Studies on the taxonomy and distribution of freshwater sponges in Lake Baikal.

During the summers of 1993-2001, we carried out expeditions in order to collect sponges and to review their taxonomy and distribution in Lake Baikal. A total of 1,539 specimens were collected in our expeditions. Most specimens were classified into 2 families 7 genera, and 14 species, though some remained unclassified because of taxonomic confusion. Most sponges belonged to the family of Lubomirskiidae which were distributed widely in Lake Baikal. A few sponges with gemmules, which were confined to the "Little sea" near Olkhon Island and to an estuary in the North Basin, belonged to the Spongillidae. In qualitative survey of vertical distribution, B. intermedia showed the highest frequency among all species and found more often in shallow zones. L. baicalensis was second with regard to frequency and also found more often in shallow zones. Though S. papyracea had been believed to inhabit only deeper zones, it occurred in shallow zones as well. In this survey, the biomass of sponges at 10 m depth showed maximum value and showed the second largest at 20m depth.