Square water flea
Alona quadrangularis
Alona quadrangularis is a widespread water flea that prefers the littoral zones of standing and slow-moving waters. Its body is characterized by a distinctive, almost rectangular shape and is usually yellowish to brownish in color. It stays primarily on the bottom of water bodies or on aquatic plants, where it grazes on detritus and algae. The species plays an important role in the benthic nutrient cycle and serves as food for various aquatic predators.
Details
Identification
Quadrangular shell shape, fine longitudinal striations on the valves, three head pores, terminal claw with a row of fine spines.
Social behavior
Lives predominantly solitary, but can reach high population densities on the substrate when food is abundant.
Diet
Feeds primarily on organic detritus, bacteria, and fine algal particles taken from the substrate.
Hunting strategy
Gathering filter feeder that brushes particles from the sediment or periphyton using its appendages.
Spawning substrate
Resting eggs are deposited in the benthic sediment.
Overwintering
Overwintering usually occurs in the egg stage via resting eggs (ephippia) in the sediment.
Ecology
Ecological role
Important primary consumer and decomposer that makes organic material available for higher trophic levels.
Natural predators
Juvenile fish, predatory insect larvae (e.g., dragonfly larvae), and larger benthic invertebrates.
Competitor species
Other chydorid species such as Alona affinis or Chydorus sphaericus.
Ecosystem service
Contributes to the reduction of organic load and water clarification in the littoral zone.
Threats
Destruction of shore habitats, excessive pesticide input, and extreme acidification of water bodies.
Scientific profile
Profile
Distinguishing features
Characterized by a broad, almost rectangular post-abdomen with 14-18 strong marginal denticles and lateral fascicles of bristles. The head shield features three connected median pores. The valves often show fine longitudinal striation or reticulation. The terminal claws possess a strong basal spine.
Reproduction
Cyclic parthenogenesis; asexual reproduction during favorable seasons, formation of males and resting eggs in ephippia under stress conditions (autumn, desiccation).
Role in food web
Important primary consumer and decomposer in the benthic food web; converts benthic primary production and detritus into biomass available for higher trophic levels.
Protection & threats
Status not on standard scale
Main threats
Destruction of littoral habitats through construction, excessive sedimentation due to eutrophication (oxygen depletion at the bottom), and input of insecticides from agriculture.