HORIZONTAL DISTRIBUTION AND ABUNDANCE OF CYSTS OF SEVERAL LARGE BRANCHIOPODS IN TEMPORARY POOL AND DITCH SEDIMENTS

Cysts of three species of anostracans (Branchipus schaefferi, Chirocep halus diaphanus, and Tarzymastigites perrieri), two species of Notostr acans (Triops numidicus and Lepidurus apus) and one species of Spinica udata (Leptestheria mayeti) were collected from the upper 2 cm of dry sediments at intervals along transects from a temporary pool in an ari d zone of Morocco and from two ditches in France. The horizontal distr ibution of viable cysts was patchy and is discussed in relation to sev eral ecological parameters prevailing during the aquatic phase. These include vegetation distribution, depth and morphometry of the pond, do minant wind pattern, and granularity of the sediments. The densities r eached more than 1700 cysts of C. diaphanus per 100 cm(2), and 1150 cy sts of L. apus per 100 cm(2) in the two ditches. The mean densities of cysts per 100 cm(2) calculated for each transect ranged from 250 to 4 50 for C. diaphanus and 240 to 260 for L, apus tin the ditch populatio ns) and about 1-6 for T. perrieri and L. mayeti, 3-15 for B. schaeffer i, and 16-58 for T. numidicus in the pool in Morocco.