Odonatological Abstracts

(1425) PETR, T., 1972. Benthic fauna of a tropical man-made lake (Volta Lake, Ghana 1965- 1968). Arch. Hydrobiol. 70 (4): 484-533. (With German s.). – (Author's recent address unknown, in the paper it is given as: Dept. Zool., Makerere Univ., Kampala. Uganda). Quantitative and qualitative changes in the individual taxa of the bottom fauna were followed in the Volta man-made lake, Ghana (largest artificial lake in Africa; alt.: 84 m, length: 380 km, depth: 80 m, surface; 8000 km2) over the filling period 1965-1968. The changes in the individual invertebrate taxa during this period are considered in relation to the changing environmental factors, such as oxygen content, substratum, degree of exposure to waves, and establishment of littoral aquatic macrophytes. >Vhile the ecology of chironomids and the ephemeropteran and chaoborid larvae is discussed in detail, the larval Odon. are but briefly considered. Anisoptera were more abundant than Zygoptera. In order of their abundance the following Zygoptera were found at the sampling station of Ampem: Pseudagrion massaicum, Pseudagrion sp., Ischnura senegalensis. P. massaicum was also collected at Dodi. The presence of the zygopteran larvae seems to be related to the abundance of aquatic plants, especially Ceratophyllum, as found during observations of the fauna of aquatic plants at Akosombo, another station on the lake (cf. T. Petr, 1968. Population changes in aquatic invertebrates living on two water plants in a tropical man-made lake. Hydrobiologia 32; 449-485). Anisopteran larvae usually appeared as single specimens, preferring the shallows down to 3 m depth, with a maximum at 10 m. The commonest sp. was Parazyxomma flavicans, collected at all stations except Akosombo. Brachythemis leucosticta and Trithemis sp. were found at Ampem in shallows rich in aquaticweeds. The latter was also present in shallows in the north of Yeji.