The development ofTriturus cristatus under osmotic stress

A recent description of genetically abnormal embryos of European crested newts was based on their development in Rugh's "urodele growing medium" (40 mM NaCl). The salinity tolerance of these embryos is tested here, showing that gastrulation is increasingly retarded at salinities above 12 mM, often incomplete above 70 mM and abortive at 120 mM NaCl. The results confirm the previous diagnosis of fat-tailed and slimtailed types of arrested tailbud embryos and show that each type occurs at a frequency of 25%, as expected for the balanced lethal system in this species. The defective gastrulation claimed to be characteristic of the fattailed phenotype, however, was caused by culture in a hypertonic medium.