Vernal Pool Fairy Shrimp


Scientific Name: Branchinecta lynchi

Fairy Shrimp

Description: Vernal pool fairy shrimp are the 1-inch-long relatives of lobsters and crabs, all of which are crustaceans. They are translucent and have 11 pairs of appendages.

Life History and Reproduction: This fairy shrimp is one of many species specialized for a short life cycle in seasonal ponds called vernal pools. Each winter, during the rainy season, dry depressions fill up with water and the fairy shrimp hatch. They grow to maturity over several weeks, eating algae and plankton. Before the vernal pool dries up again, the females produce hardy resting eggs, called cysts, which survive the dry season and hatch when the rains come again. This strategy allows them to avoid predators which can’t survive in such a temporary habitat.

Typical Lifespan: It takes 41 days to reach maturity, after which point the fairy shrimp must reproduce before dying at the end of the rainy season. Typically, the young hatch in December and live until May unless temperatures become too warm.

Diet: Vernal pool fairy shrimp swim around upside down eating algae and plankton growing in the vernal pool. In order to digest their food, they must produce a thick, glue-like substance to mix with their meal. They use their legs to filter feed or to scrape food from hard substrates.

Predation: Fairy shrimp are an important food source for waterfowl. Wildlife that eats or tramples the eggs is actually beneficial to the fairy shrimp. The eggs are hardy enough that they can withstand the harsh treatment and remain viable until they are deposited in a new location.

Habitat and Range: Habitat is limited to vernal pools in Oregon and California. Occasionally these tiny crustaceans will be found in habitats other than vernal pools, such as artificial pools created by roadside ditches. They can be found in densities of 200 shrimp per liter of water.

Fun Fact: Vernal pool fairy shrimp have 11 pairs of appendages which are used for swimming, breathing, and feeding!

Conservation Status: Federally listed as Threatened. Habitat destruction and alteration are the biggest causes of decline, but a recovery plan for vernal pool ecosystems has been put in place California and Southern Oregon.

Oregon Fish & Wildlife Office 
NatureServe Explorer 
Contra Costa County Species Accounts Archives 
California Department of Pesticide Regulation


Additional Resources:
Defenders of Wildlife: Vernal Pool Fairy Shrimp


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