oa Annals of the Natal Museum - The fresh-water Mollusca of Tongaland, with a note on Molluscan distribution in Lake Sibaya

Volume 23, Issue 1
  • ISSN : 0304-0798



Records of 31 species of fresh-water Mollusca (20 Gastropoda and 11 Lamellibranchiata) from Tongaland are collated. Attention is drawn to the differences between the aquatic malacofaunae of the Pongola River floodplain in the west and the coastal lake systems in the east. Only 10 species (9 Gastropoda and 1 Lamellibranch) are common to both environments. It is suggested that the relationship between Caelatura framesi and C. mossambicensis (Unionidae) should be investigated. Brief descriptionptions of some waterbodies are included. A comparison is made between the vertical distribution of Mollusca in submerged weed beds in sheltered and exposed situations in Lake Sibaya. In the former situation Biomphalaria pfeifferi (intermediate host of Schistosoma mansoni) was most abundant at 1,4 m but extended to 4,5 m. Bulinus (Physopsis) globosus (intermediate host of S. haematobium and S. mattheei) did not extend beyond 1,4 m at which depth it was also most abundant. In the latter situation B. pfeifferi was found to 0,4 m and B.(Ph.)globosus to 0,3 m. The diversity of Mollusca in detached waterbodies adjacent to Lake Sibaya decreased with increasing distance from the present lake shore. B.(Ph.)globosus has however spread into much of the peripheral grassland recently inundated by a rise in lake level.

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