Vernal Pool Tadpole Shrimp

Per USFWS Recovery Plan: Two other species of Lepidurus are found in California. One, the cryptic tadpole shrimp (Lepidurus cryptus), has recently been described (Rogers 2001). This species cannot be differentiated from the vernal pool tadpole shrimp by appearance, but the two species are genetically distinct (King and Hanner 1998, Rogers 2001). The cryptic tadpole shrimp occurs in the Great Basin and intermountain regions of northern California and southern and eastern Oregon, whereas the vernal pool tadpole shrimp occurs in the Central Valley, Delta, and east San Francisco Bay area (Rogers 2001). The cryptic tadpole shrimp is not known to occur within the range of the vernal pool tadpole shrimp as described in the listing rule (U.S. Fish and Wildlife Service 1994a). The other species, Lepidurus lemmoni, was described by Holmes in 1894 (Holmes 1894). This species is found in alkali playas high in calcium salts in California in the Mojave Desert in Inyo, Kern, San Bernardino, and Riverside Counties, in the Great Basin in Lassen, Modoc, and Siskiyou Counties, and also in Oregon, but does not cooccur with L. packardi (Rogers 2001, C. Rogers in litt. 2005). Lepidurus lemmoni is distinguished from L. packardi by having more than 50 leg pairs (vs. less than 40 in L. packardi), and the nuchal organ being placed behind the eyes (vs. between the eyes as in all other Lepidurus).