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Branchinecta campestris
NatureServe conservation status
Global (G-rank): G2
State (S-rank): SNR
External links
Phenology
Like other species of fairy shrimp, Branchinecta campestris females produce desiccation-resistant cysts immediately after fertilization which hatch under favorable environmental conditions (Shepard and Hill, 2001). Cysts are usually dried, frozen, or both before cues break the dormancy and the hatching sequency begins. Broch (1969) estimates that water with a low temperature (4°C) and low TDS (1080 ppm) constitutes the hatching stimulus for the large cysts and that individuals are mature about a month after hatching (smallest female with cysts in her ovisac); as early as March 2 in Washington, and by April 6 (10°C) and about 15,000 ppm TDS, nauplii of Artemia franciscana appear as B. campestris decline and disappear by April 27 (TDS 18,900 and temperature 19°C). Similarly, Lynch made all his Washington collections between late March and mid-June at water temperatures from 9-20°C (Erikson and Belk, 1999). Total longevity rarely lasts more than one year; with the exception of resting stages (cysts).
Species range
Branchinecta campestris occurs west of the continental divide in a few locations in Washington and single localities each in California and Oregon (Rogers, 2006), while occurrences east of the continental divide in Canada, Montana, Wyoming and Texas and east of the great Basin Desert in Utah and Colorado have recently been attributed to the newly described Branchinecta laterialis (Rogers, 2006).
Migration
Major agents of dispersal are cysts that can pass undamaged and undigested through the digestive tract of birds and other animals and the transfer of cyst-containing mud on the feet and feathers of birds and other animals (Proctor et al., 1967; Eriksen and Belk, 1999) including crayfish (Moore and Faust, 1972).
Habitat
Habitat includes cool to warm-water pools which are great to impressive in dissolved solids, predictable, and temporary or permanent (Eriksen and Belk, 1999). In Washington Cascades, this includes either seasonally or perennially astatic alkaline-saline waters at 335-730 m elevation; at times alternating between standing water and frozen slush and ice (Broch, 1969). Typically it occurs in freshwater layer on hypersaline lakes derived from snowmelt or rain runoff, with the adults dying as the freshwater layer mixes with the salt water layer beneath. Rarely found in hyposaline pools (Lynch, 1960; Rogers, 2006). Individuals of Branchinecta campestris sometimes coexist with those of Artemia franciscana, dividing their shared habitat by season. Branchinecta campestris prefers the cooler, relatively lower-salinity phase of seasonal lakes and pools than Artemia, which peaks later in the season as water temperature and salinity rise, but populations of the two overlap for part of the year (Belk and Serpa, 1992).
Food habits
Anostracans are basically filter-feeders (non-selective particle feeders) and are opportunistic. Specific feeding habits of Branchinecta campestris have not been studied but it can be presumed that it feeds on the dissolved solids present in its highly saline environment, along with Artemia franciscana, which occurs sequentially throughout the year with it (Eriksen and Belk, 1999).
Ecology
Habitat pools can vary widely, both geologically and seasonally, in their dissolved salt concentrations so this species maintains body fluids at constant osmotic level above that of its pool (hyperosmotic regulation). Regulation continues until concentration outside equals concentration inside and then the animals mimic TDS of fluid in which they swim (Eriksen and Belk, 1999); which is at a higher tolerance of salt in body fluids than other species of Branchinecta (Broch, 1969).The species has been found to coexist with the following other anostracan species in California: Artemia franciscana, at greater TDS than any other American anostracan except Artemia (Eriksen and Belk, 1999).
Reproductive characteristics
Broch (1969) reported that individuals of this species reached full maturity about a month after hatching. In Washington, this species hatches early in the season when water temperatures approximate 4°C and salinities are low because of snow melt and runoff (unlike Artemia which hatches at higher temperatures) (Broch, 1969).
Threats or limiting factors
Specific threats have not been addressed.
