THE ANIMAL FILES

European medicinal leech

Hirudo medicinalis

Two suckers, three jaws, and a meal that must stay liquid.

The European medicinal leech combines a simple-looking body with specialised feeding equipment. Its two ends do not do the same job, and its saliva is part of the feeding mechanism. Away from that famous meal, reproduction and habitat connect this animal to damp ground and vegetated fresh water.[1]

Follow the evidence ↓
European medicinal leech
Image: Karl Ragnar Gjertsen Please credit Karl Ragnar Gjertsen This photo was taken by Karl Ragnar Gjertsen. Please credit this photo Karl Ragnar Gjertsen in the immediate vicinity of the image. · Commons · CC BY 2.5
Body ends
An anterior and a posterior sucker[1]
Feeding equipment
Three toothed jaws[1]
Egg location
Damp shaded places near water[1]

The ends have different assignments

The posterior sucker mainly provides leverage and attachment, while feeding takes place at the anterior end. Inside the front sucker are three saw-like jaws. Their arrangement helps explain the characteristic three-part incision: a feeding trace follows the geometry of the animal’s mouthparts rather than being an arbitrary mark.[1]

Feeding involves chemistry as well as jaws

Leech saliva contains proteins with several effects relevant to feeding, including anticoagulant activity associated with hirudin. Keeping a blood meal fluid is a different task from opening the skin.[1]

The shoreline is part of the habitat

Vegetated freshwater pools and ditches provide habitat, but eggs are laid in humid, shaded locations near water rather than under it. Medicinal leeches are hermaphrodites that reproduce through mating.[1]

A COMMON MIX-UP

Do both suckers take in food?

No. Their positions conceal a division of labour. The rear sucker is mainly an attachment and leverage tool; the front end contains the feeding apparatus. Similar outlines do not guarantee identical functions.[1]

TRY A LITTLE REASONING

Why might draining a small pond affect more than swimming space?

Reveal the explanation

It changes the freshwater habitat and its damp margins together. Because eggs develop near water in humid sites, understanding the leech’s life cycle requires considering the shoreline as well as the pond itself.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — European medicinal leech (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Hirudo medicinalis (identity and classification)

Last fact check:

One discovery leads to another

Common earthwormA fallen leaf can travel down an earthworm’s burrow.Lumbricus terrestris ↗Christmas tree wormTwo little trees are feeding structures.Spirobranchus giganteus ↗Common liver flukeA leaf-shaped body with an active outer coat.Fasciola hepatica ↗