Wood Frog Freeze Tolerance: Cryoprotectant Lab (2D)

Wood frogs (Lithobates sylvaticus) are one of the very few vertebrates that survive their own body water turning to ice. This 2D lab isolates the physiology behind that trick from the 3D scene's forest-floor staging: a side panel drives ambient temperature, the concentration of cryoprotectant glucose the liver dumps into the blood once ice touches the skin, and how fast the season turns, while a live strip chart traces body temperature against ambient temperature and the freezing point in real time — the freezing point itself sits lower the more glucose is dissolved, exactly the colligative depression a chemistry class would predict. Cool the frog past that line and body temperature stalls on a plateau instead of falling straight through it, because crystallizing water between the cells releases latent heat as fast as the cold removes it — the same exotherm cryobiologists record with a thermocouple on a real freezing frog. Push past the plateau and the ice fraction climbs toward the ~65% of body water wood frogs are known to freeze solid, the heartbeat readout drops straight to zero, and the frog's own frost overlay grows to match; click "Onset of spring" and watch the reverse happen as it thaws and its heart restarts on its own Q10 metabolic curve.