HATCHING OF DAPHNIA MAGNA RESTING EGGS: THE EFFECT OF STORAGE DURATION AND STORAGE TEMPERATURE
M.M. Moreira dos Santos, G. Persoone
Abstract:
Knowledge on which environmental factors regulate diapause termination and hatching in Daphnia is important in understanding the role of the latter in the ecological and evolutionary dynamics of Daphnia populations. A controlled procedure to induce hatching is furthermore also needed to carry out genetic studies on Daphnia as well as for fundamental and applied ecotoxicology. To contribute to this objective, the influence of storage duration and storage temperature on the hatching percentage and hatching synchrony of D. magna resting eggs was investigated. Increasing storage duration up to six months was found to significantly increase both cumulative hatching and hatching synchrony. The effect of storage duration on hatching appeared to be genotype-specific. Prolonging storage duration from six to eight months revealed a temperature-dependent hatching response. This increase in storage duration was favourable for resting eggs stored at 4 C, but not for those stored at 20 C. Overall, resting eggs stored at 4 C exhibited a significantly higher cumulative hatching response and hatching synchrony than those stored at 20 C. Storing the resting eggs during approximately four years had no effect on cumulative hatching, but significantly decreased hatching synchrony.
(Laboratory for Biological Research in Aquatic Pollution, University of Gent, J. Plateaustraat 22, B-9000 Gent, Belgium)