the strange animal of his life

The creepy and strange animals

Does anybody know what animal it is called? The color of a lightning black body, almost like a leech, moves slowly and strangely when it is pressed until it is severed and each of the severed parts can walk on its own.

The head moves forward and the tail moves backward when the body is disconnected, the animal is full of mystery because it's the first time I've encountered in my life ...