Freeze-tolerant insects can survive the conversion of a substantial portion of their body water to ice. While the process of freezing induces active responses from some organisms, these responses appear absent from freeze-tolerant insects. Recovery from freezing likely requires energy expenditure to repair tissues and re-establish homeostasis, which should be evident as elevations in metabolic rate after thaw. We measured carbon dioxide (CO₂) production in the spring field cricket (Gryllus veletis) as a proxy for metabolic rate during cooling, freezing and thawing and compared the metabolic costs associated with recovery from freezing and chilling. We hypothesized that freezing does not induce active responses, but that recovery from freeze-thaw is metabolically costly. We observed a burst of CO₂release at the onset of freezing in all crickets that froze, including those killed by either cyanide or an insecticide (thiacloprid), implying that the source of this CO₂was neither aerobic metabolism or a coordinated nervous system response. These results suggest that freezing does not induce active responses from G. veletis, but may liberate buffered CO₂ from hemolymph. There was a transient ‘overshoot’ in CO₂release during the first hour of recovery, and elevated metabolic rates at 24, 48 and 72 hours, in crickets that had been frozen compared to crickets that had been chilled (but not frozen). Thus, recovery from freeze-thaw and the repair of freeze-induced damage appears metabolically costly in G. veletis, and this cost persists for several days after thawing. 

Gas exchange during cooling, freezing and thawing: Flow-through respirometry data

Respirometry parameters (CO₂ production, Q10, critical thermal minimum, supercooling point, etc.) measured with flow-through respirometry during cooling, freezing and thawing, or during cooling and rewarming. Data was used to construct Table 2, Figure 3 and Figure S5. The excel file contains a metadata tab that explains each column. See manuscript for details of methodology. 

flowthrough_respirometry_July2020.xlsx

Recovery from freeze-thaw: Stop-flow respirometry data

Respirometry parameters (CO₂ production, O₂ consumption, and calculated metabolic rates) measured with stop respirometry during recovery from chilling or freeze-thaw. Data was used to construct Table 3, Figure 4, Figure S2 and Figure S6. The excel file contains a metadata tab that explains each column. See manuscript for methodology. 

stopflow_respirometry_July2020.xlsx

Total hemolymph CO₂ data

Total hemolymph CO₂ measured in acclimated, but unchilled crickets. The excel file contains a metadata tab that explains each column. See manuscript for methodology. 

TCO2_July2020.xlsx

Sex-specific stop-flow respirometry data

Respirometry parameters (CO₂ production) measured with stop respirometry in acclimated crickets 72 h after chilling. The excel file contains a metadata tab that explains each column. See manuscript for methodology. 

sexspecific_stopflow_July2020.xlsx