IS HABITAT REQUIREMENT BY AN OXYGEN-DEPENDENT FROG (RANA-RIDIBUNDA) GOVERNED BY ITS LARVAL STAGE

According to the literature and to our own experience, R. ridibunda is absent from ponds with occasionally low oxygen concentrations. We tes ted the effects of stochastically fluctuating oxygen concentration on tadpole survival and growth under laboratory conditions. Two experimen tal treatments (constant and fluctuating oxygen regimes) were arranged in a factorial design with three populations of R. ridibunda. Stochas tic oxygen fluctuation with drops from normoxia to hypoxia did not cle arly influence long-term survival (which remained high in all blocks) or growth and development. Only in one population did survival differ between oxygen treatments, and survival was greater under the fluctuat ing than under the stable oxygen conditions. One population differed f rom the others in exhibiting slight variations in morphology between t reatments. But in no case did these laboratory experiments provide evi dence that oxygen regime can affect development of R. ridibunda tadpol es and explain oxygen-dependent habitat use by this species.