The physiological and biochemical adaptation mechanisms of heat-tolerant snail species are poorly known. We investigated cellular adaptations to heat stress in four heat-exposed snail populations (two of Xeropicta derbentina, one each of Cernuella virgata and Theba pisana). Snails were exposed to different temperature regimes (25, 33, 38, 40, 43, 45, 48, 50 and 52°C) in the laboratory for 8 h. After exposure, immobility rates were determined and a qualitative and semi-quantitative histopathological analysis of the digestive gland (calcium and digestive cells) and mucocytes in the foot was conducted. In addition, the coloration of the shells was densitometrically determined. The shells of T. pisana were significantly darker than the shells of the other populations. The immobility rates and histopathological examinations showed that X. derbentina (both populations) was slightly better adapted to heat than C. virgata, and much better adapted than T. pisana. The observed differences in heat tolerance seemed to be connected to the ability for rapid and extreme proliferation of calcium cells in the digestive gland.