Heat tolerance in Mediterranean land snails: histopathology after exposure to different temperature regimes

The physiological and biochemical adaptation mechanisms of heat-tolerantsnail species are poorly known. We investigated cellular adaptationsto heat stress in four heat-exposed snail populations (two ofXeropicta derbentina, one each of Cernuella virgata and Thebapisana). Snails were exposed to different temperature regimes(25, 33, 38, 40, 43, 45, 48, 50 and 52°C) in the laboratoryfor 8 h. After exposure, immobility rates were determined anda qualitative and semi-quantitative histopathological analysisof the digestive gland (calcium and digestive cells) and mucocytesin the foot was conducted. In addition, the coloration of theshells was densitometrically determined. The shells of T. pisanawere significantly darker than the shells of the other populations.The immobility rates and histopathological examinations showedthat X. derbentina (both populations) was slightly better adaptedto heat than C. virgata, and much better adapted than T. pisana.The observed differences in heat tolerance seemed to be connectedto the ability for rapid and extreme proliferation of calciumcells in the digestive gland. (Received 26 November 2007; accepted 25 July 2008)