Dog leech
Erpobdella octoculata
The dog leech is one of the most widespread freshwater leeches in Central European inland waters. It inhabits both standing and flowing waters and is particularly common under stones. Unlike medicinal leeches, it does not suck blood from vertebrates but feeds predatorily on small invertebrates.
Details
Identification
Eight eyes in two transverse rows at the anterior end; flattened body; coloration usually brownish with yellowish pigment spots or reticulate patterns.
Social behavior
Solitary; does not form social groups, but can occur in high densities when food is abundant.
Diet
Predatory diet consisting of chironomid larvae, sludge worms (Tubifex), small snails, and other invertebrates.
Hunting strategy
Active tracking of prey; seizing with the oral sucker and subsequently swallowing the prey whole.
Spawning substrate
Hard substrates such as stones, wood, or aquatic plants for the attachment of cocoons.
Overwintering
Overwinters in the sediment or deep under stones to avoid frost.
Ecology
Ecological role
Important regulator of insect larvae and worm populations within the benthic ecosystem.
Natural predators
Fish (e.g., gudgeon, carp), waterfowl, and predatory insect larvae such as dragonfly larvae.
Competitor species
Other predatory leech species (e.g., Erpobdella nigricollis) and predatory insect larvae.
Ecosystem service
Contribution to the nutrient cycle by consuming detritivores; food source for higher trophic levels.
Threats
Heavy chemical pollution of water bodies, habitat loss through bank reinforcement, and desiccation.
Scientific profile
Profile
Distinguishing features
The most important feature is the 8 eyes arranged in two transverse rows (4 eyes at the anterior margin, 4 eyes laterally behind). The genital pores are separated by 2.5 annuli. The body consists of segments, each subdivided into 5 rings (annuli), which are all approximately of equal width.
Diet
Primarily chironomid larvae, oligochaetes (e.g., Tubifex), small crustaceans (Isopoda, Amphipoda), and occasionally other insect larvae (mayflies).
Reproduction
Hermaphroditic with mutual fertilization. Eggs are laid in firm, oval, brownish cocoons attached to stones or plants. A cocoon usually contains 5-30 eggs. No parental care.
Role in food web
Important secondary consumer in the benthos; regulates populations of midge larvae and oligochaetes. Serves as a significant food source for fish.
Protection & threats
Main threats
Currently not threatened. Local threats due to extreme chemical toxicity or complete desiccation of small water bodies.
Conservation measures
No specific species conservation measures required. Maintaining water quality and structural diversity benefits the entire benthic biocenosis.