The cold tolerance of an adult winter-active stonefly: How Allocapnia pygmaea (Plecoptera: Capniidae) avoids freezing in Nova Scotian winters

Allocapnia pygmaea Burmeister (Plecoptera: Capniidae) is a winter-active stonefly in North America. Despite the adult's winter emergence, little is documented about the cold tolerance and cryoprotective biochemistry of A. pygmaea . To better understand the cold tolerance of this winter-active stonefly, we collected adult A. pygmaea in Antigonish, NS during March or April in both 2023 and 2024. Following different cold exposures, we measured the lower limits of activity (-8.9 °C) and the temperature at which internal freezing occurs (-11.9 °C), and confirmed that A. pygmaea could survive subzero temperatures unless they froze. We also assayed the following putative cryoprotectants: proline, glycerol, myo -inositol, trehalose, and glucose in control (field-collected) and cold-shocked groups. We detected little effect of cold shock on most cryoprotectants, except for the polyols glycerol and myo -inositol, which decreased in concentration following cold shock. These findings improve our current understanding of Capniid cold tolerance, confirming that A. pygmaea uses a freeze-avoidant strategy, and lay a foundation for future studies on how they may use cryoprotectants for winter-activity.