DIFFERENTIAL-EFFECTS OF PH AND TEMPERATURE ON EMBRYONIC-DEVELOPMENT IN THE BRITISH NEWTS (TRITURUS)

Changes in the water quality and temperature relationships of ponds ma y affect the structure of amphibian assemblages. The survival, time to hatching, hatching size and hatching stage of newt embryos were studi ed in the three British species (Triturus cristatus, T. helveticus and T. vulgaris), at two temperatures and two pHs. All T. cristatus embry os failed to hatch at pH 4.5, whereas over 80% of T. helveticus and T. vulgaris embryos hatched successfully at the same pH. At pH 7.5, T. c ristatus survival was the same as the other two species, after the 50% mortality due to the homomorphism of chromosome 1 was taken into acco unt. Temperature had no effect on survival of embryos. Time to hatchin g was two to four times longer at 12 degrees C than at 17 degrees C. L ow pH shortened development time in T. vulgaris but not in T. helvetic us. Low pH, but not temperature, affected size at hatching, with T. he lveticus and T. vulgaris embryos emerging at a smaller size and earlie r stage of development under acidic conditions. This reduction of size at low pH affected T. vulgaris more than T. helveticus. We predict th at T. cristatus embryos will be the most vulnerable of the three speci es to acidification in nature. Warm ponds will result in rapid embryon ic development, but T. helveticus and T. vulgaris larvae hatching in a cid ponds will do so at a smaller size and earlier stage of developmen t. The pattern of vulnerability to acidification within amphibian asse mblages may change during ontogeny.