Fairy shrimp
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Artemiidae Grochowski, 1896 |
Fairy shrimp (Anostraca) are branchiopods that include brine shrimp. They often appear in vernal pools, pot holes and other ephemeral pools. Although they live in fresh or saltwater they do not live in oceans or seas. 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 United States (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.
Although most fairy shrimp are small (under ½ inch, 1 cm), the largest species are over 6 inches (15 cm) long and are predatory on other fairy shrimp. The giant fairy shrimp (Branchinecta gigas) is the largest and is found in the playas of California's southern deserts. This species traps the much smaller alkali fairy shrimp (Branchinecta mackini) with its large antennae. In contrast, the newly-discovered giant fairy shrimp Branchinecta raptor from Idaho has modified raptorial phyllopodia, which it uses to stab and puncture its prey.
