Alterations in brain morphology and HSP70 expression in lizard embryos exposed to thermal stress

The teratogenic effects of thermal stress were studied in the oviparous Italian wall lizard Podarcis sicula. To this purpose, the eggs were exposed to continuous or temporary cold (15°C) or warm (30°C) stresses and the effects were analysed at the cytological and molecular levels. The results demonstrated the lethality of the continuous regimes and of the warm temporary regime, no matter if given at early (5 days) or late (15 days) stages of development. Temporary cold stress also resulted in lethality, but only if given in the early stage; later, in fact, it resulted in an abnormal development, with marked alterations in the encephalic vesicles, in the eyes and the trunk organs. By in situ hybridization, it was demonstrated that these alterations were often correlated with changes in HSP70 expression. In conclusion, our data indicate that Podarcis embryos have a limited potential to tolerate thermal changes, especially warm ones. The average predicted temperature increase of 2-4°C in the next few decades could therefore represent a real threat for lizard populations living in temperate areas.