Horse leech
Haemopis sanguisuga
The horse leech is a robust annelid that, despite its name, is not a blood-sucker but a predator. It reaches a body length of up to 15 cm and is usually dark green to blackish in color, often with yellowish lateral stripes. The species is semi-aquatic and can leave the water to hunt in moist soil or to deposit its eggs.
Details
Identification
Dark dorsal side, often with light or yellowish lateral bands; 10 eyes arranged in a horseshoe shape; robust, muscular body; posterior sucker clearly visible.
Social behavior
Solitary, often hidden under stones or in the mud.
Diet
Feeds predatorily on insect larvae, earthworms, snails, small crustaceans, and occasionally amphibian larvae.
Hunting strategy
Active tracking of prey, which is usually swallowed whole or sucked out using the muscular pharynx.
Spawning substrate
Moist soil or moss above the water line.
Overwintering
Overwinters in the mud at the bottom of the water body or in moist soil near the shore.
Ecology
Ecological role
Important predator in the benthic food web, regulating invertebrate populations.
Natural predators
Larger fish, waterfowl, and predatory aquatic insects.
Competitor species
Other predatory leeches such as Erpobdella octoculata or large predatory beetle larvae.
Ecosystem service
Contributes to nutrient cycling by consuming invertebrate biomass.
Threats
Loss of natural riparian zones and pollution of small water bodies.
Scientific profile
Profile
Distinguishing features
Possesses five pairs of eyes arranged in a regular arc at the anterior end. A key distinguishing feature from the medicinal leech (Hirudo medicinalis) is the absence of reddish longitudinal stripes and the inability to pierce human skin. The jaws are weakly developed, each bearing two rows of approximately 14 blunt teeth. The posterior sucker is significantly smaller than the maximum body width.
Diet
Feeds on various invertebrates such as earthworms, insect larvae (e.g., chironomids), snails, and other leeches. Occasionally preys on small vertebrates like tadpoles or fish fry. Prey is usually swallowed whole.
Reproduction
Hermaphroditic with copulation. Eggs are laid in spongy, cocoon-like cases deposited in moist soil or moss on the bank (outside the water). Development is direct without a larval stage.
Role in food web
Important secondary consumer and predator within the benthic food web of small water bodies and riparian zones.
Protection & threats
Main threats
Destruction of near-natural riparian structures, drainage of small water bodies, use of pesticides in agriculture, and intensive watercourse maintenance.
Conservation measures
Protection and restoration of riparian buffer zones, preservation of small water bodies and ponds, reduction of nutrient and pollutant inputs.