Osmoregulation in Desiccated Dormant Snails (Helix aspersa; Gastropoda, Pulmonata)

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Abstract
Helix aspersa were subjected to 100 days of desiccation at 19-25 C in summer and in winter; total weight declined 33%. After desiccation, winter animals showed little significant change in hemolymph protein, Na⁺ and K⁺ concentrations, or osmolality. In summer snails, desiccation caused significant increases in all of these hemolymph constituents. Seasonal differences in hemolymph components were limited, except for Na±; in both hydrated and desiccated snails, Na⁺ concentrations were significantly higher in summer than in winter. In snail kidney, desiccation did not change significantly the concentrations of Na⁺, urate, water, or kidney wet weight. In both seasons, kidney K⁺ concentration rose significantly after desiccation. Seasonal differences were found among kidney contents-especially, winter snails (both hydrated and desiccated groups) had much higher Na⁺ and K⁺ contents. The kidney urate content of desiccated winter snails was higher than that of desiccated summer snails. It is hypothesized that the abundant urate spheres in snail kidney sequester K⁺ ions released by tissue degrowth during dormancy. In summer, sufficient K⁺ seems to be sequestered during desiccation to displace Na⁺ from kidney urates, leading to the higher hemolymph Na⁺ concentrations in summer snails. Qualitative differences in regulatory processes seem to exist between summer and winter snails.