Endangered

(fws.gov)

U.S. Endangered Species Act

(fws.gov)

Their major threats include habitat loss and degradation from development and agriculture, non-native plants, climate change, and extreme natural disturbances like drought and floods (fws.gov).

They are known to be in 5 areas ranging from Contra Costa County in the north to San Luis Obispo County in the south, making them extremely rare (fws.gov).

Survey Guidelines for Listed Large Branchiopods (fws.gov)

Minimum Qualifications for Recovery Permit for the Listed Large Branchiopod Species (fws.gov)

Longhorn fairy shrimp live in clear to turbid freshwater vernal pools and are only found in California’s Central Valley. They can also survive in water-filled sandstone depressions near Tracy, CA, claypan pools near Soda Lake, and grass bottomed pools in Merced County, CA. They are opportunistic filter feeders, eating what is present in the waters such as protozoa, algae, bacteria, and other plant matter. The females carry a sac of fertilized eggs on their underside and these eggs are either dropped or fall off when the mother dies, and they sink to the bottom of the pool. The dried eggs, cysts, hatch when the pools are rehydrated from rain like other fairy shrimp species. Longhorn fairy shrimp have short life spans, maturing after 22 days and reproducing after 43 days. These shrimp die when the vernal pools dry out, with males dying first due to being less tolerant of the stressful conditions. Mammals, insects, reptiles, and aquatic birds help disperse their cysts (fws.gov).

There is little to no research regarding the potential of constructed vernal pools for this species and other fairy shrimp in general. It may be interesting to see if numbers could be recovered by converting areas into appropriate breeding habitats for longhorn fairy shrimp.

Conservation Efforts for Longhorn Fairy Shrimp (fws.gov)

Their bodies are slender, and they have large, stalked compound eyes. They consist of 11 pairs of swimming legs which they use to glide upside down and create a wavelike motion while swimming. While they look similar to most other vernal pool shrimp, longhorn fairy shrimp do not have a hard outer shell. Also, longhorn fairy shrimp males are identified by their long second antennae that is about twice the length of its body (fws.gov).

Longhorn Fairy Shrimp (Branchinecta longiantenna) | U.S. Fish & Wildlife Service (fws.gov)