THE EFFECTS OF PH, ALUMINUM CONCENTRATION AND TEMPERATURE ON THE EMBRYONIC-DEVELOPMENT OF THE EUROPEAN COMMON FROG, RANA-TEMPORARIA

The individual and combined effects of pH, aluminium concentration and temperature, on the development of common frog (Rana temporaria) embryos from an upland area of northern England, were investigated in a controlled laboratory study. There was strong evidence to suggest that embryonic survival was lower at pH 4.5 compared with pH 6.0. At pH 4.5, embryonic survival was reduced at the highest aluminium concentrations. There was no strong evidence for a reduction in embryonic survival at lower aluminium concentrations. Gastrulation and hatching appeared to be the most sensitive stages to both pH and aluminium concentration. There was strong evidence to suggest that temperature-shocked embryos had reduced survival when compared with those kept at a constant temperature, particularly at pH 4.5. There was substantial variation in the survival of embryos from different clutches in the same pond with respect to low pH, aluminium concentration and temperatures. Thus R. temporaria has a wide genetic base from which to tolerate environmental changes. It is suggested, however, that the lethal and sublethal effects of low pH, high aluminium concentration and low temperature, could lead to a decrease in recruitment to the adult populations of R. temporaria in upland, northern England.