Tolerance to extreme hot and cold temperatures in the EU-protected terrestrial slugGeomalacus maculosus

Abstract

Terrestrial molluscs are frequently exposed to a wide range of temperatures (Ansart & Vernon, 2003) but temperature tolerance studies have focussed mainly on land snails (Udaka, Goto & Numata, 2008;Slotsbo, Hansen & Holmstrup, 2011) with fewer studies on terrestrial slugs. The lack of external physical protection offered by a shell and epiphragm make slugs more sensitive to extreme heat or cold (Schweizer, Triebskorn & Köhler, 2019) as their body is in direct contact with the environmental temperatures. This, combined with the fact that their skin is covered in a layer of moisture providing mucus, makes them susceptible to inoculative freezing (Storey, Storey & Churchill, 2007;Udaka, Goto & Numata, 2008;Slotsbo, Hansen & Holmstrup, 2011; Slotsbo et al., 2012), whereby contact with external ice can induce the formation of internal ice crystals thereby freezing slug tissues. Indeed, mucus secreted by the slugs can also undergo freezing and is a potentially dangerous source of external ice crystals (R. T.