Comparative study of thermal tolerance and other physiological characteristics in C. briggsae and C. elegans

The nematode Caenorhabditis briggsae (C. briggsae) is routinely used in genetic and evolutionary studies involving its well-known cousin, C. elegans. The two species are morphologically almost identical but exhibit significant developmental, genetic, and genomic differences. The AF16 isolate of C. briggsae is an established reference strain. We used additional wild isolates from tropical and temperate regions to perform a comparative study of phenotypic characters. The analysis revealed both intra (between C. briggsae isolates) and inter (compared to C. elegans N2) species variability in dimensions and opacity. Our data also showed that C. briggsae isolates prefer higher temperatures for growth, reproduction, and survival than C. elegans N2. The preference for higher temperatures further translated into a higher tolerance for heat stress, as evidenced by its survival at temperatures lethal to N2. Interestingly, we found that while C. briggsae is more resistant to heat and shows greater sensitivity to other forms of stress, namely oxidative and osmotic, compared to C. elegans. The heat resistance of C. briggsae was correlated with efficient upregulation of the cytosolic chaperon hsp-16.2. Overall, this work has revealed significant differences in stress sensitivities between the two nematodes and forms the basis to investigate changes in underlying mechanisms that affect their stress responses.