How do water fleas use their antennae for swimming?

Water fleas, which are members of the crustacean order Anomopoda (class Branchiopoda), primarily use their antennae to navigate their environment through locomotion. Most species swim by executing powerful strokes with these antennae.1

In many species, these successive strokes result in a characteristic hopping and sinking motion. This movement is often influenced by light conditions, which help the water flea locate food. For example, in red light—which is prevalent when food sources like green algae are present—Daphnia utilizes this hop-and-drop swimming pattern to maintain its position in the water. Conversely, in the presence of blue light, which indicates a lack of food, the water flea is stimulated to swim more rapidly in a horizontal direction to search a wider area.12