Vernal pool fairy shrimp (Branchinecta lynchi)
Taxonomy:
View taxonomy in ITISListing Status: Threatened
Where Listed: WHEREVER FOUND
General Information
The vernal pool fairy shrimp (Branchinecta lynchi) is a small freshwater crustacean (0.12 to 1.5 inches long) belonging to an ancient order of branchiopods, the Anostraca. Like other anostracans, it has stalked compound eyes and eleven pairs of phyllopods (swimming legs that also function as gills). The various Branchinecta species are generally distinguished by characteristics of the males antennae and the size and shape of the females brood pouch. Branchinecta lynchi are distinguished by its medium antennae with curved rounded tips ; males have an elongated pair of antennae coming off the front of the head used to grasp the females during mating and the females have a short, pyriform brood pouch (Vollmar et al 2023). The basal segment outgrowth below and posterior to the pulvillus is ridgelike in B. lynchi, and the bulge below the middle of the basal segment is typically smaller, more moundlike, and has fewer denticles (none in some cases) (Belk et al 1990, pg. 256-257). Vernal pool fairy shrimp are found only in ephemeral freshwater habitats, in a wide range of vernal pools, and have life histories adapted to the environmental conditions of these habitats. Branchinecta lynchi can be found in extremely small or marginal vernal pools (from a small puddle only 3cm deep and covering 0.56m^2 to 10 ha) that fill with water for just long enough to allow the individuals to hatch from cysts, reach sexual maturity, reproduce, and die (Eriksen and Belk 1999, pg. 93). The time to maturity and reproduction is temperature dependent, but in general the vernal pool fairy shrimp has an average of 18.0 days and 39.7 days, respectively.The species historical range included California, Oregon. See below for information about where the species is known or believed to occur.
» Range Information
Current Range
Current range maps are only shown within the jurisdictional boundaries of the United States of America. The species may also occur outside this region.
Wherever found
Listing status: Threatened
- States/US Territories in which this population is known to or is believed to occur: California, Oregon
- US Counties in which this population is known to or is believed to occur: View All
- USFWS Refuges in which this population is known to occur: Grasslands Wildlife Management Area, Merced National Wildlife Refuge, North Central Valley Wildlife Management Area ...Show All Refuges
» Candidate Information
No Candidate information available for this species.
No Candidate Assessments available for this species.
No Candidate Notice of Review Documents currently available for this species.
No Uplisting Documents currently available for this species.
» Federal Register Documents
» Species Status Assessments (SSAs)
No Species Status Assessments (SSA's) are currently available for this species.
No Special Rule Publications currently available for this species.
» Recovery
- Species with Recovery Documents Data Explorer
- Recovery Priority Number: 2C
No Delisting Documents currently available for this species.
» Critical Habitat
To learn more about critical habitat please see https://ecos.fws.gov/crithab
» Conservation Plans
» Petitions
» Biological Opinions
To see all FWS Issued Biological Opinions please visit the BO Report.
» Life History
Habitat Requirements
The vernal pool fairy shrimp occurs only in cool-water pools. Individuals hatch from cysts during cold-weather winter storms; they require water temperatures of 50oF or lower to hatch(Helm 1998; Eriksen and Belk 1999). The time to maturity and reproduction is temperature dependent,varying between 18 days and 147 days, with a mean of 39.7 days (Helm 1998). Immature and adult shrimp are known to die off when water temperatures rise to approximately 75oF (Helm 1998).
Movement / Home Range
The vernal pool fairy shrimp is endemic to California and the Agate Desert of southern Oregon. It has the widest geographic range of the federally-listed vernal pool crustaceans, but it is seldom abundant where found, especially where it co-occurs with other species (Eng et al. 1990; Eriksen and Belk 1999). The vernal pool fairy shrimp has an ephemeral life cycle and exists only in vernal pools or vernal pool-like habitats; the species does not occur in riverine, marine, or other permanent bodies of water. Roughly 80 percent of observations of the shrimp are from vernal pools (Helm 1998; Helm and Vollmar 2002). Like most other fairy shrimps, the vernal pool fairy shrimp lacks any substantial anti-predator defenses and does not persist in waters with fish (King et al. 1996; Eriksen and Belk 1999). When the temporary pools dry, offspring persist in suspended development as desiccation-resistant embryos (commonly called cysts) in the pool substrate until the return of winter rains and appropriate temperatures allow some of the cysts to hatch (Eriksen and Belk 1999). Vernal pool habitats form in depressions above an impervious substrate layer, or claypan/duripan, in alluvial fans and terraces that are known primarily from the eastern side of the Central Valley of California (Vollmar 2002). Due to local topography and geology, the depressions are part of an undulating landscape, where soil mounds are interspersed with basins, swales, and drainages. Both flooding and the movement of wildlife within vernal pool complexes allow fairy shrimp to disperse between individual pools. These movement patterns, as well as genetic evidence, indicate that vernal pool fairy shrimp populations are defined by entire vernal pool complexes, rather than individual pools (King et al. 1996; Fugate 1998). The thermal and chemical properties of vernal pool waters are two of the primary factors affecting the distributions of specific fairy shrimp species (including the vernal pool fairy shrimp), or their appearance from year to year. Different species may appear in pools from one year to the next, depending on whether the pools fill at a different time of the year. Based on hatching and life history requirements, species may also appear in succession during one season as conditions change within the pool (Simovich and Fugate 1992; Eriksen and Belk 1999). In years with warm winter rains, vernal pool fairy shrimp apparently do not hatch in at least a portion of their range (C. Witham, CNPS, pers. comm., 2007). Active vernal pool fairy shrimp die off when water temperatures get too warm (Helm 1998). In years with low amounts of precipitation or atypical timing of precipitation, (or in substandard habitat) vernal pool species may die off before reproducing (Eriksen and Belk 1999). In some cases vernal pool fairy shrimp will cease to be found in pools where they were formerly found (Jones and Stokes 2005; Eriksen and Belk 1999). Long-distance dispersal of anostracan cysts is thought to be enabled by waterfowl and other migratory birds that ingest cysts, and by animals that provide for movementof mud and cysts in feathers, fur, and hooves (see authors cited in Fugate 1992; see also Eriksen and Belk 1999; Figuerola and Green 2002). Because the cysts are dispersed by other animals,they can be dispersed into locations that will never provide suitable habitat, or into waters that provide conditions allowing individuals to hatch in some years, but where conditions are not suitable for maintaining viable populations.
» Other Resources
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ITIS Reports-- ITIS (the Integrated Taxonomic Information System) is a source for authoritative taxonomic information on plants, animals, fungi, and microbes of North America and the world.
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