Inoculative Freezing and the Problem of Winter Survival for Freshwater Macroinvertebrates

Abstract

Due to the thermal buffering of their environment, aquatic invertebrates are less likely than their terrestrial counterparts to face temperatures substantially below 0°C. Aquatic invertebrates may not be able to avoid internal freezing by supercooling (remaining unfrozen at temperatures below the freezing point of their body fluids), however, because when their body temperatures reach the freezing point of body fluids, these organisms will likely be in contact with external ice, which may induce formation of internal ice (i.e., inoculative freezing). In this study, a variety of winter-collected, aquatic invertebrates (a clam, Sphaerium sp.; an isopod, Lirceus fontinalis; a mayfly, Stenomena femoratum; a belostomatid, Belostoma flumineum; 2 dytiscids, Ilybius oblitus and Agabus disintegratus) and, for comparison, a terrestrial beetle (Hippodamia convergens) were studied with respect to their low temperature tolerance. No species appeared to lower its freezing point appreciably by accumulating colligatively...