, factors that contribute to the species’ slow growth and extended lifespan.
Scientists estimate that the Japanese Spider Crab can live for an exceptionally long time, with some individuals potentially reaching up to 100 years of age. The crab’s body is a mottled blend of orange and white, which provides effective camouflage against the rocky and sandy seafloor of its natural environment. As an omnivorous scavenger, the crab uses its long legs to navigate the ocean floor, feeding on:
- Shellfish
- Dead animals
- Mollusks
- Plant matter
Other Contenders for “Biggest”
Other crabs hold size records in specific categories based on different physical characteristics. The Tasmanian Giant Crab (Pseudocarcinus gigas) presents a strong challenge by holding the record for the heaviest crab species. Found in the cold waters off Southern Australia, this crab has a far denser body and shorter legs compared to its Japanese counterpart.
The Tasmanian Giant Crab can reach a mass of up to 39 pounds (17.7 kilograms) and a carapace width of up to 18 inches (46 centimeters). Moving away from true marine crabs, the Coconut Crab (Birgus latro) is recognized as the largest terrestrial arthropod in the world. This land-dwelling species can weigh up to 11 pounds (5 kilograms), but its classification and habitat disqualify it from the marine crab size record.