Branchinecta gigas Lynch, 1937

Rogers, D. Christopher & Hill, Matthew A., 2013, Annotated Checklist of the large branchiopod crustaceans of Idaho, Oregon and Washington, USA, with the “ rediscovery ” of a new species of Branchinecta (Anostraca: Branchinectidae), Zootaxa 3694 (3), pp. 249-261 : 252

Branchinecta gigas Lynch, 1937

New records. OREGON: Lake Co.: Christmas Lake, May 1999, reared from soil on 20 March 2000. Bottomless Lake, May 1999, reared from soil on 20 March 2000, D.C. Rogers.

Comments. This giant, predatory species occurrs in large, generally deep, argillotrophic alkaline playa type wetlands. Field data on various collection sites in Oregon, Washington and California had pH levels of 10+ during daylight hours, when the animals were swimming. The pool substrate is typically high in calcium carbonate (5–10%), gypsum (5%), strongly saline (electrical conductivity: 16.0–33.0 mmhos/cm) and is composed of a silty clay loam.

Broch (1988) reported B. gigas from four lakes in Washington. Of those four lakes, only Twelvemile Lake (“WW”of Broch, 1988) yielded B. gigas in this survey. Two lakes in Lower Grand Coulee (lakes “BL”and “SBL” in Broch, 1988) held no B. gigas when surveyed by one of us (MAH) on 10 April 2011. Lake “BL” was clear, saline, and devoid of branchiopods, and lake “SBL”was dominated by hydrophilids and erpobdellids at time of collection. Only a single Branchinecta mackini was found in “SBL”after ten minutes of intense searching. It is likely that both lakes have been altered by a rising water table caused by artificial water level manipulation in the adjacent Blue and Park Lakes, and are no longer suitable large branchiopod habitats. Lake “SE”of Broch, 1988 could not be found and is presumed to have been converted into agricultural land.