Elephant water flea
Bosmina longirostris
The elephant water flea is a tiny crustacean widely distributed in various freshwater habitats globally. It is characterized by its distinctive, downward-curved first antennae that resemble an elephant's trunk. This species plays a central role in the pelagic food web, serving as a vital link between phytoplankton and small planktivorous fish. The body is generally rounded and protected by a transparent carapace.
Details
Identification
Trunk-like elongated first antennae, short terminal spine (mucro) at the posterior of the carapace, sensory bristles located in the middle of the proboscis.
Social behavior
Mostly lives solitarily in open water, but can reach extremely high population densities under optimal food conditions.
Diet
Primarily filter feeders that consume unicellular algae (phytoplankton), bacteria, and fine organic detritus.
Hunting strategy
Creates a water current through rhythmic leg movements, from which food particles are filtered out.
Spawning substrate
Eggs are carried in a brood chamber located beneath the dorsal carapace.
Overwintering
Production of resting eggs (ephippia) capable of surviving desiccation and freezing at the bottom of the water body.
Ecology
Ecological role
Important primary consumer and major food source for many fish larvae and predatory plankton.
Natural predators
Juvenile fish, predatory water fleas (e.g., Leptodora kindtii), backswimmers, and dragonfly larvae.
Competitor species
Other cladoceran species such as Daphnia or Ceriodaphnia as well as filtering copepods.
Ecosystem service
Contributes to the control of algal blooms and supports nutrient cycling in aquatic systems.
Threats
Input of insecticides into water bodies, invasive predatory species, and drastic changes in water temperature.
Scientific profile
Profile
Distinguishing features
The first antennae are completely fused with the rostrum, forming a rigid, trunk-like process. A short, pointed spine (mucro) is located at the posterior-ventral corner of the carapace valves. Sensory bristles of the first antennae are positioned midway along the rostrum. Distinguished from B. coregoni by the position of these bristles and the shape of the mucro.
Reproduction
Cyclical parthenogenesis: Asexual reproduction for most of the year. Under stress (cold, food shortage), production of males and sexual eggs occurs.
Role in food web
Important link between primary producers (algae/bacteria) and higher trophic levels. Due to its small size, it is often dominant in waters with high fish density, as it is harder for fish to detect than large Daphnia.
Protection & threats
Status not on standard scale
Main threats
No immediate threats known; partially benefits from anthropogenic eutrophication, but is sensitive to extreme acidification or toxic pollutants.