Low humidity enhances thermotolerance in Caenorhabditis elegans

Abstract

Humidity is an important environmental factor that causes physiological changes in organisms. In humans, high humidity disrupts thermoregulation by limiting heat dissipation, leading to heat stress. While Caenorhabditis elegans lacks comparable thermoregulatory systems, humidity may still impact its heat tolerance by affecting cellular stress responses. We tested this by subjecting C. elegans to heat shock under different humidity conditions and found that lower humidity during heat shock improved survival compared to higher humidity. These findings demonstrate that humidity is an important variable affecting thermotolerance in C. elegans and should be standardized in heat-stress experiments.

Figure 1. Low humidity improves C. elegans thermotolerance

( A ) Percent survival of day-three adult wild-type animals in six paired thermorecovery assays (35°C for 6h) with N~100 animals per condition conducted at low (32-52%) and high (77-90%) relative humidity. Bars represent the mean survival rate. **P=0.0083 by paired t -test. ( B ) Survival rate plotted against relative humidity (%) for each experiment, with solid line for linear regression fit and dotted lines for 95% confidence intervals. P=0.036 by simple linear regression. ( C ) Mean relative humidity (%) recorded every 5 min during heat-shock exposure in each paired thermorecovery assay shown in (A). Mean +/- standard deviation, ****P<0.0001 by t -test. ( D ) Mean temperature (°C) recorded every 5 min during heat-shock exposure in each paired thermorecovery assay shown in (A). Mean +/- standard deviation, ns P=0.07 by t -test. ( E ) Survival rate plotted against mean temperature (°C) for each experiment, with solid line for linear regression fit and dotted lines for 95% confidence intervals. P=0.14 by simple linear regression.