Late Pleistocene Desiccation of Lake Victoria and Rapid Evolution of Cichlid Fishes

Lake Victoria is the largest lake in Africa and harbors more than 300 endemic species of haplochromine cichlid fish. Seismic reflection profiles and piston cores show that the lake not only was at a low stand but dried up completely during the Late Pleistocene, before 12,400 carbon-14 years before the present. These results imply that the rate of speciation of cichlid fish in this tropical lake has been extremely rapid.     

Factors affecting foliar retention of some model adjuvant oil-in-water emulsions

The foliar retention of dilute oil-in-water emulsions containing three chemical types of adjuvant oil formulated either as ECs or EWs was compared in track-sprayer experiments using the water-soluble tracer, fluorescein. Although both types of emulsion enhanced tracer deposition onto water-repellant pea and barley foliage, compared with sprays containing no adjuvant, consistently better retention was achieved using the EW emulsions, irrespective of oil composition. On young plants, fluorescein retention using the EC emulsifier alone was similar to that from the corresponding emulsions. However, on older plants, retention from EC emul-sions was superior to that from the EC emulsifier. Compar-able effects were not observed using the EW stabiliser, which had little influence on the efficiency of spray deposition. The retention behaviour of the various oil-based adjuvants is discussed in relation to their effects on spray quality and their formulation ingredients. © 1998 Society of Chemical Industry