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Conservancy fairy shrimp
Branchinecta conservatio

fairy shrimp


U.S.A. Endangered.


Conservancy fairy shrimp live in ephemeral or temporary pools of fresh water (vernal pools) that form in the cool, wet months of the year. Fairy shrimp are not known to occur in permanent bodies of water, and are dependent upon seasonal fluctuations in their habitat, such as absence or presence of water during specific times of the year. Conservancy fairy shrimp inhabit highly turbid water in vernal pools. They swim or glide upside down by means of beating movements that pass along the their 11 pairs of swimming legs in a wave-like motion from head to tail. They feed on algae, bacteria, protozoa, rotifers, and bits of detritus. Females carry their eggs in a brood sac on their abdomen. Eggs are either dropped to the pool bottom or remain in the brood sac until the female dies and sinks. Resting (summer) eggs are known as cysts and are capable of withstanding heat, cold, and prolonged dry periods. The cyst bank in the soil may be comprised of cysts from several years of breeding. As the vernal pools refill with rainwater, in the same or subsequent seasons, some of the cysts may hatch. Early stages of fairy shrimp develop rapidly into adults. These non-dormant populations often disappear early in the season, long before the vernal pools dry up.

Development of agriculture has been the main factor in reducing the size and number of vernal pools and endangering the Conservancy fair shrimp. However, urbanization of the Central Valley of California currently poses the severest threat to the existence of this and other vernal pool crustaceans. The overall rate of loss of vernal pool habitat has been estimated at 2 to 3% per year.


Conservancy fairy shrimp are known from six disjunct populations in California: Vina Plains, Tehama County; south of Chico, Butte County; Jepson Prairie, Solano County; Sacramento National Wildlife Refuge, Glenn County; near Haystack Mountain northeast of Merced, Merced County; and the Lockewood Valley, northern Ventura County.


Phylum ARTHROPODA, Class CRUSTACEA, Subclass BRANCHIOPODA, Order ANOSTRACA, Genus Branchinecta, Species conservatio.








14 to 17 mm (0.6 to 1.1 inches)


In general, fairy shrimp have large-stalked compound eyes, 11 pairs of swimming legs, and elongate, distinctly segmented bodies lacking a hard protective outer cover. The ends of the antennae segments furthest from the body are distinctive when compared with other fairy shrimp species. The second pair of antennae in adult females are cylindrical and elongate. In males, the second antennae are greatly enlarged and specialized for clasping females during copulation. The female Conservancy fairy shrimp's brood sac is fusiform (tapering towards each end) and usually ends under abdominal segment 8.


Eng, L.L., D. Belk, and C.H. Erickson. 1990. California anostraca: distribution, habitat, and status. Journal of Crustacean Biology 10:247-277; Holland, R.F., and S. Jain. 1988. Vernal pools. Pp. 1012-1014, in Terrestrial Vegetation of California, New expanded ed. (M.E. Barbour and J. Major, eds). California Native Plant Soc. Spec. Publ. 9:1-1020.


C.D. Johnson and D.F. Williams

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