Eubranchipus hesperius n. sp. (Rogers, 2014)
(Western Ethologist Fairy Shrimp (unofficial))
by Thalia Grant
Eubranchipus hesperius is a fresh-water Branchiopod crustacean, growing to roughly 25 mm in length. It exhibits the typical fairy shrimp behavior of swimming “upside down” while beating its 11 pairs of abdominal thoracopods to propel itself, for respiration, and to transport organic particles to its mouth. Like all fairy shrimps it has compound eyes and lacks a carapace.
Eubranchipus hesperius occupies freshwater ephemeral rain-filled or snowmelt ponds in meadows and forests that are mildly acidic to mildly alkaline, low in dissolved solids and turbidity and have little or no flow (Eng et. al, 1990). It has been found in winter, spring and early summer months.
Eubranchipus hesperius was recently declared a new species, separate from Eubranchipus serratus Forbes 1876 (Rogers, 2014). It differs from E. serratus in the morphology of its antenna, brood pouch and abdomen, and in its geographical range; E. hesperius is found in North American transmontane and cold desert bioregions west of the Great Plains. E. serratus is now considered restricted to the Appalachian/Ozark bioregions and eastern Great Plains of the United States.
Eubranchipus hesperius has been recorded in British Columbia, eastern Washington and Oregon, Idaho, western Montana, northwestern California, northeastern Nevada and central Arizona. In British Columbia, E. hesperius has been found at altitudes of 600 to 1700 meters around Merritt, south of Merritt on Iron Mt., Selish Mt., Gillis Mt. and Shovelnose Mt., southwest and southeast of Kamloops, and in Curzon in the southeastern part of the province (Smithsonian collections, RBCM collections, Ian Gardiner, Thalia Grant).
Eubranchipus hesperius (and E. serratus) can be distinguished from other members of the genus by the shape of the male’s antennal appendages and the finger like process (ramus) on the distal segment of the antenna (see photo #39486).
The following morphologies distinguish E. hesperius from E. serratus: E. hesperius has a brood pouch that is slightly wider than long. In E. serratus it is slightly longer than wide. The abdominal segments and telson of E. hesperius are not flattened and splayed dorsolaterally as they are for E. serratus. The sides of the telson of E. hesperius are parallel. The male appendage of E. hesperius is narrower than that of E. serratus; its widest width is 1/5th the length of the appendage, as opposed to 1/3rd the length in E. serratus. Further distinguishing characteristics are detailed in Rogers, 2014.
