The cephalic segment of the leech is made up of a prostomium and four segments.
Eyes are located on the prostomium. There may be from one to ten pairs of different shapes and sizes. Eye positioning varies between species, and there are even ones that do not have eyes at all.
Adders stick out their tongue to orient themselves to their surroundings.
In doing so, they collect the scent around them and then transfer it to their mouth cavity to the so-called Jacobson’s organ, which analyzes olfactory signals.
