The Japanese spider crab, Macrocheira kaempferi, is the largest living arthropod in the world, primarily recognized for its impressive leg span. This massive marine creature inhabits the deep waters surrounding the Japanese archipelago, a habitat that kept its existence hidden from Western naturalists for centuries. Its presence in the abyssal zones meant it was known locally in Japan long before it was formally introduced to the global scientific community. The crab’s formal recognition involved a series of historical events and scientific expeditions in the early 19th century.
The Initial Discovery and Collection
The introduction of the Japanese spider crab to the Western scientific world began with the collecting efforts of the German physician and naturalist Philipp Franz von Siebold. Von Siebold was stationed on the artificial island of Dejima in Nagasaki between 1823 and 1829, when Japan was largely closed to foreign contact. He used his position to gather a vast collection of Japanese flora and fauna intended for Europe.
The crab specimens were acquired from local sources, likely fishermen operating near Suruga Province in eastern Japan. These crustaceans were often caught incidentally by local fisheries. Von Siebold shipped these specimens back to the Netherlands, where they formed the foundation for a landmark publication on Japanese natural history.
Formal Classification and Scientific Naming
The specimens collected by Philipp Franz von Siebold led to the species’ formal description. Dutch zoologist Coenraad Jacob Temminck provided the first scientific description in 1836, classifying the species as Maja kaempferi in his major work, Fauna Japonica.
The specific epithet, kaempferi, honors the earlier German naturalist Engelbert Kaempfer, who documented Japan’s natural history between 1690 and 1692. The genus was later revised, and the species was moved into its current genus, Macrocheira, established in 1886, finalizing the binomial name Macrocheira kaempferi.
Defining Characteristics of the Species
The Japanese spider crab possesses the largest leg span of any arthropod, reaching up to 4 meters (13 feet) from claw to claw. The body, or carapace, is relatively smaller, typically measuring up to 40 centimeters (16 inches) in width. The entire animal can weigh up to 19 kilograms (42 pounds).
This species is indigenous to the waters surrounding Japan, primarily found off the southern coasts of Honshū, with Suruga Bay being a notable population center. Adult crabs inhabit the deep ocean floor at depths ranging from 50 to 600 meters (160 to 1,970 feet). Individuals are thought to live for up to 100 years. The crab’s orange body and white-spotted legs are often covered in sponges and anemones, which provide effective camouflage.