Two-eyed flat leech
Helobdella stagnalis
The two-eyed flat leech is a small, typically 8 to 12 mm long leech with a whitish, yellowish, or greyish coloration. It features a single pair of eyes at the anterior end and a characteristic, lens-shaped dorsal plate (scute) in the anterior third of its body. This species is extremely adaptable and inhabits almost all types of inland water bodies.
Details
Identification
One pair of eyes, small yellowish-brown dorsal plate (scute) in the anterior third of the body, flattened body shape.
Social behavior
Solitary, but exhibits distinct parental care towards offspring.
Diet
Predatory lifestyle; feeds on small invertebrates such as chironomid larvae, oligochaetes, and small snails.
Hunting strategy
Ambushes prey or actively searches substrates; sucks out prey using a proboscis.
Spawning substrate
Eggs are carried in cocoons on the ventral side of the parent.
Overwintering
Overwinters in the sediment or under stones in deeper water zones.
Ecology
Ecological role
Important predator in the macrozoobenthos, regulating populations of small invertebrates.
Natural predators
Fish, predatory insect larvae (e.g., dragonfly larvae), waterfowl.
Competitor species
Other flat leech species (e.g., Glossiphonia complanata), predatory leeches like Erpobdella octoculata.
Ecosystem service
Contributes to the nutrient cycle through predation and by serving as prey for higher trophic levels.
Threats
River engineering, extreme desiccation of small water bodies, severe chemical toxicity.
Scientific profile
Profile
Distinguishing features
The definitive identification feature is the brown neck shield (scutum) on the dorsal side. Additionally, the species possesses exactly two eyes, which are positioned closely together at the anterior end. Unlike many other leeches, Helobdella stagnalis cannot swim and moves exclusively by crawling.
Diet
Small invertebrates, especially Oligochaeta (worms), Chironomidae (midge larvae), small Gastropoda (snails), and Crustacea (crustaceans).
Reproduction
Hermaphroditic with intensive parental care. Eggs are carried in thin-walled cocoons on the ventral side of the parent. After hatching, the young attach themselves to the parent's belly with their posterior sucker and are carried and protected until their first independent feeding.
Role in food web
Secondary consumer; plays an important role in regulating populations of small invertebrates in benthic communities.
Protection & threats
Main threats
No immediate threats known; the species is highly adaptable and widespread.
Conservation measures
No specific conservation measures required; benefits indirectly from general water protection measures.