Samurai Crab

Submitted by Nasir Sadeghi.

Heikegani crabs of Japan have markings on their carapace that resemble a human face, the face of a medieval samurai to be exact. It is locally believed that these crabs are reincarnations of the spirits of the Heike warriors defeated at the Battle of Dan-no-ura as told in the >Heike Monogatari ("The Tale of the Heike"). It is believed that when caught, these crabs are not eaten, but are thrown back into the water because if they're resemblance to a human face. This raises a question: how could the face of a samurai end up on the carapace of a Japanese crab?

It is thought that from the first crab that had a carapace shaped remotely like a human face, it was thrown back into the water, and thus humans were applying artificial selection on the crabs. Fishermen were probably reluctant to eat a crab with a human face, and because of this, these crabs were selected for, and thus this phenotype was passed down the hereditary line. Over the generation of interaction between humans and these crabs, the crabs with patterns resembling the samurai face preferentially survived. None of this involves the crab making a conscious decision about its carapace pattern (Lamarkian Evolution), but it is the artificial selection being imposed on the crabs from the outside that is responsible for this phenomena.