Seasonal changes in the freezing tolerance of the intertidal pulmonate gastropod Melampus bidentatus Say

Abstract

The mean lethal temperature of Melampus bidentatus Say ranged from −5 °C in July to −13 °C in December. The percentage of tissue water frozen measured at the mean lethal temperatures was 3% for snails collected in the summer and 74.9% for snails collected in the winter. The supercooling point of the whole snails ranged from −9 °C in September to −6.4 °C in February. The presence of an ice nucleator is indicated by an increase in the supercooling point of the haemolymph from −11.5 °C in the fall to −7.5 °C in the winter. Water content in the snails varied from 2.6 mg water/mg dry weight to 3.6 mg water/mg dry weight; however, there was no correlation between low water contents and an increase in freezing tolerance. Whole animal glycerol contents ranged from 1.14 to 2.96 μmol/g fresh weight and proline contents ranged from 1.20 to 2.19 μmol/g fresh weight. Sorbitol and trehalose were not detected.

Comparative freeze tolerance and physiological adaptations of three species of vertically distributed rocky intertidal gastropods from southeast Alaska

“…Proline was found in high enough concentration to be protective of cellular structures. Likewise, Loomis (1985) identified low levels of glycerol and proline in the pulmonate snail M. bidentatus which would protect cellular structures but he did not identify any specific colligative cryoprotectants (Loomis, 1995). The selective advantages of the organic osmolyte systems are, firstly, a compatibility with macromolecular structure and function at high or variable (or both) osmolyte concentrations during extracellular freezing which draws water out of the intracellular compartment, and, secondly, a greatly reduced selective pressure to modify proteins to function in concentrated intracellular solutions (Yancey et al, 1982).…”

“…Cold hardiness of rocky intertidal molluscs has been thoroughly reviewed by Ansart and Vernon (2003). All species studied are freeze tolerant; the upper intertidal salt marsh pulmonate snail, Melampus bidentatus and the mid-tidal Nucella lima exhibit a supercooling point for freeze avoidance which lowers the freezing point of the snail below that of the osmolality of the extracellular fluid compartment during the initial aerial exposure (Hayes and Loomis, 1885;Hilbish, 1981;Loomis, 1985;Madison et al, 1991 andStickle et al, 2010). Because the duration of aerial emersion increases with intertidal height, the duration of freeze exposure should be considerably shorter during emersion for the mid-tidal N. lima (Stickle et al, 2010) than the upper tidal M. bidentatus (Loomis, 1995).…”

Physiological response to low temperature in the freshwater apple snail, Pomacea canaliculata (Gastropoda: Ampullariidae)

“…For instance, increased freeze tolerance in the intertidal pulmonate gastropod, Melampus bidentatus, is associated with an increase in glycerol and proline contents within the body (Loomis, 1985). The strategy of the land snail, Helix aspersa, to cope with low temperature is known to change from freezing avoidance to freezing tolerance as body size increases (Ansart and Vernon, 2004).…”

Survival of the gemmules of Anheteromeyenia ryderi (Potts) following aerial exposure during winter in New England

“…The cups were placed into 50 ml plastic centrifuge tubes which were immersed in a covered (dark) ethylene glycol bath. The temperature of the bath was lowered from 5 C to the desired temperature at a rate of about 0.2 C/min., and then the temperature was held constant for 24 h. Although gemmules in the wild may be subjected to subzero temperatures for varying periods of time, 24 h was chosen as a reasonable yet convenient period for testing low temperature tolerance (Murphy, 1975;Loomis, 1985). At the end of this period the cups containing the gemmules were removed from the bath, filled with 5 C pond water and placed in a dark 5 C incubator overnight.…”