Why are leeches assigned to a separate class?

Leeches are representatives of the Ringworm type, since outwardly their body has a segmental structure.

But they were singled out in a separate class, because, unlike other annelids:

– they have no bristles on their bodies;

– they feed exclusively on the blood of vertebrates;

– there are suckers on the front and back ends of the body;

– there are no segmental septa inside the body;

– the body cavity is practically absent – the space between the organs is filled with parenchyma;

– no circulatory system.