The effect of pH on embryonic and larval development in smooth and palmate newts, Triturus vulgaris and T. helveticus



The distribution of smooth newts, Triturus vulgaris, and palmate newts, Triturus helveticus, in north-west Europe is related to geology and water quality. This study compared the development of the eggs and larvae of the two species under sublethal acidic and neutral conditions. Newt embryos raised under low pH hatched at an earlier stage of development, at a smaller size, and before those raised under neutral conditions. T. vulgaris hatched at a smaller size than T. helveticus, but pH did not affect the species differentially. Larvae of both species grew to a larger size under neutral than under acid conditions. Larvae raised in heterospecific pairs grew at least as well as those raised in conspecific pairs. Feeding was depressed under acid conditions, and reduced growth may therefore be associated with changes in the behaviour of newt larvae and their prey.