Redescription ofDiaphanosoma volzi Stingelin, 1905 (Crustacea: Daphniiformes: Sididae) with remarks on comparative morphology,biology and geographical distribution

The rareDiaphanosoma volzi Stingelin, long confused withD. sarsi Richard andD. celebensis Stingelin, is redescribed, based on extensive material of parthenogenetic and gamogenetic females and males from Thailand. Indonesia, Malaysia, Philippines, India, Australia and Sudan, and a study of intra- and interpopulation morphological variability. Compared with otherDiaphanosoma species, it shows the greatest degree of oligomerization and specialization. It is widely distributed in the tropics and subtropics of the Eastern hemisphere, and mostly occurs in shallow, vegetated habitats.