Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are 0.2–6.0 mm (0.0079–0.24 in) long, with a down-turned head, and a carapace covering the apparently unsegmented thorax and abdomen. There is a single median compound eye. Most species show cyclical parthenogenesis, where asexual reproduction is occasionally supplemented by sexual reproduction, which produces resting eggs that allow the species to survive harsh conditions and disperse to distant habitats.
Bosmina is a genus in the order Cladocera. Its members can be distinguished from those of Bosminopsis (the only other genus in the family Bosminidae) by the separation of the antennae; in Bosminopsis, the antennae are fused at their bases.
Bosmina are filter feeders consuming algae and protozoans about 1–3 μm long. Bosmina are known to have a dual feeding mechanism. They can filter the water using their second and third legs and the first leg will grab the particles. The second and third legs have small setules attached to the seta to make a mesh-like structure for filtering.