Water Flea

Statistics

Taxonomic order: Cladocera

Length: 0.2 to 5 mm

Average life span: 5 to 6 months

When To See

All year round.

Photo credit: Brittanica

Habitat

Water fleas are planktonic crustaceans that can be found in any permanent, nutrient rich body of water.  They are found throughout the water column but mostly concentrated around the vegetation. They filter microscopic particles of food using their appendages to bring the food to them by creating tiny water currents.  Daphnia spp. are more likely to be found in still waters as the water fleas are small and unable to swim against very strong currents.

How To Identify

Body can be translucent, globular and is not obviously segmented. The head is down-turned with a single compound black eye and has a rostrum (or beak). The water flea has two pairs of antennae, the first pair are smaller and unsegmented – used for olfactory sensing with hairs – and the second pair are much larger with segmentation and powerful muscles. These antennae are used for swimming. Swimming can be erratic with a characteristic hopping and skipping motion.

Seen It?

Been kicking about in your local river and come across one of these invertebrates? Not sure? Share it with us at trust@forthriverstrust.org, we enjoy chatting about inverts with you.