Bosmina (snout water flea)

Bosmina spp. · Aquatic life

Under the microscope · Photo: CC0

NativeCladoceran (water flea)

Also called Eubosmina, Small cladoceran, Bosmina longirostris, Elephant snout water flea

How to identify Bosmina (snout water flea)

Very small water flea, about 0.3 to 0.6 mm
Long, curved front antennae that hang down like an elephant trunk
Rounded, clear shell, often with short spines at the bottom rear corners
Hard to see by eye; looks like a tiny moving speck

Similar species

Chydorus is also tiny and round but has short antennae and no trunk; young Daphnia have a tail spine and no trunk.

Profile

Season	Present most of the year; often peaks in spring and fall and can dominate in summer when Daphnia are scarce.
Depth	Open water
How it spreads or reproduces	Females clone themselves through summer; resting eggs in a dark saddle (ephippium) survive drying and freezing and ride on birds, boots and boats
Habitat	Open water of ponds, lakes and reservoirs; common in both nutrient poor and nutrient rich water.

Why it matters in a lake

Grazes on small algae and bacteria. When Bosmina and other small water fleas replace Daphnia, fish are usually eating the larger zooplankton hard, which often means more algae.