Fairy shrimp

Fairy shrimp (Anostraca) are branchiopods, ½ to 1½ inches in length that include brine shrimp. They often appear in vernal pools, pot holes and other ephemeral pools. They are well-adapted to living in arid areas where water is present for only part of the year. Their eggs will survive drought for several years and hatch about 30 hours after rains fill the pools where they live. Some eggs may not hatch until going through several wet/dry cycles, ensuring the animals' survival through times that the pools don't last long enough for the shrimp to reproduce.

The western US (especially California) is home to many species of fairy shrimp, five of which are threatened or endangered: the vernal pool fairy shrimp (Branchinecta lynchi, threatened), the Conservancy fairy shrimp (Branchinecta conservatio, endangered), the San Diego fairy shrimp (Branchinecta sandiegonensis, endangered), the longhorn fairy shrimp (Branchinecta longiantenna, endangered), and the Riverside fairy shrimp (Streptocephalus wootoni, endangered). All these listed species are endemic to the west coast, some found in fewer than a dozen populations in a very small area. The vernal pool fairy shrimp (Branchinecta lynchi) was thought to exist only in California until a population was discovered in the Agate Desert area of Oregon in 1998.