Hairy crab velvet.

A black mass on the pincers of hairy crabs is the hairy crab's villi, which is one of the characteristics of the river crab hairy crab, and is the most important appearance feature that distinguishes hairy crabs from other seawater crabs or two-hop water crabs. The function of the villi is to feel the change of the external water environment, the water current vector, and to feel the flavor stimulation or danger.

The hairs on the pincers of male crabs have the following roles:

1. It helps to block some dirt and acts as a filter.

2. It can also sense changes in the water flow around it so that it can pounce on food or escape from natural enemies.

3, male crabs with chelipeds are also conducive to fighting for mates of the opposite sex, or a kind of bragging capital.

When you eat crabs, you don't need to remove the chelal hairs, just use a brush to clean them.