How do land snails prevent their bodies from drying out?

Land snails employ several physiological and behavioral adaptations to prevent desiccation (drying out) in terrestrial environments.1

• Physical Barriers: Prosobranchs use an operculum to seal their shell opening. Pulmonates, which lack an operculum, secrete mucous coverings called epiphragms or, in arid regions, a thick, calcium-impregnated seal across the shell aperture.1
• Behavioral Adjustments: Most land snails primarily rely on behavior, such as remaining in moist microhabitats, retreating into damp niches during dry spells, or burrowing into the soil. Some species survive extended droughts by remaining dormant.1
• Water Conservation: To minimize water loss, land prosobranchs secrete nearly crystalline urine, while land pulmonates utilize a ureteric groove or closed ureter to resorb water from their waste.2
• Specialized Structures: In tropical environments, some land operculates have evolved elaborate breathing tubes that facilitate gas exchange during dry periods while minimizing water loss.1

In humid regions where moisture is constant, some species have evolved toward shell reduction, as the shell's primary function—protection against desiccation—becomes less critical.1