Fairy shrimp are between 0.5 and two inches in length and have 10 pairs of leg-like appendages called phyllopods that are used for swimming. They swim slowly and belly-side up. Their diet affects their color—they are most often orange, but may also be white, blue or green. Females have smaller heads than the males.
Fairy shrimp are filter-feeders that scrape food off the bottom of their vernal pools. They eat algae, flatworm eggs and Arcella—a type of amoeba that have holes through their centers.
Predatory fish do not live in vernal pools, which make them a safe habitat for fairy shrimp. Birds, frogs, salamanders and insect larvae eat species of fairy shrimp.
Fairy shrimp generally mate between April and May. Males die shortly after mating, while the females live until the pool dries up. The eggs are released into the water and remain dormant throughout the dry season. Once the pool fills with water again—often October or November—the eggs hatch. The larvae go through a variety of molts and gain body segments with each stage, reaching 20 segments as adults.