Effects of low ambient pH on perivitelline fluid of Ambystoma maculatum (Shaw) eggs

Egg clumps of Ambystoma maculatum were collected from a pond on the south side of the Gaspereau Valley, Kings County, Nova Scotia, to determine the effects of low ambient pH levels on the perivitelline fluid pH. Egg masses were placed in aquaria filled with pond water adjusted to pH 4.0, 5.0, 6.0 and 7.0. Perivitelline fluid was withdrawn from the eggs at 1, 3, 5, 7, 24, 48, 96 and 120 h after initial immersion, and its pH measured. Initial perivitelline fluid values decreased significantly 7 to 96 h after initial immersion in treatments altered to pH 4.0 and 5.0. Rate of H(+) influx into the perivitelline fluid is much greater in eggs immersed in water at pH 4 than in water at pH 5 or 6. Median Tolerance Limit tests indicated a critical pH value between 3.5 and 4.0 for newly hatched larvae.