U.S. Department of Defense


Date of this Version



A Report Prepared for the U.s. Fish and Wildlife Service (Under Contract No. 60181-2-1619) by Arthur H. Clarke, Ph.D. (1996) 1-29


In late September and early October, 1995, a brail survey was carried out to determine the distribution of Leptodea leptodon (Rafinesque) in the Missouri River near Yankton and Vermillion, South Dakota. We did not find L. leptodon but useful information in three areas was nevertheless brought to light, viz. :

(1) Leptodea leptodon is unusual in that adults are deeply buried and are not available by brail. Subsequent investigations which seek to determine its abundance at its only known location in the research area, close below Gavin's Point Dam, can only be carried out with the help of a diver during a period of very low water, e.g. when flow at the dam is cut off.

(2) A survey of major museum holdings of L. leptodon shows that historical records exist for a few sites in the Great Lakes Drainage and for a moderately large number of sites throughout the Ohio-Mississippi-Missouri River System. Examination of those records indicates, however, that with the exception of one collection in the Green River, Kentucky (in a site where it is now extinct), it has not been found east of, or in, the Mississippi River since 1950. The desirability of a status survey is therefore indicated.

(3) There is need for systematic and taxonomic studies of L. leptodon. Gravid specimens should be sought and glochidia should be photographed with a scanning electron microscope so that the generic placement of the species can be more firmly established. Our examination of Rafinesque's original description indicates that the name leptodon is apparently not applicable to this species. Other early literature and type material, therefore, should be critically reexamined to determine what its specific name should be.